J/ApJ/501/153 VRB photometry of red supergiants (Massey 1998)
Evolved massive stars in the local group.
I. Identification of red supergiants in NGC 6822, M31, and M33.
Massey P.
<Astrophys. J. 501, 153 (1998)>
=1998ApJ...501..153M 1998ApJ...501..153M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, supergiant ; Photometry, CCD ; Radial velocities
Keywords: galaxies: individual (NGC 6822, M33, M31) - stars: late-type -
stars: Wolf-Rayet - supergiants
Abstract:
Knowledge of the red supergiant (RSG) population of nearby galaxies
allows us to probe massive star evolution as a function of
metallicity; however, contamination by foreground Galactic dwarfs
dominates surveys for red stars in Local Group galaxies beyond the
Magellanic Clouds. Model atmospheres predict that low-gravity
supergiants will have B-V values that are redder by several tenths of
a magnitude than foreground dwarfs at a given V-R color, a result that
is largely independent of reddening. We conduct a BVR survey of
several fields in the Local Group galaxies NGC 6822, M33, and M31 as
well as neighboring control fields and identify RSG candidates from
CCD photometry. The survey is complete to V=20.5, corresponding to
MV=-4.5 or an Mbol of -6.3 for the reddest stars. Follow-up
spectroscopy at the Ca II triplet of 130 stars is used to demonstrate
that our photometric criterion for identifying RSGs is highly
successful (96% for stars brighter than V=19.5; 82% for V=19.5-20.5).
Classification spectra are also obtained for a number of stars in
order to calibrate color with spectral type empirically.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 113 912 Survey of red stars
table3.dat 79 138 Spectroscopy of red stars
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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- 14 A14 --- Star Star name
16- 17 I2 h RAh Right ascension (J2000)
19- 20 I2 min RAm Right ascension (J2000)
22- 26 F5.2 s RAs Right ascension (J2000)
28 A1 --- DE- Declination sign (J2000)
29- 30 I2 deg DEd Declination (J2000)
32- 33 I2 arcmin DEm Declination (J2000)
35- 38 F4.1 arcsec DEs Declination (J2000)
40- 44 F5.2 mag Vmag V magnitude
46- 49 F4.2 mag e_Vmag rms uncertainty on Vmag
51- 54 F4.2 mag B-V B-V colour index
56- 59 F4.2 mag e_B-V rms uncertainty on B-V
61- 64 F4.2 mag V-R V-R colour index
66- 69 F4.2 mag e_V-R rms uncertainty on V-R
71- 73 A3 --- Class Photometric classification (1)
75- 79 F5.2 mag D(B-V) Distance from the cutoff curve
81 A1 --- Crd? [IC] Isolated or crowded star? (2)
83- 86 A4 --- ClassS Spectroscopyc classification (1)
88- 95 A8 --- SType Spectral type
97-113 A17 --- CrossID Cross-identification (3)
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Note (1): fgd, Fgd: foreground star
rsg, RSG: red supergiant
Note (2): "I" indicates that the star is isolated, and
"C" indicates that the star is crowded, depending upon whether or not
there are any stars brighter than 1.0mag fainter within 3" or any
star as bright or brighter within 3"-5".
Note (3): Cross-identifications are given for stars with previous spectroscopy
by Humphreys (1980ApJ...238...65H 1980ApJ...238...65H) for NGC 6822,
Humphreys (1980ApJ...241..587H 1980ApJ...241..587H) for M33,
and Humphreys et al. (1988, Cat. J/AJ/96/1884) for M31.
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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- 14 A14 --- Star Star name (1)
16- 20 F5.2 mag Vmag V magnitude
22- 25 F4.2 mag B-V B-V colour index
27- 30 F4.2 mag V-R V-R colour index
32- 34 A3 --- Class rsg or fgd from photometry
36- 40 F5.2 mag D(B-V) Distance from the cutoff curve
42 A1 --- Crd? [IC] Isolated or crowded star? (2)
44- 47 I4 km/s RV ? Radial velocity (4)
48 A1 --- u_RV Uncertainty flag on RV
50- 60 A11 --- Lines Ca II triplet feature intensity (3)
62- 65 A4 --- RSG? rsg or fgd from spectroscopy
67- 69 A3 --- Agree? Yes, No
71- 80 A10 --- SType Spectral type
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Note (1): N6Con: NGC 6822 Control Field
Note (2): "I" indicates that the star is isolated, and
"C" indicates that the star is crowded, depending upon whether or not
there are any stars brighter than 1.0mag fainter within 3" or any
star as bright or brighter within 3"-5".
Note (3): "Weak," "moderate," and "strong" correspond to equivalent widths of
less than 8Å, 8-10Å, and greater than 10Å, respectively.
Note (4): Fields radio velocities
NGC 6822-A: RV = -75km/s
NGC 6822-B: RV = -55km/s
NGC 6822-C: RV = -42km/s
M33-A: RV = -200km/s
M33-B: RV = -220km/s
M33-D: RV = -155km/s
M33-E: RV = -130km/s
M33-F: RV = -130km/s
M33-G: RV = -135km/s
M31ob8: RV = -115km/s
M31ob48: RV = -145km/s
M31ob69: RV = -430km/s
M31ob78: RV = -555km/s
M31ob102: RV = -40km/s
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History: From ApJ electronic version
(End) James Marcout, Patricia Bauer [CDS] 19-Nov-1998