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J/ApJ/523/248       Variable stars in the Galactic center    (Ott+, 1999)

Variable and embedded stars in the Galactic center. Ott T., Eckart A., Genzel R. <Astrophys. J. 523, 248 (1999)> =1999ApJ...523..248O
ADC_Keywords: Binaries, eclipsing ; Stars, variable ; Polarization ; Photometry, infrared Keywords: binaries: eclipsing - Galaxy: center - polarization - stars: variables: other (long-period variables) Abstract: We report results of a time series analysis of high-resolution K-band imaging, photometry, and polarimetry of stars in the Galactic center cluster covering 7 consecutive years. In our statistical sample with mK<13, about half of the stars show indication of variability consistent with most of them being long-period variable, asymptotic giant branch stars. Some long-period variables already proposed in the literature are confirmed. They are identified with asymptotic giant branch stars. For the first time we show that the bright He I source IRS 16SW is a short-period variable with a period of ∼9.72 days. It is most likely an eclipsing binary with a lower mass limit of ≥100M. This confirms previous modeling of characteristics of the near-infrared spectra, which also indicated that IRS 16SW is a massive, young hot star. We also present the results of a polarization survey covering the central parsec of the Galaxy. Stars whose polarization vectors differ from the overall polarization, which is parallel to the Galactic plane, are mostly situated in the "minispiral", a region of high thermal flux density at centimeter radio wavelengths. Some of these sources appear extended in the high-resolution images and have featureless red spectra. We interpret these objects as young stars that may have just recently been formed and are still embedded in a dust shell. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 57 41 Polarization of individual sources table2.dat 51 218 Photometry of sources brighter than mK=13
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 13 A13 --- Name Object name 15- 18 F4.2 % p Degree of polarization 20- 22 I3 deg q Position angle of polarization vector 24- 27 F4.2 % e_p rms uncertainty on p (1) 29- 30 I2 deg e_q rms uncertainty on q (1) 32- 36 F5.2 mag Kmag K magnitude
Note (1): The standard errors of e_p=1.9% for the degree of polarization and e_q=18° for the position angle are the mean of standard deviations of all 27 sources that were contained in more than one pointing. These values have been adopted for sources that could only be measured in a single mosaic pointing as a save upper value.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 3 I3 --- [OEG99] Sequential number 5- 18 A14 --- Name Object name 20- 24 F5.2 arcsec oRA Offset in right ascension (1) 26- 31 F6.2 arcsec oDE Offset in declination (1) 33- 37 F5.2 mag Kmag K magnitude 39- 42 F4.2 mag e_Kmag rms uncertainty on Kmag 44- 50 F7.2 --- Chi2 Chi2 value (2)
Note (1): The offset is given relative to IRS 7 in arcseconds and is positive for north and east. Typical residual errors on the distances are ±0.1" (1σ). Note (2): Χ2 value is a reliable measure of variability of the sources.
History: From ApJ electronic version
(End) James Marcout, Patricia Bauer [CDS] 08-Nov-1999
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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