J/ApJ/685/947 SX Phe stars in Fornax. II. (Poretti+, 2008)
Variable stars in the Fornax dSph galaxy.
II. Pulsating stars below the horizontal branch.
Poretti E., Clementini G., Held E.V., Greco C., Mateo M.,
Dell'Arciprete L., Rizzi L., Gullieuszik M., Maio M.
<Astrophys. J., 685, 947-957 (2008)>
=2008ApJ...685..947P 2008ApJ...685..947P
ADC_Keywords: Stars, variable ; Photometry, UBV ; Galaxies, optical
Keywords: blue stragglers - delta Scuti - galaxies: distances and redshifts -
galaxies: individual (Fornax) - stars: variables: other -
techniques: photometric
Abstract:
We have carried out an intensive survey of the northern region of the
Fornax dwarf spheroidal galaxy with the aim of detecting the galaxy's
short-period pulsating stars (P<0.25 days). Observations collected
over three consecutive nights with the Wide Field Imager of the 2.2m
MPI telescope at ESO allowed us to detect 85 high-amplitude
(0.20-1.00mag in B light) variable stars with periods in the range
from 0.046 to 0.126 days, similar to SX Phoenicis stars in Galactic
metal-poor stellar populations. The plots of the observed periods vs.
the B and V magnitudes show a dispersion largely exceeding the
observational errors. To disentangle the matter, we separated the
first-overtone from the fundamental-mode pulsators and tentatively
identified a group of subluminous variables, about 0.35mag fainter
than the others. Their nature as either metal-poor intermediate-age
stars or stars formed by the merging of close binary systems is
discussed. The rich sample of the Fornax variables also led us to
reconstruct the period-luminosity relation for short-period pulsating
stars. An excellent linear fit, MV=-1.83(±0.08)-3.65(±0.07)logPF,
was obtained using 153 δ Scuti and SX Phoenicis stars in a
number of different stellar systems.
Description:
Observations of one field north of the center of Fornax dSph, centered
at 2:39:59 -34:10:00 (J2000.0), were obtained using the Wide-Field
Imager (WFI) at the 2.2m ESO/MPI telescope. The Fornax field was
observed on three consecutive nights (2001 November 8-11) for 6.2,
7.5, and 7.7hr, respectively.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 63 85 Identification and properties of the Fornax dSph
SX Phe stars
table3.dat 36 5838 BV photometry of the Fornax dSph SX Phe stars
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See also:
J/AJ/131/912 : BR photometry of Fornax dSph center (Olszewski+, 2006)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- [PCH2008] Variable identification (N-VNNNNN) (1)
10 I1 h RAh Hour of Right Ascension (J2000)
12- 13 I2 min RAm Minute of Right Ascension (J2000)
15- 18 F4.1 s RAs Second of Right Ascension (J2000)
20 A1 --- DE- Sign of the Declination (J2000)
21- 22 I2 deg DEd Degree of Declination (J2000)
24- 25 I2 arcmin DEm Arcminute of Declination (J2000)
27- 30 F4.1 arcsec DEs Arcsecond of Declination (J2000)
32- 38 F7.5 d Per Period
40- 44 F5.3 d Tmax Time of maximum: HJD-2452222.0
46- 50 F5.2 mag <Bmag> Mean WFI B-band mean magnitude
52- 55 F4.2 mag Bamp WFI B-band amplitude
57- 60 F4.2 mag <B-V> ? WFI mean B-V color index
62- 63 A2 --- Type Variability type (2)
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Note (1): Variable stars are ordered by increasing period, the first digit
of the ID gives the number of the CCD in the WFI mosaic, the second
part is the DAOPHOT identifier.
Note (2): Variability type as follows:
F = fundamental radial-mode pulsator;
FO = first overtone radial-mode pulsator;
SL = subluminous variable.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- [PCH2008] Variable identification (N-VNNNNN)
10 A1 --- Filt [BV] Filter used
12- 18 F7.5 d Per Period
20- 30 F11.3 d HJD Heliocentric Julian Date
32- 36 F5.2 mag mag Observed magnitude in Filt
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History:
From electronic version of the journal
References:
Greco et al. Paper I. 2007ApJ...670..332G 2007ApJ...670..332G
Greco et al. Paper III. 2009ApJ...701.1323G 2009ApJ...701.1323G
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 13-Dec-2010