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J/AJ/134/2099    Variability of point sources in infrared    (Robitaille+, 2007)

Infrared point-source variability between the Spitzer and Midcourse Space Experiment surveys of the Galactic midplane. Robitaille T.P., Cohen M., Whitney B.A., Meade M., Babler B., Indebetouw R., Churchwell E. <Astron. J., 134, 2099-2112 (2007)> =2007AJ....134.2099R (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Infrared sources ; Stars, variable ; Photometry, infrared Keywords: infrared: stars - stars: variables: other - surveys Abstract: We present a list of 552 sources with suspected variability, based on a comparison of mid-infrared photometry from the GLIMPSE I and Midcourse Space Experiment (MSX) surveys, which were carried out nearly a decade apart. We were careful to address issues such as the difference in resolution and sensitivity between the two surveys, as well as the differences in the spectral responses of the instruments. We selected only sources where the IRAC 8.0um and MSX 8.28um fluxes differ by more than a factor of 2, in order to minimize contamination from sources where the difference in fluxes at 8um is due to a strong 10um silicate feature. We present a subset of 40 sources for which additional evidence suggests variability, using 2MASS and MIPSGAL data. Based on a comparison with the variability flags in the IRAS and MSX point-source catalogs we estimate that at least a quarter of the 552 sources and at least half of the 40 sources in the subset are truly variable. In addition, we tentatively confirm the variability of one source using multiepoch IRAS LRS spectra. We suggest that most of the sources in our list are likely to be asymptotic giant branch stars. Description: In order to search for point-source variability, we made use of the following data: * The MSX survey of the Galactic plane (Price et al., 2001AJ....121.2819P, Cat. V/114), which was carried out between 1996 and 1997 and consisted of imaging in four bands: A (8.28um), C (12.13um), D (14.65um), and E (21.3um). * The Two Micron All Sky Survey (2MASS; Skrutskie et al., 2006, Cat. VII/233), which was carried out between 1997 and 2001. The observations consist of imaging in three bands: J (1.25um), H (1.65um), and Ks (2.15um). * The GLIMPSE I survey of the Galactic midplane (Benjamin et al., 2003PASP..115..953B, see Cat. II/293), which was carried out in 2004 at 3.6, 4.5, 5.8, and 8.0um using the IRAC instrument on board Spitzer. * The MIPSGAL survey of the same region as GLIMPSE I, carried out in 2005 and 2006 at 24, 70, and 160um using the MIPS instrument on board Spitzer. We make use only of the data taken at 24um. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 150 552 The sample of 552 sources with apparent variability at 8 microns
See also: V/114 : MSX6C Infrared Point Source Catalog (Egan+ 2003) VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 17 A17 --- MSX MSX source name (GLLL.llll+BB.bbbb) 19- 25 A7 --- --- [SSTGLMC] 27- 43 A17 --- SSTGLMC GLIMPSE source name (GLLL.llll+BB.bbbb) 45- 53 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000) 55- 63 F9.5 deg DEdeg Declination in decimal degrees (J2000) 65- 70 F6.1 mJy FJ ? 2MASS J band flux density (1) 72- 77 F6.1 mJy FH ? 2MASS H band flux density (1) 79- 84 F6.1 mJy FKs ? 2MASS Ks band flux density (1) 86- 90 F5.1 mJy F3.6 ? Spitzer/IRAC 3.6 micron band flux density (1) 92- 96 F5.1 mJy F4.5 ? Spitzer/IRAC 4.5 micron band flux density (1) 98-103 F6.1 mJy F5.8 Spitzer/IRAC 5.8 micron band flux density (1) 105-110 F6.1 mJy F8.0 Spitzer/IRAC 8.0 micron band flux density (1) 112-117 F6.1 mJy F8.3 MSX 8.28 micron band flux density (1) 119-124 F6.1 mJy F12 ? MSX 12.13 micron band flux density (1) 126-131 F6.1 mJy F15 ? MSX 14.65 micron band flux density (1) 133-138 F6.1 mJy F21 ? MSX 21.3 micron band flux density (1) 140-145 F6.1 mJy F24 ? Spitzer/MIPS 24 micron band flux density (1) 147 I1 --- Mvar [0/4] Sum of MSX point source catalog variability flags in all bands (2) 149-150 I2 % Ivar ? IRAS variability likelihood
Note (1): The uncertainties are not shown for clarity. However, these are bright sources at mid-IR wavelengths in the Spitzer data, and therefore the uncertainties are very low in IRAC and MIPS 24 microns. In fact, the main source of uncertainty at IRAC and MIPS 24 microns wavelengths are likely to be the calibration uncertainties. For MSX data, one of the requirements used in Section 3.3 was the uncertainty at 8.28 microns should be less than 10%. For the JHK and MSX errors we refer the reader to the original catalogs. The IRAC 8 micron flux calculated from the smoothed mosaics is not shown, but for sources to be in this list we required the original IRAC 8 micron flux to agree with our calculated IRAC 8 micron flux from smoothed mosaics by less than 20%. Finally, we note that this table does not show all fluxes present in the original MSX Catalog (i.e. fluxes have been removed when a source was not seen, or seen with a very low signal-to-noise, in the images). Note (2): Each variability flag is set to 1 when the variation of the measurements over the mission exceeds the 3σ limit.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 07-Feb-2010
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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