J/A+A/335/510 Optical spectra of 7 hot UV bright stars in GC (Moehler+, 1998)
Hot UV bright stars in globular clusters.
Moehler S., Landsman W., Napiwotzki R.
<Astron. Astrophys., 335, 510-516 (1998)>
=1998A&A...335..510M 1998A&A...335..510M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, giant ; Spectroscopy
Keywords: stars: post-AGB - globular clusters: individual:
NGC 2808, NGC 6121, NGC 6723, NGC 6752 - ultraviolet: stars
Abstract:
We have obtained medium-resolution spectra of seven UV-bright stars
discovered on images of four southern globular clusters obtained with
the Ultraviolet Imaging Telescope (UIT). Effective temperatures,
surface gravities and helium abundances are derived from LTE and
non-LTE model atmosphere fits. Three of the stars have sdO spectra,
including M4-Y453 (Teff=58800K, logg=5.15), NGC 6723-III60
(Teff=40600K, logg=4.46) and NGC 6752-B2004 (Teff=37000K,
logg=5.25). All seven stars lie along either post-extended horizontal
branch (EHB) or post-early AGB evolutionary tracks. The post-early AGB
stars show solar helium abundances, while the post-EHB stars are
helium deficient, similar to their EHB progenitors. Based on
observations collected at the European Southern Observatory (ESO No
57.E-0101)
Description:
Optical low-resolution spectra of 7 UV bright stars in globular
clusters are presented together with the atmospheric parameters
derived from them. The following globular clusters have been observed:
NGC2808, NGC6121, NGC6723, NGC6752. The continuum of the spectra has
ben normalized and they were resampled to laboratory wavelengths.
Effective temperatures, surface gravities, and helium abundances were
derived from line profile fits.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 70 7 List of stars with atmospheric parameters and
velocities
spectra.dat 102 2579 Spectra of stars
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Cluster Globular Cluster name
9- 14 A6 --- Star Star name
16- 17 I2 h RAh Right Ascension J2000 (hours)
19- 20 I2 min RAm Right Ascension J2000 (minutes)
22- 26 F5.2 s RAs Right Ascension J2000 (seconds)
28 A1 --- DE- Declination J2000 (sign)
29- 30 I2 deg DEd Declination J2000 (degrees)
32- 33 I2 arcmin DEm Declination J2000 (minutes)
35- 38 F4.1 arcsec DEs Declination J2000 (seconds)
40- 44 I5 K Teff Effective temperature
46- 49 F4.2 [cm/s2] logg logarithmic surface gravity
51- 55 F5.2 [-] logHe/H logarithmic helium abundance by particle
number relative to hydrogen
57- 60 I4 km/s HRV Heliocentric radial velocity
62- 70 A9 --- Status Evolutionary status
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Byte-by-byte Description of file: spectra.dat
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Bytes Format Units Label Explanations
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1- 11 E11.5 nm lambda Wavelength
13- 24 E12.5 --- C2946 ?=0 Normalized spectrum for NGC2808-C2946
26- 37 E12.5 --- C2947 ?=0 Normalized spectrum for NGC2808-C2947
39- 50 E12.5 --- C4594 ?=0 Normalized spectrum for NGC2808-C4594
52- 63 E12.5 --- Y453 ?=0 Normalized spectrum for NGC6121-Y453
65- 76 E12.5 --- III-60 ?=0 Normalized spectrum for NGC6723-III-60
78- 89 E12.5 --- IV-9 ?=0 Normalized spectrum for NGC6723-IV-9
91-102 E12.5 --- B2004 ?=0 Normalized spectrum for NGC6752-B2004
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Acknowledgements:
Sabine Moehler, smoehler(at)eso.org
(End) Patricia Vannier [CDS] 17-Dec-2015