scholarly journals Photometric Properties of L and T Dwarf Binaries

2021 ◽  
Vol 5 (12) ◽  
pp. 286
Author(s):  
Alyssa C Leone ◽  
William M. J. Best ◽  
Michael C. Liu ◽  
Eugene A. Magnier ◽  
Trent J. Dupuy
Keyword(s):  
Spectral Type ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Supporting Evidence ◽  
Limited Sample

Abstract Recent studies using volume-limited samples of brown dwarfs have revealed the photometric evolution of single L and T dwarfs and unresolved binaries as they age and cool, in particular as they transition from L to T spectral types. We demonstrate that the near-infrared photometric evolution of the resolved components of L and T dwarf binaries is consistent with that of single objects using a volume-limited sample. In addition, we provide supporting evidence that the L9 dwarf WISE J185101.83+593508.6 is an unresolved binary and identify three more candidate or confirmed unresolved binaries all from being overluminous for their spectral type. We calculate a new binary fraction of 13.1% ± 1.8% for L0–T8 dwarfs.

scholarly journals The First Young Brown Dwarf in the Serpens Cloud

2003 ◽  
Vol 211 ◽  
pp. 83-86
Author(s):  
Jean-Louis Monin ◽  
Emmanuel Caux ◽  
Alain Klotz ◽  
Nicolas Lodieu
Keyword(s):  
Star Formation ◽  
Spectral Type ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Brown Dwarfs ◽  
Brown Dwarf ◽  
Star Formation Region ◽  
Formation Region

We report the discovery of the first young brown dwarf in the Serpens cloud (BD-Ser 1). It is obscured by more than ten magnitudes of visual absorption as indicated by near infrared (NIR) photometric survey at the NTT and confirmed by NIR spectroscopy at the VLT. We estimate the mass of this brown dwarf to be M ~ 0.05 M⊙ and its age to be ~ 3.5 Myr. Available NIR indices in the literature (designed for field brown dwarfs) fail to provide its current spectral type but using a model they correctly determine its future spectral type to be T. This is the first young brown dwarf ever found deeply embedded in the Serpens star formation region

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

2019 ◽  
Vol 486 (1) ◽  
pp. 1260-1282 ◽  
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.

scholarly journals Variability of L Dwarfs in the Near Infrared

2003 ◽  
Vol 211 ◽  
pp. 455-456 ◽  
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.

scholarly journals A Deep Large area Search for Low Luminosity Stars

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.

scholarly journals The radio-loud narrow-line Seyfert 1 galaxy 1H 0323+342 in a galaxy merger

2020 ◽  
Vol 496 (2) ◽  
pp. 1757-1765 ◽  
Author(s):  
Akihiro Doi ◽  
Motoki Kino ◽  
Nozomu Kawakatu ◽  
Kazuhiro Hada
Keyword(s):  
Black Holes ◽  
Near Infrared ◽  
Gamma Ray ◽  
Linear Structure ◽  
Seyfert Galaxies ◽  
Mass Function ◽  
High Mass ◽  
Host Galaxy ◽  
Supporting Evidence ◽  
Narrow Line

ABSTRACT The supermassive black holes (SMBHs) of narrow-line Seyfert 1 galaxies (NLS1s) are at the lower end of the mass function of active galactic nuclei (AGNs) and reside preferentially in late-type host galaxies with pseudobulges, which are thought to be formed by internal secular evolution. On the other hand, the population of radio-loud NLS1s presents a challenge for the relativistic jet paradigm, which states that powerful radio jets are associated exclusively with very high mass SMBHs in elliptical hosts, which are built up through galaxy mergers. We investigated distorted radio structures associated with the nearest gamma-ray-emitting, radio-loud NLS1, 1H 0323+342. This provides supporting evidence for the merger hypothesis based on past optical/near-infrared observations of its host galaxy. The anomalous radio morphology consists of two different structures: the inner curved structure of the currently active jet and an outer linear structure of low-brightness relics. Such coexistence might be indicative of the stage of an established black hole binary with precession before the black holes coalesce in the galaxy merger process. 1H 0323+342 and other radio-loud NLS1s under galaxy interactions may be extreme objects on the evolutionary path from radio-quiet NLS1s to normal Seyfert galaxies with larger SMBHs in classical bulges through mergers and merger-induced jet phases.

scholarly journals Constraining the multiplicity statistics of the coolest brown dwarfs: binary fraction continues to decrease with spectral type

2018 ◽  
Vol 479 (2) ◽  
pp. 2702-2727 ◽  
Author(s):  
Clémence Fontanive ◽  
Beth Biller ◽  
Mariangela Bonavita ◽  
Katelyn Allers
Keyword(s):  
Spectral Type ◽  
Brown Dwarfs

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

2018 ◽  
Vol 620 ◽  
pp. A132 ◽  
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.

Bayesian Spectroscopic Characterization of Directly Imaged Planets and Brown Dwarfs and Implications for Ultracool Model Atmospheres

2021 ◽  
Author(s):  
Zhoujian Zhang ◽  
Michael Liu ◽  
Mark Marley ◽  
Michael Line ◽  
William Best
Keyword(s):  
Physical Properties ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Spectroscopic Characterization ◽  
Cool Temperature ◽  
Brown Dwarf ◽  
Modeling Framework ◽  
High Quality ◽  
Model Predictions

<p>Spectroscopic characterization of imaged exoplanets and brown dwarfs is essential for understanding their atmospheres, formation, and evolution, but such work is challenged by the unavoidably simplified model atmospheres needed to interpret spectra. While most previous work has focused on single or at most a few objects, comparing a large collection of spectra to models can uncover trends in data-model inconsistencies needed to improve model predictions, thereby leading to robust properties from exoplanet and brown dwarf spectra. Therefore, we are conducting a systematic analysis of a valuable but underutilized resource: the numerous high-quality spectra of (directly imaged and free-floating) exoplanets and brown dwarfs already accumulated by the community.<span class="Apple-converted-space"> </span></p> <p>Focusing on the cool-temperature end, we have constructed a Bayesian modeling framework using the new Sonora-Bobcat model atmospheres and have applied it to study near-infrared low-resolution spectra of >50 late-T imaged planets and brown dwarfs (≈600-1200K, ≈10-70 M<sub>Jup</sub>) and infer their physical properties (effective temperature, surface gravity, metallicity, radii, mass). By virtue of having such a large sample of high-quality spectra, our analysis identifies the systematic offsets between observed and model spectra as a function of wavelength and physical properties to pinpoint specific shortcomings in model predictions. We have also found that the spectroscopically inferred metallicities, ages, and masses of our sample all considerably deviate from expectations, suggesting the physical and chemical assumptions made within these models need to be improved to fully interpret data. Our work has established a systematic validation of cloudless model atmospheres to date and we discuss extending such analysis to wider temperature and wavelength (e.g., JWST) ranges, as well as finding new planetary-mass and brown dwarf benchmarks, in order to validate ultracool model atmospheres over larger parameter space.</p>

scholarly journals The Substellar Members of the Pleiades

2003 ◽  
Vol 211 ◽  
pp. 181-182
Author(s):  
Paul D. Dobbie ◽  
Richard F. Jameson ◽  
Samantha L. Osborne ◽  
Simon T. Hodgkin ◽  
David J. Pinfield
Keyword(s):  
Dark Matter ◽  
Spatial Distribution ◽  
Power Law ◽  
Spatial Model ◽  
Total Mass ◽  
Brown Dwarfs ◽  
Mass Function ◽  
Core Radius ◽  
Brown Dwarf ◽  
Limited Sample

We have compiled the largest magnitude limited sample of candidate substellar Pleiads to date. We fit King profiles to their spatial distribution to determine the Pleiades brown dwarf core radius to be Subsequently we have used our improved spatial model to place stringent limits on the shape of the cluster mass function across and below the stellar/substellar regime. We find this to be a power law with index α = 0.41±0.08 (0.3M⊙ ≥M≥ 0.035M⊙). Extrapolation of this mass function to M= 0.012M⊙ indicates that brown dwarfs contribute only ~ 2% to the total mass of the cluster hence we conclude that brown dwarfs do not contribute significantly to disk dark matter.

scholarly journals A LARGE-SCALE OPTICAL-NEAR-INFRARED SURVEY FOR BROWN DWARFS AND VERY LOW MASS STARS IN THE ORION OB1 ASSOCIATION

2008 ◽  
Vol 136 (1) ◽  
pp. 51-66 ◽  
Author(s):  
Juan José Downes ◽  
César Briceño ◽  
Jesús Hernández ◽  
Nuria Calvet ◽  
Lee Hartmann ◽  
...  
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Low Mass Stars ◽  
Low Mass ◽  
Infrared Survey
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