Identifying Variability in Deeply Embedded Protostars with ALMA and CARMA. (arXiv:1902.00588v1 [astro-ph.SR]) <a href="">Logan Francis</a>, <a href="">Doug Johnstone</a>, <a href="">Michael M. Dunham</a>, <a href="">Todd R. Hunter</a>, <a href="">Steve Mairs</a> Variability of pre-main-sequence stars observed at optical wavelengths has been attributed tofluctuations in the mass accretion rate from the circumstellar disk onto the forming star.Detailed models of accretion disks suggest that young deeply embedded protostars should also exhibit variations in their accretion rates, and that these changes can be tracked indirectly by monitoring the response of the dust envelope at mid-IR to millimeter wavelengths. Interferometers such as ALMA offer the resolution and sensitivity to observe smallRead More →

Testing systematics of Gaia DR2 parallaxes with empirical surface brightness – color relations applied to eclipsing binaries. (arXiv:1902.00589v1 [astro-ph.SR]) <a href="">Dariusz Graczyk</a>, <a href="">Grzegorz Pietrzynski</a>, <a href="">Wolfgang Gieren</a>, <a href="">Jesper Storm</a>, <a href="">Nicolas Nardetto</a>, <a href="">Alexandre Gallenne</a>, <a href="">Pierre F. L. Maxted</a>, <a href="">Pierre Kervella</a>, <a href="">Zbigniew Kolaczkowski</a>, <a href="">Piotr Konorski</a>, <a href="">Bogumil Pilecki</a>, <a href="">Bartlomiej Zgirski</a>, <a href="">Marek Gorski</a>, <a href="">Ksenia Suchomska</a>, <a href="">Paulina Karczmarek</a>, <a href="">Monica Taormina</a>, <a href="">Piotr Wielgorski</a>, <a href="">Weronika Narloch</a>, <a href="">Radoslaw Smolec</a>, <a href="">Rolf Chini</a>, <a href="">Louise Breuval</a> Using a sample of 81 galactic, detached eclipsing binary stars we investigated the global zero-point shift of their parallaxes with theRead More →

Scientists study organization of life on a planetary scale When we think of life on Earth, we might think of individual examples ranging from animals to bacteria. When astrobiologists study life, however, they have to consider not only individual organisms, but also ecosystems, and the biosphere as a whole. Go to SourceRead More →

How Big Would a Generation Ship Need to be to Keep a Crew of 500 Alive for the Journey to Another Star? In their latest in a series of studies concerning generation ships, the team addresses how large the ship would need to be to sustain a multi-generational crew. The post How Big Would a Generation Ship Need to be to Keep a Crew of 500 Alive for the Journey to Another Star? appeared first on Universe Today. Universe Today Go to SourceRead More →

Two Newly-Discovered Exoplanets are Probably the Result of a Catastrophic Collision How can two planets so similar in some respects have such different densities? According to a new study, a catastrophic collision may be to blame. In our Solar System, all the inner planets are small rocky worlds with similar densities, while the outer planets are gas giants with their own similar densities. But not all … Continue reading “Two Newly-Discovered Exoplanets are Probably the Result of a Catastrophic Collision” The post Two Newly-Discovered Exoplanets are Probably the Result of a Catastrophic Collision appeared first on Universe Today. Universe Today Go to SourceRead More →

How The Sun’s Scorching Corona Stays So Hot We’ve got a mystery on our hands. The surface of the sun has a temperature of about 6,000 Kelvin – hot enough to make it glow bright, hot white. But the surface of the sun is not its last later, just like the surface of the Earth is not its outermost layer. The sun has … Continue reading “How The Sun’s Scorching Corona Stays So Hot” The post How The Sun’s Scorching Corona Stays So Hot appeared first on Universe Today. Universe Today Go to SourceRead More →

Highly collimated jet spotted from the Red Square Nebula Astronomers have detected a highly collimated, bipolar jet from the so-called Red Square Nebula (RSN) surrounding the B[e]-type star MWC 922. The newly discovered jet could reveal more insights into the nature of the RSN and its emission. The finding is detailed in a paper published January 24 on the arXiv pre-print repository. Go to SourceRead More →

Influence of Magnetic Force on the Flow Stability in a Rectangular duct. (arXiv:1902.00620v1 [physics.flu-dyn]) <a href="">Rahman Anisur</a>, <a href="">Wenqia Xu</a>, <a href="">Kunhang Li</a>, <a href="">Hua-ShuDou</a>, <a href="">Boo Cheong Khoo</a>, <a href="">Jie Mao</a> The stability of the flow under the magnetic force is one of the classical problems in fluid mechanics. In this paper, the flow in a rectangular duct with different Hartmann (Ha) number is simulated. The finite volume method and the SIMPLE algorithm are used to solve a system of equations and the energy gradient theory is then used to study the (associated) stability of magnetohydrodynamics (MHD). The flow stability of MHD flow forRead More →

Effects of strong magnetic fields on neutron $^{3}P_{2}$ superfluidity in spin-orbit interactions. (arXiv:1902.00674v1 [nucl-th]) <a href="">Shigehiro Yasui</a>, <a href="">Chandrasekhar Chatterjee</a>, <a href="">Muneto Nitta</a> We discuss neutron $^{3}P_{2}$ phases in the core of neutron stars in strong magnetic field (magnetars). The neutron $^{3}P_{2}$ pairing provides a wide variety of condensates, such as the uniaxial nematic and (D$_{2}$ and D$_{4}$) biaxial nematic, with different symmetries stemming from the combinations of spin and momentum. Based on the spin-orbital angular momentum coupling and the spin-magnetic field coupling of the neutrons, we derive the Ginzburg-Landau equation containing higher order terms of the magnetic field. We investigate the phase diagram ofRead More →

The SMC X-ray binary SXP4.78 : a new Type II outburst and the identification and study of the optical counterpart. (arXiv:1902.00677v1 [astro-ph.HE]) <a href="">Itumeleng Monageng</a>, <a href="">Malcolm Coe</a>, <a href="">Lee Townsend</a>, <a href="">David Buckley</a>, <a href="">Vanessa McBride</a>, <a href="">Paul Roche</a>, <a href="">Jamie Kennea</a>, <a href="">Andrzej Udalski</a>, <a href="">Phil Evans</a> SXP4.78 was originally discovered in 2000 as a pulsar in the Small Magellanic Cloud (SMC) by the Rossi X-ray Timing Explorer (RXTE) but it was not spatially located at that time. A new detection in 2018 with the Niels Gehrels Swift telescope during a Type II outburst permitted its position to be accurately located and itsRead More →

Searching for Dual AGN in Galaxies with Double-Peaked Emission Line Spectra using Radio Observations. (arXiv:1902.00689v1 [astro-ph.GA]) <a href="">K.Rubinur</a>, <a href="">M. Das</a>, <a href="">P. Kharb</a> Supermassive black hole (SMBH) binaries form due to galaxy mergers and minor accretion events. When the SMBHs are accreting, they form dual or binary AGN and can give rise to double-peaked emission lines in the optical spectra of the merger remnant. The double-peaked emission lines could also be due to jet-ISM interaction or rotating disks. One of the best ways to confirm dual/binary AGN in double-peaked AGN (DPAGN) is by using high resolution radio observations. We have observed a sample ofRead More →

Debiasing inference with approximate covariance matrices and other unidentified biases. (arXiv:1902.00709v1 [astro-ph.CO]) <a href="">Elena Sellentin</a>, <a href="">Jean-Luc Starck</a> When a posterior peaks in unexpected regions of parameter space, new physics has either been discovered, or a bias has not been identified yet. To tell these two cases apart is of paramount importance. We therefore present a method to indicate and mitigate unrecognized biases: Our method runs any pipeline with possibly unknown biases on both simulations and real data. It computes the coverage probability of posteriors, which measures whether posterior volume is a faithful representation of probability or not. If found to be necessary, the posteriorRead More →

ALMA study of the HD 100453 AB system and the tidal interaction of the companion with the disk. (arXiv:1902.00720v1 [astro-ph.SR]) <a href="">G. van der Plas</a>, <a href="">F. M&#xe9;nard</a>, <a href="">J.-F. Gonzalez</a>, <a href="">S. Perez</a>, <a href="">L. Rodet</a>, <a href="">C. Pinte</a>, <a href="">L. Cieza</a>, <a href="">S. Casassus</a>, <a href="">M. Benisty</a> Context: The complex system HD 100453 AB with a ring-like circumprimary disk and two spiral arms, one of which is pointing to the secondary, is a good laboratory to test spiral formation theories. Aims: To quantify the interaction of HD 100453 B with the circumprimary disk. Methods: Using ALMA band 6 dust continuum and CO isotopologueRead More →

Envelopes and vertical amplitudes of disk-crossing orbits. (arXiv:1902.00723v1 [astro-ph.GA]) <a href="">Ronaldo S. S. Vieira</a>, <a href="">Javier Ramos-Caro</a> We recently found that regular orbits in axially symmetric galactic disks have their envelopes $Z(R)$ accurately described by the relation $Z(R)propto[Sigma_I(R)]^{-1/3}$, if their amplitudes are comparable to the disk thickness, where $Sigma_I$ is the surface density of the disk (integrated over its whole vertical range). Moreover, the usual adiabatic approximation gives a good description of the orbits’ envelopes for low vertical amplitudes. However, these two approaches are apparently disconnected, since their expressions differ qualitatively. Our purpose in this paper is to fill this gap by extending these previousRead More →

Development of the Warm Astrometric Mask for MICADO astrometry calibration. (arXiv:1902.00738v1 [astro-ph.IM]) <a href="">Gabriele Rodeghiero</a>, <a href="">Miriam Sawczuck</a>, <a href="">J&#xf6;rg Uwe Pott</a>, <a href="">Martin Gl&#xfc;ck</a>, <a href="">Enrico Biancalani</a>, <a href="">Maximilian H&#xe4;berle</a>, <a href="">Hannes Reichert</a>, <a href="">Claudio Pernechele</a>, <a href="">Vianak Naranjo</a>, <a href="">Javier Moreno Ventas</a>, <a href="">Peter Bizenberger</a>, <a href="">Luigi Lessio</a> The achievement of $mu$arcsec relative astrometry with ground-based, near infrared, extremely large telescopes requires a significant endeavour of calibration strategies. In this paper we address the removal of instrument optical distortions coming from the ELT first light instrument MICADO and its adaptive optics system MAORY by means of an astrometric calibration mask. The results ofRead More →

IFU spectroscopy of Southern PNe: VII Photo-ionization modelling of intermediate excitation class objects. (arXiv:1902.00742v1 [astro-ph.SR]) <a href="">A. Ali</a>, <a href="">M.A. Dopita</a> We present integral field unit spectroscopic observations of southern Galactic planetary nebulae (PNe), IC 2501, Hen 2-7, and PB4. The goal of studying these objects together is that, although they have roughly similar intermediate excitation and evolution of central stars (CSs), they display very different evolution in their nebular structure which needs to be understood. The morphologies and ionisation structures of the objects are investigated using a set of emission-line maps representative of the different ionisation zones. We use those in order to constructRead More →

The role of magnetic field in molecular cloud formation and evolution. (arXiv:1902.00798v1 [astro-ph.GA]) <a href="">Patrick Hennebelle</a>, <a href="">Shu-ichiro Inutsuka</a> We review the role that magnetic field may have on the formation and evolution of molecular clouds. After a brief presentation and main assumptions leading to ideal MHD equations, their most important correction, namely the ion-neutral drift is described. The nature of the multi-phase interstellar medium (ISM) and the thermal processes that allows this gas to become denser are presented. Then we discuss our current knowledge of compressible magnetized turbulence, thought to play a fundamental role in the ISM. We also describe what is known regardingRead More →

Origin of radio-quiet coronal mass ejections in flare stars. (arXiv:1902.00810v1 [astro-ph.SR]) <a href="">D. J. Mullan</a>, <a href="">R. R. Paudel</a> Type II radio bursts are observed in the Sun in association with many coronal mass ejections (CME’s. In view of this association, there has been an expectation that, by scaling from solar flares to the flares which are observed on M dwarfs, radio emission analogous to solar Type II bursts should be detectable in association with M dwarf flares. However, several surveys have revealed that this expectation does not seem to be fulfilled. Here we hypothesize that the presence of larger global field strengths in low-massRead More →

Cosmological constraints on the velocity-dependent baryon-dark matter coupling. (arXiv:1902.00826v1 [astro-ph.CO]) <a href="">Junpei Ooba</a>, <a href="">Horoyuki Tashiro</a>, <a href="">Kenji Kadota</a> We present the cosmological constraints on the cross section of baryon-dark matter interactions for the dark matter mass below the MeV scale from the Planck CMB (cosmic microwave background) and SDSS (Sloan Digital Sky Survey) Lyman-$alpha$ forest data. To explore the dark matter mass $m_{chi}lesssim 1$ MeV for which the dark matter’s free-streaming effect can suppress the observable small scale density fluctuations, in addition to the acoustic oscillation damping in existence of the baryon-dark matter coupling, we apply the approximated treatment of dark matter free-streaming analogousRead More →