TY - JOUR
T1 - An unusually low density ultra-short period super-Earth and three mini-Neptunes around the old star TOI-561
AU - Lacedelli, G.
AU - Malavolta, L.
AU - Borsato, L.
AU - Piotto, G.
AU - Nardiello, D.
AU - Mortier, A.
AU - Stalport, M.
AU - Cameron, A. Collier
AU - Poretti, E.
AU - Buchhave, L. A.
AU - López-Morales, M.
AU - Nascimbeni, V.
AU - Wilson, T. G.
AU - Udry, S.
AU - Latham, D. W.
AU - Bonomo, A. S.
AU - Damasso, M.
AU - Dumusque, X.
AU - Jenkins, J. M.
AU - Lovis, C.
AU - Rice, K.
AU - Sasselov, D.
AU - Winn, J. N.
AU - Andreuzzi, G.
AU - Cosentino, R.
AU - Charbonneau, D.
AU - Di Fabrizio, L.
AU - Martinez Fiorenzano, A. F.
AU - Ghedina, A.
AU - Harutyunyan, A.
AU - Lienhard, F.
AU - Micela, G.
AU - Molinari, E.
AU - Pagano, I.
AU - Pepe, F.
AU - Phillips, D. F.
AU - Pinamonti, M.
AU - Ricker, G.
AU - Scandariato, G.
AU - Sozzetti, A.
AU - Watson, C. A.
N1 - Funding: GL acknowledges support by CARIPARO Foundation, according to the agreement CARIPARO-Universit`a degli Studidi Padova (Pratica n. 2018/0098), and scholarship support by the “Soroptimist International d’Italia” association (Cortina d’Ampezzo Club). GLa, LBo, GPi, VN, GS, and IPa acknowledge the funding support from Italian Space Agency (ASI) regulated by “Accordo ASI-INAF n. 2013-016-R.0 del 9 luglio 2013 e integrazione del 9 luglio 2015 CHEOPS Fasi A/B/C”. DNa acknowledges the support from the French Centre National d’Etudes Spatiales (CNES). AM acknowledges support from the senior Kavli Institute Fellowships. ACC acknowledges support from STFC consolidated grant ST/R000824/1 and UK Space Agency grant ST/R003203/1. ASB and MPi acknowledge financial contribution from the ASI-INAF agreement n.2018-16-HH.0. XD is grateful to the Branco-Weiss Fellowship for continuous support.This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No. 851555). JNW thanks the Heising-Simons Foundation for support).
PY - 2021/3
Y1 - 2021/3
N2 - Based on HARPS-N radial velocities (RVs) and TESS photometry, we present a full characterisation of the planetary system orbiting the late G dwarf After the identification of three transiting candidates by TESS, we discovered two additional external planets from RV analysis. RVs cannot confirm the outer TESS transiting candidate, which would also make the system dynamically unstable. We demonstrate that the two transits initially associated with this candidate are instead due to single transits of the two planets discovered using RVs. The four planets orbiting TOI-561 include an ultra-short period (USP) super-Earth (TOI-561 b) with period Pb = 0.45 d, mass Mb = 1.59 ± 0.36 M⊕ and radius Rb = 1.42 ± 0.07 R⊕, and three mini-Neptunes: TOI-561 c, with Pc = 10.78 d, Mc = 5.40 ± 0.98 M⊕, Rc = 2.88 ± 0.09 R⊕; TOI-561 d, with Pd = 25.6 d, Md = 11.9 ± 1.3 M⊕, Rd = 2.53 ± 0.13 R⊕; and TOI-561 e, with Pe = 77.2 d, Me = 16.0 ± 2.3 M⊕, Re = 2.67 ± 0.11 R⊕. Having a density of 3.0 ± 0.8 g cm−3, TOI-561 b is the lowest density USP planet known to date. Our N-body simulations confirm the stability of the system and predict a strong, anti-correlated, long-term transit time variation signal between planets d and e. The unusual density of the inner super-Earth and the dynamical interactions between the outer planets make TOI-561 an interesting follow-up target.
AB - Based on HARPS-N radial velocities (RVs) and TESS photometry, we present a full characterisation of the planetary system orbiting the late G dwarf After the identification of three transiting candidates by TESS, we discovered two additional external planets from RV analysis. RVs cannot confirm the outer TESS transiting candidate, which would also make the system dynamically unstable. We demonstrate that the two transits initially associated with this candidate are instead due to single transits of the two planets discovered using RVs. The four planets orbiting TOI-561 include an ultra-short period (USP) super-Earth (TOI-561 b) with period Pb = 0.45 d, mass Mb = 1.59 ± 0.36 M⊕ and radius Rb = 1.42 ± 0.07 R⊕, and three mini-Neptunes: TOI-561 c, with Pc = 10.78 d, Mc = 5.40 ± 0.98 M⊕, Rc = 2.88 ± 0.09 R⊕; TOI-561 d, with Pd = 25.6 d, Md = 11.9 ± 1.3 M⊕, Rd = 2.53 ± 0.13 R⊕; and TOI-561 e, with Pe = 77.2 d, Me = 16.0 ± 2.3 M⊕, Re = 2.67 ± 0.11 R⊕. Having a density of 3.0 ± 0.8 g cm−3, TOI-561 b is the lowest density USP planet known to date. Our N-body simulations confirm the stability of the system and predict a strong, anti-correlated, long-term transit time variation signal between planets d and e. The unusual density of the inner super-Earth and the dynamical interactions between the outer planets make TOI-561 an interesting follow-up target.
KW - Planets and satellites: detection
KW - Plants and satellites: composition
KW - Star: individual: TOI-561 (TIC 377064495, Gaia DR2 3850421005290172416)
KW - Techniques: photometric
KW - Techniques: radial velocities
U2 - 10.1093/mnras/staa3728
DO - 10.1093/mnras/staa3728
M3 - Article
SN - 0035-8711
VL - 501
SP - 4148
EP - 4166
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -