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To TDE or not to TDE: the luminous transient ASASSN-18jd with TDE-like and AGN-like qualities
Gromadzki, M.; Kochanek, C. S.; Foley, R. J. +26 more
We present the discovery of ASASSN-18jd (AT 2018bcb), a luminous optical/ultraviolet(UV)/X-ray transient located in the nucleus of the galaxy 2MASX J22434289-1659083 at z = 0.1192. Over the year after discovery, Swift UltraViolet and Optical Telescope (UVOT) photometry shows the UV spectral energy distribution of the transient to be well modelled …
Hic sunt dracones: Cartography of the Milky Way spiral arms and bar resonances with Gaia Data Release 2
Katz, D.; Haywood, M.; Gerhard, O. +5 more
In this paper we introduce a new method for analysing Milky Way phase-space which allows us to reveal the imprint left by the Milky Way bar and spiral arms on the stars with full phase-space data in Gaia Data Release 2. The unprecedented quality and extended spatial coverage of these data allowed us to discover six prominent stellar density struct…
The Gaia reference frame for bright sources examined using VLBI observations of radio stars
Lindegren, Lennart
Context. Positions and proper motions of Gaia sources are expressed in a reference frame that ideally should be non-rotating relative to distant extragalactic objects, coincident with the International Celestial Reference System (ICRS), and consistent across all magnitudes. For sources fainter than 16th magnitude, this is achieved through Gaia's d…
Fundamental parameters for 45 open clusters with Gaia DR2, an improved extinction correction and a metallicity gradient prior
Cantat-Gaudin, T.; Moitinho, A.; Paunzen, E. +4 more
Reliable fundamental parameters of open clusters (OCs) such as distance, age, and extinction are key to our understanding of Galactic structure and stellar evolution. In this work, we use Gaia Data Release 2 (DR2) to investigate 45 OCs listed in the New catalogue of optically visible open clusters and candidates (DAML) but with no previous astrome…
Nondetection of Helium in the Upper Atmospheres of Three Sub-Neptune Exoplanets
Désert, Jean-Michel; Mansfield, Megan; Kasper, David +5 more
We present a search for helium in the upper atmospheres of three sub-Neptune-sized planets to investigate the origins of these ubiquitous objects. The detection of helium for a low-density planet would be strong evidence for the presence of a primary atmosphere accreted from the protoplanetary nebula because large amounts of helium are not expecte…
Are inner disc misalignments common? ALMA reveals an isotropic outer disc inclination distribution for young dipper stars
Tazzari, M.; Williams, J. P.; Ansdell, M. +12 more
Dippers are a common class of young variable star exhibiting day-long dimmings with depths of up to several tens of per cent. A standard explanation is that dippers host nearly edge-on (Id ≈ 70°) protoplanetary discs that allow close-in (<1 au) dust lifted slightly out of the mid-plane to partially occult the star. The identification…
Varstrometry for Off-nucleus and Dual Subkiloparsec AGN (VODKA): Methodology and Initial Results with Gaia DR2
Shen, Yue; Hwang, Hsiang-Chih; Liu, Xin +1 more
Gaia’s precision astrometry allows systematic identification of optically selected subkiloparsec dual active galactic nuclei (AGNs), off-nucleus AGNs, and small-scale lensed quasars by “varstrometry”—where variability-induced astrometric jitter, I.e., temporal displacements of photocenter in unresolved sources, can be reasonably well detected or c…
Globular clusters in the inner Galaxy classified from dynamical orbital criteria
Barbuy, Beatriz; Bica, Eduardo; Pérez-Villegas, Angeles +3 more
Globular clusters (GCs) are the most ancient stellar systems in the Milky Way. Therefore, they play a key role in the understanding of the early chemical and dynamical evolution of our Galaxy. Around 40 per cent of them are placed within ∼4 kpc from the Galactic centre. In that region, all Galactic components overlap, making their disentanglement …
Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602
Barbieri, M.; Henning, T.; Winn, J. N. +42 more
We report the discovery of TOI 837b and its validation as a transiting planet. We characterize the system using data from the NASA Transiting Exoplanet Survey Satellite mission, the ESA Gaia mission, ground-based photometry from El Sauce and ASTEP400, and spectroscopy from CHIRON, FEROS, and Veloce. We find that TOI 837 is a T = 9.9 mag G0/F9 dwar…
Three Lyα Emitting Galaxies within a Quasar Proximity Zone at z ∼ 5.8
Ellis, Richard S.; Bosman, Sarah E. I.; Meyer, Romain A. +3 more
Quasar proximity zones at $z\gt 5.5$ correspond to overdense and overionized environments. Galaxies found inside proximity zones can therefore display features that would otherwise be masked by absorption in the intergalactic medium. We demonstrate the utility of this quasar-galaxy synergy by reporting the discovery of the first three "proximate L…