Spectroscopic Identification of DENIS-selected Brown Dwarf Candidates in the Upper Scorpius OB Association

Martín, E. L.; Delfosse, X.; Guieu, S.

doi:10.1086/380226

Cited by 81 publications

(192 citation statements)

References 36 publications

Supporting

Mentioning

180

Contrasting

Order By: Relevance

“…3, all of the 7 targets in the Upper Sco OB association (solid hexagons) have weak NaI as expected for young brown dwarfs. Putting this result together with the 28 very low-mass objects confirmed by Martín et al 2004, brings the total number of DENIS discovered Upper Sco members to 35. Two of our candidates have relatively early M type and no detectable NaI doublet.…”

Section: Nm) Doublet Detectable But Weaker Than Field Counterparts Obmentioning

confidence: 95%

See 1 more Smart Citation

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

Martín¹,

Phan-Bao²,

Bessell³

et al. 2010

A&A

View full text Add to dashboard Cite

Aims. We search for new ultracool dwarfs and report here our observations of 78 ultracool dwarf candidates that have been photometrically selected using the DENIS survey point source catalogue. We analyze low-resolution optical spectroscopic observations to estimate spectral types of all candidates. Methods. We derive spectral types for each object using measurements of the PC3 spectral index as defined in Martín et al. They range from M6 to L3. The Hα emission and NaI subordinate doublet (818.3 nm and 819.9 nm) equivalent widths are measured in the spectra to identify young stellar objects. Spectroscopic indices of TiO, VO, CrH, and FeH molecular features are also reported. Results. A rule-of-thumb criterion for selecting young very low-mass objects using the NaI doublet equivalent width is given. It is used to confirm seven new members of the Upper Sco OB association and two new members of the R Cr-A star-forming region. Four of our field objects are also classified as very young, but are not members of any known nearby young association. The frequency of lower-gravity young objects in our field ultracool sample is 8.5%. Our results provide the first spectroscopic classification for 42 ultracool dwarfs in the solar vicinity with spectrophotometric distances in the range 17 pc to 65 pc (3 of them being new L dwarfs within 20 pc).

show abstract

Section: Nm) Doublet Detectable But Weaker Than Field Counterparts Obmentioning

confidence: 95%

“…The PC3 index defined by the latter authors has been used in several papers to determine spectral types (Crifo et al 2005;Martín et al 2004Martín et al , 2006Phan-Bao & Bessell 2006Reylé et al 2006). Comparisons with other methods of spectral type determination have found that the results are consistent.…”

Section: Spectral Typesmentioning

confidence: 99%

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

Martín¹,

Phan-Bao²,

Bessell³

et al. 2010

A&A

View full text Add to dashboard Cite

show abstract

“…Our sample consists of three groups of objects: firstly photometric USco candidates selected from the UKIDSS GCS Science Verification (Lodieu et al 2007b); secondly, a few known spectroscopic members falling in the instrument field-of-view and published in the literature (Martín et al 2004;Slesnick et al 2006), and, finally a sample of photometric non-members.…”

Section: The Samplesmentioning

confidence: 99%

“…The second sample consists of five known spectroscopic members with spectral types estimated from optical data with an accuracy of half a subclass: DENIS1610−2212 (Martín et al 2004), SCH1611−2217, SCH1612−2349, SCH1612−2338, and SCH1613−2305 (Slesnick et al 2006). These five objects fell in the AAOmega field-of-view and serve as spectral templates for assigning spectral types to our candidates.…”

Section: The Samplesmentioning

confidence: 99%

“…The association was targeted in X-rays (Walter et al 1994;Kunkel 1999;Preibisch et al 1998), with Hipparcos (de Bruijne et al 1997;de Zeeuw et al 1999), and more recently at optical (Preibisch et al 2001;Preibisch & Zinnecker 2002;Ardila et al 2000;Martín et al 2004;Slesnick et al 2006) and near-infrared (Lodieu et al 2006(Lodieu et al , 2007b wavelengths. As a result of the latest surveys, several tens of brown dwarfs were confirmed spectroscopically as members of the association (Martín et al 2004;Slesnick et al 2006;Lodieu et al 2006;Slesnick et al 2008;Lodieu et al 2008;Martin et al 2010), resulting in a total of 92 substellar members divided into 76 M6-M9, and 16 L0-L2 dwarfs. Slesnick et al (2008) presented the first spectroscopic mass function in USco over the full area of the association down to M = 0.02 M .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Multi-fibre optical spectroscopy of low-mass stars and brown dwarfs in Upper Scorpius

Lodieu

Dobbie

Hambly

2011

A&A

114

View full text Add to dashboard Cite

Context. Knowledge of the mass function in open clusters constitutes one way to critically examine the formation mechanisms proposed to explain the existence of low-mass stars and brown dwarfs. Aims. The aim of the project is to determine as accurately as possible the shape of the mass function across the stellar/substellar boundary in the young (5 Myr) and nearby (d = 145 pc) Upper Sco association. Methods. We have obtained multi-fibre intermediate-resolution (R ∼ 1100) optical (∼5750−8800 Å) spectroscopy of 94 photometric and proper motion selected low-mass star and brown dwarf candidates in Upper Sco with the AAOmega spectrograph on the AngloAustralian Telescope. Results. We have estimated the spectral types and measured the equivalent widths of youth (Hα) and gravity (Na I and K I) diagnostic features to confirm the spectroscopic membership of about 95% of the photometric and proper motion candidates extracted from 6.5 square degrees surveyed in Upper Sco by the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Clusters Survey (GCS). We also detect lithium in the spectra with the highest signal-to-noise, consolidating our conclusions about their youth. Furthermore, we derive an estimate of the efficiency of the photometric and proper motion selections used in our earlier studies using spectroscopic data obtained for a large number of stars falling into the instrument's field-of-view. We have estimated the effective temperatures and masses for each new spectroscopic member using the latest evolutionary models available for low-mass stars and brown dwarfs. Combining the current optical spectroscopy presented here with near-infrared spectroscopy obtained for the faintest photometric candidates, we confirm the shape and slope of our earlier photometric mass function. The luminosity function drawn from the spectroscopic sample of 113 USco members peaks at around M6 and is flat at later spectral type. We may detect the presence of the M7/M8 gap in the luminosity function as a result of the dust properties in substellar atmospheres. The mass function may peak at 0.2 M and is quite flat in the substellar regime. We observe a possible excess of cool low-mass brown dwarfs compared to IC 348 and the extrapolation of the field mass functions, supporting the original hypothesis that Upper Sco may possess an excess of brown dwarfs compared to other young regions. Conclusions. This result shows that the selection of photometric candidates based on five band photometry available from the UKIDSS GCS and complemented partially by proper motions can lead to a good representation of the spectroscopic mass function.

show abstract

VISIR/VLT observations of brown dwarfs in Upper Scorpius

Huélamo¹,

Bouy

Sterzik

et al. 2005

Astron Nachr

View full text Add to dashboard Cite

Abstract. We present mid-IR observations of a sample of very low-mass stars and brown dwarfs in the Upper Scorpius association. The main goal of these observations is to derive the disk frequency and the disk properties of the sample in order to shed light on brown dwarf formation theories. The observations have been performed with VISIR at the Very Large Telescope (VLT, Paranal). A total of ten targets were observed and six were detected. In this paper we show preliminary results for two of them: DENIS-PJ160334 and DENIS-PJ161939. While the former shows mid-IR fluxes consistent with pure photospheric emission, the latter displays strong mid-IR excesses which are probably related with a circumstellar disk.

show abstract

Spectroscopic Identification of DENIS-selected Brown Dwarf Candidates in the Upper Scorpius OB Association

Cited by 81 publications

References 36 publications

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

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

Multi-fibre optical spectroscopy of low-mass stars and brown dwarfs in Upper Scorpius

VISIR/VLT observations of brown dwarfs in Upper Scorpius

Contact Info

Product

Resources

About