J/A+A/562/A75 Spectra of 8 supergiants in nearby galaxies (Britavskiy+, 2014)
Identification of red supergiants in nearby galaxies with mid-IR photometry.
Britavskiy N.E., Bonanos A.Z., Mehner A., Garcia-Alvarez D., Prieto J.L.,
Morrell N.I.
<Astron. Astrophys. 562, A75 (2014)>
=2014A&A...562A..75B 2014A&A...562A..75B
ADC_Keywords: Galaxies, nearby ; Stars, supergiant ; Stars, late-type ;
Spectral types ; Spectroscopy
Keywords: stars: massive - stars: late-type - galaxies: individual: IC 1613 -
galaxies: individual: Sex A
Abstract:
The role of episodic mass loss in massive star evolution is one of the
outstanding questions of current stellar evolution theory. Episodic
mass loss produces dust and therefore causes evolved massive stars to
be very luminous in the mid-infrared and dim at optical wavelengths.
We aim to increase the number of investigated luminous mid-IR sources
to shed light on the late stages of these objects. To achieve this we
explore mid-IR selection criteria to identity dusty evolved massive
stars in two nearby galaxies. The method is based on mid-IR colors,
using 3.6um and 4.5um photometry from archival Spitzer Space Telescope
images of nearby galaxies and J-band from 2MASS. We apply our criteria
to two nearby star-forming dwarf-irregular galaxies: Sextans A and IC
1613, selecting 8 targets, which we follow up with spectroscopy.
Our spectral classification and analysis yielded the discovery of 2
M-type supergiants in IC 1613, 3 K-type supergiants and 1 candidate
F-type giant in Sextans A, and 2 foreground M giants. We show that the
proposed criteria provide an independent way for identifying dusty
evolved massive stars, which can be extended to all nearby galaxies
with available Spitzer/IRAC images at 3.6um and 4.5um.
Description:
The spectra of all program stars are presented. The log of
observations and other information about these spectra are available
into the article. The names of the files with spectra are the same as
in the article.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 135 8 Characteristics of the program stars: coordinates,
visual magnitude and optical color indices
table2.dat 73 8 Log of observations and derived radial velocities,
CaT* indices and spectral types
sp/* . 8 Individual spectrum as FITS files
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Star Star name
11- 12 I2 h RAh Right ascension (J2000)
14- 15 I2 min RAm Right ascension (J2000)
17- 22 F6.3 s RAs Right ascension (J2000)
24 A1 --- DE- Declination sign (J2000)
25- 26 I2 deg DEd Declination (J2000)
28- 29 I2 arcmin DEm Declination (J2000)
31- 36 F6.3 arcsec DEs Declination (J2000)
38- 43 F6.3 mag Vmag ?=- V magnitude
45- 49 F5.3 mag e_Vmag ? rms uncertainty on Vmag
50 A1 --- n_Vmag [*] Several magnitude measurements (1)
51- 55 F5.3 mag B-V ? B-V colour index
57- 61 F5.3 mag e_B-V ? rms uncertainty on B-V
63- 67 F5.3 mag V-R ? V-R colour index
69- 73 F5.3 mag e_V-R ? rms uncertainty on V-R
75- 80 F6.2 mag M3.6 Absolute 3.6um magnitude (2)
82- 87 F6.3 mag [3.6/4.5] IRAC [3.6]-[4.5] colour index
89- 92 F4.2 mag J-[3.6] J-[3.6] colour index
94- 97 F4.2 mag e_J-[3.6] rms uncertainty on J-[3.6]
99-103 F5.3 mag J-H J-H colour index
105-109 F5.3 mag e_J-H rms uncertainty on J-H
111-116 F6.3 mag H-K H-K colour index
118-122 F5.3 mag e_H-K rms uncertainty on H-K
124-128 F5.2 --- Q1 Near-IR index Q1 (3)
130-135 F6.2 --- Q2 ?=- Near-IR index Q2 (3)
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Note (1): Several independent estimates of magnitude and colors are available
for this star (17.97, 18.98, 19.33 for Vmag). Details in Section 4.2.
Note (2): The distance modulus that we used is 25.61±0.07mag for Sextans A
(Dolphin et al.. 2003AJ....125.1261D 2003AJ....125.1261D), and 24.32±0.06mag for IC 1613
(Dolphin et al., 2001ApJ...550..554D 2001ApJ...550..554D).
Note (3): Q1 and Q2 indices measure the deviation from the interstellar
reddening vector:
* Q1 in the J-H versus H-Ks diagram
* Q2 in the J-Ks versus Ks-[8.0] diagram.
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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- 9 A9 --- Star Star Name
11- 20 F10.5 d Date UT Date (HJD-2450000)
22- 25 I4 s Texp Exposure time
27- 29 I3 --- SNR Signal-to-noise ratio
31- 34 I4 km/s RV Radial velocity (4)
36- 37 I2 km/s e_RV rms uncertainty on RV
39- 42 F4.1 --- CaT* Calcium triplet index (defined by Cenarro
et al., 2001MNRAS.326..959C 2001MNRAS.326..959C)
44- 46 F3.1 --- e_CaT* rms uncertainty on CaT*
48- 54 A7 --- SpType Spectral temperature class (F, early K,
late K, M0-2, M2-4, or late M)
56- 60 A5 --- SpLum Luminosity classification
62- 73 A12 --- FileName Name of FITS file with spectrum in
subdirectory "sp"
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Note (4): RV(SexA)_=323km/s and RV(IC 1613)=-238km/s.
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Acknowledgements:
Nikolay Britavskiy, britavskiy(at)noa.gr
(End) Nikolay Britavskiy [NOA, Greece], Patricia Vannier [CDS] 20-Dec-2013