HD 219134 Revisited: Planet d Transit Upper Limit and Planet f Transit Nondetection with ASTERIA and TESS

Abstract

HD 219134 is a K3V dwarf star with six reported radial-velocity discovered planets. The two innermost planets b and c show transits, raising the possibility of this system to be the nearest (6.53 pc), brightest (V = 5.57) example of a star with a compact multiple transiting planet system. Ground-based searches for transits of planets beyond b and c are not feasible because of the infrequent transits, long transit duration (∼5 hr), shallow transit depths (<1%), and large transit time uncertainty (∼half a day). We use the space-based telescopes the Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) and the Transiting Exoplanet Survey Satellite (TESS) to search for transits of planets f (P = 22.717 days and ) and d (P = 46.859 days and ). ASTERIA was a technology demonstration CubeSat with an opportunity for science in an extended program. ASTERIA observations of HD 219134 were designed to cover the 3σ transit windows for planets f and d via repeated visits over many months. While TESS has much higher sensitivity and more continuous time coverage than ASTERIA, only the HD 219134 f transit window fell within the TESS survey’s observations. Our TESS photometric results definitively rule out planetary transits for HD 219134 f. We do not detect the Neptune-mass HD 219134 d transits and our ASTERIA data are sensitive to planets as small as 3.6 R ⊕. We provide TESS updated transit times and periods for HD 219134 b and c, which are designated TOI 1469.01 and 1469.02 respectively.

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

“…In this section, we present a summary of the α Cen data reduction and photometry, with details of the pipeline described in Knapp et al (2020) and Seager et al (2021).…”

“…Although bias frames are typically used to correct for offsets, flat frames are used to correct column-dependent pixel-to-pixel gain variations caused due to the presence of an amplifier and ADC converter at every column and an amplifier at every pixel. We attempted to take on-orbit flat frames by illuminating the detector with scattered sunlight, following the procedure outlined in Knapp et al (2020) and Seager et al (2021). However, these observations failed because the camera did not initialize properly.…”