Constraining $alpha$-attractor models from reheating. (arXiv:2010.09795v2 [astro-ph.CO] UPDATED) <a href="">Gabriel German</a> We eliminate the parameters originally present in models of inflation of the $alpha$-attractor type in favor of the scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$. We then write expressions for the number of $e$-folds during reheating $ N_ {re} $. By imposing reasonable conditions on $N_{re}$ we can restrict $n_s$ and $r$ and in turn, we use these constraints in order to find bounds for cosmological quantities of interest such as the number of $e$-folds during inflation and the radiation dominated eras, as well as for the reheating temperature and the runningRead More →

First observations from the SPICE EUV spectrometer on Solar Orbiter. (arXiv:2110.11252v1 [astro-ph.SR]) <a href="">A. Fludra</a>, <a href="">M. Caldwell</a>, <a href="">A. Giunta</a>, <a href="">T. Grundy</a>, <a href="">S. Guest</a>, <a href="">S. Leeks</a>, <a href="">S. Sidher</a>, <a href="">F. Auch&#xe8;re</a>, <a href="">M. Carlsson</a>, <a href="">D. Hassler</a>, <a href="">H. Peter</a>, <a href="">R. Aznar Cuadrado</a>, <a href="">&#xc9;. Buchlin</a>, <a href="">S. Caminade</a>, <a href="">C. DeForest</a>, <a href="">T. Fredvik</a>, <a href="">M. Haberreiter</a>, <a href="">L. Harra</a>, <a href="">M. Janvier</a>, <a href="">T. Kucera</a>, <a href="">D. M&#xfc;ller</a>, <a href="">S. Parenti</a>, <a href="">W. Schmutz</a>, <a href="">U. Sch&#xfc;hle</a>, <a href="">S.K. Solanki</a>, <a href="">L. Teriaca</a>, <a href="">W.T. Thompson</a>, <a href="">S. Tustain</a>, <a href="">D. Williams</a>, <a href="">P.R. Young</a>, <a href="">L.P.Read More →

HD144941: The most extreme helium-strong star. (arXiv:2110.11267v1 [astro-ph.SR]) <a href="">N. Przybilla</a>, <a href="">L. Fossati</a>, <a href="">C.S. Jeffery</a> Since its discovery about 50 years ago, HD144941 has generally been classified as a peculiar member of the extreme helium (EHe) supergiant stars, a very rare class of low-mass hydrogen-deficient stars. We report the detection of a strong longitudinal magnetic field based on spectropolarimetry with FORS2 on the ESO VLT with surface-averaged longitudinal field strengths as large as -9kG. This is further constrained by the detection of Zeeman splitting of spectral lines to a field strength of at least 15kG, explaining the recent finding of surface spots forRead More →

A unique hot Jupiter spectral sequence with evidence for compositional diversity. (arXiv:2110.11272v1 [astro-ph.EP]) <a href="">Megan Mansfield</a>, <a href="">Michael R. Line</a>, <a href="">Jacob L. Bean</a>, <a href="">Jonathan J. Fortney</a>, <a href="">Vivien Parmentier</a>, <a href="">Lindsey Wiser</a>, <a href="">Eliza M.-R. Kempton</a>, <a href="">Ehsan Gharib-Nezhad</a>, <a href="">David K. Sing</a>, <a href="">Mercedes L&#xf3;pez-Morales</a>, <a href="">Claire Baxter</a>, <a href="">Jean-Michel D&#xe9;sert</a>, <a href="">Mark R. Swain</a>, <a href="">Gael M. Roudier</a> The emergent spectra of close-in, giant exoplanets (“hot Jupiters”) are expected to be distinct from those of self-luminous objects with similar effective temperatures because hot Jupiters are primarily heated from above by their host stars rather than internally from the release of energyRead More →

Precision calculation of neutrino evolution in the early Universe. (arXiv:2110.11296v1 [hep-ph]) <a href="">Julien Froustey</a> In the primordial Universe, neutrino decoupling occurs only slightly before electron-positron annihilations. This leads notably to an increased neutrino energy density compared to the standard instantaneous decoupling approximation, parametrized by the effective number of neutrino species $N_{rm eff}$. A precise calculation of neutrino evolution is needed to assess its consequences during the later cosmological stages, and requires to take into account multiple effects such as neutrino oscillations, which represents a genuine numerical challenge. Recently, several key improvements have allowed such a precise numerical calculation, leading to the new reference value $N_{rmRead More →

The impact of precession on the observed population of ULXs. (arXiv:2110.11318v1 [astro-ph.HE]) <a href="">Norman Khan</a>, <a href="">Matthew. J. Middleton</a>, <a href="">Grzegorz Wiktorowicz</a>, <a href="">Thomas Dauser</a>, <a href="">Timothy P. Roberts</a>, <a href="">Joern Wilms</a> The discovery of neutron stars powering several ultraluminous X-ray sources (ULXs) raises important questions about the nature of the underlying population. In this paper we build on previous work studying simulated populations by incorporating a model where the emission originates from a precessing, geometrically beamed wind-cone, created by a super-critical inflow. We obtain estimates — independent of the prescription for the precession period of the wind — for the relative number of ULXsRead More →

Dynamic Europa ocean shows transient Taylor columns and convection driven by ice melting and salinity. (arXiv:2006.02242v2 [astro-ph.EP] UPDATED) <a href="">Yosef Ashkenazy</a>, <a href="">Eli Tziperman</a> The deep (~100 km) ocean of Europa, Jupiter’s moon, covered by a thick icy shell, is one of the most probable places in the solar system to find extraterrestrial life. Yet, its ocean dynamics and its interaction with the ice cover have received little attention. Previous studies suggested that Europa’s ocean is turbulent using a global model and taking into account non-hydrostatic effects and the full Coriolis force. Here we add critical elements, including consistent top and bottom heating boundary conditionsRead More →

Electromagnetic Waves in Hot and Dense Media. (arXiv:2006.10556v2 [hep-ph] UPDATED) <a href="">Samina Masood</a> It is known that the finite temperature and density (FTD) corrections increase the electron mass, charge and modify the properties of the emitted radiation. All the signals, travelling through the astronomical bodies, carry over the information of their origin and bring minor details about the structure and composition of the source. It has been noticed that temperatures of the early universe add physically measureable mass to electron and large chemical potential lead to an increase in mass as well. However, the QED coupling is slowly increased with temperature but is decreased withRead More →

Higgs inflation in Einstein-Cartan gravity. (arXiv:2007.14978v2 [hep-ph] UPDATED) <a href="">Mikhail Shaposhnikov</a>, <a href="">Andrey Shkerin</a>, <a href="">Inar Timiryasov</a>, <a href="">Sebastian Zell</a> We study inflation driven by the Higgs field in the Einstein-Cartan formulation of gravity. In this theory, the presence of the Holst and Nieh-Yan terms with the Higgs field non-minimally coupled to them leads to three additional coupling constants. For a broad range of parameters, we find that inflation is both possible and consistent with observations. In most cases, the spectral index is given by $n_s=1-2/N_star$ (with $N_star$ the number of e-foldings) whereas the tensor-to-scalar ratio $r$ can vary between about $10^{-10}$ and $1$. Thus,Read More →

Impact of the ISM magnetic field on GRB afterglow polarization. (arXiv:2008.10624v2 [astro-ph.HE] UPDATED) <a href="">O. Teboul</a>, <a href="">N. Shaviv</a> Linear polarization has been measured in several GRB afterglows. After a few days, polarization arises from the forward shock emission which depends on the post-shock magnetic field. The latter can originate both from compression of existing fields, here the ISM magnetic field, and from shock generated instabilities. For short GRBs, previous modelling of the polarization arising from the forward shock considered a random field fully or partially confined to the shock plane. However, the ISM magnetic field likely consists of both random and ordered components. HereRead More →

Propagation effects in the FRB 20121102A spectra. (arXiv:2010.15145v4 [astro-ph.HE] UPDATED) <a href="">D.G. Levkov</a>, <a href="">A.G. Panin</a>, <a href="">I.I. Tkachev</a> We advance theoretical methods for studying propagation effects in the Fast Radio Burst (FRB) spectra. We derive their autocorrelation function in the model with diffractive lensing and strong Kolmogorov-type scintillations and analytically obtain the spectra lensed on different plasma density profiles. With these tools, we reanalyze the highest frequency 4-8 GHz data of Gajjar et al. (2018) for the repeating FRB 20121102A (FRB 121102). In the data we discover, first, a remarkable spectral structure of almost equidistant peaks separated by $95pm 16$ MHz. We suggest thatRead More →

Numerical and experimental evidence for a new interpretation of residence times in space. (arXiv:2110.11213v1 []) <a href="">A. Vogt</a>, <a href="">N. E. Engelbrecht</a>, <a href="">B. Heber</a>, <a href="">A. Kopp</a>, <a href="">K. Herbst</a> We investigate the energy dependence of Jovian electron residence times, which allows for a deeper understanding of adiabatic energy changes that occur during charged particle transport, as well as of their significance for simulation approaches. Thereby we seek to further validate an improved approach to estimate residence times numerically by investigating the implications on previous analytical approaches, and possible effects detectable by spacecraft data. Utilizing a propagation model based on a Stochastic Differential EquationRead More →

Approximate Analytical Solution to the Zonal Harmonics Problem Using Koopman Operator Theory. (arXiv:2012.09620v3 [astro-ph.EP] UPDATED) <a href="">David Arnas</a>, <a href="">Richard Linares</a> This work introduces the use of the Koopman operator theory to generate approximate analytical solutions for the zonal harmonics problem of a satellite orbiting a non-spherical celestial body. Particularly, the solution proposed directly provides the osculating evolution of the system under the effects of any order of the zonal harmonics, and can be automated to obtain any level of accuracy in the approximated solution. Moreover, this paper defines a modified set of orbital elements that can be applied to any kind of orbit andRead More →

Determination of dynamical ages of open clusters through the A$^+$ parameter — I. (arXiv:2102.07409v2 [astro-ph.GA] UPDATED) <a href="">Khushboo K. Rao</a>, <a href="">Kaushar Vaidya</a>, <a href="">Manan Agarwal</a>, <a href="">Souradeep Bhattacharya</a> The sedimentation level of blue straggler stars (BSS) has been shown to be a great tool to investigate the dynamical states of globular clusters (GCs). The area enclosed between the cumulative radial distributions of BSS and a reference population up to the half-mass radius of the clusters, $A^+_{mathrm{rh}}$, is known to be a measure of the sedimentation of BSS in GCs. In this work, we calculate $A^+_{mathrm{rh}}$ for 11 open clusters (OCs) using a combined listRead More →

An Improved and Physically-Motivated Scheme for Matching Galaxies with Dark Matter Halos. (arXiv:2102.13122v2 [astro-ph.GA] UPDATED) <a href="">Stephanie Tonnesen</a> (1), <a href="">Jeremiah P. Ostriker</a> (1,2,3) ((1) Flatiron Institute, CCA, (2) Princeton University, (3) Columbia University) The simplest scheme for predicting real galaxy properties after performing a dark matter simulation is to rank order the real systems by stellar mass and the simulated systems by halo mass and then simply assume monotonicity – that the more massive halos host the more massive galaxies. This has had some success, but we study here if a better motivated and more accurate matching scheme is easily constructed by looking carefullyRead More →

The Early Solar System Had a Gap Where the Asteroid Belt is Today Wind the cosmic clock back a few billion years and our Solar System looked much different than it does today. About 4.5 billion years ago, the young Sun shone much like it does now, though it was a little smaller. Instead of being surrounded by planets, it was ensconced in a swirling disk of gas and dust. That disk is called a protoplanetary disk and it’s where the planets eventually formed. There was a conspicuous gap in the early Solar System’s protoplanetary disk, between where Mars and Jupiter are now, and whereRead More →

Astronomers discover infant planet One of the youngest planets ever found around a distant infant star has been discovered by an international team of scientists led by University of Hawaiʻi at Mānoa faculty, students, and alumni. Go to SourceRead More →

Gravitational self-lensing of massive black hole binaries A “massive” black hole (MBH) is one whose mass is more than about one hundred thousand solar-masses. MBHs reside at the centers of most galaxies, and when they actively accrete gas and dust onto their surrounding hot disk environments they radiate across the electromagnetic spectrum and are classified as active galactic nuclei. Go to SourceRead More →

Black hole thermodynamics: A history from Penrose to Hawking In 1969, English physicist Roger Penrose discovered a property which would later allow for a long-awaited link between thermodynamics, and the far stranger mechanics of black holes. Through new analysis published in EPJ H, Carla Rodrigues Almeida, based at the University of São Paulo, Brazil, sheds new light on Penrose’s motivations and methods, and explores their historical influence on the groundbreaking discovery of Hawking radiation. Go to SourceRead More →

Examining the accelerating universe A special edition of EPJST, edited by Balasubramanian Ananthanarayan, Centre for High Energy Physics, Indian Institute of Science, Bangalore, and Subhendra Mohanty, Department of Theoretical Physics, Physical Research Laboratory, Navrangpura, Ahmedabad, brings together a collection of papers focusing improving our understanding of the accelerating expansion of the Universe and the nature of the dark energy that drives it. Go to SourceRead More →