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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
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:
FileName Lrecl Records Explanations
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
Note on table4.dat: Only stars with K0mag≤0.7 from the list of Blum et al. (1996AJ....112.1988B) are included in this table.
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
Bytes Format Units Label Explanations
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)
Note (2): 'j' indicates that this star is located in the Quintuplet cluster Moneti et al. (1994MNRAS.268..194M) and is included for reference. Photometry is taken from Moneti et al. (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). 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) and Ramirez et al. (2000ApJ...537..205R), respectively. Long period variable (LPV) candidates are given by Blum et al. (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.
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
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)
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). 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.
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
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 H_2_O 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
Note (2): Star 72 is included because it was observed and analyzed at high spectral resolution by Ramirez et al. (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). Note (8): To account for the range of intrinsic color in the GC stars. DelAK = AK(BDS96) - AK(Corrected). See text.
Byte-by-byte Description of file: table13.dat
Bytes Format Units Label Explanations
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 ? H_2_O 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)
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) or LVR92 (Lancon & Rocca-Volmerange, 1992, Cat. III/196).
Byte-by-byte Description of file: refs.dat
Bytes Format Units Label Explanations
1- 6 A6 --- Ref Reference code 10- 28 A19 --- BibCode BibCode 30- 57 A28 --- Aut Authors' name 58- 77 A20 --- Com Comments
Global notes: Note (G1): As given by Becklin & Neugebauer (1975ApJ...200L..71B, GCIRS NN), Lebofsky et al. (1982ApJ...263..736L), Tollestrup, Becklin, & Capps (1989AJ.....98..204T, GCIRS NNWWW), Krabbe et al. (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) Note (G3): Bol = K0mag + BCK + DelAK - the distance modulus to the GC (14.52) for 8kpc Reid (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.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 19-Dec-2003
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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