_version_ 1866918520486363136
author Rea, Erika
Günther, Maximilian N.
Dransfield, George
Guillot, Tristan
Triaud, Amaury H. M. J.
Stassun, Keivan G.
Espinoza-Retamal, Juan I.
Brahm, Rafael
Ulmer-Moll, Solène
Beltrame, Matteo
Deloupy, Vincent
Timmermans, Mathilde
Abe, Lyu
Agabi, Karim
Bendjoya, Philippe
Mekarnia, Djamel
Schmider, Francois-Xavier
Suarez, Olga
Heras, Ana M.
Lüftinger, Theresa
Merín, Bruno
Bouchy, François
Henning, Thomas
Jordán, Andrés
Lendl, Monika
Tala-Pinto, Marcelo
Trifonov, Trifon
Barkaoui, Khalid
Bouma, Luke G.
Boyle, Gavin
Briceño, César
Castro-González, Amadeo
Claringbold, Alastair
Collins, Karen A.
Horne, Keith
Howell, Steve B.
Mann, Andrew W.
Murgas, Felipe
Palle, Enric
Quinn, Samuel
Rodriguez, Joseph E.
Schwarz, Richard P.
Tan, T. G.
Zhou, George
Ziegler, Carl
Seager, Sara
Winn, Joshua N.
author_facet Rea, Erika
Günther, Maximilian N.
Dransfield, George
Guillot, Tristan
Triaud, Amaury H. M. J.
Stassun, Keivan G.
Espinoza-Retamal, Juan I.
Brahm, Rafael
Ulmer-Moll, Solène
Beltrame, Matteo
Deloupy, Vincent
Timmermans, Mathilde
Abe, Lyu
Agabi, Karim
Bendjoya, Philippe
Mekarnia, Djamel
Schmider, Francois-Xavier
Suarez, Olga
Heras, Ana M.
Lüftinger, Theresa
Merín, Bruno
Bouchy, François
Henning, Thomas
Jordán, Andrés
Lendl, Monika
Tala-Pinto, Marcelo
Trifonov, Trifon
Barkaoui, Khalid
Bouma, Luke G.
Boyle, Gavin
Briceño, César
Castro-González, Amadeo
Claringbold, Alastair
Collins, Karen A.
Horne, Keith
Howell, Steve B.
Mann, Andrew W.
Murgas, Felipe
Palle, Enric
Quinn, Samuel
Rodriguez, Joseph E.
Schwarz, Richard P.
Tan, T. G.
Zhou, George
Ziegler, Carl
Seager, Sara
Winn, Joshua N.
contents We present the analysis of five long-period TESS Objects of Interest (TOIs), all orbiting Sun-like stars, with orbital periods exceeding one month. Initially identified by the Transiting Exoplanet Survey Satellite (TESS), we extensively monitored these targets with the Antarctic Search for Transiting Exoplanets (ASTEP), supported by other facilities in the TESS Follow-up Observing Program (TFOP) network. These targets occupy a relatively underexplored region of the period-radius parameter space, offering valuable primordial probes for planetary formation and migration as warm planets better maintain their evolutionary fingerprints. To characterise these systems, we leveraged high-resolution speckle imaging to search for nearby stellar companions, and refine stellar parameters using both reconnaissance spectroscopy and spectral energy distribution (SED) fitting. We combined TESS photometry with high-precision ground-based observations from ASTEP, and when available, included additional photometry and radial velocity data. We applied statistical validation to assess the planetary nature of each candidate and used Allesfitter to jointly model the photometric and spectroscopic datasets. We validate the planetary nature of three TOIs, including the two warm Saturns TOI-4507b (8.2 Earth radii, 104d) and TOI-3457b (10.0 Earth radii, 32.6d), as well as the warm sub-Neptune TOI-707b (2.4 Earth radii, 52.8d). The remaining two candidates are most consistent with eclipsing binaries, namely TOI-2404 and TOI-4404. These results help populate the sparse regime of warm planets, which serve as key tracers of planetary evolution, and demonstrate ASTEP's effectiveness as a ground-based follow-up instrument for long-period systems.
format Preprint
id arxiv_https___arxiv_org_abs_2510_01725
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle High five from ASTEP: Three validated planets and two eclipsing binaries in a diverse set of long-period candidates
Rea, Erika
Günther, Maximilian N.
Dransfield, George
Guillot, Tristan
Triaud, Amaury H. M. J.
Stassun, Keivan G.
Espinoza-Retamal, Juan I.
Brahm, Rafael
Ulmer-Moll, Solène
Beltrame, Matteo
Deloupy, Vincent
Timmermans, Mathilde
Abe, Lyu
Agabi, Karim
Bendjoya, Philippe
Mekarnia, Djamel
Schmider, Francois-Xavier
Suarez, Olga
Heras, Ana M.
Lüftinger, Theresa
Merín, Bruno
Bouchy, François
Henning, Thomas
Jordán, Andrés
Lendl, Monika
Tala-Pinto, Marcelo
Trifonov, Trifon
Barkaoui, Khalid
Bouma, Luke G.
Boyle, Gavin
Briceño, César
Castro-González, Amadeo
Claringbold, Alastair
Collins, Karen A.
Horne, Keith
Howell, Steve B.
Mann, Andrew W.
Murgas, Felipe
Palle, Enric
Quinn, Samuel
Rodriguez, Joseph E.
Schwarz, Richard P.
Tan, T. G.
Zhou, George
Ziegler, Carl
Seager, Sara
Winn, Joshua N.
Earth and Planetary Astrophysics
We present the analysis of five long-period TESS Objects of Interest (TOIs), all orbiting Sun-like stars, with orbital periods exceeding one month. Initially identified by the Transiting Exoplanet Survey Satellite (TESS), we extensively monitored these targets with the Antarctic Search for Transiting Exoplanets (ASTEP), supported by other facilities in the TESS Follow-up Observing Program (TFOP) network. These targets occupy a relatively underexplored region of the period-radius parameter space, offering valuable primordial probes for planetary formation and migration as warm planets better maintain their evolutionary fingerprints. To characterise these systems, we leveraged high-resolution speckle imaging to search for nearby stellar companions, and refine stellar parameters using both reconnaissance spectroscopy and spectral energy distribution (SED) fitting. We combined TESS photometry with high-precision ground-based observations from ASTEP, and when available, included additional photometry and radial velocity data. We applied statistical validation to assess the planetary nature of each candidate and used Allesfitter to jointly model the photometric and spectroscopic datasets. We validate the planetary nature of three TOIs, including the two warm Saturns TOI-4507b (8.2 Earth radii, 104d) and TOI-3457b (10.0 Earth radii, 32.6d), as well as the warm sub-Neptune TOI-707b (2.4 Earth radii, 52.8d). The remaining two candidates are most consistent with eclipsing binaries, namely TOI-2404 and TOI-4404. These results help populate the sparse regime of warm planets, which serve as key tracers of planetary evolution, and demonstrate ASTEP's effectiveness as a ground-based follow-up instrument for long-period systems.
title High five from ASTEP: Three validated planets and two eclipsing binaries in a diverse set of long-period candidates
topic Earth and Planetary Astrophysics
url https://arxiv.org/abs/2510.01725