J/MNRAS/455/2163 BI light curves of DDO210 pulsating variables (Ordonez+, 2016)
The pulsating variable star population in DDO210.
Ordonez A.J., Sarajedini A.
<Mon. Not. R. Astron. Soc., 455, 2163-2177 (2016)>
=2016MNRAS.455.2163O 2016MNRAS.455.2163O (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, variable ; Photometry, HST
Keywords: stars: abundances - stars: variables: Cepheids -
stars: variables: RR Lyrae- galaxies: dwarf -
galaxies: individual: DDO210
Abstract:
We have probed the pulsating variable star content of the isolated
Local Group dwarf galaxy, DDO210 (Aquarius), using archival Advanced
Camera for Surveys/Hubble Space Telescope imaging in the F475W and
F814W passbands. We find a total of 32 RR Lyrae stars (24 ab-type; 8
c-type) and 75 Cepheid variables. The mean periods of the ab-type and
c-type RR Lyrae stars are calculated to be <Pab≥0.609±0.011 and
<Pc≥0.359±0.025d, respectively. The light-curve properties of the
fundamental mode RR Lyrae stars yield a mean metallicity of
<[Fe/H]≥-1.63±0.11dex for this ancient population, consistent with
a recent synthetic colour-magnitude diagram analysis. We find this
galaxy to be Oosterhoff-intermediate and lacking in high-amplitude,
short-period ab-type RR Lyrae, consistent with behaviour recently
observed for many dwarf spheroidals and ultrafaint dwarfs in the Local
Group. We find a distance modulus of µ=25.07±0.12 as determined
by the RR Lyrae stars, slightly larger but agreeing with recent
distance estimates from the red giant branch tip. We also find a
sizable population of Cepheid variables in this galaxy. We provide
evidence in favour of most if not all of these stars being
short-period classical Cepheids. Assuming all of these stars to be
classical Cepheids, we find that most of these Cepheids are ∼ 300 Myr
old, with the youngest Cepheids being offset from the older Cepheids
and the centre of the galaxy. We conclude that this may have resulted
from a migration of star formation in DDO210.
Description:
The data set used by Cole et al. (2014ApJ...794...64M 2014ApJ...794...64M) is very deep
and covers a time baseline conducive to identifying short-period
variable stars. These observations of DDO210 were originally intended
for use in a detailed SFH analysis for this dwarf, and thus cover a
significant portion of the galaxy while reaching photometric depths to
the main-sequence turnoff. The observations consisting of 22920s in
F475W and 33480s in F814W were taken with a cadence well suited for
identifying short-period variable stars. We retrieved these images
from the Mikulski Archive for Space Telescopes (MAST) for use in our
study.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 79 107 Properties of the pulsating variables in DDO210
table1.dat 34 5064 Time series photometry set for all variable
star candidates in DDO210
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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- 5 A5 --- VName Star variable name (VNNNN)
7- 8 I2 h RAh right ascension (J2000)
10- 11 I2 min RAm right ascension (J2000)
13- 20 F8.5 s RAs right ascension (J2000)
22 A1 --- DE- Declination sign (J2000)
23- 24 I2 deg DEd Declination (J2000)
26- 27 I2 arcmin DEm Declination (J2000)
29- 36 F8.5 arcsec DEs Declination (J2000)
38- 41 A4 --- VType Variable type
43- 47 F5.3 d Per Period
49- 53 F5.3 mag AB Amplitude of variation on B band
55- 59 F5.3 mag AI Amplitude of variation on I band
61- 66 F6.3 mag <Bmag> Mean Johnson B magnitude (Vega)
68- 73 F6.3 mag <Imag> Mean Cousins I magnitude (Vega)
75- 79 F5.3 mag <B-I> Mean B-I colour index
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- VName Star variable name (VNNNN)
7- 11 A5 --- Filter [F475W F814W] Filter
13- 21 F9.5 d HJD Heliocentric Julian date (HJD-2456000)
23- 28 F6.3 mag mag Magnitude in Filter
30- 34 F5.3 mag e_mag rms uncertainty on mag
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 29-Jul-2016