Help for "Is My Favorite Object an X-Ray, Gamma-Ray, or EUV Source?"

Description
Frequency Regime
Cone Radius
Caveats
References

Description

This simple tool queries the HEASARC's master compilations of X-ray sources, gamma-ray sources, or EUV sources in the Browse database system, and lists up to 10 of the matches that it finds in a cone of (user-specified) radius around the given astronomical coordinates or object name. The matches are listed in order of increasing offset from the selected position for X-ray and EUV source searches, and in order of decreasing energy band for gamma-ray sources. When available, it gives the observed source strength in either counts per second (X-ray and EUV sources) or flux units (gamma-ray sources).

Frequency Regime

You can specify the frequency regime for your search to be X-ray, gamma-ray, or extreme ultra-violet (EUV).

Regime	Energy Range	Wavelength Range
Gamma-Ray	> 50 keV	< 0.25 Å
X-Ray	0.12 - 50 keV	0.25 - 100 Å
EUV	0.014 - 0.12 keV	100 - 912 Å

Cone Radius

The radius of the cone search is specified in degrees. The default is 0.05 degrees (or 3 arcminutes), and is generally an appropriate value for the X-ray and EUV frequency regimes; a larger value of 1.0 degree should be used for the gamma-ray frequency regime. You can choose your own radius value, of course, but we suggest that you do not specify a radius larger than 1 degree for X-ray or EUV source searches, or 15.0 degrees for gamma-ray source searches, as you will likely get spurious matches for larger search areas. A valid cone radius must be greater than 0.00001 degrees and less than or equal to 3.0 degrees when searching the X-ray and EUV regimes or 30.0 degrees for the gamma-ray regime.

Caveats

(1) The larger the radius of the cone search used, the more chance there is of finding a match with a random source rather than with the object/position specified. This is particularly true for X-ray sources: given the several hundred thousand known X-ray sources, there is a several percent chance of finding an unrelated match when using the default 0.05 degrees search radius.

(2) Some X-ray detectors have some sensitivity to ultraviolet light as well as to X-rays, i.e., have a so-called UV light leak. Particular instruments known to have had this feature include the Einstein High Resolution Instrument (HRI), the EXOSAT Low-Energy Telescope Channel Multiplier Array (LET CMA), and the ROSAT HRI. Some objects rich in UV emission, such as stars of spectral types O, B, and A, may thus be listed in X-ray source catalogs, even though they detected due to their UV rather than X-ray emission. For information on the Einstein HRI UV leak, see Appendix B of Schmitt et al. (1985, ApJ, 290,307), and on the ROSAT HRI UV leak, see Barbera et al. (2000, ApJ, 545, 449). To estimate the EXOSAT LE UV leak, you can use the FTOOLS utility exoleuv.

References

Software developed and maintained by Edward J. Sabol of the HEASARC. Tool suggested by Dr. Steve Drake. Special thanks to Christina Heikkila of the Browse Software Development Team.

This file was last modified on Tuesday, 03-Aug-2004 00:31:56 EDT

For feedback or questions concerning this tool, please use our feedback facility.