HAT-P-57b: A Short-period Giant Planet Transiting a Bright Rapidly Rotating A8V Star Confirmed Via Doppler Tomography

Hartman, J. D. and Bakos, G. A. and Buchhave, L. A. and Torres, G. and Latham, D. W. and Kovacs, G. and Bhatti, W. and Csubry, Z. and de Val-Borro, M. and Penev, K. and Huang, C. X. ORCID: https://orcid.org/0000-0003-0918-7484 and Beky, B. and Bieryla, A. and Quinn, S. N. and Howard, A. W. and Marcy, G. W. and Johnson, J. A. and Isaacson, H. and Fischer, D. A. and Noyes, R. W. and Falco, E. and Esquerdo, G. A. and Knox, R. P. and Hinz, P. and Lazar, J. and Papp, I. and Sari, P. (2015) HAT-P-57b: A Short-period Giant Planet Transiting a Bright Rapidly Rotating A8V Star Confirmed Via Doppler Tomography. The Astronomical Journal, 150 (6):197. pp. 1-17. ISSN 0004-6256

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We present the discovery of HAT-P-57b, a P = 2.4653 day transiting planet around a V = 10.465 ± 0.029 mag, Teff = 7500 ± 250 K main sequence A8V star with a projected rotation velocity of v sin i = 102.1 ± 1.3 km s-1. We measure the radius of the planet to be R = 1.413 ± 0.054 RJ and, based on RV observations, place a 95% confidence upper limit on its mass of M < 1.85 MJ. Based on theoretical stellar evolution models, the host star has a mass and radius of 1.47 ± 0.12 M and 1.500 ± 0.050 R, respectively. Spectroscopic observations made with Keck-I/HIRES during a partial transit event show the Doppler shadow of HAT-P-57b moving across the average spectral line profile of HAT-P-57, confirming the object as a planetary system. We use these observations, together with analytic formulae that we derive for the line profile distortions, to determine the projected angle between the spin axis of HAT-P-57 and the orbital axis of HAT-P-57b. The data permit two possible solutions, with -16°.7 < l < 3°.3 or 27°.6 < l < 57°.4 at 95% confidence, and with relative probabilities for the two modes of 26% and 74%, respectively. Adaptive optics imaging with MMT/Clio2 reveals an object located 2.7 from HAT-P-57 consisting of two point sources separated in turn from each other by 0.22. The H- and L-band magnitudes of the companion stars are consistent with their being physically associated with HAT-P-57, in which case they are stars of mass 0.61 ± 0.10 M and 0.53 ± 0.08 M. HAT-P-57 is the most rapidly rotating star, and only the fourth main sequence A star, known to host a transiting planet.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version deposited in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 01 Apr 2022 00:06
Last Modified: 17 May 2022 23:27
Uncontrolled Keywords: planetary systems; stars: individual (HAT-P-57); techniques: photometric; techniques: spectroscopic; Astrophysics - Earth and Planetary Astrophysics
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Identification Number or DOI: https://doi.org/10.1088/0004-6256/150/6/197
URI: http://eprints.usq.edu.au/id/eprint/47417

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