J/A+A/712/A142 TOI-4409 b TESS light curves (Reller+, 2026) ================================================================================ Confirmation of the long-period exoplanet TOI-4409 b. Reller P., Brahm R., Merin B., Waldmann I., Trifonov T., Standing M.R., Vojtekova A., Guenther M., Guillot T., Stassun K.G., del Burgo C., Heras A.M., Lueftinger T., Triaud A.H.M.J., Isaak K., Dransfield G., Crouzet N., Pala A.F., Abe L., Mekarnia D., Schmider F.-X., Suarez O., Bendjoya P., Agabi A., Mura D., Gasparetto T., Buttu M., Eberhardt J., Henning T., Hobson M.J., Jordan A., Rojas F.I., Tala Pinto M., Teske J., Butler R.P., Crane J.D., Shectman S., Osip D., Boyle G., Leiva R., Suc V., Bakos G.A., Bhatti W., Hartman J.D., Csubry Z., Collins K.A., Watkins C.N., Schwarz R.P., Relles H.M., Srdoc G., Tan T.-G., Ziegler C. =2026A&A...712A.142R (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Stars, double and multiple ; Exoplanets ; Photometry ; Optical Keywords: methods: data analysis - techniques: photometric - techniques: radial velocities - planets and satellites: detection - planets and satellites: fundamental parameters - planets and satellites: individual: TOI-4409 b Abstract: Long-period transiting planets are essential edge-cases for understanding exoplanet formation and evolution. Their detection is challenging due to the infrequent nature of their transits, making every observation of these objects very valuable. Our goal is to confirm and further characterise the long-period planetary candidate TOI-4409 b (initially identified by TESS) through additional observations using the Antarctica-based ASTEP telescope, supplemented with CHAT, OMES, LCOGT, and PEST light-curve data and radial-velocity (RV) measurements collected with the HARPS, FEROS, and PFS instruments. We jointly analysed the photometric data from eight TESS, four ASTEP, one CHAT, two OMES, four LCOGT, and one PEST light curve(s), and RV data from the HARPS, FEROS, and PFS instruments, covering observations from 2018 to 2024. TOI-4409 b is a bona fide puffy warm super-Neptune exoplanet with a planet radius of 7.44+/-0.19R_{Earth}_ and a mass of 0.047+/-0.017M_J_ (3{sigma} upper limit <0.095M_J_) orbiting a low-mass main-sequence star (effective temperature of 4928+/-48 K and a stellar radius of 0.720+/-0.018R_{sun}_) with a period of 92.49179+/-0.00010 days. The integration of various observational methods and consistent transit signals across multiple instruments confirms the planetary nature of TOI-4409 b. The combined transit, imaging, chromaticity, and RV evidence supports the confirmation of the planet. With a radius of 7.44+/-0.19R_{Earth}_ and a low bulk density of 0.20+/-0.07g/cm^3^, TOI-4409 b occupies a sparsely populated region of parameter space among warm, puffy super-Neptunes on long-period orbits. The detection of candidate transit timing variations with an ~10-minute semi-amplitude hints at the presence of an additional body in the system. The favourable host-star brightness and extended transit duration (~7 hours) make TOI-4409 b a promising target for atmospheric characterisation with JWST and Ariel. Description: TOI-4409 b is a long-period (P=92.49 days) transiting warm super-Neptune around a low-mass main-sequence star (Teff=4928+/-48K, R*=0.720+/-0.018R_{sun}_). It has a planet radius of 7.44+/-0.19R_{Earth}_ and a mass of 0.047+/-0.017M_Jup_ (3-sigma upper limit <0.095M_Jup_), giving a low bulk density of 0.20+/-0.07g/cm^3^. Confirmation rests on joint analysis of TESS, ASTEP, CHAT, OMES, LCOGT, and PEST photometry plus HARPS, FEROS, and PFS radial velocities collected from 2018 to 2024. Candidate transit-timing variations with a ~10-minute semi-amplitude hint at a companion. TESS photometric time series for the eight transit windows of TOI-4409 b observed by TESS between 2018 and 2023. Each file covers approximately two days centred on one transit event and contains normalised PDCSAP flux extracted from the TESS pipeline products. The data were prepared using a transit-window extraction script that selects a baseline window around each transit epoch. Cadences range from 20s (sectors 31, 38) through 120 s (sectors 28, 65) to 1800s (sectors 1, 4, 8, 11). Objects: ------------------------------------------------------- RA (2000) DE Designation(s) ------------------------------------------------------- 05 27 16.49 -54 56 46.2 TOI-4409 = TIC 382200986 ------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file t1336.dat 38 94 TESS LC, transit window near BTJD 1336 t1429.dat 38 96 TESS LC, transit window near BTJD 1429 t1521.dat 38 95 TESS LC, transit window near BTJD 1521 t1614.dat 38 93 TESS LC, transit window near BTJD 1614 t2076.dat 38 1727 TESS LC, transit window near BTJD 2076 t2169.dat 38 10367 TESS LC, transit window near BTJD 2169 t2354.dat 38 10314 TESS LC, transit window near BTJD 2354 t3094.dat 38 1440 TESS LC, transit window near BTJD 3094 -------------------------------------------------------------------------------- Byte-by-byte Description of file: t*.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 F10.5 d BJD [1335.42/3094.76] Mid-exposure time, TDB (BJD-2457000) (1) 12- 23 F12.10 --- Flux [0.964/1.033] Normalised PDCSAP flux (2) 25- 38 F14.12 --- e_Flux [0.0006/0.0111] Per-cadence flux uncertainty (1-sigma) (3) -------------------------------------------------------------------------------- Note (1): Barycentric TESS Julian Date, defined as BJD_TDB_-2457000.0, following the native TESS pipeline convention. To recover full BJD, add 2457000.0 to the BTJD values. Note (2): Flux is normalised Pre-search Data Conditioning Simple Aperture Photometry (PDCSAP) flux from the TESS Science Processing Operations Centre (SPOC) pipeline. Nominal out-of-transit level is 1.0. Transit events produce dips of approximately 0.01 (1%). Note (3): The eight files correspond to eight observed transits of TOI-4409 b across TESS sectors 1, 4, 8, 11, 28, 31, 38, and 65. File naming encodes the approximate BTJD of the transit midpoint. Cadence varies: 1800 s (sectors 1, 4, 8, 11), 120 s (sectors 28, 65), and 20 s (sectors 31, 38). -------------------------------------------------------------------------------- Acknowledgements: From Patricio Rellerm patricio.reller(at)ucl.ac.uk This work uses data from the Transiting Exoplanet Survey Satellite (TESS) mission, obtained from the Mikulski Archive for Space Telescopes (MAST) at STScI. License: CC-BY-4.0 References: Ricker et al., TESS, 2015JATIS...1a4003R Jenkins et al., SPOC pipeline, 2016SPIE.9913E..3EJ ================================================================================ (End) Patricio Reller [UCL/ESA], Patricia Vannier [CDS] 26-May-2026