Sanduleak 3
Sanduleak 3 is one of the hottest known stars, showing strong emission lines of HeII, OVI through OVIII, and CIV and CV. It has no apparent surrounding nebula. Sand 3 is also a very complex multiperiodic nonradially pulsating star, with typical periods near 900 seconds (Bond, Ciardullo & Kawaler 1993). This time scale is intermediate between the pulsating PNNs and the GW Vir (pulsating PG1159) stars. In 1992, a global CCD network observed Sand 3 intensively for over 1 week. These data (currently in analysis by Kawaler & Bond et al.) show that Sand 3 changed its pulsation spectrum significantly in just 2 years, and indeed changed during the course of the 1992 run. This complicates the analysis significantly compared to simpler pulsators, and the star is still not fully resolved.
Data from this run will be used to identify as many individual frequencies as possible. These frequencies will be used, along with those found in prior observing campaigns, to attempt to identify a uniform period spacing. Identification of an underlying uniform period interval allows accurate determination of the mass of the star, while deviations from the mean spacing tell us about the star's internal structure and composition (Kawaler and Bradley 1994). There is also hope of using our asteroseismological results to help calibrate the use of PNNs as distance indicators.
For more information,
consult the full Sanduleak 3 Scientific
Justification.
Some references:
Bond, Ciardullo, & Kawaler, 1993, Acta Ast, 43, 425 (survey of variable PNN)
Kawaler & Bradley, 1994, ApJ, 427, 415 (theory paper on pulsating pre-white dwarfs)
Sanduleak 3 is known to change its pulsation spectrum significantly over the years, and in fact it changed significantly during the course of the 1992 run. Therefore, as with the primary target BPM 37093, you may not see any pulsations visually in the lightcurve. A sample lightcurve is shown at the bottom of this page.
| R.A. (J2000) = 16 06 28.3 |
| Dec. (J2000) = -35 45 13 |
| mb=14.4 |
Control Center: The XCOV 16 control center is at Iowa State University's International Institute of Theoretical and Applied Physics (IITAP).
Contacting the Control Center: Consult the Phone Contact List for information on phone, fax, and email for the control center as well as the other sites for this run.
Time Check: Please do a clock time check each night before taking data and verify your time with HQ at the beginning of the run, and as often during the run as possible. HQ will have an accurate clock available for phone clock checks.
Data Transfer: There are two ways to send your data and logs at the end of each night.
Observing Logs: We ask that you send a copy of your observation log along with the data, at the same time if you can.
Run start: Please start your run on an integral multiple of ten seconds (times ending in "0"). Check the computer clock just before the start of a run, synchronizing with your master clock to within 0.1 sec if possible.
Integration time: Use 10 seconds integration time.
Filters: Use NO filter on both channels.
Guide star: The principle investigators have no specific preferences, so feel free to choose any comparison star which you see fit to use. However, please record your ch2 offsets and telescope plate scale so we can verify exactly which comparison star was observed.
Sky calibration: Observers with 3-channel photometers should record sky in all three channels near the beginning and the end of each run to permit accurate cross calibration. Observers with 2 channel photometers should take sky by moving the telescope. We have sometimes in the past used the channel 2 verniers to measure channel 2 sky (only) but we find this is not really reliable. Try to take sky as often as needed, at least once per 1/2 hour, for 4 or 5 good sky points; more are not needed and cause unwanted data gaps in the light curve of the target star.
Apertures: Please use the smallest aperture consistent with getting data of good quality (e.g. no visible loss of light to the edge of the aperture). A general rule of thumb is to use an aperture approximately 8-10 times the diameter of the seeing disk. Record the size of the aperture (in arcsec) in your observing log.
