Newly Detected Variability in HD258049
ATel #17017; Philip Langill (RAO/UCalgary), Zach Oberhamer (RAO/UCalgary)
on 6 Feb 2025; 04:41 UT
Credential Certification: Philip Langill (pplangil@ucalgary.ca)
Subjects: Optical, Star, Transient, Variables
HD258049 was observed with the Kaylie Green Memorial Telescope (KGMT) at the Rothney Astrophysical Observatory (RAO) on Jan 27, 2025 between 03:59 and 09:03 UTC. The KGMT is a 0.5 m f/1 Baker-Nunn Schmidt telescope utilizing a FLI 16Mpix MicroLine CCD camera with no filter. The overall transmission and QE mimics closely the bandpass of the GAIA G filter.
The exoplanet transit of Wasp12b was the actual target of interest and HD258049 was being used as a comparison star. Over the 5-hr run 100-30sec exposures and 10-20sec exposures were made of the star field. In doing the comparison star checking the variability of HD258049 was easily seen.
Astrometry.net was used to perform the WCS mapping verifying the J2000 coordinates of HD258049 to be 06:29:48.34 RA, +29:38:14.36 Dec. The SIMBAD database gives a G mag of 10.472+/-0.002 but is not indicated to be a variable star.
In their investigations of the Wasp12 planetary system Fossati et al use CFHT's ESPaDOnS to examine the spectrum of HD258049 (ApJ Letters, 766:L20, 2013). They report that HD258049 is a spectroscopic binary, but do not report variability.
Over the 5-hr span the apparent magnitude of HD258049 oscillated in a roughly sinusoidal fashion with a period ~0.06 days and amplitude 0.07 mag. The scatter in the magnitudes of the 20 non-varying comparison stars over the 5-hrs was within 0.005 mag indicating the variation detected in the light of HD258049 is well above the minimum detectable with the KGMT.
Timely followup observations would be helpful to verify these findings.
Rothney Astrophysical Observatory
