Aug 16, 2004: V603 Aql

Michael Richmond
Aug 17, 2004

On the night of August 16/17, 2004 EDT, I used the RIT Observatory's 12-inch Meade telescope and SBIG ST8 CCD camera to monitor the star V603 Aql, a cataclysmic variable under study by the Center for Backyard Astrophysics.

The plan:

• the Meade 12-inch telescope SBIG ST-8E CCD (no focal reducer)
• no filter
• 15 second exposure times

Notes from the night

• relatively warm at first (air temp 24 C), but then cooled off quickly (air temp 16 C at 2 AM).
• The focus changed quite a bit over the first few hours due to thermal contraction. I adjusted it two hours into the night, and it stayed relatively steady at 2.4 pix = 4.4 arcsec.
• the sky was clear at sunset, but high cirrus moved in after midnight. There was a brief period of thicker cloud from about JD 234.66 - 234.68.
• no moon, thank goodness
• at about JD 234.65, I neglected to rotate the dome quickly enough, so that a portion of the telescope's aperture was covered by the dome slit.

Here's a chart of the field of V603 Aql taken last night. The field is about 20 arcminutes wide. Click on the picture for a larger version.

Note that

• star A = HD 174066 = BD+00 4023, V mag = 8.5
• star B = BD+00 4022 = GSC 00448-00731, V mag = 9.9
• star C = USNOA2.0 0900-13635049, B = 13.0, R = 11.9
• star E = USNOA2.0 0900-13636967, B = 14.3, R = 12.8
• the variable, V603 Aql, is roughly V mag = 11.

I measured the instrumental magnitude of each star with aperture photometry, using a radius of 4 pixels = 7.4 arcseconds, and sky defined by an annulus around each star. Following the procedures outlined by Kent Honeycutt's article on inhomogeneous ensemble photometry, I used all stars available in each image to define a reference frame, and measured each star against this frame.

Below is a graph of the scatter in differential magnitude versus magnitude. Note that star "A" (the brightest, at differential magnitude 0) is very saturated, and star "B" (next brightest, at diff mag = 1.0) was very close to the saturation point; I did not include either one in the solution as a reference. The best comparison stars appear to me to be "C" (diff mag = 3.25) "E" (diff mag = 4.2) and "N" (diff mag = 3.1).

The big outlier at differential mag = 3.0 is V603 Aql.

Light curves for selected stars in the field are shown below. It is clear that most of the stars in the field are not varying appreciably, but V603 Aql is, as the green light curve shows. The other data belong -- from the top downward -- to stars N, C, G, D, F, and E.

Here's a closeup of the variation in V603 Aql itself:

I've made a table of the measurements themselves, with three different flavors of time. Here's the start of the table:

# Measurements of V603Aql made at RIT Obs, Aug_ 17, 2004 UT, 
#   taken by Michael Richmond. 
# All data taken with 12-inch LX-200 + no filter + SBIG ST-8 CCD 
#    no focal reducer, so at native f/10 
# Each exposure 15 seconds long; the tabulated times are midexposure 
#    and accurate only to +/- 1 second. 
# 'mag' is a differential magnitude based on ensemble photometry 
#    tabulated value is 'mag fainter than star C = USNOA2.0 0900-13635049' 
# 
# UT day      JD-2,450,000  HJD-2,450,000   mag 
Aug_17.03729     3234.53729   3234.54133  -0.325 
Aug_17.03769     3234.53769   3234.54173  -0.288 
Aug_17.03809     3234.53809   3234.54213  -0.298 

• download the entire table (plain ASCII)

Last modified 8/17/2004 by MWR.