ULAS J141623.94+134836.3 – a faint common proper motion companion of a nearby L dwarf

We present the spectroscopic analysis of a large sample of late-M, L, and T dwarfs from the United Kingdom Deep Infrared Sky Survey. Using the YJHK photometry from the Large Area Survey and the red-optical photometry from the Sloan Digital Sky Survey we selected a sample of 262 brown dwarf candidates and we have followed-up 196 of them using the echelle spectrograph X-shooter on the Very Large Telescope. The large wavelength coverage (0.30 − 2.48µm) and moderate resolution (R∼ 5000 − 9000) of X-shooter allowed us to identify peculiar objects including 22 blue L dwarfs, 2 blue T dwarfs, and 2 low gravity M dwarfs. Using a spectral indices-based technique we identified 27 unresolved binary candidates, for which we have determined the spectral type of the potential components via spectral deconvolution. The spectra allowed us to measure the equivalent width of the prominent absorption features and to compare them to atmospheric models. Cross-correlating the spectra with a radial velocity standard, we measured the radial velocity for our targets, and we determined the distribution of the sample, which is centred at -1.7±1.2 km s −1 with a dispersion of 31.5 km s −1 . Using our results we estimated the space density of field brown dwarfs and compared it with the results of numerical simulations. Depending on the binary fraction, we found that there are (0.85±0.55)×10 −3 to (1.00±0.64)×10 −3 objects per cubic parsec in the L4-L6.5 range, (0.73 ± 0.47) × 10 −3 to (0.85 ± 0.55) × 10 −3 objects per cubic parsec in the L7-T0.5 range, and (0.74 ± 0.48) × 10 −3 to (0.88 ± 0.56) × 10 −3objects per cubic parsec in the T1-T4.5 range. We notice that there seem to be an excess of objects in the L to T transition with respect to the late T dwarfs, a discrepancy that could be explained assuming a higher binary fraction than expected for the L to T transition, or that objects in the high-mass end and low-mass end of this regime form in different environments, i.e. following different Initial Mass Functions.

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“…This apparent inconsistency is in common with the bluest T dwarf known, SDSS J1416+1348B Scholz 2010) which has young disk kinematics as well. …”

Section: Blue T Dwarfsmentioning

confidence: 86%

A large spectroscopic sample of L and T dwarfs from UKIDSS LAS: peculiar objects, binaries, and space density

Marocco¹,

Jones²,

Day-Jones³

et al. 2015

Monthly Notices of the Royal Astronomical Society

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“…Measurements were taken from the following references: BailerJones (2004), Berger et al (2008), Blake et al (2007), Bochanski et al (2011), Caballero et al (2004, Crossfield et al (2014), Del Burgo et al (2009), Deshpande et al (2012, Gizis et al (2013), Joergens & Guenther (2001), Jones et al (2005), Konopacky et al (2012), Kurosawa et al (2006), Martin et al (1997), Mohanty et al (2003Mohanty et al ( , 2005, Muzerolle et al (2003), Reid et al (2002), Reiners & Basri (2006, 2010, Reiners et al (2007), Rice et al (2010), Snellen et al (2014), Tinney & Reid (1998), White & Basri (2003), and Zapatero .…”

Section: Projected Rotation Velocitymentioning

confidence: 99%

Doppler imaging of exoplanets and brown dwarfs

Crossfield

2014

A&A

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Doppler imaging produces 2D global maps of rotating objects using high-dispersion spectroscopy. When applied to brown dwarfs and extrasolar planets, this technique can constrain global atmospheric dynamics and/or magnetic effects on these objects in unprecedented detail. I present the first quantitative assessment of the prospects for Doppler imaging of substellar objects with current facilities and with future giant ground-based telescopes. Observations will have the greatest sensitivity in K band, but the H and L bands will also be useful for these purposes. To assess the number and availability of targets, I also present a compilation of all measurements of photometric variability, rotation period (P), and projected rotational velocity (v sin i) for all known brown dwarfs. Several bright objects are already accessible to Doppler imaging with currently available instruments. With the development of giant ground-based telescopes, Doppler imaging will become feasible for many dozens of brown dwarfs and for the few brightest directly imaged extrasolar planets (such as β Pic b). The present set of measurements of P, v sin i, and variability are incomplete for many objects, and the sample is strongly biased toward early-type objects (

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“…(A color version of this figure is available in the online journal.) J0458+64 can be compared to the NIR spectra of the very late T dwarfs 2MASS J0415−09 (Burgasser et al 2002), ULAS J003402.77−005206.7 (hereafter ULAS J0034−00; Warren et al 2007), CFBDS J005910.90−011401.3 (CFBDS J0059−00; Delorme et al 2008), ULAS J133553.45+113005.2 (ULAS J1335+11; Burningham et al 2008), and SDSS J1416+13B (Burningham et al 2010a;Scholz 2010). As shown in Figure 5, WISEPC J0458+64 appears to best match the spectrum of the T9 dwarfs, although formal assignment of a spectral type will have to wait for the identification of spectral standards for objects this late.…”

Section: Spectral Analysismentioning

confidence: 99%

“…This distance is in rough agreement with the photometric distance of 9.0 ± 1.9 pc, using the apparent J magnitude of 17.47 ± 0.05 and absolute magnitude M J = 17.7 ± 0.45. This was computed from a weighted average of M J for the late T dwarfs Wolf 940B (Burningham et al 2009), ULAS0034−00 (Smart et al 2010), and SDSS J1416+13B (Scholz 2010), using the worst-case error.…”

Section: Spectral Analysismentioning

confidence: 99%

The First Ultra-Cool Brown Dwarf Discovered by the Wide-Field Infrared Survey Explorer

Mainzer

Cushing

Skrutskie

et al. 2010

ApJ

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We report the discovery of the first new ultra-cool brown dwarf (BDs) found with the Wide-field Infrared Survey Explorer (WISE). The object's preliminary designation is WISEPC J045853.90+643451.9. Follow-up spectroscopy with the LUCIFER instrument on the Large Binocular Telescope indicates that it is a very late-type T dwarf with a spectral type approximately equal to T9. Fits to an IRTF/SpeX 0.8-2.5 μm spectrum to the model atmospheres of Marley and Saumon indicate an effective temperature of approximately 600 K as well as the presence of vertical mixing in its atmosphere. The new BD is easily detected by WISE, with a signal-to-noise ratio of ∼36 at 4.6 μm. Current estimates place it at a distance of 6-10 pc. This object represents the first in what will likely be hundreds of nearby BDs found by WISE that will be suitable for follow-up observations, including those with the James Webb Space Telescope. One of the two primary scientific goals of the WISE mission is to find the coolest, closest stars to our Sun; the discovery of this new BD proves that WISE is capable of fulfilling this objective.

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ULAS J141623.94+134836.3 – a faint common proper motion companion of a nearby L dwarf

Cited by 62 publications

References 26 publications

A large spectroscopic sample of L and T dwarfs from UKIDSS LAS: peculiar objects, binaries, and space density

A large spectroscopic sample of L and T dwarfs from UKIDSS LAS: peculiar objects, binaries, and space density

Doppler imaging of exoplanets and brown dwarfs

The First Ultra-Cool Brown Dwarf Discovered by the Wide-Field Infrared Survey Explorer

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