Revisiting the HD 21749 planetary system with stellar activity modelling
Article
Article Title | Revisiting the HD 21749 planetary system with stellar activity modelling |
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ERA Journal ID | 1074 |
Article Category | Article |
Authors | Gan, Tianjun (Author), Wang, Sharon Xuesong (Author), Teske, Johanna K. (Author), Mao, Shude (Author), Howard, Ward S. (Author), Law, Nicholas M. (Author), Batalha, Natasha E. (Author), Vanderburg, Andrew (Author), Dragomir, Diana (Author), Huang, Chelsea X. (Author), Feng, Fabo (Author), Butler, R. Paul (Author), Crane, Jeffrey D. (Author), Shectman, Stephen A. (Author), Beletsky, Yuri (Author), Shporer, Avi (Author), Montet, Benjamin T. (Author), Burt, Jennifer A. (Author), Feinstein, Adina D. (Author), Flowers, Erin (Author), Nandakumar, Sangeetha (Author), Barbieri, Mauro (Author), Corbett, Hank (Author), Ratzloff, Jeffrey K. (Author), Galliher, Nathan (Author), Chavez, Ramses Gonzalez (Author), Vasquez, Alan (Author), Glazier, Amy (Author) and Haislip, Joshua (Author) |
Journal Title | Monthly Notices of the Royal Astronomical Society |
Journal Citation | 501 (4), pp. 6042-6061 |
Number of Pages | 20 |
Year | 2020 |
Publisher | Oxford University Press |
Place of Publication | United Kingdom |
ISSN | 0035-8711 |
1365-2966 | |
Digital Object Identifier (DOI) | https://doi.org/10.1093/mnras/staa3886 |
Web Address (URL) | https://academic.oup.com/mnras/article/501/4/6042/6047182 |
Abstract | HD 21749 is a bright (V = 8.1 mag) K dwarf at 16 pc known to host an inner terrestrial planet HD 21749c as well as an outer sub-Neptune HD 21749b, both delivered by Transiting Exoplanet Survey Satellite (TESS). Follow-up spectroscopic observations measured the mass of HD 21749b to be 22.7 ± 2.2 M with a density of 7.0^{+1.6}_{-1.3} g cm-3, making it one of the densest sub-Neptunes. However, the mass measurement was suspected to be influenced by stellar rotation. Here, we present new high-cadence PFS RV data to disentangle the stellar activity signal from the planetary signal. We find that HD 21749 has a similar rotational time-scale as the planet's orbital period, and the amplitude of the planetary orbital RV signal is estimated to be similar to that of the stellar activity signal. We perform Gaussian process regression on the photometry and RVs from HARPS and PFS to model the stellar activity signal. Our new models reveal that HD 21749b has a radius of 2.86 ± 0.20 R, an orbital period of 35.6133 ± 0.0005 d with a mass of Mb = 20.0 ± 2.7 M and a density of 4.8^{+2.0}_{-1.4} g cm-3 on an eccentric orbit with e = 0.16 ± 0.06, which is consistent with the most recent values published for this system. HD 21749c has an orbital period of 7.7902 ± 0.0006 d, a radius of 1.13 ± 0.10 R, and a 3σ mass upper limit of 3.5 M. Our Monte Carlo simulations confirm that without properly taking stellar activity signals into account, the mass measurement of HD 21749b is likely to arrive at a significantly underestimated error bar. |
Keywords | stars: individual: HD 21749; planetary systems; Astrophysics - Earth and Planetary Astrophysics; Astrophysics - Solar and Stellar Astrophysics |
ANZSRC Field of Research 2020 | 510109. Stellar astronomy and planetary systems |
Public Notes | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2020 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Byline Affiliations | Tsinghua University, China |
Carnegie Institution of Washington, United States | |
University of North Carolina, United States | |
NASA Ames Research Center, United States | |
University of Wisconsin-Madison, United States | |
University of New Mexico, United States | |
Massachusetts Institute of Technology, United States | |
University of New South Wales | |
California Institute of Technology (Caltech), United States | |
University of Chicago, United States | |
Princeton University, United States | |
University of Atacama, Chile | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q725w/revisiting-the-hd-21749-planetary-system-with-stellar-activity-modelling
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