TOI-3493 b: A planet with a Neptune-like density transiting a bright G0-type star

¹ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
² Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai 400005, India
³ Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, 10125 Torino, Italy
⁴ Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 43992 Onsala, Sweden
⁵ Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5, 87-100 Toruń, Poland
⁶ Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
⁷ Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
⁸ McDonald Observatory, The University of Texas, Austin, TX, USA
⁹ Center for Planetary Systems Habitability, The University of Texas, Austin, TX, USA
¹⁰ Caltech/IPAC, Mail Code 100-22, Pasadena, CA 91125, USA
¹¹ NASA Ames Research Center, Moffett Field, CA 94035, USA
¹² Lund Observatory, Division of Astrophysics, Department of Physics, Lund University, Box 118, 22100 Lund, Sweden
¹³ Astrobiology Center, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁴ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁵ Astronomical Science Program, Graduate University for Advanced Studies, SOKENDAI, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁶ Instituto de Astrofísica de Canarias (IAC), Calle Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
¹⁷ Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
¹⁸ Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
¹⁹ Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
²⁰ Department of Aeronautics and Astronautics, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
²¹ Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
²² SETI Institute, Mountain View, CA 94043, USA/NASA Ames Research Center, Moffett Field, CA 94035, USA
²³ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK
²⁴ Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
²⁵ Department of Physics, Engineering and Astronomy, Stephen F. Austin State University, 1936 North St, Nacogdoches, TX 75962, USA

^★ Corresponding author; priyanka.chaturvedi@tifr.res.in

Received: 18 December 2024
Accepted: 2 April 2025

Abstract

We report the discovery of TOI-3493 b, a sub-Neptune-sized planet on an 8.15-d orbit transiting the bright (V=9.3) G0 star HD 119355 (aka TIC 203377303) initially identified by NASA’s TESS space mission. With the aim of confirming the planetary nature of the transit signal detected by TESS and determining the mass of the planet, we performed an intensive Doppler campaign with the HARPS spectrograph, collecting radial velocity measurements. We found that TOI-3493 b lies in a nearly circular orbit and has a mass of 9.0 ± 1.2 M_⊕ and a radius of 3.22 ± 0.08 R_⊕, implying a bulk density of 1.47_-0.22^+0.23 g cm⁻³, consistent with a composition comprising a small solid core surrounded by a thick H/He-dominated atmosphere.