UVOTBSCAT - UVOT Bright Star Catalog
A. B-V < -0.3 V <= 12.0 B. -0.3 <= B-V < -0.17 V <= 11.0 C. -0.17 <= B-V < 0.01 V <= 10.0 D. 0.01 <= B-V V <= 9.5Most faint objects with V higher than B could be thrown out according to these rules. This reduced the number of objects in this catalog by almost half.
All missing V or B magnitudes were generated in preprocessing. If V was missing, V was set to "B - 0.3"; likewise, missing B was set to "V + 0.3". These values were chosen to indicate that the object could be "very blue". A "B - V" value of less than "-0.3" causes the object to be retained in the UVOT catalog after the "red" objects are eliminated. Even if this "B - V" value is invented, the UVOT monitor is prevented from looking at potentially bright objects.
Just over 800 of the stars from the Tycho-2 catalogue gave data in epoch 1991.5, while around 3000 variable stars from the GCVS gave information in epoch 1950 coordinates. An awk script precessed right ascension and declination, both given in degrees, using these equations:
"RA_new" = "RA_old" + (15/3600)years(3.074+1.336*sin((pi/360)* "RA_old")*tan((pi/360)* "Dec_old")) "Dec_new" = "Dec_old" + (1/3600)years(20.038*cos((pi/360)* "RA_old"))where "years" is the number of years between 2000.0 and the epoch given. This precession equation produces values accurate to < 1 second of right ascension and 5 arcseconds of declination. The equation was found on an Arizona State University astronomy class web page:
The Right Ascension of the source in the selected equinox. The RA was provided in J2000.0 equatorial coordinates to a variety of implied precisions in the original table.
The Declination of the source in the selected equinox. The Declination was provided in J2000.0 equatorial coordinates to a variety of implied precisions in the original table.
The Galactic Longitude of the source.
The Galactic Latitude of the source.
The V magnitude (Johnson System) of the source.
The B magnitude (Johnson System) of the source.
The reference catalog from which the source was taken: GCVS, Hipparcos (for Hipparcos Project Tycho-2 Catalog or the Yale Bright Star Catalog), or NGC.
This flag parameter is set to 'B' if the B magnitude value for the source was invented: see the above Description section for more details on this procedure.