A Near-Infrared, Wide-Field, Proper-Motion Search for Brown Dwarfs

The infrared search for substellar companions to nearby white dwarfs has been going on for a little more than a decade. The most recent phase has been a wide field proper motion search carried out primarily at Steward Observatory, where we are complete down to J = 18. Earlier phases included near field searches at the IRTF and Keck Observatory. In the last year we have discovered ten previously unrecognized faint proper motion companions. Of the recent discoveries, most are white dwarfs and a few M dwarfs. GD165B, discovered in 1988 as part of our program, is still the only known companion to a white dwarf with spectral type later than M.

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Substellar and low-mass dwarf identification with near-infrared imaging space observatories

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832838 ◽

2018 ◽

Vol 620 ◽

pp. A132 ◽

Cited By ~ 4

Author(s):

B. W. Holwerda ◽

J. S. Bridge ◽

R. Ryan ◽

M. A. Kenworthy ◽

N. Pirzkal ◽

...

Keyword(s):

Near Infrared ◽

Infrared Imaging ◽

High Redshift ◽

Brown Dwarfs ◽

Wide Field ◽

Space Telescope ◽

Low Mass ◽

Space Observatories ◽

Broad Type ◽

Selection Of

Aims. We aim to evaluate the near-infrared colors of brown dwarfs as observed with four major infrared imaging space observatories: the Hubble Space Telescope (HST), the James Webb Space Telescope (JWST), the Euclid mission, and the WFIRST telescope. Methods. We used the SPLAT SPEX/ISPEX spectroscopic library to map out the colors of the M-, L-, and T-type dwarfs. We have identified which color–color combination is optimal for identifying broad type and which single color is optimal to then identify the subtype (e.g., T0-9). We evaluated each observatory separately as well as the narrow-field (HST and JWST) and wide-field (Euclid and WFIRST) combinations. Results. The Euclid filters perform equally well as HST wide filters in discriminating between broad types of brown dwarfs. WFIRST performs similarly well, despite a wider selection of filters. However, subtyping with any combination of Euclid and WFIRST observations remains uncertain due to the lack of medium, or narrow-band filters. We argue that a medium band added to the WFIRST filter selection would greatly improve its ability to preselect brown dwarfs its imaging surveys. Conclusions. The HST filters used in high-redshift searches are close to optimal to identify broad stellar type. However, the addition of F127M to the commonly used broad filter sets would allow for unambiguous subtyping. An improvement over HST is one of two broad and medium filter combinations on JWST: pairing F140M with either F150W or F162M discriminates very well between subtypes.

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A Search for Brown Dwarfs in the Alpha Persei Cluster

Symposium - International Astronomical Union ◽

10.1017/s0074180900210528 ◽

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.

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A Deep JI Survey of the Pleiades for Freely-Floating Superplanets and Brown Dwarfs at the Deuterium Burning Limit

Symposium - International Astronomical Union ◽

10.1017/s0074180900210553 ◽

2003 ◽

Vol 211 ◽

pp. 185-186

Author(s):

M. J. Schwartz ◽

E. E. Becklin ◽

B. Zuckerman

Keyword(s):

Energy Distribution ◽

Proper Motion ◽

Near Infrared ◽

Profile Analysis ◽

Spectral Energy Distribution ◽

Brown Dwarfs ◽

Spectral Energy ◽

Preliminary Results ◽

Methane Absorption ◽

Lower Limits

We present preliminary results from a deep near-infrared J-band and I-band photometric survey of the Pleiades for freely-floating superplanets and brown dwarfs (BD) near the deuterium burning limit (DBL). With limiting magnitudes of J=20.5 and I=23.5, we have selected candidate Pleiads on the basis of evolutionary tracks, color-magnitudes, and I-J color lower limits (non-detections at deep I-band). Likelihoods of membership will be ultimately determined by a combination of image profile analysis, spectral energy distribution, proper motion, and low-resolution measurements of near-infrared water and/or methane absorption slopes. If confirmed, our faintest candidates are predicted to have made the transition from L to T spectral types with temperatures down to 820 K, and masses approaching 10 MJup.

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Microlensing by Free-Floating Brown Dwarfs

Symposium - International Astronomical Union ◽

10.1017/s0074180900211236 ◽

2003 ◽

Vol 211 ◽

pp. 509-514

Author(s):

Hans Zinnecker

Keyword(s):

Optical Depth ◽

Mass Distribution ◽

Surface Density ◽

Near Infrared ◽

Galactic Center ◽

Brown Dwarfs ◽

Wide Field ◽

Full Width

We propose a near-infrared microlensing survey of the central 2 degree field of the Galactic Center, in an attempt to estimate the surface density and mass distribution of distant free-floating brown dwarfs in the bulge and in the disk, acting as lenses of bright stars towards the Galactic Center. We estimate the probability (optical depth) of microlensing events to be 10-7 and the typical timescale (full-width) of the amplification lightcurve to be about 1 week. The necessary wide-field NIR survey technology should soon be available on UKIRT, CFHT, and with VISTA at ESO/Paranal.

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Astrometric detection and characterization of brown dwarfs

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308018589 ◽

2007 ◽

Vol 3 (S248) ◽

pp. 30-35

Author(s):

R.-D. Scholz ◽

M. J. McCaughrean ◽

S. Röser ◽

E. Schilbach

Keyword(s):

Proper Motion ◽

Near Infrared ◽

Critical Mass ◽

Brown Dwarfs ◽

Solar Neighborhood ◽

Sky Survey ◽

Nearby Stars ◽

Rare Class ◽

Low Mass

AbstractAs a result of failed star formation, brown dwarfs (BDs) do not reach the critical mass to ignite the fusion of hydrogen in their cores. Different from their low-mass stellar brothers, the red dwarfs, BDs cool down with their lifetime to very faint magnitudes. Therefore, it was only about 10 to 20 years ago that such ultracool objects began to be detected. Accurate astrometry can be used to detect them indirectly as companions to stars by the signature of the so-called astrometric wobble. Resolved faint BD companions of nearby stars can be identified by their common proper motion (CPM). A direct astrometric detection of the hidden isolated BDs in the Solar neighborhood is possible with deep high proper motion (HPM) surveys. This technique led to the discovery of the first free-floating BD, Kelu 1, and of the nearest BD, ε Indi B. Both were meanwhile found to be binary BDs. The astrometric orbital monitoring of ε Indi Ba+Bb, for which we know an accurate distance from the Hipparcos measurement of its primary, ε Indi A, will allow the determination of individual masses of two low-mass BDs. Hundreds of BDs have been identified for the last decade. Deep optical sky survey (SDSS) and near-infrared sky surveys (DENIS, 2MASS), played a major role in the search mainly based on colours, since BDs emit most of their light at longer wavelengths. However, alternative deep optical HPM surveys based on archival photographic data are not only sensitive enough to detect some of the nearest representatives, they do also uncover many of the rare class of ultracool halo objects crossing the Solar neighborhood at large velocities. SSSPM 1444, with the extremely large proper motion of 3.5 arcsec/yr, is one of the nearest among these subdwarfs with masses at the substellar boundary. We present preliminary parallax results for this and two other ultracool subdwarfs (USDs) from the Calar Alto Omega 2000 parallax program.

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Primeval very low-mass stars and brown dwarfs – VI. Population properties of metal-poor degenerate brown dwarfs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz777 ◽

2019 ◽

Vol 486 (1) ◽

pp. 1260-1282 ◽

Cited By ~ 8

Author(s):

Z H Zhang (张曾华) ◽

A J Burgasser ◽

M C Gálvez-Ortiz ◽

N Lodieu ◽

M R Zapatero Osorio ◽

...

Keyword(s):

Transition Zone ◽

Spectral Type ◽

Near Infrared ◽

Brown Dwarfs ◽

Absolute Magnitude ◽

Wide Field ◽

Low Mass Stars ◽

Low Mass ◽

Infrared Survey ◽

K Band

ABSTRACT We presented 15 new T dwarfs that were selected from UKIRT Infrared Deep Sky Survey, Visible and Infrared Survey Telescope for Astronomy , and Wide-field Infrared Survey Explorer surveys, and confirmed with optical to near-infrared spectra obtained with the Very Large Telescope and the Gran Telescopio Canarias. One of these new T dwarfs is mildly metal-poor with slightly suppressed K-band flux. We presented a new X-shooter spectrum of a known benchmark sdT5.5 subdwarf, HIP 73786B. To better understand observational properties of brown dwarfs, we discussed transition zones (mass ranges) with low-rate hydrogen, lithium, and deuterium burning in brown dwarf population. The hydrogen burning transition zone is also the substellar transition zone that separates very low-mass stars, transitional, and degenerate brown dwarfs. Transitional brown dwarfs have been discussed in previous works of the Primeval series. Degenerate brown dwarfs without hydrogen fusion are the majority of brown dwarfs. Metal-poor degenerate brown dwarfs of the Galactic thick disc and halo have become T5+ subdwarfs. We selected 41 T5+ subdwarfs from the literature by their suppressed K-band flux. We studied the spectral-type–colour correlations, spectral-type–absolute magnitude correlations, colour–colour plots, and HR diagrams of T5+ subdwarfs, in comparison to these of L–T dwarfs and L subdwarfs. We discussed the T5+ subdwarf discovery capability of deep sky surveys in the 2020s.

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Variability of L Dwarfs in the Near Infrared

Symposium - International Astronomical Union ◽

10.1017/s0074180900211121 ◽

2003 ◽

Vol 211 ◽

pp. 455-456 ◽

Cited By ~ 2

Author(s):

José A. Caballero ◽

Víctor J. S. Béjar ◽

Rafael Rebolo

Keyword(s):

Time Scales ◽

Near Infrared ◽

Brown Dwarfs ◽

L Dwarfs ◽

Atmospheric Changes ◽

Changes Over Time ◽

Over Time

We have obtained series of images in the near infrared J and Ks bands for seven L-type dwarfs with a duration of 3 to 6 hours. We present results on: 1) the amplitude of variability associated with atmospheric changes over time scales from minutes to several hours; 2) the search for cool companions in wide orbits; 3) the search for transits of brown dwarfs and planetary companions in very close orbits.

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