J/ApJ/661/1119 Spectroscopy in the 25 Ori group (Briceno+, 2007)
25 Orionis: a kinematically distinct 10 Myr old group in Orion OB1a.
Briceno C., Hartmann L., Hernandez J., Calvet N., Vivas A.K., Furesz G.,
Szentgyorgyi A.
<Astrophys. J., 661, 1119-1128 (2007)>
=2007ApJ...661.1119B 2007ApJ...661.1119B
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Radial velocities ;
Equivalent widths
Keywords: open clusters and associations: individual (Orion OB1) -
stars: kinematics - stars: pre-main sequence
Abstract:
We report here on the photometric and kinematic properties of a
well-defined group of nearly 200 low-mass pre-main-sequence stars,
concentrated within ∼1° of the early-B star 25 Ori, in the Orion
OB1a subassociation. We refer to this stellar aggregate as the 25
Orionis group. The group also harbors the Herbig Ae/Be star V346 Ori
and a dozen other early-type stars with photometry, parallaxes, and
some with IR excess emission, indicative of group membership.
Description:
We obtained low-resolution optical spectra of our candidate PMS stars
with a variety of telescopes and instruments. The brighter stars
(V~>16) were observed at the 1.5m telescope of the Whipple
Observatory equipped with the FAST Spectrograph.
For the fainter (V~<16) candidates in our photometric survey the bulk
of the spectroscopic follow-up was done with the Hectospec multifiber
spectrograph on the 6.5m MMT telescope at Mount Hopkins.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 82 78 Low-mass pre-main sequence members in our
25 Orionis and Ori OB1b Hectochelle fields
--------------------------------------------------------------------------------
See also:
J/AJ/131/2959 : Candidate low-mass PMS in 25 Orionis group (McGehee+, 2006)
J/AJ/129/907 : New Ori OB1 members (Briceno+, 2005)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- CVSO CIDA Variability Survey of Orion
running number (1)
5- 6 I2 h RAh Hour of Right Ascension (J2000)
8- 9 I2 min RAm Minute of Right Ascension (J2000)
11- 15 F5.2 s RAs Second of Right Ascension (J2000)
17 A1 --- DE- Sign of the Declination (J2000)
18- 19 I2 deg DEd Degree of Declination (J2000)
21- 22 I2 arcmin DEm Arcminute of Declination (J2000)
24- 27 F4.1 arcsec DEs Arcsecond of Declination (J2000)
29- 33 F5.2 mag Vmag The V band magnitude
35- 38 F4.2 mag V-Ic The Johnson-Cousins V-Ic color index
40- 43 A4 --- SpT Spectral type; errors are 1 subclass (2)
45- 49 F5.1 0.1nm EWHal Low-resolution equivalent width of Hα (2)
51- 53 F3.1 0.1nm EWLi ? Equivalent width of LiI line (6707Å) (2)
55- 60 F6.2 0.1nm EWHah High-resolution equivalent width of Hα (3)
62- 65 F4.1 km/s RV Radial velocity (3)
67- 69 F3.1 km/s e_RV The 1σ error in RV (3)
71- 74 F4.1 --- R The cross-correlation process R value (4)
76 A1 --- Type [CW] Classical or Weak T Tau star (5)
78- 82 A5 --- Loc Object location (25Ori or OB1b)
--------------------------------------------------------------------------------
Note (1): Continuing the numbering sequence from Briceno et al. (2005, Cat.
J/AJ/129/907); stars from that article have CVSO numbers ≤197. The
newly identified young members of 25 Ori and Orion OB1b presented here
start with object CVSO-198.
Note (2): Measurements from low-resolution spectra (FAST, Hydra, Hectospec).
Note (3): Measurements from the high-resolution Hectochelle spectra.
Note (4): A measurement of the ratio of the peak of the cross-correlation
to the estimated noise, and is therefore an indicator of the accuracy
of the results (Tonry & Davis, 1979AJ.....84.1511T 1979AJ.....84.1511T).
Note (5): The classification is based on spectral dependent threshold
W(Hα) following White & Basri (2003ApJ...582.1109W 2003ApJ...582.1109W). Stars
CVSO-200, 238 and 246 have no low-resolution spectra available yet.
They were classified as T Tauri stars from the Hectochelle spectra
based on the following criteria: having the appropriate magnitudes and
colors, radial velocity within 1-σ of the peak of the velocity
distribution for their location, peculiar Hα emission, either a
blue-shifted absorption component to Hα or this line very
strongly in emission (the later is the case for CVSO-238).
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 04-Apr-2009