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Neutrinos in N-body simulations. (arXiv:2102.05690v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Nascimento_C/0/1/0/all/0/1">Caio Bastos de Senna Nascimento</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Loverde_M/0/1/0/all/0/1">Marilena Loverde</a> In the next decade, cosmological surveys will have the statistical power to detect the absolute neutrino mass scale. N-body simulations of large-scale structure formation play a central role in interpreting data from such surveys. Yet these simulations are Newtonian in nature. We provide a quantitative study of the limitations to treating neutrinos, implemented as N-body particles, in N-body codes, focusing on the error introduced by neglecting special relativistic effects. Special relativistic effects are potentially important due to the large thermal velocities of neutrino particles in the simulation box. We deriveRead More →

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Hidden in Plain Sight: A Double-lined White Dwarf Binary 26 pc Away and a Distant Cousin. (arXiv:2102.05688v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Kilic_M/0/1/0/all/0/1">Mukremin Kilic</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bedard_A/0/1/0/all/0/1">A. Bedard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bergeron_P/0/1/0/all/0/1">P. Bergeron</a> We present high-resolution spectroscopy of two nearby white dwarfs with inconsistent spectroscopic and parallax distances. The first one, PG 1632+177, is a 13th magnitude white dwarf only 25.6 pc away. Previous spectroscopic observations failed to detect any radial velocity changes in this star. Here, we show that PG 1632+177 is a 2.05 d period double-lined spectroscopic binary (SB2) containing a low-mass He-core white dwarf with a more-massive, likely CO-core white dwarf companion. After L 870-2, PG 1632+177 becomesRead More →

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Preventing Anomalous Torques in Circumbinary Accretion Simulations. (arXiv:2102.05684v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Dittmann_A/0/1/0/all/0/1">Alexander Dittmann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ryan_G/0/1/0/all/0/1">Geoffrey Ryan</a> Numerical experiments are the primary method of studying the evolution of circumbinary disks due to the strong nonlinearities involved. Many circumbinary simulations also require the use of numerical mass sinks: source terms which prevent gas from unphysically accumulating around the simulated point masses by removing gas at a given rate. However, special care must be taken when drawing physical conclusions from such simulations to ensure that results are not biased by numerical artifacts. We demonstrate how the use of improved sink methods reduces some of these potential biases in vertically-integratedRead More →

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Quantum Theory Proposes That Cause and Effect Can Go In Loops Causality is one of those difficult scientific topics that can easily stray into the realm of philosophy.  Science’s relationship with the concept started out simply enough: an event causes another event later in time.  That had been the standard understanding of the scientific community up until quantum mechanics was introduced.  Then, with the introduction of the famous “spooky action at a distance” that is a side effect of the concept of quantum entanglement, scientists began to question that simple interpretation of causality. Now, researchers at the Université Libre de Bruxelles (ULB) and the UniversityRead More →

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Perseverance Will Make Sure it has a Safe Landing To casual observers, landing a rover on Mars can seem kind of like old news, believe it or not. Especially after all of NASA’s successes. But many are likely not aware of the so-called ‘Mars Curse.‘ The fact is, many of the spacecraft that attempt to land there fail and crash. Next to run the gauntlet of the Mars Curse is NASA’s Perseverance rover. It’ll attempt its long-awaited landing at Jezero Crater on February 18th. The people at NASA have given the Perseverance rover some finely-tuned tools to get it to the Martian surface safely andRead More →

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Revisiting the complex kinematics of ionized gas at the central region of NGC 1068: evidence of an additional active galactic nucleus?. (arXiv:2102.05043v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Shin_J/0/1/0/all/0/1">Jaejin Shin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Woo_J/0/1/0/all/0/1">Jong-Hak Woo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kim_M/0/1/0/all/0/1">Minjin Kim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_J/0/1/0/all/0/1">Junfeng Wang</a> We present a spatially resolved analysis of ionized gas at the nuclear region of the nearby galaxy NGC 1068. While NGC 1068 has been known to have gas outflows driven by its active galactic nucleus (AGN), more complex kinematical signatures were recently reported, which were inconsistent with a rotation or simple biconical outflows. To account for the nature of gas kinematics, we performed a spatially resolved kinematical study, finding aRead More →

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Measuring magnetization with rotation measures and velocity centroids in supersonic MHD turbulence. (arXiv:2102.05647v1 [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:+Hu_Y/0/1/0/all/0/1">Yue Hu</a> The interstellar turbulence is magnetized and thus anisotropic. The anisotropy of turbulent magnetic fields and velocities is imprinted in the related observables, rotation measures (RMs), and velocity centroids (VCs). This anisotropy provides valuable information on both the direction and strength of the magnetic field. However, its measurement is difficult especially in highly supersonic turbulence in cold interstellar phases due to the distortions by isotropic density fluctuations. By using 3D simulations of supersonic and sub-Alfv’enic magnetohydrodynamic(MHD) turbulence, we find that the problem can be alleviated whenRead More →

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Modified Gravity (MOG), Cosmology and Black Holes. (arXiv:2006.12550v4 [gr-qc] UPDATED) <a href="http://arxiv.org/find/gr-qc/1/au:+Moffat_J/0/1/0/all/0/1">J. W. Moffat</a> A covariant modified gravity (MOG) is formulated by adding to general relativity two new degrees of freedom, a scalar field gravitational coupling strength $G= 1/chi$ and a gravitational spin 1 vector field $phi_mu$. The $G$ is written as $G=G_N(1+alpha)$ where $G_N$ is Newton’s constant, and the gravitational source charge for the vector field is $Q_g=sqrt{alpha G_N}M$, where $M$ is the mass of a body. Cosmological solutions of the theory are derived in a homogeneous and isotropic cosmology. Black holes in MOG are stationary as the end product of gravitational collapse andRead More →

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On the Color-Metallicity Relation of the Red Clump and the Reddening Toward the Magellanic Clouds. (arXiv:2006.03603v2 [astro-ph.SR] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Nataf_D/0/1/0/all/0/1">David M. Nataf</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cassisi_S/0/1/0/all/0/1">Santi Cassisi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Casagrande_L/0/1/0/all/0/1">Luca Casagrande</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yuan_W/0/1/0/all/0/1">Wenlong Yuan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Riess_A/0/1/0/all/0/1">Adam G. Riess</a> The zero point of the reddening toward the Large Magellanic Cloud (LMC) has been the subject of some dispute. Its uncertainty propagates as a systematic error for methods which measure the extragalactic distance scale through knowledge of the absolute extinction of LMC stars. In an effort to resolve this issue, we used three different methods to calibrate the most widely-used metric to predict LMC extinction, the intrinsic color of theRead More →

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Constraining Cosmological and Galaxy Parameters using Strong Gravitational Lensing Systems. (arXiv:2002.06354v2 [astro-ph.CO] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Kumar_D/0/1/0/all/0/1">Darshan Kumar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jain_D/0/1/0/all/0/1">Deepak Jain</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mahajan_S/0/1/0/all/0/1">Shobhit Mahajan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mukherjee_A/0/1/0/all/0/1">Amitabha Mukherjee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rani_N/0/1/0/all/0/1">Nisha Rani</a> Strong gravitational lensing along with the distance sum rule method can constrain both cosmological parameters as well as density profiles of galaxies without assuming any fiducial cosmological model. To constrain galaxy parameters and cosmic curvature $(Omega_{k0})$, we use the distance ratio data from a recently compiled database of $161$ galactic scale strong lensing systems. We use databases of supernovae type-Ia (Pantheon) and Gamma Ray Bursts (GRBs) for calculating the luminosity distance. To study the model of theRead More →

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Threshold of primordial black hole formation in Eddington-inspired-Born-Infeld gravity. (arXiv:1912.10690v4 [gr-qc] UPDATED) <a href="http://arxiv.org/find/gr-qc/1/au:+Chen_C/0/1/0/all/0/1">Che-Yu Chen</a> It is believed that primordial black holes (PBHs), if they exist, can serve as a powerful tool to probe the early stage of the cosmic history. Essentially, in the radiation dominated universe, PBHs could form by the gravitational collapse of overdense primordial perturbations produced during inflation. In this picture, one important ingredient is the threshold of density contrast, which defines the onset of PBH formation. In the literature, most of the estimations of threshold, no matter numerically or analytically, are implemented in the framework of general relativity (GR). In thisRead More →

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Variable Modified Newtonian Mechanics II: Baryonic Tully Fisher Relation. (arXiv:1802.01493v7 [astro-ph.GA] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Wong_C/0/1/0/all/0/1">C. C. Wong</a> Recently we find a single-metric solution for a point mass residing in an expanding universe cite{wong}, which apart from the Newtonian acceleration, gives rise to an additional MOND-like acceleration in which the MOND acceleration $a_0$ is replaced by the cosmological acceleration. We study a Milky Way size protogalactic cloud in this acceleration, in which the growth of angular momentum can lead to an end of the over-density growth. Within realistic redshifts, the over-density stops growing at a value where the MOND-like acceleration dominates over Newton and the outer massRead More →

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Possible Super-Earth in the Habitable Zone at Alpha Centauri Astronomers using a new technique may have not only found a super-Earth at a neighbouring star, but they may also have directly imaged it. And it could be nice and cozy in the habitable zone around Alpha Centauri. It’s much easier to see giant planets than Earth-size planets. No matter which detection method is being used, larger planets are simply a larger needle in the cosmic haystack. But overall, astronomers are very interested in planets that are similar to Earth. And finding them is much more difficult. We thought we’d have to wait for the ultra-powerfulRead More →

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It’s Starting to Look Like Super-Earths Really are Just Great big Terrestrial Planets We’ve learned a thing or two about exoplanets in the past several years. One of the more surprising discoveries is that our solar system is rather unusual. The Sun’s worlds are easily divided into small rocky planets and large gas giants. Exoplanets are much more diverse, both in size and composition. The Sun’s planets can be divided into gas giants such as Jupiter and Saturn, gas dwarfs such as Neptune and Uranus, and terrestrial worlds like Earth and Mars. But many exoplanets fall into a new category known as super-Earths. Super-Earths fillRead More →

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Three Storms Have Dumped Snow on Mauna Loa and Mauna Kea The words “snow” and “Hawai’i” are not often mentioned in the same paragraph – or even on the same vacation. But snow does fall in Hawai’i almost every year, and 2021 has seen a deep cold front drop snow on the summits of Mauna Loa and Mauna Kea on the Big Island at least three times in the past few weeks – as well as on Haleakala on Maui. This means there are currently in snowcaps on Hawai’i’s three tallest mountains. In this image from February 6, 2021, the Operational Land Imager (OLI) onRead More →

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Hubble uncovers concentration of small black holes Globular clusters are extremely dense stellar systems, in which stars are packed closely together. They are also typically very old—the globular cluster that is the focus of this study, NGC 6397, is almost as old as the Universe itself. It resides 7800 light-years away, making it one of the closest globular clusters to Earth. Because of its very dense nucleus, it is known as a core-collapsed cluster. phys.org Go to SourceRead More →

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A new way of forming planets In the last 25 years, scientists have discovered over 4000 planets beyond the borders of our solar system. From relatively small rock and water worlds to blisteringly hot gas giants, the planets display a remarkable variety. This variety is not unexpected. The sophisticated computer models, with which scientists study the formation of planets, also spawn very different planets. What the models have more difficulty to explain is the observed mass distribution of the planets discovered around other stars. The majority have fallen into the intermediate mass category—planets with masses of several Earth masses to around that of Neptune. EvenRead More →

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Vaporised crusts of Earth-like planets found in dying stars Remnants of planets with Earth-like crusts have been discovered in the atmospheres of four nearby white dwarf stars by University of Warwick astronomers, offering a glimpse of the planets that may have once orbited them up to billions of years ago. phys.org Go to SourceRead More →