Eta Geminorum: An Eclipsing Semiregular Variable Star Orbited by a Companion Surrounded by an Extended Disc
arXiv:2208.07375 · doi:10.1093/mnras/stac2322
Abstract
We report 11 yr of spectroscopic monitoring of the M-type asymptotic giant branch star eta Gem, a semiregular variable and a known spectroscopic binary with a period of 8.2 yr. We combine our radial velocities with others from the literature to provide an improved spectroscopic orbital solution giving a period of 2979 days, which we then use to predict past times of eclipse. We examine archival photometry from amateur variable star observers, and other sources, and find many instances of dimmings that occurred at the right time. This confirms previous indications that the system is eclipsing, and it now ranks among those with the longest known periods. No secondary eclipses are seen. The 0.4 mag eclipses lasting about 5 months are much too deep to be produced by a stellar companion. We propose instead that the companion is surrounded by a large disk that is at least 1.5 au in diameter, but is likely larger. We predict the center of the next eclipse will occur on New Year's day, 2029.
arXiv commentAccepted for publication in MNRAS, 8 pages in emulateapj format including tables and figures
References in corpus (14)
- emcee: The MCMC Hammer
- Gaia Data Release 2. Summary of the contents and survey properties
- MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
- A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
- Eclipsing binaries in open clusters. II. V453 Cyg in NGC 6871
- Fundamental parameters and infrared excesses of Hipparcos stars
- Fundamental parameters and infrared excesses of Tycho-Gaia stars
- Taming the Invisible Monster: System Parameter Constraints for Epsilon Aurigae from the Far-Ultraviolet to the Mid-Infrared
- An Extreme Analogue of Aurigae: An M-giant Eclipsed Every 69 Years by a Large Opaque Disk Surrounding a Small Hot Source
- Epsilon Aurigae: An improved spectroscopic orbital solution
- Discovery of an unusual bright eclipsing binary with the longest known period: TYC 2505-672-1 / MASTER OT J095310.04+335352.8
- Angular Diameters and Fundamental Parameters of Forty-Four Stars from the Navy Precision Optical Interferometer
- Angular diameter measurements of evolved variables by lunar occultations at 2.2 and 3.8 micron
- International observational campaign of the 2014 eclipse of EE Cep