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ABYSS. I. Targeting Strategy for the APOGEE and BOSS Young Star Survey in SDSS-V
Kounkel, Marina; Stringfellow, Guy; Rojas-Ayala, Bárbara +15 more
The fifth iteration of the Sloan Digital Sky Survey is set to obtain optical and near-infrared spectra of ~5 million stars of all ages and masses throughout the Milky Way. As a part of these efforts, APOGEE and BOSS Young Star Survey (ABYSS) will observe ~105 stars with ages <30 Myr that have been selected using a set of homogeneous …
Spiral arms and the angular momentum gap in Milky Way Cepheids
Schönrich, Ralph; Dehnen, Walter; Semczuk, Marcin +1 more
The angular momentum distribution of classical Cepheids in the outer Milky Way disc is bimodal with a gap at $L_\mathrm{gap}=2950\, \rm{km\,s^{-1}}$ kpc, corresponding to $R=13\,$ kpc, while no similar feature has been found in the general population of disc stars. We show that star formation in multiple spiral arm segments at the same azimuth lea…
Hubble Space Telescope survey of Magellanic Cloud star clusters: UV-dim stars in young clusters
Di Criscienzo, M.; Milone, A. P.; Cordoni, G. +11 more
Young and intermediate-age star clusters of both Magellanic Clouds exhibit complex colour-magnitude diagrams. In addition to the extended main-sequence turn-offs (eMSTOs), commonly observed in star clusters younger than ~2 Gyr, the clusters younger than ~800 Myr exhibit split main sequences (MSs). These comprise a blue MS, composed of stars with l…
Progenitor Constraint with Circumstellar Material for the Magnetar-hosting Supernova Remnant RCW 103
Uchida, Hiroyuki; Tsuru, Takeshi Go; Tanaka, Takaaki +2 more
Stellar winds blown out from massive stars (≳10 M ⊙) contain precious information on the progenitor itself, and in this context the most important elements are carbon (C), nitrogen (N), and oxygen (O), which are produced by the CNO cycle in the H-burning layer. Although their X-ray fluorescence lines are expected to be detected in swept…
Unbound stars hold the key to young star cluster history
Pfalzner, Susanne; Arunima, Arunima; Govind, Amith
Aims.Gaia delivers the positions and velocities of stars at an unprecedented precision. Therefore, for star clusters, there exists much higher confidence in whether a specific star is a member of a particular cluster or not. However, membership determination is still especially challenging for young star clusters. At ages 2−10 Myr, the gas is expe…
Late-time Hubble Space Telescope Observations of AT 2018cow. I. Further Constraints on the Fading Prompt Emission and Thermal Properties 50-60 days Post-discovery
Kilpatrick, Charles D.; Drout, Maria R.; Foley, Ryan J. +6 more
The exact nature of the luminous fast blue optical transient AT 2018cow is still debated. In this first of a two-paper series, we present a detailed analysis of three Hubble Space Telescope (HST) observations of AT 2018cow covering ~50-60 days post-discovery in combination with other observations throughout the first two months and derive signific…
BU Canis Minoris - the most compact known flat doubly eclipsing quadruple system
Powell, Brian P.; Borkovits, Tamás; Gagliano, Robert +25 more
We have found that the 2+2 quadruple star system BU CMi is currently the most compact quadruple system known, with an extremely short outer period of only 121 d. The previous record holder was TIC 219006972 (Kostov et al.), with a period of 168 d. The quadruple nature of BU CMi was established by Volkov, Kravtsova & Chochol, but they misidenti…
White Dwarfs with Infrared Excess from LAMOST Data Release 5
Wang, Lin; Gu, Wei-Min; Wang, Junfeng +5 more
Infrared (IR) excess is an important probe for substellar companions and/or debris disks around white dwarfs (WDs). Such systems are still rare, so an in-depth understanding of their formation and long-term evolution has yet to be developed. One of the largest spectroscopic surveys, carried out by the Large Sky Area Multi-Object Fibre Spectroscopi…
ELM of ELM-WD: An Extremely-low-mass Hot Star Discovered in LAMOST Survey
Chen, Xuefei; Li, Zhenwei; Zhang, Haotong +7 more
The extremely-low-mass white dwarfs (ELM WDs) and pre-ELM WDs are helium-core white dwarfs with mass <~ 0.3M ⊙. Evolution simulations show that a lower mass limit for ELM WDs exists at ≈0.14M ⊙ and no ELM WD is proposed by observation to be less massive than that. Here we report the discovery of a binary system, LAMOST J22…
TOI-1801 b: A temperate mini-Neptune around a young M0.5 dwarf
Nagel, E.; Amado, P. J.; Caballero, J. A. +79 more
We report the discovery, mass, and radius determination of TOI-1801 b, a temperate mini-Neptune around a young M dwarf. TOI-1801 b was observed in TESS sectors 22 and 49, and the alert that this was a TESS planet candidate with a period of 21.3 days went out in April 2020. However, ground-based follow-up observations, including seeing-limited phot…