TOI-1728b: The Habitable-zone Planet Finder Confirms a Warm Super-Neptune Orbiting an M-dwarf Host

Shubham Kanodia, Caleb I. Cañas, Gudmundur Stefansson, Joe P. Ninan, Leslie Hebb, Andrea S.~J. Lin, Helen Baran, Marissa Maney, Ryan C. Terrien, Suvrath Mahadevan, William D. Cochran, Michael Endl, Jiayin Dong, Chad F. Bender, Scott A. Diddams, Eric B. Ford, Connor Fredrick, Samuel Halverson, Fred Hearty, Andrew J. Metcalf, Andrew Monson, Lawrence W. Ramsey, Paul Robertson, Arpita Roy, Christian Schwab, Jason T. Wright

August 1, 2020

Project DOI

Abstract

We confirm the planetary nature of TOI-1728b using a combination of ground-based photometry, near-infrared Doppler velocimetry and spectroscopy with the Habitable-zone Planet Finder. TOI-1728 is an old, inactive M0 star with $T{\mathrm eff} = 3980^{+31}{−32} $K, w h i c h h o s t s a t r a n s i t i n g s u p e r - N e p t u n e a t a n o r b i t a l p e r i o d o f$ \sim $3.49 d a y s . J o i n t f i t t i n g o f t h e r a d i a l v e l o c i t i e s a n d T E S S a n d g r o u n d - b a s e d t r a n s i t s y i e l d s a p l a n e t a r y r a d i u s o f$ 5.05^{+0.16}{−0.17}R\oplus $, m a s s$ 26.78^{+5.43}{−5.13} M\oplus $, a n d e c c e n t r i c i t y$ 0.057^{+0.054}{−0.039} $. W e e s t i m a t e t h e s t e l l a r p r o p e r t i e s, a n d p e r f o r m a s e a r c h f o r H e 10830 Å a b s o r p t i o n d u r i n g t h e t r a n s i t o f t h i s p l a n e t a n d c l a i m a n u l l d e t e c t i o n w i t h a n u p p e r l i m i t o f 1.1$ 1.14^{+0.26}{−0.24} $g c m$ ^{-3}$, and orbiting a bright host star (J ∼ 9.6, V ∼ 12.4), TOI-1728b is also a promising candidate for transmission spectroscopy both from the ground and from space, which can be used to constrain planet formation and evolutionary models.

Type

Journal article

Publication

ApJ