BANYAN. V. A SYSTEMATIC ALL-SKY SURVEY FOR NEW VERY LATE-TYPE LOW-MASS STARS AND BROWN DWARFS IN NEARBY YOUNG MOVING GROUPS

AbstractWe describe in this work the BASS survey for brown dwarfs in young moving groups of the solar neighborhood, and summarize the results that it generated. These include the discovery of the 2MASS J01033563–5515561 (AB)b and 2MASS J02192210–3925225 B young companions near the deuterium-burning limit as well as 44 new low-mass stars and 69 new brown dwarfs with a spectroscopically confirmed low gravity. Among those, ~20 have estimated masses within the planetary regime, one is a new L4 γ bona fide member of AB Doradus, three are TW Hydrae candidates with later spectral types (L1–L4) than all of its previously known members and six are among the first contenders for low-gravity ≥ L5 β/γ brown dwarfs, reminiscent of WISEP J004701.06+680352.1, PSO J318.5338–22.8603 and VHS J125601.92–125723.9 b. Finally, we describe a future version of this survey, BASS-Ultracool, that will specifically target ≥ L5 candidate members of young moving groups. First experimentations in designing the survey have already led to the discovery of a new T dwarf bona fide member of AB Doradus, as well as the serendipitous discoveries of an L9 subdwarf and an L5 + T5 brown dwarf binary.

Download Full-text

Primeval very low-mass stars and brown dwarfs – VII. The discovery of the first wide M + L extreme subdwarf binary

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2196 ◽

2019 ◽

Vol 489 (1) ◽

pp. 1423-1435 ◽

Cited By ~ 1

Author(s):

ZengHua Zhang (张曾华)

Keyword(s):

Binary System ◽

White Dwarf ◽

High Surface ◽

Brown Dwarfs ◽

Mass Range ◽

Surface Gravity ◽

Late Type ◽

Low Mass Stars ◽

Classification Schemes ◽

Low Mass

ABSTRACT I present the discovery of the first wide M + L extreme subdwarf binary system Gaia J0452−36AB. The binary is located at a distance of 137.27 $^{+0.68}_{-0.67}$ pc with a projected separation of 15828 ± 78 au. I classified Gaia J0452−36AB as esdM1 and esdL0 subdwarfs, respectively. Gaia J0452−36AB have typical halo kinematics, metallicity of [Fe/H] ≈−1.4, and temperature of ∼ 3550 and 2600 K, respectively. Gaia J0452−36AB is a pair of very low-mass stars with masses of 0.151 $^{+0.029}_{-0.019}$ and 0.0855$^{+0.0014}_{-0.0010}$ M$\odot$, and is a gravitationally bound system. I tested the metallicity consistency of existing M subdwarf classification schemes with Gaia J0452−36AB and a sample of M and L subdwarfs with known metallicity. I found that the metallicity of each M subclass defined by the the metallicity index ζCaH/TiO is not consistent from mid-to-late M subtypes. Because late-type M and L subdwarfs have dusty atmospheres and high surface gravity which have significant impacts on CaH and TiO indices that used in the classification. The metallicity scale of late-type M subdwarfs would be overestimated by the ζCaH/TiO index. I discussed the mass range of M subdwarfs, and explained the lack of late-type M extreme and ultra subdwarfs, and decreasing binary fraction from sdM, to esdM, and usdM subclasses. The four M subclasses have different mass ranges. The comparison between M subclasses is between populations in different mass ranges. I also present the discovery of Ruiz 440-469B, an M8 dwarf wide companion to a cool DA white dwarf, Ruiz 440-469.

Download Full-text

A kinematically unbiased, all-sky search for nearby, young, low-mass stars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3019 ◽

2019 ◽

Vol 491 (1) ◽

pp. 215-234 ◽

Cited By ~ 2

Author(s):

Alexander S Binks ◽

Matthieu Chalifour ◽

Joel H Kastner ◽

David Rodriguez ◽

Simon J Murphy ◽

...

Keyword(s):

Young Star ◽

Photometric Data ◽

Young Stars ◽

Stellar Clusters ◽

Late Type ◽

Low Mass Stars ◽

Near Ir ◽

Field Star ◽

Low Mass ◽

Moving Groups

ABSTRACT The past two decades have seen dramatic progress in our knowledge of the population of young stars of age $\lt \!200\,$ Myr that lie within $150\,$ pc of the Sun. These nearby, young stars, most of which are found in loose, comoving groups, provide the opportunity to explore (among many other things) the dissolution of stellar clusters and their diffusion into the field star population. Here, we exploit the combination of astrometric and photometric data from Gaia and photometric data from GALEX (UV) and 2MASS (near-IR) in an attempt to identify additional nearby, young, late-type stars. Specifically, we present a sample of 146 GALEX UV-selected late-type (predominantly K-type) field stars with Gaia-based distances $\lt \!125\,$ pc (based on Gaia Data Release 1) that have isochronal ages $\lt \!80\,$ Myr even if equal-components binaries. We investigate the spectroscopic and kinematic properties of this sample. Despite their young isochronal ages, only ∼10 per cent of stars among this sample can be confidently associated with established nearby, young moving groups (MGs). These candidate MG members include five stars newly identified in this study. The vast majority of our sample of 146 nearby young star candidates have anomalous kinematics relative to the known MGs. These stars may hence represent a previously unrecognized population of young stars that has recently mixed into the older field star population. We discuss the implications and caveats of such a hypothesis – including the intriguing fact that, in addition to their non-young-star-like kinematics, the majority of the UV-selected, isochronally young field stars within $50\,$ pc appear surprisingly X-ray faint.

Download Full-text

A Review on Substellar Objects below the Deuterium Burning Mass Limit: Planets, Brown Dwarfs or What?

Geosciences ◽

10.3390/geosciences8100362 ◽

2018 ◽

Vol 8 (10) ◽

pp. 362 ◽

Cited By ~ 7

Author(s):

José Caballero

Keyword(s):

Brown Dwarfs ◽

Open Clusters ◽

Formation Mechanisms ◽

Mass Limit ◽

Low Mass Stars ◽

Open Clusters And Associations ◽

Substellar Objects ◽

History Of ◽

Low Mass ◽

Moving Groups

“Free-floating, non-deuterium-burning, substellar objects” are isolated bodies of a few Jupiter masses found in very young open clusters and associations, nearby young moving groups, and in the immediate vicinity of the Sun. They are neither brown dwarfs nor planets. In this paper, their nomenclature, history of discovery, sites of detection, formation mechanisms, and future directions of research are reviewed. Most free-floating, non-deuterium-burning, substellar objects share the same formation mechanism as low-mass stars and brown dwarfs, but there are still a few caveats, such as the value of the opacity mass limit, the minimum mass at which an isolated body can form via turbulent fragmentation from a cloud. The least massive free-floating substellar objects found to date have masses of about 0.004 Msol, but current and future surveys should aim at breaking this record. For that, we may need LSST, Euclid and WFIRST.

Download Full-text

Optical Spectroscopy of Young Brown Dwarfs in Orion

Symposium - International Astronomical Union ◽

10.1017/s0074180900210280 ◽

2003 ◽

Vol 211 ◽

pp. 69-70

Author(s):

Fiona C. Riddick ◽

Patrick F. Roche ◽

Philip W. Lucas

Keyword(s):

Optical Spectroscopy ◽

Spectral Characteristics ◽

Brown Dwarfs ◽

Late Type ◽

Low Mass Stars ◽

Cluster Membership ◽

Show Evidence ◽

Low Mass ◽

Orion Trapezium

Red spectra of a sample of low-mass stars and brown dwarfs in the Orion Trapezium cluster are discussed. They show late-type spectral characteristics confirming cluster membership and some show evidence of circumstellar activity.

Download Full-text

The Late-Type Extension to MoVeRS (LaTE-MoVeRS): Proper Motion Verified Low-mass Stars and Brown Dwarfs from SDSS, 2MASS, andWISE

The Astronomical Journal ◽

10.3847/1538-3881/153/3/92 ◽

2017 ◽

Vol 153 (3) ◽

pp. 92 ◽

Cited By ~ 10

Author(s):

Christopher A. Theissen ◽

Andrew A. West ◽

Guillaume Shippee ◽

Adam J. Burgasser ◽

Sarah J. Schmidt

Keyword(s):

Proper Motion ◽

Brown Dwarfs ◽

Late Type ◽

Low Mass Stars ◽

Low Mass ◽

Late Movers

Download Full-text

Very Low-Mass Stars and Brown Dwarfs

10.1017/cbo9780511564758 ◽

2000 ◽

Cited By ~ 2

Keyword(s):

Brown Dwarfs ◽

Low Mass Stars ◽

Low Mass

Download Full-text

Giant planets around AF and M stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313007898 ◽

2013 ◽

Vol 8 (S299) ◽

pp. 64-65

Author(s):

Julien Rameau ◽

Gaël Chauvin ◽

Anne-Marie Lagrange ◽

Philippe Delorme ◽

Justine Lannier

Keyword(s):

Giant Planets ◽

Early Type ◽

Late Type ◽

M Dwarfs ◽

Low Mass Stars ◽

Planetary Mass ◽

Nearby Stars ◽

Low Mass ◽

M Stars ◽

The One

AbstractWe present the results of two three-year surveys of young and nearby stars to search for wide orbit giant planets. On the one hand, we focus on early-type and massive, namely β Pictoris analogs. On the other hand, we observe late type and very low mass stars, i.e., M dwarfs. We report individual detections of new planetary mass objects. According to our deep detection performances, we derive the observed frequency of giant planets between these two classes of parent stars. We find frequency between 6 to 12% but we are not able to assess a/no correlation with the host-mass.

Download Full-text