Spitzer
                    Identification of the Least Massive Known Brown Dwarf with a Circumstellar Disk

Abstract We analyse the 100 pc Gaia white dwarf volume-limited sample by means of VOSA (Virtual Observatory SED Analyser) with the aim of identifying candidates for displaying infrared excesses. Our search focuses on the study of the spectral energy distribution (SED) of 3,733 white dwarfs with reliable infrared photometry and GBP − GRP colours below 0.8 mag, a sample which seems to be nearly representative of the overall white dwarf population. Our search results in 77 selected candidates, 52 of which are new identifications. For each target we apply a two-component SED fitting implemented in VOSA to derive the effective temperatures of both the white dwarf and the object causing the excess. We calculate a fraction of infrared-excess white dwarfs due to the presence of a circumstellar disk of 1.6±0.2%, a value which increases to 2.6±0.3% if we take into account incompleteness issues. Our results are in agreement with the drop in the percentage of infrared excess detections for cool (<8,000 K) and hot (>20,000 K) white dwarfs obtained in previous analyses. The fraction of white dwarfs with brown dwarf companions we derive is ≃0.1–0.2%.

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HubbleandSpitzerObservations of an Edge‐on Circumstellar Disk around a Brown Dwarf

The Astrophysical Journal ◽

10.1086/520712 ◽

2007 ◽

Vol 666 (2) ◽

pp. 1219-1225 ◽

Cited By ~ 48

Author(s):

K. L. Luhman ◽

Lucia Adame ◽

Paola D’Alessio ◽

Nuria Calvet ◽

Kim K. McLeod ◽

...

Keyword(s):

Circumstellar Disk ◽

Brown Dwarf

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The circumstellar disk of the Be star 28 (ω) CMa

EAS Publications Series ◽

10.1051/eas:2003024 ◽

2003 ◽

Vol 6 ◽

pp. 257-257

Author(s):

S. Štefl ◽

W. Nowotny-Schipper ◽

J. Reunanen

Keyword(s):

Circumstellar Disk ◽

Be Star

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An Improved Optical Spectrum and New Model Fits of the Likely Brown Dwarf GD 165B

The Astrophysical Journal ◽

10.1086/307380 ◽

1999 ◽

Vol 519 (2) ◽

pp. 834-843 ◽

Cited By ~ 91

Author(s):

J. Davy Kirkpatrick ◽

France Allard ◽

Tom Bida ◽

Ben Zuckerman ◽

E. E. Becklin ◽

...

Keyword(s):

Optical Spectrum ◽

Brown Dwarf ◽

New Model ◽

Model Fits

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A Deep Large area Search for Low Luminosity Stars

Highlights of Astronomy ◽

10.1017/s1539299600021675 ◽

1998 ◽

Vol 11 (1) ◽

pp. 435-435

Author(s):

Hugh R.A. Jones ◽

Mike R.S. Hawkins

Keyword(s):

Spectral Type ◽

Low Temperatures ◽

Current Model ◽

Brown Dwarfs ◽

Evolutionary Models ◽

Spectral Indices ◽

Late Type ◽

Brown Dwarf ◽

Large Area ◽

M Dwarfs

In a recent survey for faint red stars from a digital stack of Schmidt plates a number of candidate objects were identified. Parallax’s for three of these objects have been reported showing them to have luminosities which interpreted within the available evolutionary models indicate them to be good brown dwarf candidates. Here we examine spectra of these objects and others from the plate stack. Using standard spectral indices we find that for a given spectral type their spectra are more consistent with the Pleiades brown dwarfs (PPL 15, Teide 1 and Calar 3) than with standard late-type M dwarfs. Our interpretation is that this is due to their selection by RF IN colours which at values > 3 preferentially selects objects with relatively low gravities. For late-type M dwarfs and brown dwarfs low gravities are expected to be a reliable indication of youth. We also notice that the stack objects generally have strong FeH absorption for their spectral type. Current model atmospheres suggest that FeH strongly increases in strength toward lower metallicities and lower temperatures. We believe that this is not consistent with the available observational evidence from late-type M dwarfs. It is possible that solid Fe is forming inthe low temperature atmospheres relatively depleting FeH strengths toward lower temperatures. We find some evidence that for dwarfs at low temperatures dust formation is less prevalent in lower gravity objects suggesting that dwarfs at low temperatures stronger FeH may be an indication of youth. In addition to the spectral evidence the three stack objects whose parallax’s have been measured show small tangential velocities which is a further indication of youth.

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