J/MNRAS/450/3490 15 new brown dwarfs in Orion OB1a/25 Ori group (Downes+, 2015)
The number fraction of discs around brown dwarfs in Orion OB1a and the
25 Orionis group.
Downes J.J., Roman-Zuniga C., Ballesteros-Paredes J., Mateu C., Briceno C.,
Hernandez J., Petr-Gotzens M.G., Calvet N., Hartmann L., Mauco K.
<Mon. Not. R. Astron. Soc., 450, 3490-3502 (2015)>
=2015MNRAS.450.3490D 2015MNRAS.450.3490D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, late-type ; Photometry, SDSS ;
Photometry, infrared
Keywords: brown dwarfs - stars: low-mass -
open clusters and associations: individual: 25 Orionis
Abstract:
We present a study of 15 new brown dwarfs belonging to the ∼7Myr old
25 Orionis group and Orion OB1a subassociation with spectral types
between M6 and M9 and estimated masses between ∼0.07 and
∼0.01M☉. By comparing them through a Bayesian method with
low-mass stars (0.8≲M/M☉ ≲0.1) from previous works in the 25
Orionis group, we found statistically significant differences in the
number fraction of classical T Tauri stars, Weak T Tauri stars, class
II, evolved discs and purely photospheric emitters at both sides of
the substellar mass limit. Particularly, we found a fraction of
3.9+2.4-1.6 percent low-mass stars classified as Classic T Tauri
star and class II or evolved discs, against a fraction of
33.3+10.8-9.8 percent in the substellar mass domain. Our results
support the suggested scenario in which the dissipation of discs is
less efficient for decreasing mass of the central object.
Description:
For this work, we studied 21 targets from the sample of photometric BD
candidates with expected spectral types between M6 and L1, obtained
during the survey of the 25 Orionis group and its surroundings carried
out by Downes et al. (2014, Cat. J/MNRAS/444/1793).
We have carried out the spectroscopic observations of the 21
candidates with the OSIRIS instrument at the Gran Telescopio de
Canarias (GTC).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 59 21 Observing log for the observations with OSIRIS
at GTC
table2.dat 43 21 Spectroscopic catalogue for the candidates
observed with OSIRIS
table3.dat 327 15 Photometric catalog of the new BDs confirmed as
members of 25 Ori or Orion OB1a
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See also:
J/MNRAS/444/1793 : 25 Ori group low-mass stars (Downes+, 2014)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Target [1/21] Target ID
4- 26 A23 --- Obs.date Beginning of the observation
(YYYY-MM-DDThh:mm:ss.sss)
28- 31 I4 s Tint Integration time
33- 36 F4.2 --- Airmass Airmass
38- 40 F3.1 s Seeing Seeing
42- 59 A18 --- Obs Observing conditions
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Target [1/21] Target ID
4- 7 A4 --- SpType MK spectral type
9- 11 F3.1 --- e_SpType Error on SpType
13- 14 I2 --- CaHa [-1/1] Flag for CaHA feature (1)
16- 17 I2 --- VO1 [-1/1] Flag for VO1 feature (1)
19- 20 I2 --- VO2 [-1/1] Flag for VO2 feature (1)
22- 23 I2 --- KI [-1/1] Flag for KI feature (1)
25- 26 I2 --- NaI [-1/1] Flag for NaI feature (1)
28- 31 I4 0.1nm EWHa ?=0 Hα line width
33- 36 F4.2 mag AV ?=0 Extincion in V-band
38- 43 A6 --- Memb Membership
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Note (1): Flag that indicates if the spectral feature is consistent with:
1 = a young BD
-1 = a field dwarf
0 = not conclusive
See Section 3 for details.
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Target [1/21] Target ID
4- 22 A19 --- WISE WISE (JHHMMSS.ss+DDMMSS.s)
24- 39 A16 --- 2MASS 2MASS name (HHMMSSss+DDMMSSs)
41- 59 A19 --- SDSS9 SDSS9 name (JHHMMSS.ss+DDMMSS.s)
61- 70 F10.7 deg RAdeg VISTA Right ascension (J2000)
72- 80 F9.7 deg DEdeg VISTA Declination (J2000)
82- 87 F6.3 mag gmag ? SDSS g magnitude
89- 93 F5.3 mag e_gmag ? rms uncertainty on gmag
95-100 F6.3 mag rmag ? SDSS r magnitude
102-106 F5.3 mag e_rmag ? rms uncertainty on rmag
108-113 F6.3 mag imag ? SDSS i magnitude
115-119 F5.3 mag e_imag ? rms uncertainty on imag
121-126 F6.3 mag Imag VISTA I magnitude
128-132 F5.3 mag e_Imag rms uncertainty on Imag
134-139 F6.3 mag zmag ? SDSS z magnitude
141-145 F5.3 mag e_zmag ? rms uncertainty on zmag
147-153 F7.4 mag Zmag VISTA Z magnitude
155-164 F10.8 mag e_Zmag rms uncertainty on Zmag
166-172 F7.4 mag Ymag VISTA Y magnitude
174-183 F10.8 mag e_Ymag rms uncertainty onYmag
185-190 F6.3 mag Jmag VISTA J magnitude
192-201 F10.8 mag e_Jmag rms uncertainty on Jmag
203-208 F6.3 mag Hmag VISTA H magnitude
210-219 F10.8 mag e_Hmag rms uncertainty on Hmag
221-226 F6.3 mag Kmag VISTA Ks magnitude
228-236 F9.7 mag e_Kmag rms uncertainty on Kmag
238-243 F6.3 mag [3.4] ? WISE 3.4um magnitude
245-249 F5.3 mag e_[3.4] ? rms uncertainty on [3.4]
251-256 F6.3 mag [3.6] IRAC 3.6um magnitude
258-262 F5.3 mag e_[3.6] rms uncertainty on [3.6]
264-269 F6.3 mag [4.5] IRAC 4.5um magnitude
271-275 F5.3 mag e_[4.5] rms uncertainty on [4.5]
277-282 F6.3 mag [4.6] ? WISE 4.6um magnitude
284-288 F5.3 mag e_[4.6] ? rms uncertainty on [4.6]
290-295 F6.3 mag [5.8] ? IRAC 5.8um magnitude
297-301 F5.3 mag e_[5.8] ? rms uncertainty on [5.8]
303-308 F6.3 mag [8.0] ? IRAC 8.0um magnitude
310-314 F5.3 mag e_[8.0] ? rms uncertainty on [8.0]
316-321 F6.3 mag [12] ? WISE 12um magnitude
323-327 F5.3 mag e_[12] ? rms uncertainty on [12]
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 11-Dec-2015