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To Be or Not to Be: Alicante-8, a Cluster or Not?
Rejkuba, M.; Negueruela, I.; Ivanov, V. D. +3 more
Recent surveys have uncovered new young massive clusters that host dozens of red supergiants (RSGs) near the inner Galaxy. However, many of them have still not been fully studied. Using Very Large Telescope/X-shooter near-infrared spectra, we present the first radial velocity analysis for the putative members of the candidate RSG cluster Alicante-…
A Wide View of the Galactic Globular Cluster NGC 2808: Red Giant and Horizontal Branch Star Spatial Distributions
Rest, Armin; Mastrobuono-Battisti, Alessandra; Johnson, Christian I. +7 more
Wide-field and deep DECam multiband photometry, combined with HST data for the core of the Galactic globular cluster NGC 2808, allowed us to study the distribution of various stellar subpopulations and stars in different evolutionary phases out to the cluster tidal radius. We used the C ugi = (u - g) - (g - i) index to identify three …
Stable Coronal X-Ray Emission over 20 yr of XZ Tau
Schneider, P. C.; Principe, David A.; Wolk, Scott J. +3 more
XZ Tau AB is a frequently observed binary young stellar object in the Taurus Molecular Cloud; XZ Tau B has been classified as an EXOr object. We present new Chandra/HETG-ACIS-S observations of XZ Tau AB, complemented with variability monitoring of the system with XMM-Newton, to constrain the variability of this system and identify high-resolution …
Precise Age for the Binary Star System 12 Com in the Coma Berenices Cluster
Klement, Robert; Monnier, John D.; Schaefer, Gail H. +11 more
We present measurements of the interferometrically resolved binary star system 12 Com and the single giant star 31 Com in the cluster Coma Berenices. 12 Com is a double-lined spectroscopic binary system consisting of a G7 giant and an A3 dwarf at the cluster turnoff. Using an extensive radial velocity data set and interferometric measurements from…
Active Asteroid 311P/PanSTARRS: Rotational Instability as the Origin of its Multitails?
Li, Fei; Liu, Bin; Liu, Xiaodong +3 more
The active asteroid 311P/PanSTARRS is one of the two targets of the planned Chinese asteroid exploration mission Tianwen-2. During 2013, 311P experienced several mass-loss events and exhibited multiple comet-like tails. Here we analyze the morphology and surface brightness of the tails to investigate the dust environment around the nucleus and the…
Investigating Stellar Variability in the Open Cluster Region NGC 381
Joshi, Y. C.; Panchal, A.; Maurya, Jayanand +1 more
We study variable stars in the field of the open cluster NGC 381 using photometric data observed over 27 nights and identify a total of 57 variable stars, six of which are member stars. The variable stars are classified based on their periods, amplitudes, light-curve shapes, and locations in the H-R diagram. We found a rich variety of variable sta…
Astrometric Calibration of the Beijing-Arizona Sky Survey
Fan, Xiaohui; Jiang, Linhua; Dey, Arjun +13 more
We present the astrometric calibration of the Beijing-Arizona Sky Survey (BASS). The BASS astrometry was tied to the International Celestial Reference Frame via the Gaia Data Release 2 reference catalog. For effects that were stable throughout the BASS observations, including differential chromatic refraction and the low charge transfer efficiency…
A uvbyCaHβ CCD Analysis of the Open Cluster Standard, M67, and Its Relation to NGC 752
Twarog, Bruce A.; Anthony-Twarog, Barbara J.; Deliyannis, Constantine P.
Precision CCD uvbyCaHβ photometry is presented of the old cluster, M67, covering one square degree with typical internal precision at the 0.005-0.020 mag level to V ~ 17. The photometry is calibrated using standards over a wide range in luminosity and temperature from NGC 752 and zeroed to the standard system via published photoelectric observatio…
Robust Estimates of Orientation between Astrometric Catalogs
Frouard, Julien
Accurately comparing two celestial reference frames based on the observed position of a number of common objects requires to detect and appropriately process outliers, lest they spuriously influence the results. It is thus of practical importance to use algorithms able to minimize the impact of those outliers when comparing radio and/or optical as…
Validation of TOI-1221 b: A Warm Sub-Neptune Exhibiting Transit Timing Variations around a Sun-like Star
Kristiansen, Martti H.; Torres, Guillermo; Hellier, Coel +25 more
We present a validation of a long-period ( ${91.68278}_{-0.00041}^{+0.00032}$ days) transiting sub-Neptune planet, TOI-1221 b (TIC 349095149.01), around a Sun-like (m V = 10.5) star. This is one of the few known exoplanets with a period >50 days, and belongs to the even smaller subset of which have bright enough hosts for detailed …