Two warm Neptunes transiting HIP 9618 revealed by TESS and Cheops

Osborn, H P; Nowak, G; Hébrard, G; Masseron, T; Lillo-Box, J; Pallé, E; Bekkelien, A; Florén, H-G; Guterman, P; Simon, A E; Adibekyan, V; Bieryla, A; Borsato, L; Brandeker, A; Ciardi, D R; Collier Cameron, A; Collins, K A; Egger, J A; Gandolfi, D; Hooton, M J; Latham, D W; Lendl, M; Matthews, E C; Tuson, A; Ulmer-Moll, S; Vanderburg, A; Wilson, T G; Ziegler, C; Alibert, Y; Alonso, R; Anglada, G; Arnold, L; Asquier, J; Barrado y Navascues, D; Baumjohann, W; Beck, T; Belinski, A A; Benz, W; Biondi, F; Boisse, I; Bonfils, X; Broeg, C; Buchhave, L A; Bárczy, T; Barros, S C C; Cabrera, J; Cardona Guillen, C; Carleo, I; Castro-González, A; Charnoz, S; Christiansen, J; Cortes-Zuleta, P; Csizmadia, S; Dalal, S; Davies, M B; Deleuil, M; Delfosse, X; Delrez, L; Demory, B-O; Dunlavey, A B; Ehrenreich, D; Erikson, A; Fernandes, R B; Fortier, A; Forveille, T; Fossati, L; Fridlund, M; Gillon, M; Goeke, R F; Goliguzova, M V; Gonzales, E J; Günther, M N; Güdel, M; Heidari, N; Henze, C E; Howell, S; Hoyer, S; Frey, J I; Isaak, K G; Jenkins, J M; Kiefer, F; Kiss, L; Korth, J; Maxted, P F L; Laskar, J; Lecavelier des Etangs, A; Lovis, C; Lund, M B; Luque, R; Magrin, D; Almenara, J M; Martioli, E; Mecina, M; Medina, J V; Moldovan, D; Morales-Calderón, M; Morello, G; Moutou, C; Murgas, F; Jensen, E L N; Nascimbeni, V; Olofsson, G; Ottensamer, R; Pagano, I; Peter, G; Piotto, G; Pollacco, D; Queloz, D; Ragazzoni, R; Rando, N; Rauer, H; Ribas, I; Ricker, G; Demangeon, O D S; Smith, A M S; Santos, N; Scandariato, G; Seager, S; Sousa, S G; Steller, M; Szabó, G M; Ségransan, D; Thomas, N; Udry, S; Ulmer, B; Van Grootel, V; Vanderspek, R; Walton, N; Winn, J N

doi:10.1093/mnras/stad1319

Two warm Neptunes transiting HIP 9618 revealed by TESS and Cheops

Osborn, H P; Nowak, G; Hébrard, G; Masseron, T; Lillo-Box, J; Pallé, E; Bekkelien, A; Florén, H-G; Guterman, P; Simon, A E; Adibekyan, V; Bieryla, A; Borsato, L; Brandeker, A; Ciardi, D R; Collier Cameron, A; Collins, K A; Egger, J A; Gandolfi, D; Hooton, M J; Latham, D W; Lendl, M; Matthews, E C; Tuson, A; Ulmer-Moll, S; Vanderburg, A; Wilson, T G; Ziegler, C; Alibert, Y; Alonso, R; Anglada, G; Arnold, L; Asquier, J; Barrado y Navascues, D; Baumjohann, W; Beck, T; Belinski, A A; Benz, W; Biondi, F; Boisse, I; Bonfils, X; Broeg, C; Buchhave, L A; Bárczy, T; Barros, S C C; Cabrera, J; Cardona Guillen, C; Carleo, I; Castro-González, A; Charnoz, S; Christiansen, J; Cortes-Zuleta, P; Csizmadia, S; Dalal, S; Davies, M B; Deleuil, M; Delfosse, X; Delrez, L; Demory, B-O; Dunlavey, A B; Ehrenreich, D; Erikson, A; Fernandes, R B; Fortier, A; Forveille, T; Fossati, L; Fridlund, M; Gillon, M; Goeke, R F; Goliguzova, M V; Gonzales, E J; Günther, M N; Güdel, M; Heidari, N; Henze, C E; Howell, S; Ho...

Authors

H P Osborn

G Nowak

G Hébrard

T Masseron

J Lillo-Box

E Pallé

A Bekkelien

H-G Florén

P Guterman

A E Simon

V Adibekyan

A Bieryla

L Borsato

A Brandeker

D R Ciardi

A Collier Cameron

K A Collins

J A Egger

D Gandolfi

M J Hooton

D W Latham

M Lendl

E C Matthews

A Tuson

S Ulmer-Moll

A Vanderburg

T G Wilson

C Ziegler

Y Alibert

R Alonso

G Anglada

L Arnold

J Asquier

D Barrado y Navascues

W Baumjohann

T Beck

A A Belinski

W Benz

F Biondi

I Boisse

X Bonfils

C Broeg

L A Buchhave

T Bárczy

S C C Barros

J Cabrera

C Cardona Guillen

I Carleo

A Castro-González

S Charnoz

J Christiansen

P Cortes-Zuleta

S Csizmadia

S Dalal

M B Davies

M Deleuil

X Delfosse

L Delrez

B-O Demory

A B Dunlavey

D Ehrenreich

A Erikson

R B Fernandes

A Fortier

T Forveille

L Fossati

M Fridlund

M Gillon

R F Goeke

M V Goliguzova

E J Gonzales

M N Günther

M Güdel

N Heidari

C E Henze

S Howell

S Hoyer

J I Frey

K G Isaak

J M Jenkins

F Kiefer

L Kiss

J Korth

Pierre Maxted p.maxted@keele.ac.uk

J Laskar

A Lecavelier des Etangs

C Lovis

M B Lund

R Luque

D Magrin

J M Almenara

E Martioli

M Mecina

J V Medina

D Moldovan

M Morales-Calderón

G Morello

C Moutou

F Murgas

E L N Jensen

V Nascimbeni

G Olofsson

R Ottensamer

I Pagano

G Peter

G Piotto

D Pollacco

D Queloz

R Ragazzoni

N Rando

H Rauer

I Ribas

G Ricker

O D S Demangeon

A M S Smith

N Santos

G Scandariato

S Seager

S G Sousa

M Steller

G M Szabó

D Ségransan

N Thomas

S Udry

B Ulmer

V Van Grootel

R Vanderspek

N Walton

J N Winn

Abstract

HIP 9618 (HD 12572, TOI-1471, TIC 306263608) is a bright (G = 9.0 mag) solar analogue. TESS photometry revealed the star to have two candidate planets with radii of 3.9 ± 0.044 R⊕ (HIP 9618 b) and 3.343 ± 0.039 R⊕ (HIP 9618 c). While the 20.77291 d period of HIP 9618 b was measured unambiguously, HIP 9618 c showed only two transits separated by a 680-d gap in the time series, leaving many possibilities for the period. To solve this issue, CHEOPS performed targeted photometry of period aliases to attempt to recover the true period of planet c, and successfully determined the true period to be 52.56349 d. High-resolution spectroscopy with HARPS-N, SOPHIE, and CAFE revealed a mass of 10.0 ± 3.1M⊕ for HIP 9618 b, which, according to our interior structure models, corresponds to a $6.8\pm 1.4~{{\ \rm per\ cent}}$ gas fraction. HIP 9618 c appears to have a lower mass than HIP 9618 b, with a 3-sigma upper limit of &lt;18M⊕. Follow-up and archival RV measurements also reveal a clear long-term trend which, when combined with imaging and astrometric information, reveal a low-mass companion ($0.08^{+0.12}_{-0.05} M_\odot$) orbiting at $26.0^{+19.0}_{-11.0}$ au. This detection makes HIP 9618 one of only five bright (K &lt; 8 mag) transiting multiplanet systems known to host a planet with P &gt; 50 d, opening the door for the atmospheric characterization of warm (Teq &lt; 750 K) sub-Neptunes.

Citation

Osborn, H. P., Nowak, G., Hébrard, G., Masseron, T., Lillo-Box, J., Pallé, E., …Winn, J. N. (2023). Two warm Neptunes transiting HIP 9618 revealed by TESS and Cheops. Monthly Notices of the Royal Astronomical Society, 523(2), 3069-3089. https://doi.org/10.1093/mnras/stad1319

Journal Article Type	Article
Acceptance Date	Apr 5, 2023
Online Publication Date	Jun 8, 2023
Publication Date	May 30, 2023
Deposit Date	Jun 29, 2023
Journal	Monthly Notices of the Royal Astronomical Society
Print ISSN	0035-8711
Publisher	Oxford University Press
Peer Reviewed	Peer Reviewed
Volume	523
Issue	2
Pages	3069-3089
DOI	https://doi.org/10.1093/mnras/stad1319
Keywords	Space and Planetary Science, Astronomy and Astrophysics