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the Simons Foundation and Leiden University.

Astrophysics

New submissions

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New submissions for Mon, 30 Mar 20

[1]  arXiv:2003.12071 [pdf, other]
Title: IceCube Search for High-Energy Neutrino Emission from TeV Pulsar Wind Nebulae
Comments: 11 pages, 2 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Pulsar wind nebulae (PWNe) are main gamma-ray emitters in the Galactic plane. They are diffuse nebulae that emit non-thermal radiation. Pulsar winds, relativistic magnetized outflows from the central star, shocked in the ambient medium produce a multiwavelength emission from the radio through gamma rays. Although the leptonic scenario is able to explain most PWNe emission, a hadronic contribution cannot be excluded. A possible hadronic contribution to the high-energy gamma-ray emission inevitably leads to the production of neutrinos. Using 9.5 years of all-sky IceCube data, we report results from a stacking analysis to search for neutrino emission from 35 PWNe that are high-energy gamma-ray emitters. In the absence of any significant correlation, we set upper limits on the total neutrino emission from those PWNe and constraints on hadronic spectral components.

[2]  arXiv:2003.12072 [pdf, ps, other]
Title: Primordial Rotating Black Holes
Comments: 7 pages, PRD submitted
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

Primordial black holes formed in an early post-inflation matter-dominated epoch during preheating provide a novel pathway for a source of the dark matter that utilizes known physics in combination with plausible speculations about the role of quantum gravity. Two cases are considered here: survival of Planck-scale relics and an early universe accretion scenario for formation of primordial black holes of asteroid-scale masses.

[3]  arXiv:2003.12073 [pdf, other]
Title: The Changing-look Optical Wind of the Flaring X-ray Transient Swift J1858.6-0814
Comments: Accepted for publication in ApJ Letters
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

We present the discovery of an optical accretion disk wind in the X-ray transient Swift J1858.6-0814. Our 90-spectrum data set, taken with the 10.4m GTC telescope over 8 different epochs and across five months, reveals the presence of conspicuous P-Cyg profiles in He I at 5876 Angs and Halpha. These features are detected throughout the entire campaign, albeit their intensity and main observational properties are observed to vary on time-scales as short as five minutes. In particular, we observe significant variations in the wind velocity, between a few hundreds and ~ 2400 km/s. In agreement with previous reports, our observations are characterised by the presence of frequent flares, although the relation between the continuum flux variability and the presence/absence of wind features is not evident. The reported high activity of the system at radio waves indicates that the optical wind of Swift J1858.6-0814 is contemporaneous with the radio-jet, as is the case for the handful of X-ray binary transients that have shown so far optical P-Cyg profiles. Finally, we compare our results with those of other sources showing optical accretion disk winds, with emphasis on V404 Cyg and V4641 Sgr, since they also display strong and variable optical wind features as well as similar flaring behaviour.

[4]  arXiv:2003.12074 [pdf, other]
Title: Fast cloud-cloud collisions in a strongly barred galaxy: Suppression of massive star formation
Comments: 15 pages, 13 figures, accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Recent galaxy observations show that star formation activity changes depending on galactic environments. In order to understand the diversity of galactic-scale star formation, it is crucial to understand the formation and evolution of giant molecular clouds in an extreme environment. We focus on observational evidence that bars in strongly barred galaxies lack massive stars even though quantities of molecular gas are sufficient to form stars. In this paper, we present a hydrodynamical simulation of a strongly barred galaxy, using a stellar potential which is taken from observational results of NGC1300, and we compare cloud properties between different galactic environments: bar, bar-end and spiral arms. We find that the mean of cloud's virial parameter is ~1 and that there is no environmental dependence, indicating that the gravitationally-bound state of a cloud is not behind the observational evidence of the lack of massive stars in strong bars. Instead, we focus on cloud-cloud collisions, which have been proposed as a triggering mechanism for massive star formation. We find that the collision speed in the bar is faster than those in the other regions. We examine the collision frequency using clouds' kinematics and conclude that the fast collisions in the bar could originate from random-like motion of clouds due to elliptical gas orbits shifted by the bar potential. These results suggest that the observed regions of lack of active star-formation in the strong bar originate from the fast cloud-cloud collisions, which are inefficient in forming massive stars, due to the galactic-scale violent gas motion.

[5]  arXiv:2003.12075 [pdf, other]
Title: Galaxy redshift-space bispectrum: the Importance of Being Anisotropic
Comments: 26 pages + Appendix, 15 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We forecast the benefits induced by adding the bispectrum anisotropic signal to the standard, two- and three-point, clustering statistics analysis. In particular, we forecast cosmological parameter constraints including the bispectrum higher multipoles terms together with the galaxy power spectrum (monopole plus quadrupole) and isotropic bispectrum (monopole) data vectors. To do so, an analytical covariance matrix model is presented. This template is carefully calibrated on well-known terms of a numerical covariance matrix estimated from a set of simulated galaxy catalogues. After testing the calibration using the power spectrum and isotropic bispectrum measurements from the same set of simulations, we extend the covariance modelling to the galaxy bispectrum higher multipoles. Using this covariance matrix we proceed to perform cosmological parameter inference using a suitably generated mock data vector. Including the bispectrum mutipoles up to the hexadecapole, yields 1-D $68\%$ credible regions for the set of parameters $(b_1,b_2,f,\sigma_8,f_\mathrm{NL},\alpha_\perp, \alpha_\parallel)$ tighter by a factor of 30$\%$ on average for $k_\mathrm{max}=0.09\,h$/Mpc, significantly reducing at the same time the degeneracies present in the posterior distribution.

[6]  arXiv:2003.12078 [pdf, other]
Title: Detection of the strongest magnetic field in a sunspot light bridge
Comments: Accepted for publication in ApJ. 3 videos available upon request to the first author
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Plasma Physics (physics.plasm-ph); Space Physics (physics.space-ph)

Traditionally, the strongest magnetic fields on the Sun have been measured in sunspot umbrae. More recently, however, much stronger fields have been measured at the ends of penumbral filaments carrying the Evershed and Counter-Evershed flows. Super-strong fields have also been reported within a light bridge separating two umbrae of opposite polarities. We aim to accurately determine the strengths of the strongest fields in a light bridge using an advanced inversion technique and to investigate their detailed structure. We analyze observations from the spectro-polarimeter onboard the Hinode spacecraft of the active region AR11967. The thermodynamic and magnetic configurations are obtained by inverting the Stokes profiles using an inversion scheme that allows multiple height nodes. Both, the traditional 1D inversion technique and the so-called 2D coupled inversions, which take into account the point spread function of the Hinode telescope, are used. We find a compact structure with an area of 32.7 arcsec$^2$ within a bipolar light bridge with field strengths exceeding 5 kG, confirming the strong fields in this light bridge reported in the literature. Two regions associated with downflows of $\sim$5 km s$^{-1}$ harbour field strengths larger than 6.5 kG, covering a total area of 2.97 arcsec$^2$. The maximum field strength found is 8.2 kG, which is the largest ever observed field in {a bipolar light bridge} up to now.

[7]  arXiv:2003.12083 [pdf, other]
Title: The MUSE Hubble Ultra Deep Field Survey XIV. The evolution of the Lya emitter fraction from z=3 to z=6
Comments: 25 pages, 17 figures, 5 tables, accepted for publication in A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The Lya emitter (LAE) fraction, X_LAE, is a potentially powerful probe of the evolution of the intergalactic neutral hydrogen gas fraction. However, uncertainties in the measurement of X_LAE are still debated. Thanks to deep data obtained with MUSE, we can measure the evolution of X_LAE homogeneously over a wide redshift range of z~3-6 for UV-faint galaxies (down to M_1500~-17.75). This is significantly fainter than in former studies, and allows us to probe the bulk of the population of high-z star-forming galaxies. We construct a UV-complete photo-redshift sample following UV luminosity functions and measure the Lya emission with MUSE using the second data release from the MUSE HUDF Survey. We derive the redshift evolution of X_LAE for M_1500 in [-21.75;-17.75] for the first time with a equivalent width range EW(Lya)>=65 A and find low values of X_ LAE<~30% at z<~6. For M_1500 in [-20.25;-18.75] and EW(Lya)<~25 A, our X_LAE values are consistent with those in the literature within 1sigma at z<~5, but our median values are systematically lower than reported values over the whole redshift range. In addition, we do not find a significant dependence of X_LAE on M_1500 for EW(Lya)>~50 A at z~3-4, in contrast with previous work. The differences in X_LAE mainly arise from selection biases for Lyman Break Galaxies (LBGs) in the literature: UV-faint LBGs are more easily selected if they have strong Lya emission, hence X_LAE is biased towards higher values. Our results suggest either a lower increase of X_LAE towards z~6 than previously suggested, or even a turnover of X_LAE at z~5.5, which may be the signature of a late or patchy reionization process. We compared our results with predictions from a cosmological galaxy evolution model. We find that a model with a bursty star formation (SF) can reproduce our observed X_LAE much better than models where SF is a smooth function of time.

[8]  arXiv:2003.12100 [pdf, other]
Title: Study of galaxy morphology and merging time of two interacting galaxies under different initial rotation and orientation configurations
Comments: 17 pages,17 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Using the GADGET-2 N-body code, we make a study of the galaxy morphology and merging time due to two interacting galaxies (for the same types and different sizes and masses, $1:1$ and $1:10$ ratio masses) merging due to gravity interaction. This is done for different initial relative orientation and rotation of these galaxies (modes of interaction) but with the same relative bulge separation and the same relative initial velocities. It was found that the resulting galaxy morphology resemble many of the observed galaxies in our Universe, and that, in general, a binary galaxy system with 1:10 mass ratio has larger merging time than a binary galaxy system with 1:1 mass ratio. This difference is due to the different evolution of the masses during the interaction in both cases. For the case with a 1:10 mass ratio, the global mass maximum is located at the end evolution, meaning that the second galaxy increases its mass constantly. For the case with mass ratio 1:1, the global maximum is located around $t=0.35$ Gy, causing a reduction of the merging time.

[9]  arXiv:2003.12116 [pdf, other]
Title: The Mira-Titan Universe. III. Emulation of the Halo Mass Function
Comments: 21 pages, 10 figures, 2 tables. For associated emulator code, see this https URL
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We construct an emulator for the halo mass function over group and cluster mass scales for a range of cosmologies, including the effects of dynamical dark energy and massive neutrinos. The emulator is based on the recently completed Mira-Titan Universe suite of cosmological $N$-body simulations. The main set of simulations spans 111 cosmological models with 2.1 Gpc boxes. We extract halo catalogs in the redshift range $z=[0.0, 2.0]$ and for masses $M_{200\mathrm{c}}\geq 10^{13}M_\odot/h$. The emulator covers an 8-dimensional hypercube spanned by {$\Omega_\mathrm{m}h^2$, $\Omega_\mathrm{b}h^2$, $\Omega_\nu h^2$, $\sigma_8$, $h$, $n_s$, $w_0$, $w_a$}; spatial flatness is assumed. We obtain smooth halo mass functions by fitting piecewise second-order polynomials to the halo catalogs and employ Gaussian process regression to construct the emulator while keeping track of the statistical noise in the input halo catalogs and uncertainties in the regression process. For redshifts $z\lesssim1$, the typical emulator precision is better than $2\%$ for $10^{13}-10^{14} M_\odot/h$ and $<10\%$ for $M\simeq 10^{15}M_\odot/h$. For comparison, fitting functions using the traditional universal form for the halo mass function can be biased at up to 30\% at $M\simeq 10^{14}M_\odot/h$ for $z=0$. Our emulator is publicly available at \url{https://github.com/SebastianBocquet/MiraTitanHMFemulator}.

[10]  arXiv:2003.12117 [pdf, other]
Title: STRIDES: Spectroscopic and photometric characterization of the environment and effects of mass along the line of sight to the gravitational lenses DES J0408-5354 and WGD 2038-4008
Comments: 40 pages, 18 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

In time-delay cosmography, three of the key ingredients are 1) determining the velocity dispersion of the lensing galaxy, 2) identifying galaxies and groups along the line of sight with sufficient proximity and mass to be included in the mass model, and 3) estimating the external convergence $\kappa_\mathrm{ext}$ from less massive structures that are not included in the mass model. We present results on all three of these ingredients for two time-delay lensed quasar systems, DES J0408-5354 and WGD 2038-4008. We use the Gemini, Magellan and VLT telescopes to obtain spectra to both measure the stellar velocity dispersions of the main lensing galaxies and to identify the line-of-sight galaxies in these systems. Next, we identify 10 groups in DES J0408-5354 and 2 groups in WGD 2038-4008using a group-finding algorithm. We then identify the most significant galaxy and galaxy-group perturbers using the "flexion shift" criterion. We determine the probability distribution function of the external convergence $\kappa_\mathrm{ext}$ for both of these systems based on our spectroscopy and on the DES-only multiband wide-field observations. Using weighted galaxy counts, calibrated based on the Millennium Simulation, we find that DES J0408-5354 is located in a significantly underdense environment, leading to a tight (width $\sim3\%$), negative-value $\kappa_\mathrm{ext}$ distribution. On the other hand, WGD 2038-4008 is located in an environment of close to unit density, and its low source redshift results in a much tighter $\kappa_\mathrm{ext}$ of $\sim1\%$, as long as no external shear constraints are imposed.

[11]  arXiv:2003.12118 [pdf, other]
Title: Correlation between UV resilience and wavelength of narrow DIBs
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Carriers of diffuse interstellar bands (DIBs) still need to be identified. In a recent paper, we reported a correlation between the DIB wavelength and the apparent UV resilience (or boost) of their carriers. We proposed that this might be an indication of the important role of conjugated elongated molecules among the DIB carriers. The aim of this paper is to further understand the origin of this correlation. The analysis of 509 optical DIBs on the lines of sight of HD 183143 and/or HD 204827 reported in the literature shows that this correlation mainly implies the 386 narrow DIBs with a band width < 1.1 A, which include most of the identified DIBs of the C2 and zeta families, while the majority of the 123 broader DIBs, including the identified sigma DIBs, do not display such a correlation. We present a possible origin of this correlation from very strong bands of large conjugated elongated molecules, such as carbon chains, polyacenes, or other catacondensed polycyclic aromatic hydrocarbons. The total amount of carbon contained in all the carriers of these narrow DIBs is a very small fraction of the interstellar carbon if their oscillator strengths are <~1. The amount of carbon locked in the carriers of the broader DIBs is higher, especially if their oscillator strengths are significantly weaker.

[12]  arXiv:2003.12138 [pdf, other]
Title: Sixteen overlooked open clusters in the fourth Galactic quadrant. A combined analysis of UBVI photometry and Gaia DR2 with ASteCA
Comments: 70 figures. Accepted for publication in A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Aims: This paper has two main objectives: (1) To determine the intrinsic properties of 16 faint and mostly unstudied open clusters in the poorly known sector of the Galaxy at 270$^\circ-$300$^\circ$, to probe the Milky Way structure in future investigations. (2) To address previously reported systematics in Gaia DR2 parallaxes by comparing the cluster distances derived from photometry with those derived from parallaxes. Methods: Deep UBVI photometry of 16 open clusters was carried out. Observations were reduced and analyzed in an automaticway using the ASteCA package to get individual distances, reddening, masses, ages and metallicities. Photometric distances were compared to those obtained from a Bayesian analysis of Gaia DR2 parallaxes. Results: Ten out of the 16 clusters are true or highly probable open clusters. Two of them are quite young and follow the trace of the Carina Arm and the already detected warp. The rest of the clusters are placed in the interarm zone between the Perseus and Carina Arms as expected for older objects. We found that the cluster van den Berg-Hagen 85 is 7.5$\times$10$^9$ yrs old becoming then one of the oldest open cluster detected in our Galaxy so far. The relationship of these ten clusters with the Galaxy structure in the solar neighborhood is discussed. The comparison of distances from photometry and parallaxes data, in turn, reveals a variable level of disagreement. Conclusions: Various zero point corrections for Gaia DR2 parallax data recently reported were considered for a comparison between photometric and parallax based distances. The results tend to improve with some of these corrections. Photometric distance analysis suggest an average correction of $\sim$+0.026 mas (to be added to the parallaxes). The correction may have a more intricate distance dependency, but addressing that level of detail will require a larger cluster sample.

[13]  arXiv:2003.12152 [pdf, other]
Title: Shouts and Murmurs: Combining Individual Gravitational-Wave Sources with the Stochastic Background to Measure the History of Binary Black Hole Mergers
Comments: Submitted to ApJL
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

One of the goals of gravitational-wave astronomy is to quantify the evolution of the compact binary merger rate with redshift. The redshift distribution of black hole mergers would offer considerable information about their evolutionary history, including their progenitor formation rate, the dependence of black hole formation on stellar metallicity, and the time delay distribution between formation and merger. Efforts to measure the binary redshift distribution are currently limited, however, by the detection range of existing instruments, which can individually resolve compact binary merger events only out to $z\lesssim1$. We present a novel strategy with which to measure the redshift distribution of binary black hole mergers well beyond the detection range of current instruments. By synthesizing direct detections of individually resolved mergers with \textit{indirect} searches for the stochastic gravitational-wave background due to unresolved distant sources, we can glean information about the peak redshift, $z_p$, at which the binary black hole merger rate attains its maximum, even when this redshift is beyond the detection horizon. Using data from Advanced LIGO and Virgo's first and second observing runs, we employ this strategy to place joint constraints on $z_p$ and the slope $\alpha$ with which the binary merger rate increases at low redshifts, ruling out merger rates that grow faster than $\alpha \gtrsim 7$ and peak beyond $z_p \gtrsim 1.5$. Looking ahead, we project that approximately one year of observation with design-sensitivity Advanced LIGO will further break remaining degeneracies, enabling a direct measurement of the peak redshift of the binary black hole merger history.

[14]  arXiv:2003.12155 [pdf, other]
Title: Discovery of new members of the nearby young stellar association in Cepheus
Comments: 16 pages, 14 figures, 2 tables (46 pages, 27 figures, and 10 tables when including online material). Accepted for publication in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

Young field stars are hardly distinguishable from older ones because their space motion rapidly mixes them with the stellar population of the Galactic plane. Nevertheless, a careful target selection allows for young stars to be spotted throughout the sky.
We aim to identify additional sources associated with the four young comoving stars that we discovered towards the CO Cepheus void and to provide a comprehensive view of the Cepheus association.
Based on multivariate analysis methods, we have built an extended sample of 193 young star candidates, which are the optical and infrared counterparts of ROSAT All-Sky Survey and XMM-Newton X-ray sources. From optical spectroscopic observations, we measured their radial velocity with the cross-correlation technique. We derived their atmospheric parameters and projected rotational velocity with the code ROTFIT. We applied the subtraction of inactive templates to measure the lithium equivalent width, from which we infer their lithium abundance and age. Finally, we studied their kinematics using the second Gaia data release.
Our sample is mainly composed of young or active stars and multiple systems. We identify two distinct populations of young stars that are spatially and kinematically separated. Those with an age between 100 and 300 Myr are mostly projected towards the Galactic plane. In contrast, 23 of the 37 sources younger than 30 Myr are located in the CO Cepheus void, and 21 of them belong to the stellar kinematic group that we previously reported in this sky area. We report a total of 32 bona fide members and nine candidates for this nearby (distance = 157$\pm$10 pc) young (age = 10-20 Myr) stellar association. According to the spatial distribution of its members, the original cluster is already dispersed and partially mixed with the local population of the Galactic plane.

[15]  arXiv:2003.12190 [pdf, other]
Title: A broadband X-ray study of a sample of AGNs with [OIII] measured inclinations
Comments: 22 pages, 10 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

In modeling the X-ray spectra of active galactic nuclei (AGNs), the inclination angle is a parameter that can play an important role in analyzing the X-ray spectra of AGN, but it has never been studied in detail. We present a broadband X-ray spectral analysis of the joint NuSTAR-XMM-Newton observations of 13 sources with [OIII] measured inclinations determined by Fischer et al. 2013. By freezing the inclination angles at the [OIII] measured values when modeling the observations, the spectra are well fitted and the geometrical properties of the obscuring structure of the AGNs are slightly better constrained than those fitted when the inclination angles are left free to vary. We also test if one could freeze the inclinations at other specific angles in fitting the AGN X-ray spectra as commonly did in the literatures. We find that one should always let the inclination angle free to vary in modeling the X-ray spectra of AGNs, while fixing the inclination angle at [OIII] measured values and fixing the inclination angle at 60$^\circ$ also present correct fits of the sources in our sample.Correlations between the covering factor and the average column density of the obscuring torus with respect to the Eddington ratio are also measured, suggesting that the distribution of the material in the obscuring torus is regulated by the Eddington ratio, which is in agreement with previous studies. In addition, no geometrical correlation is found between the narrow line region of the AGN and the obscuring torus, suggesting that the geometry might be more complex than what is assumed in the simplistic unified model.

[16]  arXiv:2003.12231 [pdf, ps, other]
Title: Gamma-ray Burst Spectrum with a Time-dependent Injection Rate of High-energy Electrons
Comments: 9 pages, 3 figures, accepted for publication in ApJ Letters
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Although the physical origin of prompt emission in gamma-ray bursts (GRBs) remains inconclusive, previous studies have considered the synchrotron radiation of relativistic electrons as a promising mechanism. These works usually adopted a invariable injection rate of electrons ($Q$) which may be discordant with that in a Poynting-flux dominated jet. In a Poynting-flux dominated jet (e.g., ICMART model, Zhang & Yan 2011), the number of magnetic reconnections occurred simultaneously may grow rapidly with time and results in an increase of $Q$ with time. This paper is dedicated to study the synchrotron radiation spectrum in this scenario. It is found that the radiation spectrum would obviously get harder if an increasing $Q$ is adopted and a Band-like radiation spectrum can be obtained if the increase of $Q$ is fast enough. The latter is related to the fact that a bump-shape rather than a power-law spectrum appears in the low-energy regime of the obtained electron spectrum. This effect can strongly harden the low-energy radiation spectrum. It indicates that an increasing $Q$ can help to alleviate the "fast-cooling problem" of synchrotron radiation for GRBs. Our studies also reveal that a Poynting-flux dominated jet with a large emission radius, a small length of the magnetic reconnection region, or a low-minimum energy of injected electron would prefer to form a Band-like radiation spectrum. We suggest that the Band spectrum found in GRBs may be the synchrotron emission of the electrons with a bump-shape distribution in its low-energy regime.

[17]  arXiv:2003.12284 [pdf, other]
Title: The MESAS Project: ALMA observations of the F-type stars $γ$ Lep, $γ$ Vir A, and $γ$ Vir B
Comments: Accepted to ApJ, 13 pages, 7 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

The spectrum of stars in the submillimeter to centimeter wavelength range remains poorly constrained due to a lack of data for most spectral types. An accurate characterization of stellar emission in this regime is needed to test stellar atmosphere models, and is also essential for revealing emission associated with unresolved circumstellar debris. We present ALMA observations of the three nearby, main-sequence, debris-poor, F-type stars $\gamma$ Lep, $\gamma$ Vir A, and $\gamma$ Vir B at 0.87 and 1.29 millimeters. We use these data to constrain semi-empirical atmospheric models. We discuss the atmospheric structure of these stars, explore potential short term variability, and the potential impact on debris disk studies. These results are part of an ongoing campaign to obtain long wavelength observations of debris-poor stars, entitled Measuring the Emission of Stellar Atmospheres at Submillimeter/millimeter wavelengths (MESAS).

[18]  arXiv:2003.12297 [pdf, other]
Title: How runaway stars boost galactic outflows
Comments: 14 pages, 10 figures, accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Roughly ten per cent of OB stars are kicked out of their natal clusters before ending their life as supernovae. These so called runaway stars can travel hundreds of parsecs into the low-density interstellar medium, where momentum and energy from stellar feedback is efficiently deposited. In this work we explore how this mechanism affects large scale properties of the galaxy, such as outflows. To do so we use a new model which treats OB stars and their associated feedback processes on a star-by-star basis. With this model we compare two hydrodynamical simulations of Milky Way-like galaxies, one where we include runaways, and one where we ignore them. Including runaway stars leads to twice as many supernovae explosions in regions with gas densities ranging from 1e-5 cm^-3 to 1e-3 cm^-3. This results in more efficient heating of the inter-arm regions, and drives strong galactic winds with mass loading factors boosted by up to one order of magnitude. These outflows produce a more massive and extended multi-phase circumgalactic medium, as well as a population of dense clouds in the halo. Conversely, since less energy and momentum is released in the dense star forming regions, the cold phase of the interstellar medium is less disturbed by feedback effects.

[19]  arXiv:2003.12306 [pdf, other]
Title: Cosmic magnetic fields with MASCLET: an application to galaxy clusters
Comments: 14 pages, 13 figures, accepted for publication in MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)

We describe and test a new version of the adaptive mesh refinement (AMR) cosmological code MASCLET. The new version of the code includes all the ingredients of its previous version plus a description of the evolution of the magnetic field under the approximation of the ideal magneto-hydrodynamics (MHD). To preserve the divergence-free condition of MHD, the original divergence cleaning algorithm of Dedner et al. (2002) is implemented. We present a set of well-known 1D and 2D tests, such as several shock-tube problems, the fast rotor and the Orszag-Tang vortex. The performance of the code in all the tests is excellent with estimated median relative errors of $\nabla \cdot {\bf B}$ in the 2D tests smaller than $5 \times 10^{-5}$ for the fast rotor test, and $5 \times 10^{-3}$ for the Orszag-Tang vortex. As an astrophysical application of the code, we present a simulation of a cosmological box of 40 comoving Mpc side length in which a primordial uniform comoving magnetic field of strength 0.1 nG is seeded. The simulation shows how the magnetic field is channelled along the filaments of gas and is concentrated and amplified within galaxy clusters. Comparison with the values expected from pure compression reveals an additional amplification of the magnetic field caused by turbulence in the central region of the cluster. Values of the order of $\sim 1 \mu$G are obtained in clusters at $z\sim 0$ with median relative errors of $\nabla \cdot {\bf B}$ below 0.4\%. The implications of a proper description of the dynamics of the magnetic field and their possible observational counterparts in future facilities are discussed.

[20]  arXiv:2003.12337 [pdf, ps, other]
Title: Hydrogen Non-Equilibrium Ionisation Effects in Coronal Mass Ejections
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

A new generation of coronagraphs to study the solar wind and CMEs are being developed and launched. These coronagraphs will heavily rely on multi-channel observations where visible light (VL) and UV-EUV observations provide new plasma diagnostics. One of these instruments, Metis on board ESA-Solar Orbiter, will simultaneously observe VL and the UV Lyman-$\alpha$ line. The number of neutral Hydrogen atoms (a small fraction of coronal protons) is a key parameter for deriving plasma properties such as temperature from the observed Lyman-$\alpha$ line intensity. However, these measurements are significantly affected if non-equilibrium ionisation effects occur. The aim of this work is to determine if non-equilibrium ionisation effects are relevant in CMEs and in particular when and in which regions of the CME. We use a magneto-hydrodynamic simulation of a magnetic flux rope ejection to generate a CME. From this we then reconstruct the ionisation state of Hydrogen atoms in the CME by evaluating both the advection of neutral and ionised Hydrogen atoms and the ionisation and recombination rates in the MHD simulation. We find that the equilibrium ionisation assumption holds mostly in the core of the CME. In contrast non-equilibrium ionisation effects are significant at the CME front, where we find about 100 times more neutral Hydrogen atoms than prescribed by ionisation equilibrium conditions, even if this neutral Hydrogen excess might be difficult to identify due to projection effects. This work provides key information for the development of a new generation of diagnostic techniques that aim at combining visible light and Lyman-$\alpha$ line emissions. The results show that non-ionisation equilibrium effects need to be considered when we analyse CME fronts. To incorrectly assume equilibrium ionisation in these regions would lead to a systematic underestimate of plasma temperatures.

[21]  arXiv:2003.12350 [pdf, other]
Title: Properties of Streamer Wave Events Observed During the STEREO Era
Comments: 20 pages, 12 figures, 1 table. Accepted for publication in The Astrophysical Journal
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

Transverse waves are sometimes observed in solar helmet streamers, typically after the passage of a coronal mass ejection (CME). The CME-driven shock wave moves the streamer sideways, and a decaying oscillation of the streamer is observed after the CME passage. Previous works generally reported observations of streamer oscillations taken from a single vantage point (typically the SOHO spacecraft). We conduct a data survey searching for streamer wave events observed by the COR2 coronagraphs onboard the STEREO spacecraft. For the first time, we report observations of streamer wave events from multiple vantage points, by using the COR2 instrument on both STEREO A and B, as well as the SOHO/LASCO C2+C3 coronagraphs. We investigate the properties of streamer waves by comparing the different events and performing a statistical analysis. Common observational features give us additional insight on the physical nature of streamer wave events. The most important conclusion is that there appears to be no relation between the speed of the CME and the phase speed of the resulting streamer wave, indicating that the streamer wave speed is determined by the physical properties of the streamer rather than the properties of the CME. This result makes streamer waves events excellent candidates for coronal seismology studies. From a comparison between the measured phase speeds and the phase speeds calculated from the measured periods and wavelengths, we could determine that the speed of the post-shock solar wind flow in our streamers is around 300 $\mathrm{km \ s}^{-1}$.

[22]  arXiv:2003.12368 [pdf, other]
Title: Optical spectroscopic observations of gamma-ray blazar candidates. IX. Optical archival spectra and further observations from SOAR and OAGH
Comments: 30 pages and 65 figures
Journal-ref: Pe{\~n}a-Herazo et al. (2019) Ap&SS 364 85P
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

Nearly one-third of the sources in the $Fermi$-LAT catalogs lack a lower energy counterpart, hence being referred as unidentified/unassociated gamma-ray sources (UGSs). In order to firmly classify them, dedicated multifrequency follow-up campaigns are necessary. These will permit to unveil their nature and identify the fraction that could belong to the class of active galaxies known as blazars that is the largest population of extragalactic $\gamma$-ray sources. In $Fermi$-LAT catalogs there are also gamma-ray sources associated with multifrequency blazar-like objects known as Blazars Candidates of Uncertain type (i.e., BCUs) for which follow up spectroscopic campaigns are mandatory to confirm their blazar nature. Thus, in 2013 we started an optical spectroscopic campaign to identify blazar-like objects potential counterparts of UGSs and BCUs. Here we report the spectra of 31 additional targets observed as part of our follow up campaign. Thirteen of them are BCUs for which we acquired spectroscopic observations at Observatorio Astrof\'isico Guillermo Haro (OAGH) and at Southern Astrophysical Research Observatory (SOAR) telescopes, while the rest has been identified thanks to the archival observations available from the Sloan Digital Sky Survey (SDSS). We confirm the blazar nature of all BCUs: three of them are in blazar of quasar type (BZQs) while the remaining ones can be spectroscopically classified as BL Lac objects (BZBs). Then we also discovered 18 BL Lac objects lying within the positional uncertainty regions of UGSs that could be their potential counterparts.

[23]  arXiv:2003.12389 [pdf, other]
Title: Properties of Short GRB Pulses in the Fourth BATSE Catalog: Implications for Structure and Evolution of the Jetted Outflows
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Considering the shortage of comparative studies on pulse temporal characteristics between single-peaked short gamma-ray bursts (sGRBs) and double-peaked sGRBs, we examine the pulse properties of a sample of 100 BATSE sGRBs using the BATSE Time-Tagged Event (TTE) data with a 5-ms resolution. 243 individual pulses of the single-peaked, double-peaked and triple-peaked sGRBs are fitted to get their statistical properties such as the pulse asymmetry, amplitude, peak time, and pulse width, etc. For the double-peaked sGRBs, according to the overlapping ratio between two adjacent peaks, we first define two kinds of double-peaked sGRBs as M-loose and M-tight types and find that most of the first pulses are similar to the single-peaked ones. We study the dependence of the Full Width at Half Maximum (FWHM) on the photon energy among different energy bands. Interestingly, it is found that a power-law relation with an index of -0.4 does exist between the FWHM and the photon energy for the single- and double-peaked sGRBs. More interestingly, we notice that the power-law relation with a positive index also exist for several special short bursts. In view of the three typical timescales of pulses, namely the angular spreading timescale, the dynamic timescale, and the cooling timescale, we propose that the diverse power-law indexes together with the profile evolution of GRB pulse can be used as an effective probe to diagnose the structure and evolution of the relativistically jetted outflows.

[24]  arXiv:2003.12416 [pdf, ps, other]
Title: Multiwavelength morphological study of active galaxies
Authors: Betelehem Bilata-Woldeyes (1 and 2), Mirjana Pović (2 and 3), Zeleke Beyoro-Amado (2), Tilahun Getachew-Woreta (2), Shimeles Terefe (2) ((1) Debre Berhan University (DBU), Debre Berhan, Ethiopia, (2) Ethiopian Space Science and Technology Institute (ESSTI), Addis Ababa, Ethiopia, (3) Instituto de Astrofísica de Andalucía (IAA-CSIC), Granada, Spain)
Comments: Proceedings paper of the IAU symposium "Nuclear Activity in Galaxies Across Cosmic Time" (Ethiopia) accepted for publishing under the Cambridge University Press, eds. M. Povi\'c, P. Marziani, J. Masegosa, H. Netzer, S. H. Negu, and S. B. Tessema
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Studying the morphology of a large sample of active galaxies at different wavelengths and comparing it with active galactic nuclei (AGN) properties, such as black hole mass ($M_{BH}$) and Eddington ratio ($\lambda_{Edd}$), can help us in understanding better the connection between AGN and their host galaxies and the role of nuclear activity in galaxy formation and evolution. By using the BAT-SWIFT hard X-ray public data and by extracting those parameters measured for AGN and by using other public catalogues for parameters such as stellar mass ($M_*$), star formation rate (SFR), bolometric luminosity ($L_{bol}$), etc., we studied the multiwavelength morphological properties of host galaxies of ultra-hard X-ray detected AGN and their correlation with other AGN properties. We found that ultra hard X-ray detected AGN can be hosted by all morphological types, but in larger fractions (42%) they seem to be hosted by spirals in optical, to be quiet in radio, and to have compact morphologies in X-rays. When comparing morphologies with other galaxy properties, we found that ultra hard X-ray detected AGN follow previously obtained relations. On the SFR vs. stellar mass diagram, we found that although the majority of sources are located below the main sequence (MS) of star formation (SF), still non-negligible number of sources, with diverse morphologies, is located on and/or above the MS, suggesting that AGN feedback might have more complex influence on the SF in galaxies than simply quenching it, as it was suggested in some of previous studies.

[25]  arXiv:2003.12426 [pdf, other]
Title: Chemical Evolution of Galaxy Clusters: Dissecting the Iron Mass Budget of the Intracluster Medium
Comments: Accepted for publication in A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We study the chemical evolution of galaxy clusters by measuring the iron mass in the ICM after dissecting the abundance profiles into different components. We use Chandra archival observations of 186 morphologically regular clusters in the redshift range [0.04, 1.07]. For each cluster we compute the iron abundance and gas density profiles. We aim at identifying in the iron distribution a central peak associated with the BCG, and an approximately constant plateau associated with early enrichment. We are able to firmly identify the two components in a significant fraction of the sample, simply relying on the fit of the abundance profile. We compute the iron mass included in the iron peak and plateau, and the gas mass-weighted iron abundance out to $r_{500}$. While the iron plateau shows no evolution, we find marginal decrease with redshift in the iron peak. We measure that the fraction of iron peak mass is typically a few percent (~1%) of the total iron mass within $r_{500}$. Therefore, since the total iron mass budget is dominated by the plateau, we find consistently that the global gas mass-weighted iron abundance does not evolve significantly. We are also able to reproduce past claims of evolution in the global iron abundance, which turn out to be due to the use of cluster samples with different selection methods combined to the use of emission-weighted instead of gas mass-weighted abundance values. Finally, while the intrinsic scatter in the iron plateau mass is consistent with zero, the iron peak mass exhibits a large scatter, in line with the fact that the peak is produced after the virialization of the halo and depends on the formation of the hosting cool core and the associated feedback processes. We conclude that only a spatially-resolved approach can resolve the issue of the ICM iron evolution, reconciling the contradictory results obtained in the last ten years.

[26]  arXiv:2003.12438 [pdf, other]
Title: Radiation from the impact of broad-line region clouds onto AGN accretion disks
Comments: 9 pages, 8 figures, 6 tables. Accepted for publication in A&A
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Active galactic nuclei are supermassive black holes surrounded by an accretion disk, two populations of clouds, bipolar jets, and a dusty torus. The clouds move in Keplerian orbits at high velocities. In particular, the broad-line region (BLR) clouds have velocities ranging from $1000$ to $10000$ km s$^{-1}$. Given the extreme proximity of these clouds to the supermassive black hole, frequent collisions with the accretion disk should occur. The impact of BLR clouds onto the accretion disk can produce strong shock waves where particles might be accelerated. The goal of this work is to investigate the production of relativistic particles, and the associated non-thermal radiation in these events. In particular, we apply the model we develop to the Seyfert galaxy NGC 1068. We analyze the efficiency of diffusive shock acceleration in the shock of colliding clouds of the BLR with the accretion disk. We calculate the spectral energy distribution of photons generated by the relativistic particles and estimate the number of simultaneous impacts needed to explain the gamma radiation observed by the Fermi satellite in Seyfert galaxies. We find that is possible to understand the measured gamma emission in terms of the interaction of clouds with the disk if the hard X-ray emission of the source is at least obscured between $20\%$ and $40\%$. The total number of clouds contained in the BLR region might be between $3\times10^{8}$ and $6\times10^{8}$, which are values in good agreement with the observational evidence. The maximum energy achieved by the protons ($\sim$ PeV) in this context allows the production of neutrinos in the observing range of IceCube.

[27]  arXiv:2003.12451 [pdf, other]
Title: The Effect of Dark Matter on Stars at the Galactic Center: The Paradox of Youth Problem
Comments: 14 Pages, 6 Figures, 1 Table, Accepted for publication in International Journal of Modern Physics D (IJMPD) journal
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

Stars that evolve near the Galactic massive black hole show strange behaviors. The spectroscopic features of these stars show that they must be old. But their luminosities are much higher than the amounts that are predicted by the current stellar evolutionary models, which means that they must be active and young stars. In fact this group of stars shows signatures of old and young stars, simultaneously. This is a paradox known as the "paradox of youth problem" (PYP). Some people tried to solve the PYP without supposing dark matter effects on stars. But, in this work, we implemented Weakly Interacting Massive Particles (WIMPs) annihilation as a new source of energy inside such stars. This implementation is logical for stars that evolve at high dark matter density environments. The new source of energy causes stars to follow different evolutionary paths on the H-R diagram in comparison with classical stellar evolutionary models. Increasing dark matter density in stellar evolutionary simulations causes the deviations from the standard H-R diagrams becomes more pronounced. By investigating the effects of WIMPs density on stellar structures and evolutions, we concluded that by considering dark matter effects on stars at the Galactic center, it is possible to solve the PYP. In addition to dark matter effect, complete solutions to PYP must consider all extreme and unique physical conditions that are present near the Galactic massive black hole.

[28]  arXiv:2003.12479 [pdf]
Title: Digitizing analogic spectrograms recorded by the Nançay Decameter Array on 35 mm film rolls from 1970 to 1990
Comments: Proceeding to the PV2018 conference - Adding value and preserving data, Rutherford Appleton Laboratory, Harwell Space Cluster (UK), 15th-17th May 2018
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

The Nan\c{c}ay Decameter Array (NDA), which has now passed 40 years old, acquires daily observations of Jovian and Solar low frequency radio emissions over a continuous spectrum ranging from 10 up to 100MHz, forming the largest database of LW radio observations of these two bodies. It also intermittently observed intense radio sources since its opening in 1977. Before that date, decametric observations were conducted on the same site with an interferometer formed of a pair of log-periodic Yagi antennas mounted on mobile booms. These observations have been recorded with a series of analogic recorders (before 1990) and then digital receivers (after 1990), with increasing performances and sensitivities. The NDA scientific team recently retrieved and inventoried the archives of analogic data (35mm film rolls) covering two decades (1970 to 1990). We now plan to digitize those observations, in order to recover their scientific value and to include them into the currently operational database covering a time span starting in 1990 up to now, still adding new files every day. This modern and interoperable database has virtual observatory interfaces. It is a required element to foster scientific data exploitation, including Jovian and Solar data analysis over long timescales. We present the status of this project.

[29]  arXiv:2003.12485 [pdf, ps, other]
Title: Astrophotonics: astronomy and modern optics
Comments: 83 pages, 6 figures - Invited review article for The Astronomy and Astrophysics Review. Submitted on 9 Nov 2018
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Much of the progress in Astronomy has been driven by instrumental developments, from the first telescopes to fiber fed spectrographs. In this review we describe the field of astrophotonics, a combination of photonics and astronomical instrumentation that has the potential to drive the next generation of developements. We begin with the science cases that have been identified as possibly benefiting from astrophotonic devices. We then discuss devices, methods and developments in the field along with the advantages they provide. We conclude by describing possible future developments in the field and their influence on astronomy.

[30]  arXiv:2003.12498 [pdf, other]
Title: New observations of DW Cnc: where is the 38 min signal?
Comments: 9 pages, 13 figures
Journal-ref: 2020 10.1093/mnras/staa856
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

We present extensive radial-velocity observations of the intermediate polar DW Cnc during its 2018-2019 low state. We show that the 86 min signal, associated with the orbital period is strong in our radial velocity analysis, power spectrum search, as well as in our Doppler Tomography. However, we find that the velocity modulation associated with the 70-min beat period and the 38-min spin cycle are dramatically weaker than previously observed. We put forward two interpretations for this change. The first is that a sudden drop into a low state detected in 2018-2019 caused an episode of low mass transfer from the companion, thus inhibiting the light-house effect produced by the rebound emission. The second is that this is a consequence of a rare outburst detected in 2007 by Crawford (2008). We find this post-outburst hypothesis to be less likely. If the first scenario is correct, we predict that DW Cnc will recover its intermediate polar characteristics. A new ephemeris is presented by combining Patterson et aal. (2004) radial velocities with ours.

[31]  arXiv:2003.12509 [pdf, other]
Title: Periodicity in recurrent fast radio bursts and the origin of ultra long period magnetars
Comments: 12 pages, 5 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The recurrent fast radio burst FRB 180916 was recently shown to exhibit a 16 day period (with possible aliasing) in its bursting activity. Given magnetars as widely considered FRB sources, this period has been attributed to precession of the magnetar spin axis or the orbit of a binary companion. Here, we make the simpler connection to a {\it rotational period}, an idea observationally motivated by the 6.7 hour period of the Galactic magnetar candidate, 1E 161348--5055. We explore three physical mechanisms that could lead to the creation of ultra long period magnetars: (i) enhanced spin-down due to episodic mass-loaded charged particle winds (e.g. as may accompany giant flares), (ii) angular momentum kicks from giant flares and (iii) fallback leading to long lasting accretion disks. We show that particle winds and fallback accretion can potentially lead to a sub-set of the magnetar population with ultra long periods, sufficiently long to accommodate FRB 180916 or 1E 161348--5055. If confirmed, such periods implicate magnetars in relatively mature states (ages $1-10$ kyr) and which possessed large internal magnetic fields at birth $B_{\rm int}\gtrsim 10^{16}$ G. In the low-twist magnetar model for FRBs, such long period magnetars may dominate FRB production for repeaters at lower isotropic-equivalent energies and broaden the energy distribution beyond that expected for a canonical population of magnetars which terminate their magnetic activity at shorter periods $P \lesssim 10$ s.

[32]  arXiv:2003.12512 [pdf]
Title: SKA1-LOW Antenna Design Document
Comments: 44 pages, 43 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The SKA1 LOW antenna has been developed over the last decade. Since 2011 an antenna of the type Log-Periodic Antenna that is now in its 4th iteration, SKALA4 (SKA Log-periodic Antenna v4), has been developed and was the selected candidate for SKA1-LOW after the Cost Control project efforts of 2017. This document describes the electromagnetic design of the antenna. In the submission for the antenna selection process, a detailed description of the antenna performance can be found. The Field Node Detailed Design Document, also submitted for the SKA LFAA Critical Design Review, presents a detailed design of the mechanics and the LNA as well.

[33]  arXiv:2003.12515 [pdf, other]
Title: Evolution of photospheric flows under an erupting filament in the quiet-Sun region
Authors: Jiří Wollmann (1), Michal Švanda (1 and 2), David Korda (1), Thierry Roudier (3) ((1) Astronomical Institute, Charles University, Prague, Czech Republic (2) Astronomical Institute, Academy of Sciences of the Czech Republic, Ondrejov, Czech Republic (3) IRAP, Université de Toulouse, France)
Comments: 11 pages, 12 figures, accepted for publication in Astronomy & Astrophysics
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We studied the dynamics of the solar atmosphere in the region of a large quiet-Sun filament, which erupted on 21 October 2010. The filament eruption started at its northern end and disappeared from the H$\alpha$ line-core filtergrams line within a few hours. The very fast motions of the northern leg were recorded in ultraviolet light by AIA.
We aim to study a wide range of available datasets describing the dynamics of the solar atmosphere for five days around the filament eruption. This interval covers three days of the filament evolution, one day before the filament growth and one day after the eruption. We search for possible triggers that lead to the eruption of the filament.
The surface velocity field in the region of the filament were measured by means of time-distance helioseismology and coherent structure tracking. The apparent velocities in the higher atmosphere were estimated by tracking the features in the 30.4 nm AIA observations. To capture the evolution of the magnetic field, we extrapolated the photospheric line-of-sight magnetograms and also computed the decay index of the magnetic field.
We found that photospheric velocity fields showed some peculiarities. Before the filament activation, we observed a temporal increase of the converging flows towards the filament's spine. In addition, the mean squared velocity increased temporarily before the activation and peaked just before it, followed by a steep decrease. We further see an increase in the average shear of the zonal flow component in the filament's region, followed by a steep decrease. The photospheric l.o.s. magnetic field shows a persistent increase of induction eastward from the filament spine. The decay index of the magnetic field at heights around 10 Mm shows a value larger than critical at the connecting point of the northern filament end.

[34]  arXiv:2003.12552 [pdf, other]
Title: Dynamical Dark sectors and Neutrino masses and abundances
Comments: 16 pages, 9 tables and 8 figures; comments are welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

We investigate generalized interacting dark matter-dark energy scenarios with a time-dependent coupling parameter, allowing also for freedom in the neutrino sector. The models are tested in the phantom and quintessence regimes, characterized by an equation of state $w_x<-1$ and $w_x>-1$, respectively. Our analyses show that for some of the scenarios the existing tensions on the Hubble constant $H_0$ and on the clustering parameter $S_8$ can be significantly alleviated. The relief is either due to \textit{(a)} a dark energy component which lies within the phantom region; or \textit{(b)} the presence of a dynamical coupling in quintessence scenarios. The inclusion of massive neutrinos into the interaction schemes does not affect neither the constraints on the cosmological parameters nor the bounds on the total number or relativistic degrees of freedom $N_{\rm eff}$, which are found to be extremely robust and, in general, strongly consistent with the canonical prediction $N_{\rm eff}=3.045$. The most stringent bound on the total neutrino mass $M_{\nu}$ is $M_{\nu}<0.116$ eV and it is obtained within a quintessence scenario in which the matter mass-energy density is only mildly affected by the presence of a dynamical dark sector coupling.

[35]  arXiv:2003.12561 [pdf, other]
Title: The 3D non-LTE solar nitrogen abundance from atomic lines
Comments: 11 pages, 7 figures, 3 tables; accepted for publication in Astronomy & Astrophysics
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Nitrogen is an important element in various fields of stellar and Galactic astronomy, and the solar nitrogen abundance is crucial as a yardstick for comparing different objects in the cosmos. In order to obtain a precise and accurate value for this abundance, we carried out N i line formation calculations in a 3D radiative-hydrodynamic STAGGER model solar atmosphere, in full 3D non-local thermodynamic equilibrium (non-LTE), using a model atom that includes physically-motivated descriptions for the inelastic collisions of N i with free electrons and with neutral hydrogen. We selected five N i lines of high excitation energy to study in detail, based on their strengths and on their being relatively free of blends. We found that these lines are slightly strengthened from non-LTE photon losses and from 3D granulation effects, resulting in negative abundance corrections of around $-0.01$ dex and $-0.04$ dex respectively. Our advocated solar nitrogen abundance is $\log\epsilon_{\mathrm{N}} = 7.77$, with the systematic $1\sigma$ uncertainty estimated to be $0.05$ dex. This result is consistent with earlier studies after correcting for differences in line selections and equivalent widths.

Cross-lists for Mon, 30 Mar 20

[36]  arXiv:2003.12077 (cross-list from hep-ph) [pdf, other]
Title: Plasmon production from dark matter scattering
Comments: 10 pages
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Experiment (hep-ex)

We present a first calculation of the rate for plasmon production in semiconductors from nuclei recoiling against dark matter. The process is analogous to bremsstrahlung of transverse photon modes, but with a longitudinal plasmon mode emitted instead. For dark matter in the 10 MeV - 1 GeV mass range, we find that the plasmon bremsstrahlung rate is 4-5 orders of magnitude smaller than that for elastic scattering, but 4-5 orders of magnitude larger than the transverse bremsstrahlung rate. Because the plasmon can decay into electronic excitations and has characteristic energy given by the plasma frequency $\omega_p$, with $\omega_p \approx 16$ eV in Si crystals, plasmon production provides a distinctive signature and new method to detect nuclear recoils from sub-GeV dark matter.

[37]  arXiv:2003.12082 (cross-list from gr-qc) [pdf, ps, other]
Title: Gravitational waves from transient neutron star f-mode oscillations
Authors: Wynn C. G. Ho (Haverford), D. I. Jones (Southampton), Nils Andersson (Southampton), Cristobal M. Espinoza (Santiago de Chile)
Comments: 6 pages, 5 figures; accepted for publication in Physical Review D
Subjects: General Relativity and Quantum Cosmology (gr-qc); Solar and Stellar Astrophysics (astro-ph.SR)

During their most recent observing run, LIGO/Virgo reported the gravitational wave (GW) transient S191110af, a burst signal at a frequency of 1.78 kHz that lasted for 0.104 s. While this signal was later deemed non-astrophysical, genuine detections of uncertain origin will occur in the future. Here we study the potential for detecting GWs from neutron star fluid oscillations, which have mode frequency and duration matching those of S191110af and which can be used to constrain the equation of state of nuclear matter. Assuming that such transient oscillations can be excited to energies typical of a pulsar glitch, we use measured properties of known glitching pulsars to estimate the amplitude of GWs produced by such events. We find that current GW detectors may observe nearby pulsars undergoing large events with energy similar to Vela pulsar glitch energies, while next generation detectors could observe a significant number of events. Finally, we show that it is possible to distinguish between GWs produced by rapidly rotating and slowly rotating pulsars from the imprint of rotation on the f-mode frequency.

[38]  arXiv:2003.12196 (cross-list from physics.comp-ph) [pdf, ps, other]
Title: Self-similar orbit-averaged Fokker-Planck equation for isotropic spherical dense clusters (i) accurate pre-collapse solution
Authors: Yuta Ito
Subjects: Computational Physics (physics.comp-ph); Astrophysics of Galaxies (astro-ph.GA)

This is the first paper of a series of our works on the self-similar orbit-averaged Fokker-Planck (OAFP) equation and shows its accurate pre-collapse solution. At the late stage of relaxation evolution of dense star clusters, standard stellar dynamics predicts that the clusters may evolve in a self-similar fashion forming a collapsing core. However, the corresponding mathematical model, the self-similar OAFP equation for distribution function of stars in isotropic star clusters, has never been solved on the whole energy domain $(-1< E < 0)$. The existing works based on kinds of finite difference methods provide solutions only on the truncated domain $-1< E<-0.2$. To broaden the range of the truncated domain, the present work resorts to a (highly accurate- and efficient-) Gauss-Chebyshev pseudo-spectral method. We provide a Chebyshev spectral solution, whose number of significant figures is four, on the whole domain. Also, The solution can reduce to a semi-analytical form whose degrees of polynomials are only eighteen holding three significant figures. We also provide the new eigenvalues; $c_{1}=9.0925\times10^{-4}$, $c_{2}=1.1118\times10^{-4}$, $c_{3}=7.1975\times10^{-2}$ and $c_{4}=3.303\times10^{-2}$, corresponding to the core collapse rate $\xi=3.64\times10^{-3}$, scaled escape energy $\chi_\text{esc}=13.881$ and power-law exponent $\alpha=2.2305$. Since the solution on the whole domain is unstable against change in degree of Chebyshev polynomials, we show spectral solutions on truncated domains ( $-1< E<E_\text{max}$, where $-0.35<E_\text{max}<-0.03$) to explain how to handle the instability. By reformulating the OAFP equation in several ways, we improve the accuracy of the spectral solution and reproduce an existing self-similar solution; we consider existing solutions have only one significant figure at most.

[39]  arXiv:2003.12279 (cross-list from gr-qc) [pdf, other]
Title: Second-order effective energy-momentum tensor of gravitational scalar perturbations with perfect fluid
Comments: 21 pages
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

We investigate the second-order gravitational scalar perturbations for a barotropic fluid. We derive the effective energy-momentum tensor described by the quadratic terms of the gravitational and the matter perturbations. We show that the second-order effective energy-momentum tensor is gauge dependent. We impose three gauge conditions (longitudinal, spatially-flat, and comoving gauges) for dust and radiation. The resulting energy-momentum tensor is described only by a gauge invariant variable, but the functional form depends on the gauge choice. In the matter-dominated epoch with dust-like fluid background, the second-order effective energy density and pressure of the perturbations evolve as 1/a^2 in all three gauge choices, like the curvature density of the Universe, but they do not provide the correct equation of state. The value of this parameter depends also on the gauge choice. In the radiation-dominated epoch, the perturbations in the short-wave limit behave in the same way as the radiation-like fluid in the longitudinal and the spatially-flat gauges. However, they behave in a different way in the comoving gauge. As a whole, we conclude that the second-order effective energy-momentum tensor of the scalar perturbation is strictly gauge dependent.

[40]  arXiv:2003.12329 (cross-list from hep-ph) [pdf, other]
Title: Dark-matter spontaneous freeze out
Authors: Hervé Partouche
Comments: Based on a talk given at the International Conference on Neutrinos and Dark Matter (NDM-2020), 11-14 January 2020, Hurghada, Egypt
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)

We consider the possibility that thermalized dark-matter particles acquire their mass thanks to the spontaneous breaking of a symmetry below some critical temperature. We describe the regime where a freeze out mechanism takes place shortly after the onset of the phase transition, while the dark-matter mass has not yet reached its final constant value. For such a "spontaneous freeze out" to yield the correct relic density, the present-time cross section of annihilation of the dark matter into Standard-Model states has to be one or two orders of magnitude larger than in the case of a constant dark-matter mass.

[41]  arXiv:2003.12376 (cross-list from physics.ins-det) [pdf, other]
Title: Cosmic muon flux measurement and tunnel overburden structure imaging
Subjects: Instrumentation and Detectors (physics.ins-det); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex)

We present a cosmic ray muon tomographic experiment for measuring the muon flux and imaging the tunnel overburden structures in Changshu, China. The device used in this study is a tracking detector based on the plastic scintillator with SiPM technology, which can be conveniently operated in field works. The compact system with sensitive area of $6400 cm^2$ can measure the angular distribution of cosmic muons. It's able to image the overburden density length from the surface of overburden to the detector along the muon tracks. The open sky muon flux measurement outside the tunnel has a good agreement with the modified Gassier Formula model. The distributions of muon flux at three positions inside the tunnel are very similar to that of open sky. Assuming the average density of overburden compact sandstone is $2.65 g/cm^3$, the overburden thickness can be obtained from the density length derived from the difference of muon flux inside and outside the tunnel. Moreover, for known penetrated lengths (i.e., topography of overburden), the density anomalies of the overburden can also been obtained. This study suggests a potential application for imaging and detecting subsurface structures in civil engineering, tunnels or caverns with the cosmic ray muon telescope.

[42]  arXiv:2003.12410 (cross-list from physics.hist-ph) [pdf]
Title: Urban Planning in the First Unfortified Spanish Colonial Town: The orientation of the historic churches of San Cristobal de La Laguna
Comments: PDF document including 1 table and 8 figures
Journal-ref: Journal of Skyscape Archaeology 4: 6-25, 2018
Subjects: History and Philosophy of Physics (physics.hist-ph); Instrumentation and Methods for Astrophysics (astro-ph.IM); Physics and Society (physics.soc-ph)

The city of San Cristobal de La Laguna in the Canary Island of Tenerife (Spain) has an exceptional value due to the original conception of its plan. It is an urban system in a grid, outlined by straight streets that form squares, its layout being the first case of an unfortified colonial city with a regular plan in the overseas European expansion. It constitutes a historical example of the so-called "Town of Peace", the archetype of a city-republic in a new land that employed its own natural boundaries to delimit and defend itself. Founded in 1496, the historical centre of the old city was declared a World Heritage Site by UNESCO in 1999. We analyse the exact spatial orientation of twenty-one historic Christian churches currently existing in the old part of La Laguna which we take as a good indicator of the original layout of the urban lattice. We find a clear orientation pattern that, if correlated with the rising or setting Sun, singles out an absolute-value astronomical declination slightly below 20 degrees, which, within the margin of error of our study, might be associated with the July 25th feast-day of San Cristobal de Licia, the saint to whom the town was originally dedicated. We also discuss at some length some recent proposals which invoke somewhat far-fetched hypotheses for the planimetry of the old city and finish up with some comments on one of its outstanding features, namely its Latin-cross structure, which is apparent in the combined layout of some of its most emblematic churches.

[43]  arXiv:2003.12483 (cross-list from physics.ins-det) [pdf, other]
Title: Finding Dark Matter Faster with Explicit Profile Likelihoods
Subjects: Instrumentation and Detectors (physics.ins-det); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex)

Liquid xenon time-projection chambers are the world's most sensitive detectors for a wide range of dark matter candidates. We show that the statistical analysis of their data can be improved by replacing detector response Monte Carlo simulations with an equivalent deterministic calculation. This allows the use of high-dimensional undiscretized models, yielding up to $\sim\! 2$ times better discrimination of the dominant backgrounds. In turn, this could significantly extend the physics reach of upcoming experiments such as XENONnT and LZ, and bring forward a potential $5 \sigma$ dark matter discovery by over a year.

[44]  arXiv:2003.12492 (cross-list from gr-qc) [pdf, ps, other]
Title: (In)stability of black holes in the 4D Einstein-Gauss-Bonnet and Einstein-Lovelock gravities
Comments: 6 pages, 3 figures, 1 ancillary Mathematica(R) notebook
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)

A (3+1)-dimensional Einstein-Gauss-Bonnet theory of gravity has been recently formulated as the $D \to 4$ limit of the higher dimensional field equations after the rescaling of the coupling constant. This theory is a nontrivial generalization of General Relativity, it bypasses the Lovelock's theorem, and avoids the Ostrogradsky instability. This approach has been extended to the four-dimensional Einstein-Lovelock gravity. Here we study the eikonal gravitational instability of asymptotically flat, de Sitter and anti-de Sitter black holes in the four dimensional Einstein-Gauss-Bonnet and Einstein-Lovelock theories. We find parametric regions of the eikonal instability for various orders of the Lovelock gravity, values of coupling and cosmological constants, and share the code which allows one to construct the instability region for an arbitrary set of parameters.

Replacements for Mon, 30 Mar 20

[45]  arXiv:1806.08050 (replaced) [pdf]
Title: Portable Adaptive Optics for exoplanet imaging
Comments: 22 pages, 11 figures, 3 tables,submitted to RAA
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)
[46]  arXiv:1808.08051 (replaced) [pdf, other]
Title: Integration with an Adaptive Harmonic Mean Algorithm
Subjects: Data Analysis, Statistics and Probability (physics.data-an); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex)
[47]  arXiv:1809.05520 (replaced) [pdf, ps, other]
Title: Studying the morphology of HI isodensity surfaces during reionization using Shapefinders and percolation analysis
Comments: 19 pages, 15 figures, 1 table, accepted for publication in MNRAS
Journal-ref: MNRAS 485 (2019), 2235-2251
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[48]  arXiv:1810.13124 (replaced) [pdf, other]
Title: Chirality and magnetic configuration associated with two-ribbon solar flares: AR 10930 versus AR 11158
Comments: 24 pages, 9 figures, 2 tables, accepted version
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[49]  arXiv:1904.07215 (replaced) [pdf, other]
Title: The surprisingly low carbon mass in the debris disk around HD 32297
Comments: accepted for publication in the ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[50]  arXiv:1904.11618 (replaced) [pdf, other]
Title: A Radio Burst Detection Method Based on the Hough Transform
Comments: 11 pages, 10 figures, substantially revised. Version accepted by MNRAS
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)
[51]  arXiv:1906.08535 (replaced) [pdf, other]
Title: Observation of high Doppler velocity wings in the nascent wind of R Doradus
Comments: 14 pages, 6 figures
Journal-ref: Communications in Physics, Vol. 20, No. 1 (2020), pp. 85-98
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[52]  arXiv:1907.00237 (replaced) [pdf, other]
Title: A generalized Higgs potential with two degenerate minima for a dark QCD matter scenario
Comments: 8 pages, five figures, published version
Subjects: High Energy Physics - Phenomenology (hep-ph); Astrophysics of Galaxies (astro-ph.GA)
[53]  arXiv:1907.03012 (replaced) [pdf, other]
Title: Motion of localized sources in general relativity: gravitational self-force from quasilocal conservation laws
Comments: v1: 41 pages, 12 figures. To be submitted for publication, comments welcome; v2: 42 pages. Comments and references added; v3: Matches published version
Journal-ref: Phys. Rev. D 101, 064060 (2020)
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)
[54]  arXiv:1907.04329 (replaced) [pdf, other]
Title: Universal Interferometric Signatures of a Black Hole's Photon Ring
Comments: 11 pages, 8 figures. Published in Science Advances
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
[55]  arXiv:1908.05626 (replaced) [pdf, other]
Title: [OII] emitters in MultiDark-Galaxies and DEEP2
Authors: G. Favole (ESAC), V. Gonzalez-Perez (Lancaster, Portsmouth), A. Orsi (CEFCA), D. Stoppacher (Madrid), J. Comparat (MPE), S. A. Cora (La Plata), C. A. Vega-Martinez (La Plata), A. R. H. Stevens (ICRAR), C. Maraston (Portsmouth), D. Croton (Swinburne), A. Knebe (Madrid), A. J. Benson (Carnegie), A. D. Montero-Dorta (Sao Paulo), N. Padilla (PUC), F. Prada (IAA), D. Thomas (Portsmouth)
Comments: 23 pages, 20 figures, submitted to MNRAS, this version incorporates the referee's comments
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[56]  arXiv:1908.10930 (replaced) [pdf, other]
Title: Fundamental Forces and Scalar Field Dynamics in the Early Universe
Comments: 6 pages, 1 figure; v2: publication version
Journal-ref: Phys.Lett. B804 (2020) 135369
Subjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)
[57]  arXiv:1909.10517 (replaced) [pdf, other]
Title: Making a supermassive star by stellar bombardment
Comments: 20 pages, 8 figures, accepted in ApJ
Journal-ref: The Astrophysical Journal, Volume 892, Number 1 (2020)
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
[58]  arXiv:1909.10946 (replaced) [pdf, other]
Title: Forecast for FAST: from Galaxies Survey to Intensity Mapping
Comments: 17 pages, 18 figures, fixed problems in references, version accepted by MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[59]  arXiv:1911.06148 (replaced) [pdf, other]
Title: Trans-Planckian censorship of multistage inflation and dark energy
Comments: 13 pages, 4 figures; references added; updated to match published version
Journal-ref: Phys. Rev. D 101, 063527 (2020)
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
[60]  arXiv:1911.06852 (replaced) [pdf]
Title: When is chemical disequilibrium in Earth-like planetary atmospheres a biosignature versus an anti-biosignature? Disequilibria from dead to living worlds
Comments: This draft was accepted by Astrophysical Journal on 2/29/20
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[61]  arXiv:1912.10188 (replaced) [pdf, other]
Title: Unveiling the importance of magnetic fields in the evolution of dense clumps formed at the waist of bipolar H II regions: a case study on Sh2-201 with JCMT SCUBA-2/POL-2
Comments: 25 pages, 10 figures, and 4 tables. Accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[62]  arXiv:1912.12518 (replaced) [pdf, other]
Title: Drifting Pulsation Structure at the Very Beginning of the 2017 September 10 Limb Flare
Comments: 14 pages, 11 figures, accepted do ApJ, language corrections
Journal-ref: ApJ, 2020, Volume 889, Issue 2, id.72
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[63]  arXiv:2001.00922 (replaced) [pdf, other]
Title: Mapping large-scale diffuse gamma-ray emission in 10-100 TeV band with Cherenkov telescopes
Authors: A.Neronov, D.Semikoz
Comments: 7 pages, 5 figures, version accepted to A&A
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[64]  arXiv:2001.06225 (replaced) [pdf, other]
Title: Massive discs around low-mass stars
Comments: 21 pages, Accepted for publication MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)
[65]  arXiv:2001.10232 (replaced) [pdf, other]
Title: Patterns in the multi-wavelength behavior of candidate neutrino blazars
Comments: accepted for publication by ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[66]  arXiv:2002.02549 (replaced) [pdf]
Title: The Impact of Planetary Rotation Rate on the Reflectance and Thermal Emission Spectrum of Terrestrial Exoplanets Around Sun-like Stars
Comments: Accepted to The Astrophysical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[67]  arXiv:2002.11873 (replaced) [pdf, other]
Title: Evidence for Returning Disk Radiation in the Black Hole X-ray Binary XTE J1550-564
Comments: 21 pages, 13 figures, accepted by ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[68]  arXiv:2002.11947 (replaced) [pdf, other]
Title: Shape model and spin state of non-principal axis rotator (5247) Krylov
Comments: 10 pages, 2 figures; Accepted for publication on Astronomy & Astrophysics
Journal-ref: A&A 635, A137 (2020)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[69]  arXiv:2003.07509 (replaced) [pdf, ps, other]
Title: Tidal and general relativistic effects in rocky planet formation at the substellar mass limit using N-body simulations
Comments: 16 pages, 17 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
[70]  arXiv:2003.08538 (replaced) [pdf, other]
Title: The braking index of PSR B0540-69 and the associated pulsar wind nebula emission after spin-down rate transition
Comments: 7 pages, 2 figures, accepted in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[71]  arXiv:2003.08832 (replaced) [pdf, other]
Title: Galaxy rotation curves from external influence on Schwarzschild geometry
Authors: A. Bhattacharyay
Comments: 5 pages and one figure. On top of what has been shown in the earlier version, this version shows that the correct number for ordinary matter content of the universe comes out from the estimations based on the parameters of the Milky Way
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics of Galaxies (astro-ph.GA)
[72]  arXiv:2003.11930 (replaced) [pdf, other]
Title: An explanation of the repetition/pulse width relation in FRBs
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[73]  arXiv:2003.11976 (replaced) [pdf, ps, other]
Title: Does a solar filament barb always correspond to a prominence foot?
Comments: 12 pages, 3 figures, accepted for publication in ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
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