J/MNRAS/448/2737 New PMS K/M Stars in Upper Scorpius (Rizzuto+, 2015)
New pre-main-sequence stars in the Upper Scorpius subgroup of Sco-Cen.
Rizzuto A.C., Ireland M.J., Kraus A.L.
<Mon. Not. R. Astron. Soc., 448, 2737-2748 (2015)>
=2015MNRAS.448.2737R 2015MNRAS.448.2737R
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Equivalent widths;
MK spectral classification
Keywords: surveys; protoplanetary discs - stars: formation -
stars: pre-main-sequence -
open clusters and associations: individual: Sco-Cen
Abstract:
We present 237 new spectroscopically confirmed pre-main-sequence K-
and M-type stars in the young Upper Scorpius subgroup of the Sco-Cen
association, the nearest region of recent massive star formation.
Using the Wide-Field Spectrograph at the Australian National
University 2.3 m telescope at Siding Spring, we observed 397
kinematically and photometrically selected candidate members of Upper
Scorpius, and identified new members by the presence of lithium
absorption. The HR-diagram of the new members shows a spread of ages,
ranging from ∼3 to 20Myr, which broadly agrees with the current age
estimates of ∼5-10Myr. We find a significant range of Li 6708
equivalent widths among the members, and a minor dependence of
HR-diagram position on the measured equivalent width of the
Li 6708Å line, with members that appear younger having more
lithium. This could indicate the presence of either populations of
different age, or a spread of ages in Upper Scorpius. We also use
Wide-Field Infrared Survey Explorer data to infer circumstellar disc
presence in 25 of the members on the basis of infrared excesses,
including two candidate transition discs. We find that 11.2±3.4% the
M0-M2 spectral type (0.4-0.8M☉) Upper Sco stars display an
excess that indicates the presence of a gaseous disc.
Description:
We have selected candidate Upper Scorpius members using kinematic and
photometric data from UCAC4 (Zacharias et al., 2013, Cat. I/322),
2MASS (Skrutskie et al., 2006, Cat. VII/233), USNO-B (Monet et al. ,
2003, Cat. I/284) and APASS (Henden et al., 2012, J. Am. Assoc. Var.
Star Obs., 40, 430)
We obtained 18 nights of time using WiFeS, split over 2013 and 2014;
however, the majority of the 2013 nights were unusable due to weather.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 52 393 Summary of all candidates observed
(397 candidates; duplicates have been removed)
table2.dat 82 257 New pre-Main Sequence (PMS) stars in Upper Sco
table3.dat 69 27 List of members with circumstellar disk
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Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (J2000)
4- 5 I2 min RAm Right ascension (J2000)
7- 11 F5.2 s RAs Right ascension (J2000)
13 A1 --- DE- Declination sign (J2000)
14- 15 I2 deg DEd Declination (J2000)
17- 18 I2 arcmin DEm Declination (J2000)
20- 23 F4.1 arcsec DEs Declination (J2000)
25- 28 F4.1 mag Vmag [8.6/20] Visual Magnitude
30- 33 F4.1 mag Kmag [6.1/12] 2MASS Ks magnitude
35- 39 F5.1 mas/yr pmRA Proper Motion in RA*cosDE
41- 45 F5.1 mas/yr pmDE Proper Motion in DE
47 A1 --- r_pmDE [a/b] Source of proper motion (1)
49- 50 I2 % pMmb [0/99]? Probability of Membership
52 A1 --- sMmb [Y] Spectroscopic Member
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Note (1): Source of proper motion as follows:
a = UCAC4 (Zacharias et al. 2012, Cat. I/322)
b = Computed from multiple catalogs
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [RIK-]
5- 7 I3 --- RIK USco Member Name (RIK-NNN)
9- 25 A17 --- 2MASS 2MASS designation (JHHMMSSss+DDMMSSs)
27- 28 I2 h RAh Right ascension (J2000)
30- 31 I2 min RAm Right ascension (J2000)
33- 37 F5.2 s RAs Right ascension (J2000)
39 A1 --- DE- Declination sign
40- 41 I2 deg DEd Declination (J2000)
43- 44 I2 arcmin DEm Declination (J2000)
46- 49 F4.1 arcsec DEs Declination (J2000)
51- 54 F4.2 0.1nm EWLi [0.09/1.07] Li(6708Å) equivalent width (Å)
56- 59 F4.2 0.1nm e_EWLi [0.01/0.25] Uncertainty in EWLi
61- 67 F7.2 0.1nm EWHa [-130/4.2] H-α Equivalent Width
69- 73 F5.2 0.1nm e_EWHa [0.01/14] Uncertainty in EWHa
75- 78 A4 --- SpT Spectral Type
80- 82 F3.1 --- AV [0/2.8] Visual Extinction
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- 2MASS 2MASS designation
19- 20 I2 h RAh Right ascension (J2000)
22- 23 I2 min RAm Right ascension (J2000)
25- 29 F5.2 s RAs Right ascension (J2000)
31 A1 --- DE- Declination sign (J2000)
32- 33 I2 deg DEd Declination (J2000)
35- 36 I2 arcmin DEm Declination (J2000)
38- 41 F4.1 arcsec DEs Declination (J2000)
43- 44 A2 --- sMmb [Y? ] Spectroscopic Member
46- 48 A3 --- Exc [EX] Excess (E) in the WISE 2,3,4 bands (1)
50- 53 A4 --- Disk Disk Type (2)
55- 59 F5.2 mag W2mag WISE W2 (4.6um) magnitude
61- 64 F4.2 mag W3mag WISE W3 (11.6um) magnitude
66- 69 F4.2 mag W4mag WISE W4 (22.1um) magnitude
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Note (1): Three characters represent the W2 (4.6um), W3 (11.6um) and
W4 (22.1um) bands respectively, with:
E = implying an excess
X = no excess above the photosphere
Note (2): Disk Type as follows:
F = Full Disk
T = Transition Disk
E = Evolved Disk
D/ET = Depleted of Evolved Transition Disk
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Acknowledgements:
A.C. Rizzuto, arizz(at)astro.as.utexas.edu
(End) A.C. Rizzuto [University of Texas at Austin], P. Vannier [CDS] 04-May-2015