TOI-2076 and TOI-1807: Two Young, Comoving Planetary Systems within 50 pc Identified by TESS that are Ideal Candidates for Further Follow Up

<jats:title>Abstract</jats:title> <jats:p>We report the discovery of two planetary systems around comoving stars: TOI-2076  (TIC 27491137) and TOI-1807 (TIC 180695581). TOI-2076  is a nearby (41.9 pc) multiplanetary system orbiting a young (204 ± 50 Myr), bright (<jats:italic>K</jats:italic> = 7.115 in TIC v8.1) start. TOI-1807 hosts a single transiting planet and is similarly nearby (42.58 pc), similarly young (180 ± 40 Myr ), and bright. Both targets exhibit significant, periodic variability due to starspots, characteristic of their young ages. Using photometric data collected by TESS  we identify three transiting planets around TOI-2076  with radii of <jats:italic>R</jats:italic> <jats:sub> <jats:italic>b</jats:italic> </jats:sub> = 3.3 ± 0.04 <jats:italic>R</jats:italic> <jats:sub>⊕</jats:sub>, <jats:italic>R</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub> = 4.4 ± 0.05 <jats:italic>R</jats:italic> <jats:sub>⊕</jats:sub>, and <jats:italic>R</jats:italic> <jats:sub> <jats:italic>d</jats:italic> </jats:sub> = 4.1 ± 0.07 <jats:italic>R</jats:italic> <jats:sub>⊕</jats:sub>. Planet TOI-2076b  has a period of <jats:italic>P</jats:italic> <jats:sub> <jats:italic>b</jats:italic> </jats:sub> = 10.356 days. For both TOI-2076c and d, TESS  observed only two transits, separated by a 2 yr interval in which no data were collected, preventing a unique period determination. A range of long periods (<17 days) are consistent with the data. We identify a short-period planet around TOI-1807 with a radius of <jats:italic>R</jats:italic> <jats:sub> <jats:italic>b</jats:italic> </jats:sub> = 1.8 ± 0.04 <jats:italic>R</jats:italic> <jats:sub>⊕</jats:sub> and a period of <jats:italic>P</jats:italic> <jats:sub> <jats:italic>b</jats:italic> </jats:sub> = 0.549 days. Their close proximity, and bright, cool host stars, and young ages make these planets excellent candidates for follow up. TOI-1807b  is one of the best-known small (<jats:italic>R</jats:italic> < 2 <jats:inline-formula> <jats:tex-math> <?CDATA ${R}_{\oplus }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊕</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ajac06cdieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) planets for characterization via eclipse spectroscopy and phase curves with JWST. TOI-1807b  is the youngest ultra-short-period planet discovered to date, providing valuable constraints on formation timescales of short-period planets. Given the rarity of young planets, particularly in multiple-planet systems, these planets present an unprecedented opportunity to study and compare exoplanet formation, and young planet atmospheres, at a crucial transition age for formation theory.</jats:p>