J/AJ/110/2166 Variables in Sextans dSph galaxy (Mateo+ 1995)
Variable Stars in the Sextans Dwarf Spheroidal Galaxy
Mateo M.,Fischer P.,Krzeminski W.
<Astron. J. 110, 2166 (1995)>
=1995AJ....110.2166M 1995AJ....110.2166M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry, CCD
Abstract:
We describe a survey for variable stars in the Sextans dwarf
spheroidal (dSph) galaxy based on the analysis of 113 B and 48 V CCD
images of four fields covering a total area of 18'x18'. We have
identified 44 variables: 36 RR Lyr star, 6 anomalous Cepheids, one
long-period red variable, all probable members of Sextans, and one
foreground contact binary. We have used the pulsating stars to derive
a true distance modulus of 19.67±0.15 for Sextans (or D=86±6kpc),
where the error is primarily due to uncertainties in the
luminosity-metallicity relation for RR Lyr stars. Based on our new
data we conclude that [Fe/H]_Sex=-1.6±0.2, somewhat higher than the
value from Suntzeff et al. (1993ApJ...418..208S 1993ApJ...418..208S) obtained from the
analysis of fiber spectroscopy of the near-IR Calcium triplet. We
present a new deep color-magnitude diagram for Sextans which reveals
the presence of anomalous Cepheids in the galaxy. This young
population may represent as much as 25% of the total stellar content
of Sextans. We find a surprisingly strong correlation between the
frequency of anomalous Cepheids in dSph galaxies and galaxian
luminosity and speculate on the possible origin of this strange
effect. The RR Lyr stars in Sextans do not exhibit the Oosterhoff
dichotomy observed in globular clusters and in the Galactic halo
field.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2 65 161 Log of Sextans observations
table8 38 1038 B-band photometry of the Sextans variables
table9 38 560 V-band photometry of the Sextans variables
table10 72 2852 Photometry of non-variable stars in the deep
Sextans images
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Byte-by-byte Description of files: table2
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Bytes Format Units Label Explanations
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1- 3 I3 --- Frame Frame number
6- 13 A8 "DD/MM/YY" Date UT Date of observation
16- 17 I2 h UTmidh Time of mid-exposure
19- 20 I2 min UTmidm Time of mid-exposure
22- 23 I2 s UTmids Time of mid-exposure
26- 30 F5.1 s Exp Exposure time
33- 37 F5.3 --- AirMass Air-mass at mid-exposure
40- 53 F14.6 --- HJD_mid HJD of mid exposure, epoch 2448000
56- 58 F3.1 arcsec Seeing Seeing
61- 62 A2 --- Field Field, NE, NW, SE, SW
65 A1 --- Filt Filter, V or B
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Byte-by-byte Description of file: table8
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Bytes Format Units Label Explanations
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1- 3 A3 --- Star Variable star number, V1, V2, ... V46
5- 18 F14.6 --- HJD Heliocentric Julian Date of observation
21- 26 F6.3 mag Bmag B magnitude
28- 32 F5.3 mag e_Bmag B magnitude error
34- 38 F5.3 --- Phase *[0/1[? Pulsation or orbital phase
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Note for Phase:
Pulsation or orbital phase calculated with the ephemerides in Table
4 of the printed paper. The phasing is defined so that phase zero
corresponds to minimum light. No phase information is given for
V16, V23, V35, or V46 because reliable periods could not be
determined for these stars.
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Byte-by-byte Description of file: table9
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Bytes Format Units Label Explanations
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1- 3 A3 --- Star Variable star number, V1, V2, ... V46
5- 18 F14.6 --- HJD Heliocentric Julian Date of observation
21- 26 F6.3 mag Vmag V magnitude
28- 32 F5.3 mag e_Vmag V magnitude error
34- 38 F5.3 --- Phase *[0/1[? Pulsation or orbital phase
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Note for Phase:
Pulsation or orbital phase calculated with the ephemerides in Table
4 of the printed paper. The phasing is defined so that phase zero
corresponds to minimum light. No phase information is given for
V16, V23, V35, or V46 because reliable periods could not be
determined for these stars.
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Byte-by-byte Description of file: table10
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Bytes Format Units Label Explanations
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1- 4 I4 --- Star Star number
6- 9 I4 pix Xpos X coordinate
11-14 I4 pix Ypos Y coordinate
17-18 A2 --- Field Field, NE, NW, SE, SW
21-22 I2 h RAh Right ascension J2000
24-25 I2 min RAm Right ascension J2000
27-31 F5.2 s RAs Right ascension J2000
33 A1 --- DE- Declination sign
34 I1 deg DEd Declination, J2000 (always "1")
36-37 I2 arcmin DEm Declination, J2000
39-43 F5.2 arcsec DEs Declination, J2000
46-51 F6.3 mag Vmag V magnitude
54-58 F5.3 mag e_Vmag V magnitude error
60-65 F6.3 mag B-V B-V color
68-72 F5.3 mag e_B-V B-V color error
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Origin: AAS CD-ROM series, Volume 5, 1995 Lee Brotzman [ADS] 03-Nov-1995
(End) Patricia Bauer [CDS] 24-Oct-1996