Spurious gauge-invariance of higher-order contributions to the spectral energy density of the relic gravitons. (arXiv:2005.04962v1 [hep-th]) <a href="http://arxiv.org/find/hep-th/1/au:+Giovannini_M/0/1/0/all/0/1">Massimo Giovannini</a> In the same way as the energy density associated with the tensor modes of the geometry modifies the evolution of the curvature perturbations, the scalar modes may also indirectly affect the cosmic backgrounds of relic gravitons by inducing higher-order corrections that are only superficially gauge-invariant. This spurious gauge-invariance gets manifest when the effective anisotropic stresses, computed in different coordinate systems, are preliminarily expressed in a form that only depends on the curvature inhomogeneities defined on comoving orthogonal hypersurfaces and on their corresponding time derivatives. Using thisRead More →

How Unusual is the Milky Way’s Assembly History?. (arXiv:2005.04969v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Evans_T/0/1/0/all/0/1">Tilly A. Evans</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fattahi_A/0/1/0/all/0/1">Azadeh Fattahi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Deason_A/0/1/0/all/0/1">Alis J. Deason</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Frenk_C/0/1/0/all/0/1">Carlos S. Frenk</a> In the $Lambda$CDM model of structure formation galactic haloes build up by accretion of mass and mergers of smaller subunits. The most recent massive merger event experienced by the Milky Way (MW) halo was the accretion of the Large Magellanic Cloud (LMC; which has a stellar mass of $sim ; 10^9M_odot$). Recent analyses of galactic stellar data from the textit{Gaia} satellite have uncovered an earlier massive accretion event, the Gaia-Enceladus-Sausage (GES), which merged with the MW around 10 Gyr ago.Read More →

Extreme close encounters between proto-Mercury and proto-Venus in terrestrial plan et formation. (arXiv:2005.05000v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Fang_T/0/1/0/all/0/1">Tong Fang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Deng_H/0/1/0/all/0/1">Hongping Deng</a> Modern models of terrestrial planet formation require solids to be confined in a narrow annulus at about 0.7-1 astronomical unit (au) initially. Earth and Venus analogs emerge after ~100 Myr collisional growth; Mars and Mercury form in the diffusive tails of the annulus. We carried out 250 N-body simulations to study the statistics of close encounters which were recently proposed as an explanation for the high iron mass fraction in Mercury by Deng (2019). We formed 39 Mercury analogs in total and all proto-Mercury analogsRead More →

Multiple outflows in the high-mass cluster forming region, G25.82-0.17. (arXiv:2005.05006v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Kim_J/0/1/0/all/0/1">Jungha Kim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kim_M/0/1/0/all/0/1">Mi Kyoung Kim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hirota_T/0/1/0/all/0/1">Tomoya Hirota</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kim_K/0/1/0/all/0/1">Kee-Tae Kim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sugiyama_K/0/1/0/all/0/1">Koichiro Sugiyama</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Honma_M/0/1/0/all/0/1">Mareki Honma</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Byun_D/0/1/0/all/0/1">Do-young Byun</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Oh_C/0/1/0/all/0/1">Chungsik Oh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Motogi_K/0/1/0/all/0/1">Kazuhito Motogi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kang_J/0/1/0/all/0/1">Jihyun Kang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kim_J/0/1/0/all/0/1">Jeongsook Kim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_T/0/1/0/all/0/1">Tie Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hu_B/0/1/0/all/0/1">Bo Hu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burns_R/0/1/0/all/0/1">Ross A. Burns</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chibueze_J/0/1/0/all/0/1">James O. Chibueze</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Matsumoto_N/0/1/0/all/0/1">Naoko Matsumoto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sunada_K/0/1/0/all/0/1">Kazuyoshi Sunada</a> We present results of continuum and spectral line observations with ALMA and 22 GHz water (H$_2$O) maser observations using KaVA and VERA toward a high-mass star-forming region, G25.82-0.17. Multiple 1.3 mm continuum sources are revealed, indicating the presence of youngRead More →

Magnetic monopoles and fermion number violation in chiral matter. (arXiv:2005.05028v1 [hep-th]) <a href="http://arxiv.org/find/hep-th/1/au:+Yamamoto_N/0/1/0/all/0/1">Naoki Yamamoto</a> We show that the presence of a magnetic monopole in position space gives rise to a violation of the fermion number conservation in chiral matter. Using the chiral kinetic theory, we derive a model-independent expression of such a violation in nonequilibrium many-body systems of chiral fermions. In local thermal equilibrium at finite temperature and chemical potential, in particular, this violation is proportional to the chemical potential with a topologically quantized coefficient. These consequences are due to the interplay between the Dirac monopole in position space and the Berry monopole in momentumRead More →

Contribution of the aging effect to the observed asymmetry of interplanetary magnetic clouds. (arXiv:2005.05049v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Demoulin_P/0/1/0/all/0/1">P. D&#xe9;moulin</a> (1 and 2), <a href="http://arxiv.org/find/astro-ph/1/au:+Dasso_S/0/1/0/all/0/1">S. Dasso</a> (3 and 4), <a href="http://arxiv.org/find/astro-ph/1/au:+Lanabere_V/0/1/0/all/0/1">V. Lanabere</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Janvier_M/0/1/0/all/0/1">M. Janvier</a> (5), <a href="http://arxiv.org/find/astro-ph/1/au:+Nous_C/0/1/0/all/0/1">C. No&#xfb;s</a> (2) ((1) LESIA, Observatoire de Paris, Universit&#xe9; PSL, CNRS, Sorbonne Universit&#xe9;, Univ. Paris Diderot, Sorbonne Paris Cit&#xe9;, France, (2) Laboratoire Cogitamus, France (3) CONICET, Universidad de Buenos Aires, Instituto de Astronomia y Fisica del Espacio, Buenos Aires, Argentina, (4) Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Ciencias de la Atmosfera y los Oc&#xe9;anos and Departamento de Fisica, Buenos Aires, Argentina, (5) InstitutRead More →

HR 1614 is not a dissolving cluster. (arXiv:2005.05054v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Kushniruk_I/0/1/0/all/0/1">Iryna Kushniruk</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bensby_T/0/1/0/all/0/1">Thomas Bensby</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Feltzing_S/0/1/0/all/0/1">Sofia Feltzing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sahlholdt_C/0/1/0/all/0/1">Christian L. Sahlholdt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Feuillet_D/0/1/0/all/0/1">Diane Feuillet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Casagrande_L/0/1/0/all/0/1">Luca Casagrande</a> The HR 1614 overdensity in velocity space and has for a long time been known as an old (~2 Gyr) and metal-rich ([Fe/H]~0.2) nearby moving group that has a dissolving cluster origin. The existence of such old and metal-rich groups in the solar vicinity is quite unexpected since the vast majority of nearby moving groups are known to be young. In the light of new and significantly larger data sets we aim to re-investigate the properties andRead More →

Gap-type particle acceleration in the magnetospheres of rotating supermassive black holes. (arXiv:2005.05076v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Katsoulakos_G/0/1/0/all/0/1">Grigorios Katsoulakos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rieger_F/0/1/0/all/0/1">Frank M. Rieger</a> The detection of rapidly variable gamma-ray emission in Active Galactic Nuclei (AGN) has generated renewed interest in magnetospheric particle acceleration and emission scenarios. In order to explore its potential, we study the possibility of steady gap acceleration around the null surface of a rotating black hole magnetosphere. We employ a simplified (1D) description along with the general relativistic expression of Gauss’s law, and assume that the gap is embedded in the radiation field of a radiatively inefficient accretion flow. The model is used to deriveRead More →

Fast Radio Bursts from reconnection events in magnetar magnetospheres. (arXiv:2005.05093v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Lyutikov_M/0/1/0/all/0/1">Maxim Lyutikov</a> (Purdue University), <a href="http://arxiv.org/find/astro-ph/1/au:+Popov_S/0/1/0/all/0/1">Sergey Popov</a> (Sternberg Astronomical Institute, Higher School of Economics) Lyutikov (2002) predicted “radio emission from soft gamma-ray repeaters (SGRs) during their bursting activity”. Detection of a Mega-Jansky radio burst in temporal coincidence with high energy bursts from a Galactic magnetar SGR 1935+2154 confirms that prediction. Similarity of this radio event with Fast Radio Bursts (FRBs) suggests that FRBs are produced within magnetar magnetospheres. We demonstrate that SGR 1935+2154 satisfies the previously derived constraints on the physical parameters at the FRBs’ loci. Coherent radio emission is generated in theRead More →

Photoevaporation of the Jovian circumplanetary disk I. Explaining the orbit of Callisto and the lack of outer regular satellites. (arXiv:2005.05132v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Oberg_N/0/1/0/all/0/1">N. Oberg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kamp_I/0/1/0/all/0/1">I. Kamp</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cazaux_S/0/1/0/all/0/1">S. Cazaux</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rab_C/0/1/0/all/0/1">Ch. Rab</a> Context: The Galilean satellites are thought to have formed from a circumplanetary disk (CPD) surrounding Jupiter. When it reached a critical mass, Jupiter opened an annular gap in the solar protoplanetary disk (PPD) that might have exposed the CPD to radiation from the young Sun or from the stellar cluster in which the Solar System formed. Aims: We investigate the radiation field to which the Jovian CPD was exposed during the processRead More →

Inflation and Decoupling. (arXiv:2005.05146v1 [hep-th]) <a href="http://arxiv.org/find/hep-th/1/au:+Dvali_G/0/1/0/all/0/1">Gia Dvali</a>, <a href="http://arxiv.org/find/hep-th/1/au:+Kehagias_A/0/1/0/all/0/1">Alex Kehagias</a>, <a href="http://arxiv.org/find/hep-th/1/au:+Riotto_A/0/1/0/all/0/1">Antonio Riotto</a> Decoupling of heavy modes in effective low energy theory is one of the most fundamental concepts in physics. It tells us that modes must have a negligible effect on the physics of gravitational backgrounds with curvature radius larger than their wavelengths. Despite this, there exist claims that trans-Planckian modes put severe bound on the duration of inflation even when the Hubble parameter is negligible as compared to the Planck mass. If true, this would mean that inflation violates the principle of decoupling or at least requires its reformulation. We clarify theRead More →

Newly Reprocessed Images of Europa Make This World Even More Interesting and Mysterious Jupiter’s moon Europa is the smoothest object in the Solar System. There are no mountains, very few craters, and no valleys. It’s tallest features are isolated massifs up to 500 meters (1640 ft) tall. But its surface is still of great interest, both visually and from a science perspective. And with a future mission to … Continue reading “Newly Reprocessed Images of Europa Make This World Even More Interesting and Mysterious” The post Newly Reprocessed Images of Europa Make This World Even More Interesting and Mysterious appeared first on Universe Today. UniverseRead More →

Scientists model Mars climate to understand habitability A Southwest Research Institute scientist modeled the atmosphere of Mars to help determine that salty pockets of water present on the Red Planet are likely not habitable by life as we know it on Earth. A team that also included scientists from Universities Space Research Association (USRA) and the University of Arkansas helped allay planetary protection concerns about contaminating potential Martian ecosystems. These results were published this month in Nature Astronomy. phys.org Go to SourceRead More →

Abell 2384: Bending the bridge between two galaxy clusters Several hundred million years ago, two galaxy clusters collided and then passed through each other. This mighty event released a flood of hot gas from each galaxy cluster that formed an unusual bridge between the two objects. This bridge is now being pummeled by particles driven away from a supermassive black hole. phys.org Go to SourceRead More →

Observations unveil the properties of neutrino-emitting blazar’s jet Using the Very Long Baseline Interferometry (VLBI) technique, astronomers have probed the parsec-scale jet of a neutrino-emitting blazar known as TXS 0506+056. Results of the new study, presented May 1 on arXiv.org, shed more light on the properties of this jet, which could improve the understanding of very-high energy (VHE) neutrinos. phys.org Go to SourceRead More →

Scientists reveal new insights of exploding massive stars and future gravitational wave detectors In a study recently published in the Monthly Notices of the Royal Astronomical Society, Dr. Jade Powell and Dr. Bernhard Mueller from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) simulated three core-collapse supernovae using supercomputers from across Australia, including the OzSTAR supercomputer at Swinburne University of Technology. The simulation models—which are 39 times, 20 times and 18 times more massive than our sun— revealed new insights into exploding massive stars and the next generation of gravitational-wave detectors. phys.org Go to SourceRead More →

A multilayer haze system on Saturn’s hexagon A rich variety of meteorological phenomena takes place in the extensive hydrogen atmosphere of Saturn, a world about 10 times the size of the Earth. They help us to better understand similar features in the Earth’s atmosphere. Among Saturn’s atmospheric phenomena is the well-known “hexagon,” an amazing wave structure that surrounds the planet’s polar region. phys.org Go to SourceRead More →

The Sloan Digital Sky Survey Reverberation Mapping Project: MgII Lag Results from Four Years of Monitoring. (arXiv:2005.03663v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Homayouni_Y/0/1/0/all/0/1">Y. Homayouni</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Trump_J/0/1/0/all/0/1">Jonathan R. Trump</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Grier_C/0/1/0/all/0/1">C. J. Grier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Horne_K/0/1/0/all/0/1">Keith Horne</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shen_Y/0/1/0/all/0/1">Yue Shen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brandt_W/0/1/0/all/0/1">W. N. Brandt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dawson_K/0/1/0/all/0/1">Kyle S. Dawson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Alvarez_G/0/1/0/all/0/1">Gloria Fonseca Alvarez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Green_P/0/1/0/all/0/1">Paul Green</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hall_P/0/1/0/all/0/1">P. B. Hall</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Santisteban_J/0/1/0/all/0/1">Juan V. Hernandez Santisteban</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ho_L/0/1/0/all/0/1">Luis C. Ho</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kinemuchi_K/0/1/0/all/0/1">Karen Kinemuchi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kochanek_C/0/1/0/all/0/1">C. S. Kochanek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_J/0/1/0/all/0/1">Jennifer I-Hsiu Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Peterson_B/0/1/0/all/0/1">B. M. Peterson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schneider_D/0/1/0/all/0/1">D. P. Schneider</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Starkey_D/0/1/0/all/0/1">D. A. Starkey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bizyaev_D/0/1/0/all/0/1">Dmitry Bizyaev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pan_K/0/1/0/all/0/1">Kaike Pan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Oravetz_D/0/1/0/all/0/1">Daniel Oravetz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Simmons_A/0/1/0/all/0/1">Audrey Simmons</a> We present reverberation mapping results for theRead More →