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Machine-learning Regression of Extinction in the Second Gaia Data Release
Bai, Yu; Wang, Song; Liu, JiFeng +1 more
Machine learning has become a popular tool to help us make better decisions and predictions, based on experiences, observations, and analyzing patterns, within a given data set without explicit functions. In this paper, we describe an application of the supervised machine-learning algorithm to the extinction regression for the second Gaia data rel…
Physical Conditions of Gas Components in Debris Disks of 49 Ceti and HD 21997
Moór, Attila; Kóspál, Ágnes; Nomura, Hideko +2 more
Characterization of the gas component in debris disks is of fundamental importance for understanding their origin. To address this goal, we have conducted non-LTE (local thermodynamic equilibrium) analyses of the rotational spectral lines of CO including those of rare isotopologues (13CO and C18O) that have been observed towa…
Geometry of the Draco C1 Symbiotic Binary
Sarazin, Craig L.; Cunha, Katia; Smith, Verne V. +14 more
Draco C1 is a known symbiotic binary star system composed of a carbon red giant and a hot, compact companion—likely a white dwarf—belonging to the Draco dwarf spheroidal galaxy. From near-infrared spectroscopic observations taken by the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2), part of Sloan Digital Sky Survey IV, we provi…
Subaru Near-infrared Imaging Polarimetry of Misaligned Disks around the SR 24 Hierarchical Triple System
Henning, Thomas; Nakagawa, Takao; Terada, Hiroshi +66 more
The SR 24 multistar system hosts both circumprimary and circumsecondary disks, which are strongly misaligned with each other. The circumsecondary disk is circumbinary in nature. Interestingly, both disks are interacting, and they possibly rotate in opposite directions. To investigate the nature of this unique twin disk system, we present 0.″1 reso…
Distorted surfaces of magnetic helium-peculiar stars: an application to a Cen
Niemczura, E.; Leone, F.; Krtička, J. +3 more
Helium-peculiar magnetic chemically peculiar stars show variations of helium abundance across their surfaces. As a result of associated atmospheric scale height variations, the stellar surface becomes distorted, with helium-rich regions dented inwards. Effectively, on top of flux variations due to opacity effects, the depressed helium-rich surface…
EVR-CB-004: An Inflated Hot Subdwarf O Star + Unseen WD Companion in a Compact Binary Discovered with the Evryscope
Law, Nicholas M.; Kupfer, Thomas; Glazier, Amy +10 more
We present the discovery of EVR-CB-004, a close binary with a remnant stellar core and an unseen white dwarf (WD) companion. The analysis in this work reveals that the primary is potentially an inflated hot subdwarf (sdO) and more likely is a rarer post-blue horizontal branch (post-BHB) star. Post-BHBs are the short-lived shell-burning final stage…
Colour-colour and colour-magnitude diagrams for hot Jupiters
Bailey, J.; Melville, G.; Kedziora-Chudczer, L.
We use ground-based and space-based eclipse measurements for the near-infrared (IR) bands (JHKs) and Spitzer 3.6- and 4.5-µm bands to construct colour-colour and colour-magnitude diagrams for hot Jupiters. We compare the results with previous observations of substellar objects and find that hot Jupiters, when corrected for their i…
Analysis of Close Stellar Encounters with the Solar System
Bobylev, V. V.; Bajkova, A. T.
We consider 36 candidates for close (within 1 pc) encounters with the Solar system. These stars have been selected in accordance with the results of an analysis of their motion obtained by various authors. For most stars from this list the kinematic characteristics have been taken from the Gaia DR2 catalogue. The parameters of the encounters of th…
Solar Filaments and Interplanetary Magnetic Field Bz
Martens, Petrus C.; Aparna, V.
The direction of the axis of an interplanetary coronal mass ejection (ICME) plays an important role in determining if it will cause a geomagnetic disturbance in the Earth's magnetosphere upon impact. Long period southward-pointing ICME fields are known to cause significant space weather impacts and thus geomagnetic storms. We present an extensive …
A New Transition Wolf-Rayet WN/C Star in the Milky Way
Shi, Jianrong; Zhang, Tianmeng; Todt, Helge +7 more
We report the discovery of a new transition type Wolf-Rayet (W-R) WN/C star in the Galaxy. According to its coordinates (R.A., decl.)J2000 = ${18}^{{\rm{h}}}{51}^{{\rm{m}}}39\buildrel{\rm{s}}\over{.} 7$ , -05°34'51"1, and the distance (7.11 ${}_{-1.22}^{+1.56}\,$ kpc away from Earth) inferred from the second Gaia data release, it is fou…