J/AJ/115/1856 Dwarf Cepheids in Carina (Mateo+, 1998)
Dwarf Cepheids in the Carina dwarf spheroidal galaxy.
Mateo M., Hurley-Keller D., Nemec J.
<Astron. J. 115, 1856 (1998)>
=1998AJ....115.1856M 1998AJ....115.1856M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry, UBV
Keywords: galaxies: dwarf - delta Scuti
Abstract:
We have discovered 20 dwarf Cepheids (DCs) in the Carina dwarf
spheroidal galaxy from an analysis of individual CCD images obtained
for a deep photometric study of the system. These short-period
pulsating variable stars are by far the most distant (∼100kpc) and
faintest (V∼23.0) DCs known. The Carina DCs obey a well-defined
period-luminosity relation, allowing us to readily distinguish between
overtone and fundamental pulsators in nearly every case. Unlike RR
Lyrae stars, the pulsation mode turns out to be uncorrelated with
light-curve shape, and the overtone pulsators do not tend toward
shorter periods compared with the fundamental pulsators. Using the
period-luminosity relations from Nemec, Nemec, & Lutz (1994,
Cat. J/AJ/108/222 and McNamara (1995AJ....109.1751M 1995AJ....109.1751M), we derive
(m-M)0=20.06±0.12, for E(B-V)=0.025 and [Fe/H]=-2.0, in good
agreement with recent, independent estimates of the distance/reddening
of Carina. The error reflects the uncertainties in the DC distance
scale, and in the metallicity and reddening of Carina. The frequency
of DCs among upper-main-sequence stars in Carina is approximately 3%.
The ratio of dwarf Cepheids to RR Lyrae stars in Carina is
0.13±0.10, though this result is highly sensitive to the star
formation history of Carina and the evolution of the horizontal
branch.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 71 20 Properties of newly discovered variable stars
in Carina
v1.dat 27 33 V1 BV photometry
v2.dat 27 40 V2 BV photometry
v3.dat 27 43 V3 BV photometry
v4.dat 27 32 V4 BV photometry
v5.dat 27 42 V5 BV photometry
v6.dat 27 42 V6 BV photometry
v7.dat 27 32 V7 BV photometry
v8.dat 27 40 V8 BV photometry
v9.dat 27 41 V9 BV photometry
v10.dat 27 32 V10 BV photometry
v11.dat 27 32 V11 BV photometry
v12.dat 27 42 V12 BV photometry
v13.dat 27 19 V13 BV photometry
v14.dat 27 20 V14 BV photometry
v15.dat 27 20 V15 BV photometry
v16.dat 27 20 V16 BV photometry
v17.dat 27 20 V17 BV photometry
v18.dat 27 20 V18 BV photometry
v19.dat 27 19 V19 BV photometry
v20.dat 27 20 V20 BV photometry
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- [MHN98] Variable name (V1 to V20), [MHN98] VNN in Simbad
5 I1 --- Field [1/3] Field number
7- 8 I2 h RAh Right ascension (B1950.0)
10- 11 I2 min RAm Right ascension (B1950.0)
13- 16 F4.1 s RAs Right ascension (B1950.0)
18 A1 --- DE- Declination sign (B1950.0)
19- 20 I2 deg DEd Declination (B1950.0)
22- 23 I2 arcmin DEm Declination (B1950.0)
25- 26 I2 arcsec DEs Declination (B1950.0)
28- 32 F5.2 mag <Vmag> Average V magnitude
34- 38 F5.2 mag <Bmag> Average B magnitude
40- 43 F4.2 mag - - colour index
45- 51 F7.5 d Per Period
53- 64 F12.4 d E0 Approximate time of minimum light
66- 69 F4.2 mag DVmag
71 A1 --- Mode [FO?] Mode (1)
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Note (1): F: stars pulsating in the fundamental mode
O: overtone pulsators
?: cases in which the mode is uncertain
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Byte-by-byte Description of file: v*.dat
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Bytes Format Units Label Explanations
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1 I1 --- Field [1/3] Field number
3 A1 --- Band [BV] Band
5- 16 F12.4 d HJD Heliocentric Julian date
18- 22 F5.2 mag mag Magnitude in Band filter
24- 27 F4.2 mag e_mag rms uncertainty on mag
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History: From AJ electronic version
(End) James Marcout, Patricia Bauer [CDS] 09-Mar-1999