J/AJ/149/50 Photometry of 105 variable stars from CSTAR (Oelkers+, 2015)
Difference image analysis of defocused observations with CSTAR.
Oelkers R.J., Macri L.M., Wang L., Ashley M.C.B., Cui X., Feng L.-L.,
Gong X., Lawrence J.S., Qiang L., Luong-Van D., Pennypacker C.R., Yang H.,
Yuan X., York D.G., Zhou X., Zhu Z.
<Astron. J., 149, 50 (2015)>
=2015AJ....149...50O 2015AJ....149...50O
ADC_Keywords: Stars, variable ; Galactic pole, south ; Photometry, SDSS
Keywords: methods: data analysis - stars: variables: general
Abstract:
The Chinese Small Telescope ARray carried out high-cadence time-series
observations of 27 square degrees centered on the South Celestial Pole
during the Antarctic winter seasons of 2008-2010. Aperture photometry
of the 2008 and 2010 i-band images resulted in the discovery of over
200 variable stars. Yearly servicing left the array defocused for the
2009 winter season, during which the system also suffered from
intermittent frosting and power failures. Despite these technical
issues, nearly 800000 useful images were obtained using g, r, and
clear filters. We developed a combination of difference imaging and
aperture photometry to compensate for the highly crowded, blended, and
defocused frames. We present details of this approach, which may be
useful for the analysis of time-series data from other small-aperture
telescopes regardless of their image quality. Using this approach, we
were able to recover 68 previously known variables and detected
variability in 37 additional objects. We also have determined the
observing statistics for Dome A during the 2009 winter season; we find
the extinction due to clouds to be less than 0.1 and 0.4mag for 40%
and 63% of the dark time, respectively.
Description:
The Chinese Small Telescope ARray (CSTAR) was deployed at Dome A on
the Antarctic Plateau in early 2008 and carried out observations
during three Antarctic winter seasons (2008-2010). It is composed of
four Schmidt-Cassegrain wide-field telescopes, each with a 145mm
aperture and a field of view (FOV) 4.5° on a side. The focal
planes contain ANDOR DV435 1K*1K frame-transfer CCDs with a pixel size
of 13µm, equivalent to a plate scale of 15''/pixel. Three of the
filters are standard SDSS gri while the remaining one is a clear
filter. The telescopes are pointed toward the South Celestial Pole.
The observations presented in this paper began on 2009-March-20, with
the exposure time set to 5s. This was increased to 20s on
2009-April-14 as the sky level decreased.
We identified a total of 46 and 92 variables in g and r, respectively.
Taking into account objects that were identified in both bands, our
final catalog contains 105 objects. Of these objects, 37 were not
identified as variables in previous CSTAR papers (Wang et al. 2011,
cat. J/AJ/142/155; Wang et al. 2013, cat. J/AJ/146/139). Table 4 lists
the properties of these stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 87 105 Variable stars
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2012)
I/305 : The Guide Star Catalog, Version 2.3.2 (GSC2.3) (STScI, 2006)
J/AJ/146/139 : 2010 photometry of variable stars from Dome A (Wang+, 2013)
J/AJ/142/155 : Variable stars photometry from Dome A (Wang+, 2011)
J/PASP/122/347 : Chinese Small Telescope ARray (CSTAR) (Zhou+, 2010)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- CSTAR CSTAR identifier
9- 18 A10 --- GSC Identifier from the Guide Star Catalog (1)
20- 21 I2 h RAh Hour of Right Ascension (J2000)
23- 24 I2 min RAm Minute of Right Ascension (J2000)
26- 30 F5.2 s RAs Second of Right Ascension (J2000)
32 A1 --- DE- Sign of the Declination (J2000)
33- 34 I2 deg DEd Degree of Declination (J2000)
36- 37 I2 arcmin DEm Arcminute of Declination (J2000)
39- 43 F5.2 arcsec DEs Arcsecond of Declination (J2000)
45- 49 F5.2 mag imag ? Standard SDSS i-band magnitude
51- 55 F5.2 mag gmag ? Standard SDSS g-band magnitude
57- 61 F5.2 mag mag ? Magnitude from a clear filter
63- 67 F5.2 mag rmag ? Standard SDSS r-band magnitude
69- 70 A2 --- Type Type of variable (2)
72- 81 F10.6 d Per ? Period
83- 87 A5 --- Ref Catalog of reference (3)
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Note (1): The Guide Star Catalog, version 2.3.2 (GSC2.3, Cat. I/305).
Note (2): Variable type defined from Wang et al. 2013 (cat. J/AJ/146/139) as
follows:
DS = δ Scuti;
EC = Eclipsing Contact binary;
ED = Eclipsing Detached binary;
ES = Eclipsing Semi-detached binary;
GD = γ Doradus;
IR = Irregular;
LT = Long-Term variation;
MP = Multi-Periodic;
PR = unclassified periodic;
RL = RR Lyrae.
Note (3): The catalog codes are defined as follows:
AAVSO = American Association of Variable Star Observers
(http://www.aavso.org/);
W11 = Wang et al. (2011, J/AJ/142/155);
W13 = Wang et al. (2013, cat. J/AJ/146/139);
New = No current catalog entry.
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 24-Feb-2015