Multiband time series photometry requested for CP Gru
Abstract:
Dr. Tom Macarrone requests photometry of a V=7.8 eclipsing binary with a 2.08 day period during the eclipse, in several bands. B, V and R are the most useful. The durations of the eclipses are about 8 hours each. In TESS, the eclipse depths are about 0.35 and 0.06 magnitudes for the primary and secondary eclipse, but we need several bands of data to solve the binary, and the very broad TESS band is not very well suited to this purpose. Relative photometry of the eclipse depths with half hour cadence and 1% accuracy should allow estimation of the temperatures and radii of both stars. The full eclipse need not be covered by a single observer in a single night; the solution can gradually be put together with data collected from many telescopes on many nights.
Justification:
CP Gru is an approximate 7.8 magnitude eclipsing binary with an A star primary and strong X-ray and radio emission and repeated strong millimeter flaring with the South Pole Telescope. As X-ray and radio emission is generally associated with magnetically active stars, the companion to the A star must be responsible for the flaring. We wish to obtain photometry of the eclipse in several bands to obtain the temperature and radius of the companion star.
Requested Data Types:
Photometry
Targets
| Name | Magnitude | Variability Type | Photometry Notes | Spectroscopy Notes |
|---|---|---|---|---|
| CP Gru | 7.73 | EA |
Cadence: Continuous Precision: 10 mmag |
Not Requested |
Spectroscopy Lines:
No spectroscopy lines provided
Photometry Filters:
B (Johnson), V (Johnson), R (Cousins)
Comparison Stars:
Finder charts with comparison stars may be created using the AAVSO Variable Star Plotter (VSP).
Co-Authorship
Observers are eligible for co-authorship.
Additional Observer Input:
We will coordinate who uses which filter on the forum (see the link below in Forum url). While data around the time of the eclipses is most beneficial, it is also of value to get some data points at other phases to ensure that the zero points are consistent among different observers. The ephemeris for the eclipse is MJD 60169.4488 +2.086150000000 N for the deeper eclipse, and 60170.4919 for the shallower eclipse, based on TESS data from 2023. The eclipses last about 0.4 days.
Additional Submission Location:
Not provided
Notes:
No public notes