Discovery of new members of the nearby young stellar association in Cepheus

Abstract

Context. Young field stars are hardly distinguishable from older ones because their space motion rapidly mixes them with the stellar population of the Galactic plane. Nevertheless, a careful target selection allows for young stars to be spotted throughout the sky. Aims. We aim to identify additional sources associated with the four young comoving stars that we discovered towards the CO Cepheus void and to provide a comprehensive view of the Cepheus association. Methods. Based on multivariate analysis methods, we have built an extended sample of 193 young star candidates, which are the optical and infrared counterparts of ROSAT All-Sky Survey and XMM-Newton X-ray sources. From optical spectroscopic observations, we measured their radial velocity with the cross-correlation technique. We derived their atmospheric parameters and projected rotational velocity with the code ROTFIT. We applied the subtraction of inactive templates to measure the lithium equivalent width, from which we infer their lithium abundance and age. Finally, we studied their kinematics using the second Gaia data release. Results. Our sample is mainly composed of young or active stars and multiple systems. We identify two distinct populations of young stars that are spatially and kinematically separated. Those with an age between 100 and 300 Myr are mostly projected towards the Galactic plane. In contrast, 23 of the 37 sources younger than 30 Myr are located in the CO Cepheus void, and 21 of them belong to the stellar kinematic group that we previously reported in this sky area. We report a total of 32 bona fide members and nine candidates for this nearby (distance = 157 ± 10 pc) young (age = 10–20 Myr) stellar association. According to the spatial distribution of its members, the original cluster is already dispersed and partially mixed with the local population of the Galactic plane.

SRG/ART-XC all-sky X-ray survey: Catalog of sources detected during the first year

“…Likely associated with the bright star Gaia EDR3 576260267526450048, a spectroscopic binary in a young stellar association (Klutsch et al 2020). Hence, likely a coronally active star.…”

SRG/ART-XC all-sky X-ray survey: Catalog of sources detected during the first year

“…Likely associated with bright star Gaia EDR3 576260267526450048, a spectroscopic binary in a young stellar association (Klutsch et al 2020). Hence, likely a coronally active star.…”

Exoplanet Detection and Its Dependence on Stochastic Sampling of the Stellar Initial Mass Function

“…The thicker portions of the error bars indicate the interquartile range, and the median values from the IMF sampling are indicated by the horizontal lines. Our motivation for this approach is to ask what the range of magma ocean detection probabilities could be due to sampling an IMF, and therefore what the range of detection probabilities would be for any hypothetical YMGs that may be newly discovered by, e.g., GaiaDR2, or later data releases (e.g., Liu et al 2020), or if the membership of existing YMGs is significantly augmented by new detections (e.g., Binks et al 2020;Klutsch et al 2020).…”

“…Most stars form in groups (often loosely referred to as clusters) with membership ranging between 10 s and 10 4 stars (Lada & Lada 2003). It is thought that planets form from circumstellar disks of dust and gas almost immediately after star formation, and certainly during the earliest stages of a premain-sequence star's life (Haisch et al 2001;ALMA Partnership et al 2015;Richert et al 2018).…”