RAS_WEB (Page 4,663)

Swift spectra of AT2018cow: A White Dwarf Tidal Disruption Event?. (arXiv:1808.08492v2 [astro-ph.HE] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Kuin_N/0/1/0/all/0/1">N. Paul M. Kuin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wu_K/0/1/0/all/0/1">Kinwah Wu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Oates_S/0/1/0/all/0/1">Samantha Oates</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lien_A/0/1/0/all/0/1">Amy Lien</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Emery_S/0/1/0/all/0/1">Sam Emery</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kennea_J/0/1/0/all/0/1">Jamie Kennea</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pasquale_M/0/1/0/all/0/1">Massimiliano de Pasquale</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Han_Q/0/1/0/all/0/1">Qin Han</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brown_P/0/1/0/all/0/1">Peter J. Brown</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tohuvavohu_A/0/1/0/all/0/1">Aaron Tohuvavohu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Breeveld_A/0/1/0/all/0/1">Alice Breeveld</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burrows_D/0/1/0/all/0/1">David N. Burrows</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cenko_S/0/1/0/all/0/1">S. Bradley Cenko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Campana_S/0/1/0/all/0/1">Sergio Campana</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Levan_A/0/1/0/all/0/1">Andrew Levan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Markwardt_C/0/1/0/all/0/1">Craig Markwardt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Osborne_J/0/1/0/all/0/1">Julian P. Osborne</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Page_M/0/1/0/all/0/1">Mat J. Page</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Page_K/0/1/0/all/0/1">Kim L. Page</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sbarufatti_B/0/1/0/all/0/1">Boris Sbarufatti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Siegel_M/0/1/0/all/0/1">Michael Siegel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Troja_E/0/1/0/all/0/1">Eleonora Troja</a> The bright transient AT2018cow has been unlike any other known type of transient. Its high brightness, rapidRead More →

Probing the pre-BBN universe with gravitational waves from cosmic strings. (arXiv:1808.08968v2 [hep-ph] UPDATED) <a href="http://arxiv.org/find/hep-ph/1/au:+Cui_Y/0/1/0/all/0/1">Yanou Cui</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Lewicki_M/0/1/0/all/0/1">Marek Lewicki</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Morrissey_D/0/1/0/all/0/1">David E. Morrissey</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Wells_J/0/1/0/all/0/1">James D. Wells</a> Many motivated extensions of the Standard Model predict the existence of cosmic strings. Gravitational waves originating from the dynamics of the resulting cosmic string network have the ability to probe many otherwise inaccessible properties of the early universe. In this study we show how the spectrum of gravitational waves from a cosmic string network can be used to test the equation of state of the early universe prior to Big Bang Nucleosynthesis (BBN). We also demonstrate that currentRead More →

Multi-Revolution Low-Thrust Trajectory Optimization Using Symplectic Methods. (arXiv:1901.02881v1 [physics.space-ph]) <a href="http://arxiv.org/find/physics/1/au:+E_Z/0/1/0/all/0/1">Zhibo E</a>, <a href="http://arxiv.org/find/physics/1/au:+Guzzetti_D/0/1/0/all/0/1">Davide Guzzetti</a> Optimization of low-thrust trajectories that involve a larger number of orbit revolutions is considered a challenging problem. This paper describes a high-precision symplectic method and optimization techniques to solve the minimum-energy low-thrust multi-revolution orbit transfer problem. First, the optimal orbit transfer problem is posed as a constrained nonlinear optimal control problem. Then, the constrained nonlinear optimal control problem is converted into an equivalent linear quadratic form near a reference solution. The reference solution is updated iteratively by solving a sequence of linear-quadratic optimal control sub-problems, until convergence. Each sub-problem isRead More →

The Distance Measurements of Supernova Remnants in The Fourth Galactic Quadrant. (arXiv:1901.02882v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Shan_S/0/1/0/all/0/1">Su-Su Shan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhu_H/0/1/0/all/0/1">Hui Zhu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tian_W/0/1/0/all/0/1">Wen-Wu Tian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_H/0/1/0/all/0/1">Hai-Yan Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yang_A/0/1/0/all/0/1">Ai-Yuan Yang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_M/0/1/0/all/0/1">Meng-Fei Zhang</a> We take advantage of the red clump stars to build the relation of the optical extinction (AV) and distance in each direction of supernova remnants (SNRs) with known extinction in the fourth Galactic quadrant. The distances of 9 SNRs are well determined by this method. Their uncertainties range from 10% to 30%, which is significantly improved for 8 SNRs, G279.0+1.1, G284.3-1.8, G296.1-0.5, G299.2-2.9, G308.4-1.4, G309.2-0.6, G309.8- 2.6, G332.4-0.4. In addition, SNR G284.3-1.8 with theRead More →

Dust scaling relations in a cosmological simulation. (arXiv:1901.02886v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Hou_K/0/1/0/all/0/1">Kuan-Chou Hou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aoyama_S/0/1/0/all/0/1">Shohei Aoyama</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hirashita_H/0/1/0/all/0/1">Hiroyuki Hirashita</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nagamine_K/0/1/0/all/0/1">Kentaro Nagamine</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shimizu_I/0/1/0/all/0/1">Ikkoh Shimizu</a> To study the dust evolution in the cosmological structure formation history, we perform a smoothed particle hydrodynamic simulation with a dust enrichment model in a cosmological volume. We adopt the dust evolution model that represents the grain size distribution by two sizes and takes into account stellar dust production and interstellar dust processing. We examine the dust mass function and the scaling properties of dust in terms of the characteristics of galaxies. The simulation broadly reproduces the observed dust mass functionsRead More →

Probing the Black Hole Merger History in Clusters using Stellar Tidal Disruptions. (arXiv:1901.02889v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Samsing_J/0/1/0/all/0/1">Johan Samsing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Venumadhav_T/0/1/0/all/0/1">Tejaswi Venumadhav</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dai_L/0/1/0/all/0/1">Liang Dai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Martinez_I/0/1/0/all/0/1">Irvin Martinez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Batta_A/0/1/0/all/0/1">Aldo Batta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lopez_M/0/1/0/all/0/1">Martin Lopez Jr.</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ramirez_Ruiz_E/0/1/0/all/0/1">Enrico Ramirez-Ruiz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kremer_K/0/1/0/all/0/1">Kyle Kremer</a> The dynamical assembly of binary black holes (BBHs) in dense star clusters (SCs) is one of the most promising pathways for producing observable gravitational wave (GW) sources, however several other formation scenarios likely operate as well. One of the current outstanding questions is how these different pathways may be distinguished apart. In this paper we suggest a new multi-messenger observable that can be used to constrainRead More →

The present-day mass-metallicity relation for galaxies using a new electron-temperature method. (arXiv:1901.02890v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Yates_R/0/1/0/all/0/1">Robert M. Yates</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schady_P/0/1/0/all/0/1">Patricia Schady</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_T/0/1/0/all/0/1">Ting-Wan Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schweyer_T/0/1/0/all/0/1">Tassilo Schweyer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wiseman_P/0/1/0/all/0/1">Philip Wiseman</a> We present a study of electron temperatures (Te) and gas-phase oxygen abundances (Z_Te) for galaxies in the local Universe (zRead More →

The superpotential method in cosmological inflation. (arXiv:1901.02892v1 [gr-qc]) <a href="http://arxiv.org/find/gr-qc/1/au:+Adam_C/0/1/0/all/0/1">C. Adam</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Varela_D/0/1/0/all/0/1">D. Varela</a> Scalar field cosmological inflation has a first integral relating the Hubble function and the lagrangian of the scalar field(s), which is known under the names of “Hamilton-Jacobi approach” or “superpotential equation”. Here we exploit the simplicity of this superpotential equation and use it as an alternative but equivalent cosmological evolution equation during inflation, replacing the Friedman-Robertson-Walker (FRW) equations. It turns out that all inflationary observables can be calculated directly from its solution (the superpotential). Further, the superpotential equation allows for a simple and direct calculation of the slow-roll expansion to arbitraryRead More →

Turbulent dynamo in a weakly ionized medium. (arXiv:1901.02893v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Xu_S/0/1/0/all/0/1">Siyao Xu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Garain_S/0/1/0/all/0/1">Sudip K. Garain</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Balsara_D/0/1/0/all/0/1">Dinshaw S. Balsara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lazarian_A/0/1/0/all/0/1">A. Lazarian</a> The small-scale turbulent dynamo is an important process contributing to the cosmic magnetization. In partially ionized astrophysical plasmas, the dynamo growth of magnetic energy strongly depends on the coupling state between ions and neutrals and the ion-neutral collisional damping effect. A new damping stage of turbulent dynamo in a weakly ionized medium was theoretically predicted by Xu & Lazarian (2016). By carrying out a 3D two-fluid dynamo simulation, here we for the first time numerically confirmed the physical conditions and the linear-in-timeRead More →

Dwarf galaxies might not be the birth sites of supermassive black holes. (arXiv:1901.02895v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Mezcua_M/0/1/0/all/0/1">Mar Mezcua</a> Intermediate-mass black holes (BHs) in local dwarf galaxies are considered the relics of the early seed BHs. However, their growth might have been impacted by galaxy mergers and BH feedback so that they cannot be treated as tracers of the early seed BH population. Intermediate-mass black holes (BHs) in local dwarf galaxies are considered the relics of the early seed BHs. However, their growth might have been impacted by galaxy mergers and BH feedback so that they cannot be treated as tracers of the early seed BH population.Read More →

The inner dark matter distribution of the Cosmic Horseshoe (J1148+1930) with gravitational lensing and dynamics. (arXiv:1901.02896v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Schuldt_S/0/1/0/all/0/1">S. Schuldt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chirivi_G/0/1/0/all/0/1">G. Chiriv&#xec;</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Suyu_S/0/1/0/all/0/1">S. H. Suyu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yildirim_A/0/1/0/all/0/1">A. Y&#x131;ld&#x131;r&#x131;m</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sonnenfeld_A/0/1/0/all/0/1">A. Sonnenfeld</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Halkola_A/0/1/0/all/0/1">A. Halkola</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lewis_G/0/1/0/all/0/1">G. F. Lewis</a> We present a detailed analysis of the inner mass structure of the Cosmic Horseshoe (J1148+1930) strong gravitational lens system observed with the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3). In addition to the spectacular Einstein ring, this systems shows a radial arc. We obtained the redshift of the radial arc counter image $z_text{s,r} = 1.961 pm 0.001$ from Gemini observations. To disentangle theRead More →

Climate sensitivity to ozone and its relevance on the habitability of Earth-like planets. (arXiv:1901.02897v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Gomez_Leal_I/0/1/0/all/0/1">Illeana Gomez-Leal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kaltenegger_L/0/1/0/all/0/1">Lisa Kaltenegger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lucarini_V/0/1/0/all/0/1">Valerio Lucarini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lunkeit_F/0/1/0/all/0/1">Frank Lunkeit</a> Atmospheric ozone plays an important role on the temperature structure of the atmosphere. However, it has not been included in previous studies on the effect of an increasing solar radiation on the Earth’s climate. Here we study the climate sensitivity to the presence/absence of ozone with an increasing solar forcing for the first time with a global climate model. We show that the warming effect of ozone increases both the humidity of the lower atmosphere and the surfaceRead More →

The birth of the Milky Way: the in-situ halo and early thick disk as uncovered by accurate stellar ages with Gaia. (arXiv:1901.02900v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Gallart_C/0/1/0/all/0/1">Carme Gallart</a> (1,2), <a href="http://arxiv.org/find/astro-ph/1/au:+Bernard_E/0/1/0/all/0/1">Edouard J. Bernard</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Brook_C/0/1/0/all/0/1">Chris B. Brook</a> (1,2), <a href="http://arxiv.org/find/astro-ph/1/au:+Ruiz_Lara_T/0/1/0/all/0/1">Tomas Ruiz-Lara</a> (1,2), <a href="http://arxiv.org/find/astro-ph/1/au:+Cassisi_S/0/1/0/all/0/1">Santi Cassisi</a> (4,5), <a href="http://arxiv.org/find/astro-ph/1/au:+Hill_V/0/1/0/all/0/1">Vanessa Hill</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Monelli_M/0/1/0/all/0/1">Matteo Monelli</a> (1,2) ((1) Instituto de Astrofisica de Canarias, Spain, (2) Departamento de Astrofisica, Universidad de La Laguna, Spain, (3) Observatoire de la Cote d&#x27;Azur, CNRS, France (4) INAF-Astronomical Observatory of Abruzzo, Italy, (5) INFN, Sezione di Pisa, Italy) As Milky Way-like galaxies form, smaller stellar systems accrete onto the main galactic progenitor, assembling aRead More →

Climate Sensitivity to Carbon Dioxide and Moist Greenhouse threshold of Earth-like planets under an increasing solar forcing. (arXiv:1901.02901v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Gomez_Leal_I/0/1/0/all/0/1">Illeana Gomez-Leal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kaltenegger_L/0/1/0/all/0/1">Lisa Kaltenegger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lucarini_V/0/1/0/all/0/1">Valerio Lucarini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lunkeit_F/0/1/0/all/0/1">Frank Lunkeit</a> Carbon dioxide is one of the major contributors to the radiative forcing, increasing both the temperature and the humidity of Earth’s atmosphere. If the stellar irradiance increases and water becomes abundant in the stratosphere of an Earth-like planet, it will be dissociated and the resultant hydrogen will escape from the atmosphere. This state is called the moist greenhouse threshold (MGT). Using a global climate model (GCM) of intermediate complexity, we explore how to identifyRead More →

Multiphase gas in the circumgalactic medium: relative role of $t_{rm cool}/t_{rm ff}$ and density fluctuations. (arXiv:1901.02903v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Choudhury_P/0/1/0/all/0/1">Prakriti Pal Choudhury</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sharma_P/0/1/0/all/0/1">Prateek Sharma</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Quataert_E/0/1/0/all/0/1">Eliot Quataert</a> We perform a suite of simulations with realistic gravity and thermal balance in shells to quantify the role of the ratio of cooling time to the free-fall time ($t_{rm cool}/t_{rm ff}$) and the amplitude of density perturbations ($delta rho/rho$) in the production of multiphase gas in the circumgalactic medium (CGM). Previous idealized simulations, focussing on small amplitude perturbations in the intracluster medium (ICM), found that cold gas condenses out of the hot ICM in global thermal balance whenRead More →