Transit Search for Exoplanets around Alpha Centauri A and B with ASTERIA

Krishnamurthy, Akshata; Knapp, Mary; Günther, Maximilian N.; Daylan, Tansu; Demory, Brice-Olivier; Seager, Sara; Bailey, Vanessa P.; Smith, Matthew W.; Pong, Christopher M.; Hughes, Kyle; Donner, Amanda; Di Pasquale, Peter; Campuzano, Brian; Smith, Colin; Luu, Jason; Babuscia, Alessandra; Bocchino, Robert L.; Loveland, Jessica; Colley, Cody; Gedenk, Tobias; ... (2021). Transit Search for Exoplanets around Alpha Centauri A and B with ASTERIA. The astronomical journal, 161(6), p. 275. American Astronomical Society 10.3847/1538-3881/abf2c0

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Alpha Centauri is a triple star system with two Sun-like stars, α Cen A (V = 0.01) and B (V = 1.33), and a third fainter red dwarf star, Proxima Centauri. Most current transit missions cannot produce precision photometry of α Cen A and B as their detectors saturate for these very bright stars. The Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) was a technology demonstration mission that successfully demonstrated two key technologies necessary for precision photometry achieving line-of-sight fine-pointing stability of 0.5'' rms and focal plane temperature control of ±0.01 K over a period of 20 minutes. The payload consisted of a 6.7 cm aperture diameter refractive camera and used a scientific complementary metal-oxide semiconductor detector that enabled monitoring of the brightest stars without saturating. We obtained spatially unresolved (blended) observations of α Cen A and B during opportunistic science campaigns as part of ASTERIA's extended mission. The resulting 1σ photometric precision for the blended α Cen A and B data is 250 ppm (parts per million) per 9 s exposure. We do not find evidence of transits in the blended data. We establish limits for transiting exoplanets around both α Cen A and B using transit signal injection and recovery tests. We find that ASTERIA is sensitive to planets with radii as small as 3.0 R⊕ around α Cen A and 3.7 R⊕ around α Cen B, corresponding to signals of ∼500 ppm (signal-to-noise ratio = 5.0) in the blended data, with periods ranging from 0.5 to 6 days.

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