J/ApJ/756/121 Variable stars in Her dwarf galaxy (Musella+, 2012)
Stellar archeology in the Galactic halo with ultra-faint dwarfs.
VII. Hercules.
Musella I., Ripepi V., Marconi M., Clementini G., Dall'Ora M.,
Scowcroft V., Moretti M.I., Di Fabrizio L., Greco C., Coppola G.,
Bersier D., Catelan M., Grado A., Limatola L., Smith H.A., Kinemuchi K.
<Astrophys. J., 756, 121 (2012)>
=2012ApJ...756..121M 2012ApJ...756..121M
ADC_Keywords: Photometry, UBV ; Stars, variable ; Galaxies, nearby
Keywords: galaxies: dwarf; galaxies: individual: Hercules;
stars: distances; stars: variables: general;
stars: variables: RR Lyrae; techniques: photometric
Abstract:
We present the first time-series study of the ultra-faint dwarf galaxy
Hercules. Using a variety of telescope/instrument facilities we
secured about 50 V and 80 B epochs. These data allowed us to detect
and characterize 10 pulsating variable stars in Hercules. Our final
sample includes six fundamental-mode (ab-type) and three
first-overtone (c-type) RR Lyrae stars, and one Anomalous Cepheid. The
average period of the ab-type RR Lyrae stars, <Pab≥0.68days
(σ=0.03days), places Hercules in the Oosterhoff II group, as
found for almost the totality of the ultra-faint dwarf galaxies
investigated so far for variability. The RR Lyrae stars were used to
obtain independent estimates of the metallicity, reddening, and
distance to Hercules, for which we find [Fe/H]=-2.30±0.15dex,
E(B-V)=0.09±0.02mag, and (m-M)0=20.6±0.1mag, in good agreement
with the literature values. We have obtained a V, B-V color-magnitude
diagram (CMD) of Hercules that reaches V∼25mag and extends beyond the
galaxy's half-light radius over a total area of 40'x36'. The CMD and
the RR Lyrae stars indicate the presence of a population as old and
metal-poor as (at least) the Galactic globular cluster M68.
Description:
Time-series observations in B and V of the Hercules UFD were obtained
over the period 2007 April to 2009 June, using a number of different
telescopes (the 2.5m INT/Wide-Field Camera, the 4.2m WHT/Prime Focus
Camera, the 2.2m ESO/Wide Field Imager, the 2m LT/Ratcam optical CCD
camera and the 2m Faulkes Telescope North/EM01).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 75 10 Identification and properties of variable stars
in the Hercules UFD (Ultra-Faint Dwarf spheroidal)
table3.dat 52 639 B, V photometry of the variable stars detected
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See also:
J/ApJ/752/42 : BV time series in Ursa Major II - Pap. VI (Dall'Ora+, 2012)
J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)
J/A+A/532/A104 : Hubble flow around Fornax cluster of gal. (Nasonova+, 2011)
J/ApJ/704/898 : Photometry of the Hercules dwarf galaxy (Sand+, 2009)
J/ApJ/674/L81 : Variable stars in dwarf galaxy CVn I - Pap. II (Kuehn+, 2008)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- ID Variable star identification (VNN) (1)
5 A1 --- f_ID [c] c: this star has very scattered light curves
7- 8 I2 h RAh [16] Hour of right ascension (J2000)
10- 11 I2 min RAm [30/31] Minute of right ascension (J2000)
13- 17 F5.2 s RAs Second of right ascension (J2000)
19 A1 --- DE- [+] Sign of declination (J2000)
20- 21 I2 deg DEd [12] Degree of declination (J2000)
23- 24 I2 arcmin DEm [40/52] Arcminute of declination (J2000)
26- 29 F4.1 arcsec DEs Arcsecond of declination (J2000)
31- 34 A4 --- Type Variable type (AC=Anomalous Cepheid)
36- 43 F8.6 d Per [0.3/0.8] Period
45- 53 F9.4 d T0 Time of maximum light (HJD-2450000)
55- 59 F5.2 mag <Vmag> [20.72/21.35] Mean V-band magnitude
61- 65 F5.2 mag <Bmag> [21.14/21.76] Mean B-band magnitude
67- 70 F4.2 mag Av [0.4/1.2] V-band extinction
72- 75 F4.2 mag Ab [0.5/1.4] B-band extinction
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Note (1): We have named the variable stars with an increasing number starting
from the center for Hercules set by Sand et al. (2009,
Cat. J/ApJ/704/898).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- ID Variable star name
5- 9 A5 --- Type Variable classification (AC=Anomalous Cepheid)
10- 19 F10.6 d HJD-V ? Heliocentric Julian Day of V band observation
(HJD-2454211)
21- 25 F5.2 mag Vmag [20.43/21.84]? The V band magnitude
27- 30 F4.2 mag e_Vmag [0.01/0.2]? The 1σ error in Vmag
32- 41 F10.6 d HJD-B Heliocentric Julian Day of B band observation
(HJD-2454211)
43- 47 F5.2 mag Bmag [20.81/22.37] The B band magnitude
49- 52 F4.2 mag e_Bmag [0.01/0.2] The 1σ error in Bmag
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History:
From electronic version of the journal
References:
Dall'Ora et al. Paper I : Bootes I 2006ApJ...653L.109D 2006ApJ...653L.109D
Kuehn et al. Paper II : CVn I 2008ApJ...674L..81K 2008ApJ...674L..81K Cat. J/ApJ/674/L81
Greco et al. Paper III: CVn II 2008ApJ...675L..73G 2008ApJ...675L..73G
Musella et al. Paper IV : Coma 2009ApJ...695L..83M 2009ApJ...695L..83M
Moretti et al. Paper V : Leo IV 2009ApJ...699L.125M 2009ApJ...699L.125M
Dall'Ora et al. Paper VI : UMaII 2012ApJ...752...42D 2012ApJ...752...42D Cat. J/ApJ/752/42
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 28-Mar-2014