Aug 08, 2004: V603 Aql

Michael Richmond
Aug 9, 2004

On the night of August 8/9, 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 mild -- air temperature 22 C at start, 19 C near end
• the sky was overcast just at sunset, and didn't clear until about two hours later. After the clouds disappeared, it was a nice night.
• the third-quarter moon rose late and didn't make the sky very bright
• I did a decent job focusing, so the FWHM was about 2.5 pixels FWHM = 4.6 arcsec FWHM (when binned 3x3, plate scale is about 1.854 arcsec/pixel)
• (sigh) I didn't notice that one set of exposures had finished, so I lost about a half hour during the good portion of the evening :-(

Here's a chart of the field of V603 Aql, taken last year with our equipment; the field is about 20 arcminutes wide.

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 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_ 9, 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_09.11991     3226.61991   3226.62439  -0.347 
Aug_09.12074     3226.62074   3226.62522  -0.292 
Aug_09.12110     3226.62110   3226.62558  -0.284 
Aug_09.12152     3226.62152   3226.62600  -0.271 

• download the entire table (plain ASCII)

Last modified 8/09/2004 by MWR.