J/ApJ/862/106 Stellar and substellar members in Coma Berenices (Tang+, 2018)
Characterization of stellar and substellar members in the Coma Berenices
star cluster.
Tang S.-Y., Chen W.P., Chiang P.S., Jose J., Herczeg G.J., Goldman B.
<Astrophys. J., 862, 106-106 (2018)>
=2018ApJ...862..106T 2018ApJ...862..106T (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; Stars, distances ; Proper motions ;
Photometry
Keywords: brown dwarfs - stars: evolution -
stars: luminosity function, mass function -
open clusters and associations: individual: Coma
Abstract:
We have identified stellar and substellar members in the nearby star
cluster Coma Berenices, using photometry, proper motions, and
distances of a combination of 2MASS, UKIDSS, URAT1, and Gaia/DR2 data.
Those with Gaia/DR2 parallax measurements provide the most reliable
sample to constrain the distance, averaging 86.7pc with a dispersion
of 7.1pc, and age of ∼800Myr, of the cluster. This age is older than
the 400-600 Myr commonly adopted in the literature. Our analysis,
complete within 5° of the cluster radius, leads to identification
of 192 candidates, among which, after field contamination is
considered, about 148 are true members. The members have J∼3mag to
∼17.5mag, corresponding to stellar masses 2.3-0.06M☉. The mass
function of the cluster peaks around 0.3M☉, and in the sense of
dN/dm=m-α, where N is the number of members and m is stellar
mass, with a slope α~=0.49±0.03 in the mass range
0.3-2.3M☉. This is much shallower than that of the field
population in the solar neighborhood. The slope α=-1.69±0.14
from 0.3M☉ to 0.06M☉, the lowest mass in our sample. The
cluster is mass-segregated and has a shape elongated toward the
Galactic plane. Our list contains nine substellar members, including
three new discoveries of an M8, an L1, and an L4 brown dwarfs,
extending from the previously known coolest members of late-M types to
even cooler types.
Description:
In this work, stellar membership is diagnosed by grouping of stars in
position in space and in kinematics. For bright stars, we use 2MASS
photometry and URAT1 (USNO Robotic Astrometric Telescope, Zacharias et
al., 2015, Cat. I/329) proper motions, whereas for faint stars, we
analyze both the photometry and proper motions from the UKIRT Infrared
Deep Sky Survey (UKIDSS, Kucas et al., 2012, Cat . II/316) and
Galactic Clusters Survey (GCS, Lawrence et al., 2012, Cat. II/314).
Distance information comes from parallax measurements by Gaia/DR2
(2018, Cat. I/345), or is estimated using the spectral type.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 101 192 Candidate Members of Coma Ber
table3.dat 89 15 Selected Literature Members beyond the
5° Radius Confirmed by This Work
table5.dat 28 158 Literature Candidates Rejected by Our Analysis
table6.dat 61 60 Stellar Colors from B2 to M4
table7.dat 76 10 Colors of M Dwarfs
table8.dat 60 24 Median Colors of Brown Dwarfs
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See also:
I/329 : URAT1 Catalog (Zacharias+ 2015)
II/316 : UKIDSS-DR6 Galactic Plane Survey (Lucas+ 2012)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- DMeth Distance method
10- 12 I3 --- Num [1/192] Internal index number
14- 22 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
24- 31 F8.5 deg DEdeg Declination in decimal degrees (J2000)
33- 38 F6.3 mag Jmag Apparent J band magnitude
40- 44 F5.3 mag e_Jmag Uncertainty in Jmag
46- 51 F6.3 mag Hmag ? Apparent H band magnitude
53- 57 F5.3 mag e_Hmag ? Uncertainty in Hmag
59- 64 F6.3 mag Ksmag Apparent Ks band magnitude
66- 70 F5.3 mag e_Ksmag Uncertainty in Ksmag
72- 76 F5.1 mas/yr pmRA Proper motion along RA*cos(DE)
78- 82 F5.1 mas/yr pmDE Proper motion along DE
84- 86 F3.1 mas/yr e_pm Uncertainty in proper motion
88- 92 F5.1 pc Dist Distance
94 A1 --- f_Dist [*] Flag on Dist (1)
96- 99 A4 --- Ref Reference codes (2)
101 I1 --- Data Data code (3)
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Note (1): Flag on Dist as follows:
* = Gaia/DR2 parallax measurements with ϖ/Δϖ<10
Note (2): Reference codes as follows:
a = Trumpler (1938LicOB..18..167T 1938LicOB..18..167T)
b = Casewell et al. (2006MNRAS.365..447C 2006MNRAS.365..447C)
c = Kraus & Hillenbrand (2007AJ....134.2340K 2007AJ....134.2340K)
d = Mermilliod et al. (2008A&A...491..951M 2008A&A...491..951M)
e = Melnikov & Eisloffel (2012A&A...544A.111M 2012A&A...544A.111M)
f = Gaia Collaboration et al. (2017A&A...601A..19G 2017A&A...601A..19G)
g = Casewell et al. (2005AN....326..991C 2005AN....326..991C)
Note (3): Data codes as follows:
1 = 2MASS photometry and Gaia/DR2 proper motions
2 = 2MASS photometry and URAT-1 proper motions
3 = UKIDSS/GCS photometry and Gaia/DR2 proper motions
4 = both photometry and proper motions are from UKIDSS/GCS
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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- 2 I2 --- Num [1/15] Internal index number
4- 12 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
14- 21 F8.5 deg DEdeg Declination in decimal degrees (J2000)
23- 28 F6.3 mag Jmag Apparent J band magnitude
30- 34 F5.3 mag e_Jmag Uncertainty in Jmag
36- 41 F6.3 mag Hmag ? Apparent H band magnitude
43- 47 F5.3 mag e_Hmag ? Uncertainty in Hmag
49- 53 F5.2 mag Ksmag Apparent Ks band magnitude
55- 59 F5.3 mag e_Ksmag Uncertainty in Ksmag
61- 66 F6.2 mas/yr pmRA Proper motion along RA*cos(DE)
68- 73 F6.2 mas/yr pmDE Proper motion along DE
75- 78 F4.2 mas/yr e_pm Uncertainty in proper motion
80- 85 F6.2 pc Dist Distance
87- 89 A3 --- Ref Reference codes (1)
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Note (1): Reference codes as follows:
a = Trumpler (1938LicOB..18..167T 1938LicOB..18..167T)
b = Casewell et al. (2006MNRAS.365..447C 2006MNRAS.365..447C)
c = Kraus & Hillenbrand (2007AJ....134.2340K 2007AJ....134.2340K)
d = Mermilliod et al. (2008A&A...491..951M 2008A&A...491..951M)
e = Melnikov & Eisloffel (2012A&A...544A.111M 2012A&A...544A.111M)
f = Gaia Collaboration et al. (2017A&A...601A..19G 2017A&A...601A..19G)
g = Casewell et al. (2005AN....326..991C 2005AN....326..991C)
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 deg RAdeg Right ascension (J2000)
13- 21 F9.6 deg DEdeg Declination (J2000)
24- 27 A4 --- Ref Reference (1)
28 I1 --- Rej Rejection code (2)
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Note (1): Reference as follows:
a = Trumpler (1938LicOB..18..167T 1938LicOB..18..167T)
b = Casewell et al. (2006MNRAS.365..447C 2006MNRAS.365..447C)
c = Kraus & Hillenbrand (2007AJ....134.2340K 2007AJ....134.2340K)
d = Mermilliod et al. (2008A&A...491..951M 2008A&A...491..951M)
e = Melnikov & Eisloffel (2012A&A...544A.111M 2012A&A...544A.111M)
f = Gaia Collaboration et al. (2017A&A...601A..19G 2017A&A...601A..19G)
g = Casewell et al. (2005AN....326..991C 2005AN....326..991C).
Note (2): Rejection code as follows:
1 = Rejection by proper motion
2 = Rejection by CMD
4 = Rejection by distance
3 = Rejection by proper motion and CMD
5 = Rejection by proper motion and distance
6 = Rejection by CMD and distance
7 = Rejection by proper motion, CMD and distance
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- SpType Spectral Type
9- 14 F6.3 mag g-r SDSS g-r colour index
17- 23 F7.4 mag r-i SDSS r-i colour index
25- 30 F6.3 mag i-z SDSS i-z colour index
33- 38 F6.4 mag z-J SDSS 2MASS i-J colour index
41- 46 F6.3 mag J-H 2MASS J-H colour index
49- 54 F6.3 mag H-Ks 2MASS H-Ks colour index
57- 61 F5.3 mag Ks-W1 2MASS WISE Ks-W1 colour index
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- SpType Spectral Type
9- 12 F4.2 mag g-r PS1 g-r colour index
17- 20 F4.2 mag r-i PS1 r-i colour index
25- 28 F4.2 mag i-z PS1 i-z colour index
33- 36 F4.2 mag z-y PS1 z-y colour index
41- 44 F4.2 mag y-J PS1 2MASS y-J colour index
49- 52 F4.2 mag J-H 2MASS J-H colour index
57- 60 F4.2 mag H-Ks 2MASS H-Ks colour index
65- 68 F4.2 mag Ks-W1 2MASS WISE Ks-W1 colour index
73- 76 F4.2 mag W1-W2 WISE W1-W2 colour index
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- SpType Spectral Type
9- 12 F4.2 mag i-z SDSS i-z colour index
17- 20 F4.2 mag z-Y SDSS UKIDSS z-Y colour index
25- 28 F4.2 mag Y-J UKIDSS Y-J colour index
32- 36 F5.2 mag J-H UKIDSS J-H colour index
40- 44 F5.2 mag H-K UKIDSS H-K colour index
49- 52 F4.2 mag K-W1 UKIDSS WISE K-W1 colour index
57- 60 F4.2 mag W1-W2 WISE W1-W2 colour index
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Acknowledgements:
Shih-Yun Tang, sytang(at)g.ncu.edu.tw
(End) Patricia Vannier [CDS] 23-Jun-2019