Spectroscopic characterization of 78 DENIS ultracool dwarf candidates in the solar neighborhood and the Upper Scorpii OB association

Martín, E. L.; Phan-Bao, N.; Bessell, M. S.; Delfosse, X.; Forveille, T.; Magazzù, A.; Reylé, C.; Bouy, H.; Tata, R.

doi:10.1051/0004-6361/201014202

Cited by 64 publications

(57 citation statements)

References 60 publications

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“…More precise U V W XY Z data for this object as well as a more expansive census of the β Pic stellar members would help refine the membership. Martín et al (2010) noted that 2MASS J1935−2846 is near the R CrA star forming region on the sky, but our proper motion of (+27.3 ± 0.9, −61.6 ± 1.1) mas yr −1 is inconsistent with the mean of known members, (+5.5, −27.0) mas yr −1 (Neuhäuser et al 2000), and our parallax distance of 70.4 +6.5 −5.5 pc is much closer than the region's best distance estimate of 130 pc (Neuhäuser & Forbrich 2008).…”

Section: Mass J19355595−2846343 (M9 Low-g/m9 Vl-g)mentioning

confidence: 99%

The Hawaii Infrared Parallax Program. Ii. Young Ultracool Field Dwarfs* †

Liu

Dupuy

Allers

2016

ApJ

241

320

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We present a large, uniform analysis of young (≈10-150 Myr) ultracool dwarfs, based on new high-precision infrared (IR) parallaxes for 68 objects. We find that low-gravity (vl-g) late-M and L dwarfs form a continuous sequence in IR color-magnitude diagrams, separate from the field population and from current theoretical models. These vl-g objects also appear distinct from young substellar (brown dwarf and exoplanet) companions, suggesting the two populations may have a different range of physical properties. In contrast, at the L/T transition, young, old, and spectrally peculiar objects all span a relatively narrow range in near-IR absolute magnitudes. At a given spectral type, the IR absolute magnitudes of young objects can be offset from ordinary field dwarfs, with the largest offsets occurring in the Y and J bands for late-M dwarfs (brighter than the field) and mid/late-L dwarfs (fainter than the field). Overall, low-gravity (vl-g) objects have the most uniform photometric behavior while intermediate-gravity (int-g) objects are more diverse, suggesting a third governing parameter beyond spectral type 1 This work is largely based on observations obtained with WIRCam, a joint project of CFHT, Taiwan, Korea, Canada, France, and the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.2 Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. -2 -and gravity class. We examine the moving group membership for all young ultracool dwarfs with parallaxes, changing the status of 23 objects (including 8 previously identified planetary-mass candidates) and fortifying the status of another 28 objects. We use our resulting age-calibrated sample to establish empirical young isochrones and show a declining frequency of vl-g objects relative to int-g objects with increasing age. Notable individual objects in our sample include high-velocity ( 100 km s −1 ) int-g objects; very red late-L dwarfs with high surface gravities; candidate disk-bearing members of the MBM20 cloud and β Pic moving group; and very young distant interlopers. Finally, we provide a comprehensive summary of the absolute magnitudes and spectral classifications of young ultracool dwarfs, using a combined sample of 102 objects found in the field and as substellar companions to young stars.Subject headings: brown dwarfs -proper motions -parallaxes -solar neighborhood IntroductionObservational studies of brown dwarfs have been inspired by two complementary perspectives. One has been the desire to expand the parameter space of classical stellar astrophysics. Brown dwarfs are t...

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Section: Mass J19355595−2846343 (M9 Low-g/m9 Vl-g)mentioning

confidence: 99%

The Hawaii Infrared Parallax Program. Ii. Young Ultracool Field Dwarfs* †

Liu

Dupuy

Allers

2016

ApJ

241

320

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“…Therefore, LP 655-48 is very likely an old field late-M dwarf. Using the spectra of 28 late-M dwarfs published in Crifo et al (2005) and Phan-Bao & Bessell (2006), we also measured EWs of the Na I doublet at 8183 Å and 8199 Å, which is an indicator for surface gravity of young M dwarfs (e.g., Lyo et al 2004;Schlieder et al 2012), over the range of 8170−8200 Å as described in Martín et al (2010). The uncertainties in the EW measurement were estimated by measuring EWs with different possible continuum levels.…”

Section: Lithium Detection In Five Late-m Dwarfsmentioning

confidence: 99%

Detection of lithium in nearby young late-M dwarfs

Phan-Bao

Bessell

Nguyen-Thanh

et al. 2017

A&A

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Context. Late M-type dwarfs in the solar neighborhood include a mixture of very low-mass stars and brown dwarfs which is difficult to disentangle due to the lack of constraints on their age such as trigonometric parallax, lithium detection and space velocity. Aims. We search for young brown dwarf candidates among a sample of 28 nearby late-M dwarfs with spectral types between M5.0 and M9.0, and we also search for debris disks around three of them. Methods. Based on theoretical models, we used the color I − J, the J-band absolute magnitude and the detection of the Li I 6708 Å doublet line as a strong constraint to estimate masses and ages of our targets. For the search of debris disks, we observed three targets at submillimeter wavelength of 850 µm. Results. We report here the first clear detections of lithium absorption in four targets and a marginal detection in one target. Our mass estimates indicate that two of them are young brown dwarfs, two are young brown dwarf candidates and one is a young very low-mass star. The closest young field brown dwarf in our sample at only ∼15 pc is an excellent benchmark for further studying physical properties of brown dwarfs in the range 100−150 Myr. We did not detect any debris disks around three late-M dwarfs, and we estimated upper limits to the dust mass of debris disks around them.

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“…DENIS1048 (spectral classification M8.5; Henry et al 2004) was identified as a UD in the DENIS survey (Epchtein et al 1997) by Delfosse et al (2001) and, at a distance of 4.00 ± 0.03 pc (Costa et al 2005), is one of the closest known stars. A recent spectroscopic study by Martín et al (2010) shows that it is unlikely to be a brown dwarf. Fuhrmeister & Schmitt (2004) reported a large optical flare and a fast projected rotation velocity of v sin i = 25 ± 2 km s −1 .…”

Section: Observations and Data Analysismentioning

confidence: 99%

The Magnetosphere of the Ultracool Dwarf Denis 1048–3956

Ravi

Hallinan

Hobbs

et al. 2011

ApJ

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Ultracool dwarfs, the least-massive contributors to the stellar mass function, exhibit striking magnetic properties that are inconsistent with trends for more massive stars. Here, we present the widest-band radio observations to date of an ultracool dwarf, DENIS-P J104814.9−395604, in four 2 GHz bandwidths between wavelengths of 1 cm and 10 cm. These data were obtained with the Australia Telescope Compact Array using the new Compact Array Broadband Backend instrument. We detected a stable negatively sloped power-law spectrum in total intensity, with spectral index α = 1.71 ± 0.09. Circular polarization fractions between 0.25 and 0.4 were found at the low-frequency end of our detection band. We interpret these results as indicative of gyrosynchrotron emission. We suggest that the radio emission originates from beyond the corotation radius, R C , of the star. Adopting this model, we find R C between 1.2 R * and 2.9 R * , and a non-thermal electron density and magnetic field strength between 10 5 and 10 7.2 cm −3 and between 70 and 260 G, respectively, at R C . The model accounts for the violation of the Güdel-Benz relation between X-ray and radio luminosities of low-mass stars by DENIS-P J104814.9−395604.

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Spectroscopic characterization of 78 DENIS ultracool dwarf candidates in the solar neighborhood and the Upper Scorpii OB association

Cited by 64 publications

References 60 publications

The Hawaii Infrared Parallax Program. Ii. Young Ultracool Field Dwarfs* †

The Hawaii Infrared Parallax Program. Ii. Young Ultracool Field Dwarfs* †

Detection of lithium in nearby young late-M dwarfs

The Magnetosphere of the Ultracool Dwarf Denis 1048–3956

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