[vsnet-alert 4558] XTE 1118+480 field star photometry

[Brian Skiff <bas@lowell.edu>]

     I had a chance to make some fairly quick observations of stars in the
XTE 1118+480 field as a check on the zero-point there.  I used a 19" diaphragm
in the single-channel photoemter on the Lowell 53cm telescope.  The calibration
is based on eight primary and secondary Stromgren standards bracketing the XTE
field stars in color (0.00 < b-y < 0.85) and airmass (1.00 < sec z < 1.18;
XTE field at sec z=1.03).  Mean residuals were 0.008 and 0.011 mag. in V and
b-y, respectively.
     Overall the AAVSO preliminary chart is roughly correct, particularly star
"109" = GSC 3451-1612, on which I made two settings.  The x-ray nova itself
maintains its brightness, and is quite blue in Stromgren b-y.
     Well-placed rumor has that Arne Henden will attempt UBVRI calibration
later this week if the weather holds.  This should improve on the numbers
below.


Name                V     b-y    Remarks
XTE 1118+480      12.95   0.06   +/-0.04; 2000 Apr 4.242 UT
HD 98075           7.85   0.65 
GSC 3451-1612     10.96   0.33   +/-0.02
GSC 3451-0938     12.98   0.63   +/-0.04


\Brian

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