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 NLTT5306B: an inflated, weakly irradiated brown dwarf

2020 ◽  
Vol 499 (4) ◽  
pp. 5318-5324
Author(s):  
S L Casewell ◽  
J Debes ◽  
I P Braker ◽  
M C Cushing ◽  
G Mace ◽  
...  
Keyword(s):  
Effective Temperature ◽  
White Dwarf ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Magnetic Interactions ◽  
Brown Dwarf ◽  
Primary Star ◽  
Brightness Temperatures ◽  
Night Side ◽  
Low Mass

ABSTRACT We present Spitzer observations at 3.6 and 4.5 µm and a near-infrared IRTF SpeX spectrum of the irradiated brown dwarf NLTT5306B. We determine that the brown dwarf has a spectral type of L5 and is likely inflated, despite the low effective temperature of the white dwarf primary star. We calculate brightness temperatures in the Spitzer wavebands for both the model radius, and Roche Lobe radius of the brown dwarf, and conclude that there is very little day–night side temperature difference. We discuss various mechanisms by which NLTT5306B may be inflated, and determine that while low-mass brown dwarfs (M < 35 MJup) are easily inflated by irradiation from their host star, very few higher mass brown dwarfs are inflated. The higher mass brown dwarfs that are inflated may be inflated by magnetic interactions or may have thicker clouds.

Deep Near-Infrared Surveys and Young Brown Dwarf Populations in Star-Forming Regions

2003 ◽  
Vol 211 ◽  
pp. 87-90
Author(s):  
M. Tamura ◽  
T. Naoi ◽  
Y. Oasa ◽  
Y. Nakajima ◽  
C. Nagashima ◽  
...  
Keyword(s):  
High Resolution ◽  
Adaptive Optics ◽  
Near Infrared ◽  
Brown Dwarf ◽  
Ir Camera ◽  
Star Forming ◽  
Star Forming Regions ◽  
New Instrument ◽  
Infrared Surveys ◽  
Low Mass

We are currently conducting three kinds of IR surveys of star forming regions (SFRs) in order to seek for very low-mass young stellar populations. First is a deep JHKs-bands (simultaneous) survey with the SIRIUS camera on the IRSF 1.4m or the UH 2.2m telescopes. Second is a very deep JHKs survey with the CISCO IR camera on the Subaru 8.2m telescope. Third is a high resolution companion search around nearby YSOs with the CIAO adaptive optics coronagraph IR camera on the Subaru. In this contribution, we describe our SIRIUS camera and present preliminary results of the ongoing surveys with this new instrument.

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.

A Search for Brown Dwarfs in the Alpha Persei Cluster

2003 ◽  
Vol 211 ◽  
pp. 179-180
Author(s):  
Nicolas Lodieu ◽  
Mark McCaughrean ◽  
Jérôme Bouvier ◽  
David Barrado y Navascués ◽  
John R. Stauffer
Keyword(s):  
Near Infrared ◽  
Open Cluster ◽  
Brown Dwarfs ◽  
Wide Field ◽  
Brown Dwarf ◽  
Young Open Cluster ◽  
Low Mass ◽  
Alpha Persei ◽  
Calar Alto ◽  
Infrared Survey

We present preliminary results from a deep near-infrared survey of a ~ 1 square degree area in the young open cluster Alpha Persei using the wide-field Omega-Prime camera on the Calar Alto 3.5m telescope, yielding a list of new low-mass cluster members, including brown dwarf candidates.

scholarly journals Discovery of a Tight Brown Dwarf Companion to the Low Mass Star LHS 2397a

2003 ◽  
Vol 211 ◽  
pp. 261-264 ◽  
Author(s):  
Melanie Freed ◽  
Laird M. Close ◽  
Nick Siegler
Keyword(s):  
Adaptive Optics ◽  
Spectral Type ◽  
Proper Motion ◽  
Near Infrared ◽  
Mass Star ◽  
Infrared Photometry ◽  
Brown Dwarf ◽  
Dynamical Mass ◽  
Low Mass ◽  
Adaptive Optics System

Using the adaptive optics system, Hōkūpa'a, at Gemini-North, we have directly imaged a companion around the UKIRT faint standard M8 star, LHS 2397a (FS 129) at a separation of 2.96 AU. Near-Infrared photometry obtained on the companion has shown it to be an L7.5 brown dwarf and confirmed the spectral type of the primary to be an M8. We also derive a substellar mass of the companion of 0.068M⊙, although masses in the range (0.061 – 0.069) are possible, and the primary mass as 0.090M⊙ (0.089 – 0.094). Reanalysis of archival imaging from HST has confirmed the secondary as a common proper motion object. This binary represents the first clear example of a brown dwarf companion within 4 AU of a low mass star, and should be the first L7.5 to have a dynamical mass. As part of a larger survey of M8-M9 stars, this object may indicate that there is no “brown dwarf desert” around low mass primaries.

scholarly journals Near-Infrared Adaptive Optics Spectroscopy of Binary Brown Dwarfs HD 130948B and HD 130948C

2003 ◽  
Vol 211 ◽  
pp. 269-270
Author(s):  
M Goto ◽  
A.T. Tokunaga ◽  
M. Cushing ◽  
D. Potter ◽  
N. Kobayashi ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Binary System ◽  
Adaptive Optics ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Brown Dwarf ◽  
Low Mass ◽  
The Individual

We present near-infrared spectroscopy of low-mass companions in the HD 130948 system (Goto et al. 2002a). Adaptive optics on the Subaru Telescope allowed for spectroscopy of the individual components of the 0″.13 binary system. Based on a direct comparison with a series of template spectra, we determined the spectral types of HD 130948B and C to be L4 ± 1. We find they are most likely a binary brown dwarf system.

scholarly journals WD1032 + 011, an inflated brown dwarf in an old eclipsing binary with a white dwarf

2020 ◽  
Vol 497 (3) ◽  
pp. 3571-3580 ◽  
Author(s):  
S L Casewell ◽  
C Belardi ◽  
S G Parsons ◽  
S P Littlefair ◽  
I P Braker ◽  
...  
Keyword(s):  
Spectral Type ◽  
White Dwarf ◽  
Light Curves ◽  
Brown Dwarf ◽  
Eclipsing Binary ◽  
The Third ◽  
Thick Disc ◽  
Low Mass ◽  
High Cadence

ABSTRACT We present the discovery of only the third brown dwarf known to eclipse a non-accreting white dwarf. Gaia parallax information and multicolour photometry confirm that the white dwarf is cool (9950 ± 150 K) and has a low mass (0.45 ± 0.05 M⊙), and spectra and light curves suggest the brown dwarf has a mass of 0.067 ± 0.006 M⊙ (70MJup) and a spectral type of L5 ± 1. The kinematics of the system show that the binary is likely to be a member of the thick disc and therefore at least 5-Gyr old. The high-cadence light curves show that the brown dwarf is inflated, making it the first brown dwarf in an eclipsing white dwarf-brown dwarf binary to be so.

scholarly journals HS 2231+2441: an HW Vir system composed of a low-mass white dwarf and a brown dwarf★

2017 ◽  
Vol 472 (3) ◽  
pp. 3093-3100 ◽  
Author(s):  
L. A. Almeida ◽  
A. Damineli ◽  
C. V. Rodrigues ◽  
M. G. Pereira ◽  
F. Jablonski
Keyword(s):  
White Dwarf ◽  
Brown Dwarf ◽  
Low Mass

scholarly journals Optical and near-infrared color distributions of the NGC 4874 globular cluster system

2012 ◽  
Vol 8 (S295) ◽  
pp. 308-308
Author(s):  
Hyejeon Cho ◽  
John P. Blakeslee ◽  
Eric W. Peng ◽  
Young-Wook Lee
Keyword(s):  
Globular Cluster ◽  
Near Infrared ◽  
Hubble Space Telescope ◽  
Elliptical Galaxy ◽  
Gaussian Mixture ◽  
Wide Field ◽  
Imaging Data ◽  
Coma Cluster ◽  
Color Distribution ◽  
Optical Color

AbstractExamining both optical and optical-infrared color distributions of the globular cluster (GC) systems in large elliptical galaxies is the key to study how non-linearities in the color-metallicity relations of their GC systems are linked to bimodal optical color distributions. In order to do this for the core of the Coma cluster of galaxies (Abell 1656), centered on the giant elliptical galaxy NGC 4874, we have combined F160W (H160) near-infrared (NIR) imaging data acquired with the Wide Field Camera 3 IR Channel (WFC3/IR), installed on Hubble Space Telescope (HST) in 2009, with F475W (g475) and F814W (I814) optical imaging data from the HST Advanced Camera for Surveys (ACS). Since optical-NIR color distributions of extragalactic GC systems reflect the underlying features of the metallicity distributions, we have probed not only optical g475–I814 and optical-NIR I814–H160 color distributions but also the color-color relation for this GC system. The features of these color distributions have been quantitatively analyzed using the Gaussian Mixture Modeling code. We find that brighter GCs have a much redder mean color than fainter ones. The optical color distribution of the GC system in the Coma cluster core shows the typical bimodality, while the evidence for bimodality is significantly weaker in the optical-NIR color distribution.

scholarly journals Orbiting a binary

2017 ◽  
Vol 608 ◽  
pp. A106 ◽  
Author(s):  
M. Bonavita ◽  
V. D’Orazi ◽  
D. Mesa ◽  
C. Fontanive ◽  
S. Desidera ◽  
...  
Keyword(s):  
Near Infrared ◽  
Speckle Pattern ◽  
Major Axis ◽  
Brown Dwarf ◽  
Semi Major Axis ◽  
Similar Frequency ◽  
Link Type ◽  
Medium Resolution ◽  
Low Mass ◽  
Imaging Mode

Aims. In this paper we present the results of the SPHERE observation of the HD 284149 system, aimed at a more detailed characterisation of both the primary and its brown dwarf companion. Methods. We observed HD 284149 in the near-infrared with SPHERE, using the imaging mode (IRDIS+IFS) and the long-slit spectroscopy mode (IRDIS-LSS). The data were reduced using the dedicated SPHERE pipeline, and algorithms such as PCA and TLOCI were applied to reduce the speckle pattern. Results. The IFS images revealed a previously unknown low-mass (~0.16 M⊙) stellar companion (HD 294149 B) at ~0.1′′, compatible with previously observed radial velocity differences, as well as proper motion differences between Gaia and Tycho-2 measurements. The known brown dwarf companion (HD 284149 b) is clearly visible in the IRDIS images. This allowed us to refine both its photometry and astrometry. The analysis of the medium resolution IRDIS long slit spectra also allowed a refinement of temperature and spectral type estimates. A full reassessment of the age and distance of the system was also performed, leading to more precise values of both mass and semi-major axis. Conclusions. As a result of this study, HD 284149 ABb therefore becomes the latest addition to the (short) list of brown dwarfs on wide circumbinary orbits, providing new evidence to support recent claims that object in such configuration occur with a similar frequency to wide companions to single stars.

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