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INTOMCVS - INTEGRAL OMC First Catalog of Optically Variable Sources

HEASARC
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Overview

The Optical Monitoring Camera (OMC) on board the high-energy INTEGRAL satellite provides photometry in the Johnson V-band within a 5 by 5 degree field of view. The OMC is able to detect optical sources brighter than around V ~ 18, from a previously selected list of potential targets of interest. After more than nine years of observations, the OMC database contains light curves for more than 70 000 sources (with more than 50 photometric points each). The objectives of the present work have been to characterize the potential variability of the objects monitored by OMC, to identify periodic sources and to compute their periods, taking advantage of the stability and long monitoring time of the OMC.

The first catalog of variable sources observed by OMC has been developed with observations from October 2002 to February 2010. To detect potential variability, the authors have performed a chi-squared test, finding 5263 variable sources, for 1337 of which the periods have been determined, out of an initial sample of 6071 objects with good photometric quality and more than 300 data points each. They have studied the potential periodicity of these sources using a method based on the phase dispersion minimization technique, optimized to handle light curves with very different shapes. For each object in the catalog, the median of the visual magnitude, the magnitude at maximum and minimum brightness in the light curve during the window of observations and the period, when found, are provided. The types of variable objects in the catalogue include eclipsing binaries, pulsating stars, rotating stars, eruptive stars, extragalactic objects, X-ray binaries, cataclysmic variables, Be stars and other objects with unknown kinds of variability.

Links to charts for each object, including the DSS image around the target, the unfolded and folded light curves with the periods that the authors have derived and/or with the cataloged ones are provided in this database.


Catalog Bibcode

2012A&A...548A..79A

References

The first INTEGRAL-OMC catalogue of optically variable sources.
    Alfonso-Garzon J., Domingo A., Mas-Hesse J.M., Gimenez A.
    <Astron. Astrophys. 548, A79 (2012)>
    =2012A&A...548A..79A        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in January 2013 based on the CDS Catalog J/A+A/548/A79 file omc-var.dat.

Data Products

For each entry in this table two data products are available at CDS: (i) an ASCII file of the photometric data containing 3 columns: the time expressed as the Barytime, the Barycentric Julian Date expressed in Barycentric Dynamical Time (TDB) (BJD-2451544.5), the observed V magnitude and the mean error in the observed V magnitude, and (ii) a web page showing the DSS red-image field of view containing the object, with a red circle representing the OMC photometric aperture, and graphs and histograms characterizing the variability of the object. The contents of these charts are described in detail in Appendix A of the reference paper, which also shows 8 sample charts.

Parameters

OMC_ID
The OMC identifier of the variable object.

Name
The SIMBAD name of the variable object. For clarity, the HEASARC has removed the SIMBAD short type prefixes of 'V*' (for variable star) and '**' (for double star) from these names, but retained the SIMBAD short type prefixes of 'SV*' (for suspected variable star), as some of the star names of this type, e.g., 'SV* BV 527', would otherwise fail to be resolved by SIMBAD.

SIMBAD_Flag
This flag parameter is set to 'N' to indicate that the object is not (or not yet) in SIMBAD.

RA
The Right Ascension of the variable object in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.01 seconds of time in the original table.

Dec
The Declination of the variable object in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.01 arcseconds in the original table.

LII
The Galactic Longitude of the variable object.

BII
The Galactic Latitude of the variable object.

SIMBAD_Short_Type
The SIMBAD object type of the variable star. These classes are described at http://simbad.u-strasbg.fr/simbad/sim-display?data=otypes .

Spect_Type
The spectral type of the object as given in Simbad.

Variability_Type
The variability type of the object as given in the Variable Star Index (VSX, available at the HEASARC as the AAVSOVSX table), else taken from the Simbad database.

Variability_Group
The variability group to which the object belongs. Based on the variability types, the authors have defined 10 different variability groups and have assigned each source to one of them: eclipsing, pulsating, rotating, eruptive, cataclysmic, Xbinaries (for X-ray binaries), Be, extragalactic, varstar (for variable stars which lack specific variability types and other (for objects of other types).

Vmag
The median V magnitude of the object.

Vmag_Error
The mean value of the V-magnitude error of the object.

Max_Vmag
The V magnitude of the object at maximum brightness.

Min_Vmag
The V magnitude of the object at minimum brightness.

Period
The period of the variability, in days.

Period_Error
The uncertainty in the variability period, in days.

Obs_Time_Span
The time span of the OMC observations, in days.

Contamination_Flags
This flag parameter contains information on possible photometric contamination of the OMC measurements by nearby stars, using three different methods, coded as a 3-digit number, one number for each method. (For the data analyzed in this study, fluxes and magnitudes were derived from a photometric aperture of 3 by 3 pixels, where 1 pixel = 17.504 arcseconds), slightly circularized, i.e., removing 1/4 of a pixel from each corner. Therefore the computed values include the contributions by any other sources inside the photometric aperture). The 3 methods are discussed in Section 3.4 of the reference paper. The individual flag values and their meanings are as follows:

        1 = source is not contaminated,
        2 = source is contaminated,
        3 = no photometric information has been found for that source.
  

Class
The HEASARC Browse object classification, based on the spectral type (the spect_type parameter), if available, or else (in some cases), on the variability type.


Contact Person

Questions regarding the INTOMCVS database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 30-Jan-2013