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High spin expansion for null geodesics. (arXiv:2006.05153v1 [gr-qc]) <a href="http://arxiv.org/find/gr-qc/1/au:+Li_P/0/1/0/all/0/1">Peng-Cheng Li</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Guo_M/0/1/0/all/0/1">Minyong Guo</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Chen_B/0/1/0/all/0/1">Bin Chen</a> We consider the high spin expansion for the null geodesics in the Kerr spacetime. We expand the null geodesic equation successively to higher orders in deviation from extremity. Via the method of matched asymptotic expansion, the radial integrals are obtained analytically. It turns out that the analytic expressions are very sensitive to the value of the shifted Carter constant $q$. We show that for a large $q$, the analytic expressions can be used to study observational electromagnetic signatures for astrophysical black holes like M87*. However, for a smallRead More →

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The accretion history of high-mass stars: An ArT’eMiS pilot study of Infrared Dark Clouds. (arXiv:2006.05155v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Peretto_N/0/1/0/all/0/1">N. Peretto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rigby_A/0/1/0/all/0/1">A. Rigby</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Andre_P/0/1/0/all/0/1">Ph. Andr&#xe9;</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Konyves_V/0/1/0/all/0/1">V. K&#xf6;nyves</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fuller_G/0/1/0/all/0/1">G. Fuller</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zavagno_A/0/1/0/all/0/1">A. Zavagno</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schuller_F/0/1/0/all/0/1">F. Schuller</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Arzoumanian_D/0/1/0/all/0/1">D. Arzoumanian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bontemps_S/0/1/0/all/0/1">S. Bontemps</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Csengeri_T/0/1/0/all/0/1">T. Csengeri</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Didelon_P/0/1/0/all/0/1">P. Didelon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Duarte_Cabral_A/0/1/0/all/0/1">A. Duarte-Cabral</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Palmeirim_P/0/1/0/all/0/1">P. Palmeirim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pezzuto_S/0/1/0/all/0/1">S. Pezzuto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reveret_V/0/1/0/all/0/1">V. Rev&#xe9;ret</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Roussel_H/0/1/0/all/0/1">H. Roussel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shimajiri_Y/0/1/0/all/0/1">Y. Shimajiri</a> The mass growth of protostars is a central element to the determination of fundamental stellar population properties such as the initial mass function. Constraining the accretion history of individual protostars is therefore an important aspect of star formationRead More →

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Towards an automatic processing of CCD images with CPCS 2.0. (arXiv:2006.05160v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Zielinski_P/0/1/0/all/0/1">Pawel Zielinski</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Wyrzykowski_L/0/1/0/all/0/1">Lukasz Wyrzykowski</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Mikolajczyk_P/0/1/0/all/0/1">Przemyslaw Mikolajczyk</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Rybicki_K/0/1/0/all/0/1">Krzysztof Rybicki</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Kolaczkowski_Z/0/1/0/all/0/1">Zbigniew Kolaczkowski</a> (2,3,4) (1. Astronomical Observatory, University of Warsaw, 2. Astronomical Institute, University of Wroclaw, 3. Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, 4. deceased) We present a new automatic tool for time-domain astronomy – the Cambridge Photometric Calibration Server 2.0 – developed under OPTICON H2020 programme. It has been designed to respond to the need of automated rapid photometric data calibration and dissemination for transient events, primarily from Gaia space mission. CPCS has beenRead More →

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Method to study the “traces” of coronal mass ejections Scientists at Skolkovo Institute of Science and Technology (skoltech), together with colleagues from the Karl-Franzens University of Graz and the Kanzelhoehe Observatory (Austria), have developed an automatic method for detecting coronal dimmings, or traces of coronal mass ejections from the sun; they have also proved that these are reliable indicators of the early diagnosis of powerful emissions of energy from the atmosphere of the sun traveling to Earth at great speed. The results of the study are published in the Astrophysical Journal. phys.org Go to SourceRead More →

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Astronomers observe X-ray reactivation of the magnetar SGR 1935+2154 Using NASA’s Swift and NuSTAR spacecraft, together with NICER instrument onboard the International Space Station, astronomers from Spain and Italy have performed an X-ray monitoring of a magnetar known as SGR 1935+2154. The new observations found that the source has once again became active, this time in the X-ray band. Results of the study were presented May 30 in a prepublished paper on arXiv.org. phys.org Go to SourceRead More →

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Preparations complete in western Australia for construction of world’s largest telescope Following seven years of design and prototyping work, the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) has completed its preparations for the construction of the Square Kilometre Array (SKA) in Western Australia, which will begin next year. phys.org Go to SourceRead More →

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Hubble Photo of Globular Cluster NGC 6441, One of the Most Massive in the Milky Way The Hubble Space Telescope has delivered another outstanding image. This one is of NGC 6441, a massive globular cluster in the constellation Scorpius. It’s one of the most massive ones in the Milky Way, and the stars in it have a combined mass of 1.6 million solar masses. NGC 6441 is a gorgeous visual spectacle. … Continue reading “Hubble Photo of Globular Cluster NGC 6441, One of the Most Massive in the Milky Way” The post Hubble Photo of Globular Cluster NGC 6441, One of the Most Massive inRead More →

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Astronomers Have Found the Star/Exoplanet Combo That’s the Best Twin to the Sun/Earth At times, it seems like there’s an indundation of announcements featuring discoveries of “Earth-like” planets. And while those announcements are exciting, and scientifically noteworthy, there’s always a little question picking away at them: exactly how Earth-like are they, really? After all, Earth is defined by its relationship with the Sun. There’s no strict definition of … Continue reading “Astronomers Have Found the Star/Exoplanet Combo That’s the Best Twin to the Sun/Earth” The post Astronomers Have Found the Star/Exoplanet Combo That’s the Best Twin to the Sun/Earth appeared first on Universe Today. UniverseRead More →

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Is the Concept of a Habitable Zone Too Wide? Exoplanets are often considered potentially habitable if they could have liquid water. But the necessities of biology set the habitability bar a bit higher. The post Is the Concept of a Habitable Zone Too Wide? appeared first on Universe Today. Universe Today Go to SourceRead More →

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Rocks on Bennu are Cracking Because of the Constant Day/Night Cycling Asteroid Bennu is blanketed by rocks and huge boulders. And now that the OSIRIS-REx spacecraft is taking a close look at those rocks, researchers are able to see something surprising for an airless body: the rocks have tiny cracks and fissures.   The cause? Most likely the cracks are from wide variations in temperatures, with … Continue reading “Rocks on Bennu are Cracking Because of the Constant Day/Night Cycling” The post Rocks on Bennu are Cracking Because of the Constant Day/Night Cycling appeared first on Universe Today. Universe Today Go to SourceRead More →

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Close-up view reveals binary proto-stars in the process of assemblage High-resolution observations of a young star forming system clearly unveil a pair of proto-stars at their earliest stages of evolution deeply embedded within the source IRAS 16293-2422 in the Ophiuchus molecular cloud. The team led by the Max Planck Institute for Extraterrestrial Physics used the ALMA interferometer not only to pin down the source configuration, but also to measure the gas and stellar kinematics, determining the mass of the young binary. The two close proto-stars are somewhat heavier than previously thought and they revolve around each other once in about 400 years. phys.org Go toRead More →

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Alternating flows and a high-latitude eastward jet explain Saturn’s polar hexagon, researchers report A pair of researchers at Harvard University has developed a computer simulation that may explain Saturn’s mysterious polar hexagon. In their paper published in Proceedings of the National Academy of Sciences, Rakesh Yadav and Jeremy Bloxham describe the factors that went into developing their simulation and what it showed. phys.org Go to SourceRead More →

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At the heart of the Milky Way, stars draw closer, threatening planets in their orbit At the center of our galaxy resides the galactic bulge, a densely packed region of stars, dust and gas. Within this massive structure, which spans thousands of light-years, there are an estimated 10 billion stars, most of which are old red giant stars. Because of this density, astronomers have often wondered if a galactic bulge is a likely place to find stars with habitable planets orbiting them. phys.org Go to SourceRead More →

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In: arXiv

How Well Can We Measure the Stellar Mass of a Galaxy: The Impact of the Assumed Star Formation History Model in SED Fitting. (arXiv:2006.03599v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Lower_S/0/1/0/all/0/1">Sidney Lower</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Narayanan_D/0/1/0/all/0/1">Desika Narayanan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Leja_J/0/1/0/all/0/1">Joel Leja</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Johnson_B/0/1/0/all/0/1">Benjamin D. Johnson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Conroy_C/0/1/0/all/0/1">Charlie Conroy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dave_R/0/1/0/all/0/1">Romeel Dav&#xe9;</a> The primary method for inferring the stellar mass ($M_*$) of a galaxy is through spectral energy distribution (SED) modeling. However, the technique rests on assumptions such as the galaxy star formation history and dust attenuation law that can severely impact the accuracy of derived physical properties from SED modeling. Here, we examine the effect that the assumed star formation history (SFH)Read More →