J/MNRAS/416/2477 STEREO observations of variable stars (Wraight+, 2011)
STEREO observations of stars and the search for exoplanets.
Wraight K.T., White G.J., Bewsher D., Norton A.J..
<Mon. Not. R. Astron. Soc. 416, 2477 (2011)>
=2011MNRAS.416.2477W 2011MNRAS.416.2477W
ADC_Keywords: Binaries, eclipsing ; Photometry, CCD
Mission_Name: STEREO
Keywords: methods: data analysis - binaries: eclipsing -
space vehicles: instruments - stars: individual: HD 213597 -
stars: individual: NSV 7359 - stars: individual: V471 Tau
Abstract:
The feasibility of using data from the NASA STEREO mission for
variable star and asteroseismology studies has been examined. A data
analysis pipeline has been developed that is able to apply selected
algorithms to the entire database of nearly a million stars to search
for signs of variability. An analysis limited to stars of magnitude
10.5 has been carried out, which has resulted in the extraction of 263
eclipsing binaries (EBs), of which 122 are not recorded as such in the
SIMBAD online database. The characteristics of the STEREO observations
are shown to be extremely well-suited to variable star studies with
the ability to provide continuous phase coverage for extended periods
as well as repeated visits that allow both short and long term
variability to be observed. This will greatly inform studies of
particular stars, such as the pre-cataclysmic variable V471 Tau, as
well as entire classes of stars, including many forms of rotational
variability. The high-precision photometry has also revealed a
potentially substellar companion to a bright (R=7.5mag) nearby star
(HD 213597), detected with 5 sigma significance. This would provide a
significant contribution to exoplanet research if follow-up
observations ascertain the mass to be within the planetary domain.
Some particularly unusual EBs from the recovered sample are discussed,
including a possible reclassification of a well-known star as an EB
rather than a rotational variable (HR 7355) and several particularly
eccentric systems, including very long-period EBs.
Description:
Description of the analysis of stars brighter than R=10.5mag from the
Heliospheric Imager on the STEREO-Ahead spacecraft (STEREO/HI-1A).
Analysis of the effectiveness of the different algorithms used.
Analysis of different trends amongst the sample of EBs detected.
Photometric lightcurves of several individual stars of interest given,
including all measurably eccentric EBs detected. Statistics for 263
eclipsing binaries. Lightcurves for all EBs provided in supporting
information in the electronic version of the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 167 263 Statistics for 263 EBs and the significance of
their detection by different algorithms
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 deg RAdeg Right Ascension (J2000)
12- 22 F11.7 deg DEdeg Declination (J2000)
24- 28 F5.3 mag PED Primary Eclipse Depth
30- 37 F8.5 d Per Period
39- 46 F8.5 mag Wmag Weighted mean magnitude (4)
48- 54 F7.5 --- BLS Box-Least-Squares variability index
(Kovacs et al., 2002A&A...391..369K 2002A&A...391..369K)
56- 69 F14.7 --- SID Stetson variability index
71- 78 F8.4 --- LS Peak Lomb-Scargle power (1982ApJ...263..835S 1982ApJ...263..835S)
80- 84 F5.3 --- ecosw ?=- Minimum eccentricity |e*cos(ω)|
86- 90 F5.3 --- e_ecosw ?=- rms uncertainty on |e*cos(ω)|
92-102 A11 --- SpType MK spectral type (1)
104-126 A23 --- SimID ID of closest star in SIMBAD at RA/DE
128-151 A24 --- SimID2 ID of alternative nearby star (2)
153 I1 --- EB [0,1] 1 = known eclipsing binary flag
155-166 F12.6 d MJD mid-eclipse Modified Julian Date
167 A1 --- Note [*] Note for CCDM J03295+2107 (3)
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Note (1): The spectral type given is of the star in SIMBAD closest to the
RA/DE coordinates (See also Note (2)).
Note (2): Due to the large (70") pixel scale of the Heliospheric Imager it is
not always possible to be confident of which star is responsible for the
variability detected. When a nearby star may potentially be the source of the
variability, its identity is recorded here. If either of these stars is
recorded as an eclipsing binary in SIMBAD, or the references imply or state
they are, then the Known EB flag is set to 1.
Note (3): For CCDM J03295+2107AB (row 11), has since been found from an
analysis including data from the STEREO-Behind spacecraft (STEREO/HI-1B) data
to be an eccentric eclipsing binary with a period of 16.6291 days and a
minimum eccentricity (|e*cos(w)|) of 0.34±0.01. The original published
version has about one third of this period, as the analysis instead identified
by mistake the time between primary and secondary eclipses. The additional
data from STEREO/HI-1B also allowed a refinement of the mid-eclipse time to
54212.12009 MJD.
Tablea1.dat contains these new data, and then differs from published version
in the paper.
Note (4): the filter bandpass is 630-730nm, with some contributions
around 400 and 950nm)
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Acknowledgements:
Karl Wraight, k.t.wraight(at)open.ac.uk
(End) K.T. Wraight [OU, England], Patricia Vannier [CDS] 22-Sep-2011