J/ApJ/597/323 Cool stars at the Galactic Center (Blum+, 2003)
Really cool stars and the star formation history at the Galactic Center.
Blum R.D., Ramirez S.V., Sellgren K., Olsen K.
<Astrophys. J., 597, 323-346 (2003)>
=2003ApJ...597..323B 2003ApJ...597..323B
ADC_Keywords: Stars, late-type ; Stars, giant ; Stars, supergiant ;
Effective temperatures ; Magnitudes ; Photometry, infrared
Keywords: Galaxy: center - stars: AGB and post-AGB - stars: late-type -
supergiants
Abstract:
We present λ/Δλ=550-1200 near-infrared H and K
spectra for a magnitude-limited sample of 79 asymptotic giant branch
and cool supergiant stars in the central ∼5pc (diameter) of the
Galaxy. We use a set of similar spectra obtained for solar
neighborhood stars with known Teff and Mbol that is in the same range
as the Galactic center (GC) sample to derive Teff and Mbol for the GC
sample. We then construct the H-R diagram for the GC sample. Using an
automated maximum likelihood routine, we derive a coarse star
formation history of the GC.
Description:
Spectroscopic observations of the comparison and GC stars were made
using the facility Infrared Spectrometer (IRS) and OSIRIS2
spectrometer mounted on the Cerro Tololo Interamerican Observatory
(CTIO) 4m Blanco Telescope over several runs beginning in 1997 and
ending in 2000 (see Tables 1 and 2). In addition, comparison stars
were observed at the Michigan-Dartmouth-MIT (MDM) 2.4m telescope on
Kitt Peak using the Ohio State University MOSAIC infrared
camera/spectrometer (Table 1).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 119 138 Galactic Center stars
table4.dat 69 13 *Galactic Center stars younger than 10Myr
table6.dat 86 81 Galactic Center star properties
table13.dat 122 43 Comparison star table of observations and indexes
refs.dat 77 21 Reference
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Note on table4.dat: Only stars with K0mag≤0.7 from the list of Blum et al.
(1996AJ....112.1988B 1996AJ....112.1988B) are included in this table.
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See also:
J/ApJ/470/864 : JHKL photometry of the Galactic Center (Blum+, 1996)
J/A+A/391/967 : H2O and SiO masers in the Galactic center (Sjouwerman+, 2002)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Object name (G1)
13 A1 --- n_Name [j] Individual note (2)
15- 17 I3 --- [BSD96] ? Blum et al. (1996, Cat. J/ApJ/470/864)
sequence number (3)
19 A1 --- f_[BSD96] [f] Flag on Blum number (4)
21- 26 F6.2 arcsec oRA ? Right Ascension offset (5)
28- 33 F6.2 arcsec oDE ? Declination offset (5)
35- 39 F5.2 mag Kmag Blum et al. (1996, Cat. J/ApJ/470/864)
K band magnitude (6)
41- 44 F4.2 mag e_Kmag Error in Kmag
46- 49 F4.2 mag J-K ? Blum et al. (1996, Cat. J/ApJ/470/864)
(J-K) color (6)
51- 54 F4.2 mag e_J-K ? Error in J-K
56- 59 F4.2 mag H-K ? Blum et al. (1996, Cat. J/ApJ/470/864)
(H-K) color (6)
61- 64 F4.2 mag e_H-K ? Error in H-K
66- 76 A11 "YYYY/MM/DD" Date Observation date
77- 95 A19 --- Ref BibCode of photometry reference
97-102 A6 --- Inst Instrument (G5)
104-117 A14 --- Notes Additional notes (8)
119 A1 --- f_Notes [gi] Flag on Notes (9)
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Note (2): 'j' indicates that this star is located in the Quintuplet
cluster Moneti et al. (1994MNRAS.268..194M 1994MNRAS.268..194M) and is included
for reference. Photometry is taken from Moneti et al.
(1994MNRAS.268..194M 1994MNRAS.268..194M). Position is 17:46:16.5-28:49:51 (J2000)
Note (3): Data tables in Blum et al. (1996, Cat. J/ApJ/470/864) were
truncated at # 147.
Note (4): 'f' (Star 72): star is included because it was observed
and analyzed at high spectral resolution by Ramirez et al.
(2000ApJ...537..205R 2000ApJ...537..205R). This star was not used in the star
formation history calculation because its K0 is below the
cut-off adopted; see Section 3.3.
Note (5): Offset is from IRS 7: 17:45:39.987-29:00:22.24 (J2000)
see Blum et al. (1996, Cat. J/ApJ/470/864).
Note (6): For #'s 1, 2, 6, 11, 40, 51, 53, 78, 81, 148, 162, 170, 174, 175,
and 183 photometry was derived using new unpublished J and/or H images
which were not available to Blum et al. (1996, Cat. J/ApJ/470/864,
hereafter BDS96). These new data were obtained with OSIRIS on 1999
March 03, but the field of view did not completely cover the same
field as for BDS96, thus some stars without H magnitudes given by
BDS96 were not observed. Improved H magnitudes could not be extracted
for several stars which were in the BDS96 field of view, primarily due
to crowding.
Note (8): Objects indicated with CSB00 or RAM00 have been observed at high
spectral resolution by Carr et al. (2000ApJ...530..307C 2000ApJ...530..307C) and Ramirez
et al. (2000ApJ...537..205R 2000ApJ...537..205R), respectively. Long period variable (LPV)
candidates are given by Blum et al. (1996AJ....112.1988B 1996AJ....112.1988B). Stars
indicated as "hot/young" are previously identified massive young stars
which lie in the K0 selected sample of this paper; see text.
Note (9): Notes as follows:
i = Analysis based on K-band spectrum only; see text, Section 2.3.
g = The spectrum of IRS 15NE shows strong characteristic cool star
features (see Table 6), but also broad He I and Brγ
emission suggesting it is a close blend. Because the cool star
features are quite strong and the emission-line stars are
generally fainter at K than the brighter M stars in the GC,
we assume the hot star contribution to this object is not
sufficient to remove it from our brightness selected sample.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Name (G1)
13- 14 I2 --- [BSD96] ? Blum et al. (1996, Cat. J/ApJ/470/864)
sequence number (1)
16- 20 I5 K Teff ? Effective temperature (2)
22- 24 I3 K e_Teff ? rms uncertainty on Teff
26- 36 A11 --- SpType Spectral type
38- 41 F4.2 mag K0mag Reddening corrected K band magnitude (3)
43- 46 F4.2 mag e_K0mag rms uncertainty in K0mag
48- 51 F4.2 mag AK Extinction in the K band (3)
53- 56 F4.2 mag e_AK rms uncertainty on AK
58- 63 F6.2 mag KMAG ? Absolute K band magnitude (G2)
65- 69 F5.1 mag Mbol ? Bolometric magnitude (2) (G3)
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Note (1): Data tables in Blum et al. (1996, Cat. J/ApJ/470/864, BDS96)
were truncated for star 147.
Note (2): Teff/Mbol for hot stars IRS 16NE, 16SW, and 13E from Najarro et
al. (1997A&A...325..700N 1997A&A...325..700N). Teff/Mbol for IRS 7 and VR 5-7 from
present work. Spectral types from reference listed in Table 2.
Note (3): Where K0Mag=Kmag-AK and AK taken from BDS96.
Stars 53, 78, and 81 use new unpublished H-band magnitudes that were
unavailable to BDS96. K0mag and AK for VR 5-7 derived using
photometry in Table 2.
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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- 11 A11 --- Name Object name (G1)
12- 14 I3 --- [BSD96] ? Blum et al. (1996, Cat. J/ApJ/470/864)
sequence number
16 A1 --- f_[BSD96] [i] Note about star 72 (2)
18- 19 I2 % CO The CO index percentage (G4)
21- 23 F3.1 % e_CO Uncertainty in CO
25- 26 I2 % H2O The H2O index percentage (G4)
28- 31 A4 --- Class Luminosity class set by CO & H20 (see text)
33- 36 I4 K Teff Effective temperature (4)
38- 40 I3 K e_Teff Uncertainty in Teff
42- 45 F4.2 mag K0mag ? Reddening corrected K band magnitude (5)
47- 50 F4.2 mag e_K0mag ? Uncertainty in K0mag
52- 57 F6.2 mag KMAG Absolute K band magnitude (G2)
59- 62 F4.2 mag AK Extinction in the K band (5)
64- 67 F4.2 mag e_AK ? Uncertainty in AK
69- 71 F3.1 mag BCK The K band bolometric correction (7)
73- 75 F3.1 mag DelAK K band extinction correction (8)
77- 81 F5.2 mag Mbol Bolometric magnitude (G3)
83- 86 F4.2 mag e_Mbol Uncertainty in Mbol
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Note (2): Star 72 is included because it was observed and analyzed at
high spectral resolution by Ramirez et al. (2000ApJ...537..205R 2000ApJ...537..205R).
This star was not used in the star formation history calculation
because its Komag is below the cut-off adopted; see Section 3.3.
Note (4): Derived from the CO index using the relationship of CO vs Teff
derived for the comparison stars. See the discussion in the text and
Figure 2.
Note (5): Where K0Mag=Kmag-AK and AK taken from Blum et al. (1996,
Cat. J/ApJ/470/864, BDS96).
For #'s 1, 2, 6, 11, 40, 148, 162, and 170 AK were derived in the
same way, but using new unpublished H magnitudes as given in Table 2.
Note (7): The correction is a linear function of Teff for giants,
and a constant for LPV's and supergiants; see text and Blum et al.
(1996AJ....112.1988B 1996AJ....112.1988B).
Note (8): To account for the range of intrinsic color in the GC stars.
DelAK = AK(BDS96) - AK(Corrected). See text.
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Byte-by-byte Description of file: table13.dat
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Bytes Format Units Label Explanations
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1 A1 --- Type [GSM] G: Giant, S: supergiant, M: Mira
3- 4 A2 --- --- [HR ]
6- 9 I4 --- HR ? HR (Bright Star, Cat. V/50) name
11- 12 A2 --- --- [HD ]
14- 19 I6 --- HD ? HD (Henry Draper, Cat. III/135) name
21- 30 A10 --- Name Other name
32- 35 I4 K Teff Effective temperature
37- 42 F6.2 mag Mbol Absolute bolometric magnitude
44- 54 A11 --- SpType MK Spectral type
56- 57 I2 % CO CO index percentage (G4)
59- 61 F3.1 % e_CO rms uncertainty on CO
63- 64 I2 % H2O ? H2O index percentage (G4)
66 I1 % e_H2O ? rms uncertainty on H2O
67 A1 --- n_H2O [bc] Note on H2O (2)
68- 84 A17 --- r_Teff Reference for Teff, in refs.dat file
86- 98 A13 --- r_Mbol Reference for Mbol, in refs.dat file
100-109 A10 "YYYY/MM/DD" Date Observation date
111-116 A6 --- Inst Instrument (G5)
118-122 A5 --- Ref Reference for observations made by others (4)
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Note (2): Note on H2O as follows:
b = Continuum may have been affected by data taking procedure; see
text. Strong expected H2O absorption not evident.
c = K-band spectrum only; continuum fit made in the same way as for
stars with H and K, but fitted only in the region between 2.20
and 2.29µm.
Note (4): Analysis uses spectrum for this star is presented by
BSD96 (Blum et al., 1996AJ....112.1988B 1996AJ....112.1988B) or
LVR92 (Lancon & Rocca-Volmerange, 1992, Cat. III/196).
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Ref Reference code
10- 28 A19 --- BibCode BibCode
30- 57 A28 --- Aut Authors' name
58- 77 A20 --- Com Comments
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Global notes:
Note (G1): As given by
Becklin & Neugebauer (1975ApJ...200L..71B 1975ApJ...200L..71B, GCIRS NN),
Lebofsky et al. (1982ApJ...263..736L 1982ApJ...263..736L),
Tollestrup, Becklin, & Capps (1989AJ.....98..204T 1989AJ.....98..204T, GCIRS NNWWW),
Krabbe et al. (1995ApJ...447L..95K 1995ApJ...447L..95K, MPE +x.x+yy.y), and
Blum et al. (1996, Cat. J/ApJ/470/864, [BSD96] NNN).
Note (G2): Derived from K0mag and a distance modulus of 14.52
(8kpc, Reid, 1993ARA&A..31..345R 1993ARA&A..31..345R)
Note (G3): Bol = K0mag + BCK + DelAK - the distance modulus to the GC
(14.52) for 8kpc Reid (1993ARA&A..31..345R 1993ARA&A..31..345R)
Note (G4): Indices are % absorption defined as 100*(1-Flux/Cont)
where Flux and Cont are the integrated fluxes in 0.015 micron bands in
the spectra. For CO, the Flux band is centered at 2.302 microns, and
the Cont band is taken at 2.284 microns. For H2O, Flux is for a band
centered at 2.0675 micron, and Cont is the same but derived from a fit
to the spectral continuum; see text. The uncertainty in the measured
H2O strength (3%) is taken from the scatter in the measurements for
comparison star IIIs and Is; see text.
Note (G5): Instruments as follows:
IRS = CTIO 4m: λ/Δλ = 560;
OSIRIS = CTIO 4m: λ/Δλ = 1200;
MOSAIC = MDM 1.3m: λ/Δλ = 750.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 19-Dec-2003