J/ApJ/767/62 RR Lyrae stars BV photometry in UMa I (Garofalo+, 2013)
Variable stars in the ultra-faint dwarf spheroidal galaxy Ursa Major I.
Garofalo A., Cusano F., Clementini G., Ripepi V., Dall'Ora M.,
Moretti M.I., Coppola G., Musella I., Marconi M.
<Astrophys. J., 767, 62 (2013)>
=2013ApJ...767...62G 2013ApJ...767...62G
ADC_Keywords: Stars, variable ; Photometry, UBV ; Galaxies, nearby ;
Abundances, [Fe/H]
Keywords: galaxies: dwarf; galaxies: individual: UMa I; techniques: photometric;
Local Group; stars: distances; stars: variables: RR Lyrae
Abstract:
We have performed the first study of the variable star population of
Ursa Major I (UMa I), an ultra-faint dwarf satellite recently
discovered around the Milky Way (MW) by the Sloan Digital Sky Survey.
Combining time series observations in the B and V bands from four
different telescopes, we have identified seven RR Lyrae stars in
UMa I, of which five are fundamental-mode (RRab) and two are
first-overtone pulsators (RRc). Our V, B-V color-magnitude diagram of
UMa I reaches V∼23mag (at a signal-to-noise ratio of ∼6) and shows
features typical of a single old stellar population. The mean
pulsation period of the RRab stars <Pab≥0.628, σ=0.071 days
(or <Pab≥0.599, σ=0.032 days, if V4, the longest period and
brightest variable, is discarded) and the position on the
period-amplitude diagram suggest an Oosterhoff-intermediate
classification for the galaxy. The RR Lyrae stars trace the galaxy
horizontal branch (HB) at an average apparent magnitude of
<V(RR)≥20.43±0.02mag (average on six stars and discarding V4),
giving in turn a distance modulus for UMa I of
(m-M)0=19.94±0.13mag, distance d=97.3-5.7+6.0kpc, in the scale
where the distance modulus of the Large Magellanic Cloud is
18.5±0.1mag. Isodensity contours of UMa I red giants and HB stars
(including the RR Lyrae stars identified in this study) show that the
galaxy has an S-shaped structure, which is likely caused by the tidal
interaction with the MW. Photometric metallicities were derived for
six of the UMa I RR Lyrae stars from the parameters of the Fourier
decomposition of the V-band light curves, leading to an average metal
abundance of [Fe/H]=-2.29dex (σ=0.06dex, average on six stars)
on the Carretta et al. (2009, J/A+A/505/117) metallicity scale.
Description:
Time series V, B photometry of UMa I was obtained in the period
2009-2010 at three different telescopes.
The first set of V images was acquired using the Bologna Faint Object
Spectrograph and Camera (BFOSC) mounted on the 1.52m Cassini
Telescope of the INAF-Bologna Observatory in Loiano in 2009 Feb 25-26
and 2009 Mar 23-25 in V filter.
The second set of 41 V images as well as 38 B exposures were obtained
using the 2.0m telescope at the Thueringer Landessternwarte Tautenburg
(TLS) in 2009 April and May.
A third data set consisting of a few V images was obtained at the
1.54m Toppo telescope TT1 of the Osservatorio Astronomico di
Castelgrande using the Toppo Telescope Scientific Camera (TTSC) in
2009 Nov 26 and 2010 Mar 20,23.
Finally, to increase the data sample and to enlarge the temporal
baseline we complemented our photometry with V-band archive images of
UMa I obtained with the Suprime-Cam at the Subaru Telescope (PI: N.
Arimoto, ID proposals: o05167/o05223). These data were acquired during
the nights from 2005 December 31 to 2006 January 3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 83 7 Identification and properties of the RR Lyrae
stars identified in UMa I
table3.dat 31 444 Johnson-Cousins B, V photometry of UMa I
variable stars
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See also:
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/ApJ/756/121 : Variable stars in Her dwarf galaxy (Musella+, 2012)
J/ApJ/756/108 : HST VI phot. of variable stars in Leo T (Clementini+, 2012)
J/ApJ/752/42 : BV time series in Ursa Major II (Dall'Ora+, 2012)
J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009)
J/ApJ/678/865 : LONEOS-I RR Lyrae stars (Miceli+, 2008)
J/ApJ/674/L81 : Variable stars in dwarf galaxy CVn I (Kuehn+, 2008)
J/A+A/421/937 : Metal abundances of LMC RR Lyrae (Gratton+, 2004)
J/A+A/312/111 : [Fe/H] from RR Lyrae light curves (Jurcsik+, 1996)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- ID Star identifier (V1 to V7)
4- 5 I2 h RAh Hour of right ascension (J2000)
7- 8 I2 min RAm Minute of right ascension (J2000)
10- 13 F4.1 s RAs Second of right ascension (J2000)
15 A1 --- DE- Sign of declination (J2000)
16- 17 I2 deg DEd Degree of declination (J2000)
19- 20 I2 arcmin DEm Arcminute of declination (J2000)
22- 25 F4.1 arcsec DEs Arcsecond of declination (J2000)
27- 30 A4 --- Type RR Lyrae type (RRab or RRc)
32- 38 F7.5 d Per [0.3/0.8] Pulsation period (1)
40- 46 F7.3 d HJD Heliocentric Julian Day of maximum light;
HJD-2454000
48- 52 F5.2 mag <Bmag> [20.5/21] Intensity-weighted mean B magnitude
54- 58 F5.2 mag <Vmag> [20/20.5] Intensity-weighted mean V magnitude
60- 63 F4.2 mag Bamp [0.3/1.4] B-band amplitude
65- 68 F4.2 mag Vamp [0.3/1.1] V-band amplitude
70- 74 F5.2 [Sun] [Fe/H] [-2.3/-2.1]? Spectroscopic metallicity (2)
76- 79 F4.1 [Sun] [Fe/H]p [-2.4/-2.2]? Photometric metallicity (3)
81- 83 F3.1 [Sun] e_[Fe/H]p [0.1/0.3]? [Fe/H]p uncertainty (3)
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Note (1): With the only exception of the period for star V2 (see Section 3),
all periods are accurate to the fifth digit.
Note (2): Metallicities from Kirby et al. (2008ApJ...685L..43K 2008ApJ...685L..43K)
Note (3): Photometric metallicities from the Fourier parameters of the V-band
light curve; they are on the Carretta et al. 2009 (J/A+A/505/117)
metallicity scale. Note that of the RRab stars only V5 fully satisfies
the Jurcsik & Kovacs (1996, J/A+A/312/111) compatibility condition
(see the text for details).
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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- 2 A2 --- ID Star identifier (V1 to V7)
4- 7 A4 --- Type RR Lyrae type (RRab or RRc)
9 A1 --- Filt Filter used in the observation (B or V)
11- 20 F10.5 d HJD Heliocentric Julian Date of the
observation; HJD-2450000
22- 26 F5.2 mag mag [19.6/21.5] Observed magnitude in Filt
28- 31 F4.2 mag e_mag [0.01/0.4] Uncertainty in mag
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 19-Nov-2014