scholarly journals Discovery of a Magnetic White Dwarf/Probable Brown Dwarf Short-Period Binary

2005 ◽  
Vol 630 (2) ◽  
pp. L173-L176 ◽  
Author(s):  
Gary D. Schmidt ◽  
Paula Szkody ◽  
Nicole M. Silvestri ◽  
Michael C. Cushing ◽  
James Liebert ◽  
...  
Keyword(s):  
White Dwarf ◽  
Brown Dwarf ◽  
Short Period

scholarly journals The Search for Close Binary Evolved Stars

1989 ◽  
Vol 114 ◽  
pp. 408-412
Author(s):  
Rex A. Saffer ◽  
James Liebert
Keyword(s):  
Binary System ◽  
White Dwarf ◽  
White Dwarfs ◽  
Binary Systems ◽  
Close Binary ◽  
Brown Dwarf ◽  
Null Results ◽  
Spectroscopic Observations ◽  
Evolved Stars ◽  
Short Period

AbstractWe report on a search for short-period binary systems composed of pairs of evolved stars. The search is being carried out concurrently with a program to characterize the kinematical properties of two different samples of stars. Each sample has produced one close binary candidate for which further spectroscopic observations are planned. We also recapitulate the discovery of a close detached binary system composed of two cool DA white dwarfs, and we discuss the null results of Hα observations of the suspected white dwarf/brown dwarf system G 29–38.

scholarly journals Simplified 3D GCM modelling of the irradiated brown dwarf WD 0137−349B

2020 ◽  
Vol 496 (4) ◽  
pp. 4674-4687 ◽  
Author(s):  
Graham K H Lee ◽  
Sarah L Casewell ◽  
Katy L Chubb ◽  
Mark Hammond ◽  
Xianyu Tan ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
White Dwarf ◽  
Near Infrared ◽  
Circulation Model ◽  
Dual Band ◽  
Phase Curve ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Brown Dwarf ◽  
Short Period

ABSTRACT White dwarf–brown dwarf short-period binaries (Porb ≲ 2 h) are some of the most extreme irradiated atmospheric environments known. These systems offer an opportunity to explore theoretical and modelling efforts of irradiated atmospheres different to typical hot Jupiter systems. We aim to investigate the three-dimensional (3D) atmospheric structural and dynamical properties of the brown dwarf WD 0137−349B. We use the 3D global circulation model (GCM) Exo-Flexible Modelling System (FMS) with a dual-band grey radiative transfer scheme to model the atmosphere of WD 0137−349B. The results of the GCM model are post-processed using the 3D Monte Carlo radiative transfer model cmcrt. Our results suggest inefficient day–night energy transport and a large day–night temperature contrast for WD 0137−349B. Multiple flow patterns are present, shifting energy asymmetrically eastward or westward depending on their zonal direction and latitude. Regions of overturning are produced on the western terminator. We are able to reproduce the start of the system near-infrared (IR) emission excess at ≳1.95 μm as observed by the Gemini Near-Infrared Spectrograph (GNIRS) instrument. Our model overpredicts the IR phase curve fluxes by factors of ≈1–3, but generally fits the shape of the phase curves well. Chemical kinetic modelling using vulcan suggests a highly ionized region at high altitudes can form on the dayside of the brown dwarf. We present a first attempt at simulating the atmosphere of a short-period white dwarf–brown dwarf binary in a 3D setting. Further studies into the radiative and photochemical heating from the ultraviolet irradiation are required to more accurately capture the energy balance inside the brown dwarf atmosphere. Cloud formation may also play an important role in shaping the emission spectra of the brown dwarf.

New line profiles of sodium and potassium perturbed by helium for brown dwarf and very cool white dwarf stars

2008 ◽  
Author(s):  
M. Christova ◽  
N. F. Allard ◽  
J. F. Kielkopf ◽  
D. Homeier ◽  
F. Allard ◽  
...  
Keyword(s):  
White Dwarf ◽  
Line Profiles ◽  
Brown Dwarf ◽  
Dwarf Stars ◽  
White Dwarf Stars ◽  
Sodium And Potassium

scholarly journals The nature of the close magnetic white dwarf + probable brown dwarf binary SDSS J121209.31+013627.7*

2006 ◽  
Vol 373 (4) ◽  
pp. 1416-1422 ◽  
Author(s):  
M. R. Burleigh ◽  
T. R. Marsh ◽  
B. T. Gänsicke ◽  
M. R. Goad ◽  
V. S. Dhillon ◽  
...  
Keyword(s):  
White Dwarf ◽  
Brown Dwarf

scholarly journals Hunting for brown dwarfs in the globular cluster M4: second epoch HST NIR observations

2019 ◽  
Vol 486 (2) ◽  
pp. 2254-2264 ◽  
Author(s):  
A Dieball ◽  
L R Bedin ◽  
C Knigge ◽  
M Geffert ◽  
R M Rich ◽  
...  
Keyword(s):  
Globular Cluster ◽  
White Dwarf ◽  
Near Infrared ◽  
Magnitude Estimate ◽  
Cluster Member ◽  
Imaging Data ◽  
Brown Dwarf ◽  
Data Set ◽  
Bona Fide ◽  
Low Mass

ABSTRACT We present an analysis of the second epoch Hubble Space TelescopeWide Field Camera 3 F110W near-infrared (NIR) imaging data of the globular cluster M 4. The new data set suggests that one of the previously suggested four brown dwarf candidates in this cluster is indeed a high-probability cluster member. The position of this object in the NIR colour–magnitude diagrams (CMDs) is in the white dwarf/brown dwarf area. The source is too faint to be a low-mass main-sequence (MS) star, but, according to theoretical considerations, also most likely somewhat too bright to be a bona-fide brown dwarf. Since we know that the source is a cluster member, we determined a new optical magnitude estimate at the position the source should have in the optical image. This new estimate places the source closer to the white dwarf sequence in the optical–NIR CMD and suggests that it might be a very cool (Teff ≤ 4500 K) white dwarf at the bottom of the white dwarf cooling sequence in M 4, or a white dwarf/brown dwarf binary. We cannot entirely exclude the possibility that the source is a very massive, bright brown dwarf, or a very low-mass MS star, however, we conclude that we still have not convincingly detected a brown dwarf in a globular cluster, but we expect to be very close to the start of the brown dwarf cooling sequence in this cluster. We also note that the MS ends at F110W ≈ 22.5 mag in the proper-motion cleaned CMDs, where completeness is still high.

scholarly journals Constraints on the Atmospheric Parameters of the Binary DA White Dwarf L870-2 (EG11)

1989 ◽  
Vol 114 ◽  
pp. 435-439
Author(s):  
P. Bergeron ◽  
F. Wesemael ◽  
J. Liebert ◽  
G. Fontaine ◽  
P. Lacombe
Keyword(s):  
Observational Data ◽  
Stellar Evolution ◽  
Effective Temperature ◽  
White Dwarf ◽  
Binary Systems ◽  
Absolute Magnitude ◽  
Atmospheric Parameters ◽  
Spectroscopic Binary ◽  
Short Period ◽  
Period System

The recent discovery that the cool DA white dwarf L870-2 (EG11, WD0135-052) is a double-lined spectroscopic binary composed of a detached pair of DA white dwarfs (Saffer, Liebert, and Olszewski 1988, SLO hereafter) has raised some challenging problems for stellar evolution theories of such binary systems. One first important step in the understanding of this short-period system is to establish the atmospheric parameters of each component. SLO have argued from previous determinations of the effective temperature and absolute magnitude of the system, and also from their own study of the composite Hα profile, that the two components should be similar. We wish here to reexamine this assertion by taking a new look at the constraints on the two components brought about by the available observational data.

scholarly journals Mid-Infrared Observations of the White Dwarf-Brown Dwarf Binary GD 1400

2005 ◽  
Vol 130 (5) ◽  
pp. 2237-2240 ◽  
Author(s):  
J. Farihi ◽  
B. Zuckerman ◽  
E. E. Becklin
Keyword(s):  
White Dwarf ◽  
Brown Dwarf ◽  
Mid Infrared ◽  
Infrared Observations

scholarly journals Erratum: ALMA reveals the aftermath of a white dwarf–brown dwarf merger in CK Vulpeculae

2019 ◽  
Author(s):  
S P S Eyres ◽  
A Evans ◽  
A Zijlstra ◽  
A Avison ◽  
R D Gehrz ◽  
...  
Keyword(s):  
White Dwarf ◽  
Brown Dwarf

scholarly journals Environmental effects on the ionisation of brown dwarf atmospheres

2018 ◽  
Vol 618 ◽  
pp. A107 ◽  
Author(s):  
M. I. Rodríguez-Barrera ◽  
Ch. Helling ◽  
K. Wood
Keyword(s):  
White Dwarf ◽  
Binary Systems ◽  
Brown Dwarfs ◽  
High Energy ◽  
Radiation Environment ◽  
Brown Dwarf ◽  
Star Forming ◽  
Star Forming Regions ◽  
Lyman Continuum ◽  
Low Mass

Context. Brown dwarfs emit bursts of Hα, white-light flares, and show radio flares and quiescent radio emission. They are suggested to form aurorae, similar to planets in the solar system, but much more energetic. All these processes require a source gas with an appropriate degree of ionisation, which, so far, is mostly postulated to be sufficient. Aims. We aim to demonstrate that the Galactic environment influences atmospheric ionisation, and that it hence amplifies or enables the magnetic coupling of the atmospheres of ultra-cool objects, like brown dwarfs and free-floating planets. Methods. We build on our previous work on thermal ionisation of ultra-cool atmospheres and explore the effect of environmental high-energy radiation on the degree of ionisation in the atmosphere. We consider the effect of photoionisation by Lyman-continuum radiation in three different environments: in the interstellar radiation field (ISRF), O and B stars in star-forming regions, and in white dwarf companions in binary systems. We apply our Monte Carlo radiation transfer code to investigate the effect of Lyman-continuum photoionisation for prescribed atmosphere structures for very low-mass objects. Results. The external radiation environment plays an important role for the atmospheric ionisation of very low-mass, ultra-cool objects. Lyman-continuum irradiation greatly increases the level of ionisation in the uppermost atmospheric regions. Our results suggest that a shell of an almost fully ionised atmospheric gas emerges for brown dwarfs in star-forming regions and brown dwarfs in white dwarf binary systems. As a consequence, brown dwarf atmospheres can be magnetically coupled, which is the presumption for chromospheric heating to occur and for aurorae to emerge. First tests for assumed chromosphere-like temperature values suggest that the resulting free-free X-ray luminosities are comparable with those observed from non-accreting brown dwarfs in star-forming regions.

Sign in / Sign up

Export Citation Format

Share Document