arXiv subjects

Yohann Tschudi

Publications and source records attributed to Yohann Tschudi.

3 recordsLinked to original sources

arXiv2026

Habitable-zone Earths at the detection frontier: Measured completeness and false-alarm rate of a transit pipeline for the PLATO M-dwarf sample

The PLATO mission will observe its first long-pointing field, LOPS2 (Long-duration Observation Phase, South field), for at least two years, bringing the habitable zones (HZ) of its M-dwarf sample within reach of a transit search. The completeness and false-alarm rate of a pipeline validated on TESS M dwarfs are measured on simulated PLATO photometry and converted into a candidate-level forecast for the LOPS2 M dwarfs. Simulated PLATO light curves (717 d baseline; three stellar cells of the faint half of the sample) were processed end to end in two arms, without and with a pre-launch model of the instrument systematics: 930 in the first (465 realisations, 525 injected planets, 465 noise-only twins) and 790 in the second. Injected planets measure completeness against the expected signal-to-noise ratio (S/N), separately for the long-period regime of the HZ; noise-only twins measure the false-alarm rate against the floor on the red-noise-aware statistic S/N_pink. Completeness reaches 50% at S/N = 7.7 +/- 0.15 over all periods and 8.6 +/- 0.3 in the long-period regime. The false-alarm rate falls from 79 +/- 2% to 0.6% as the S/N_pink floor rises from 6 to 8, and 6 +/- 1% at the adopted floor 7.5 (completeness 54 +/- 2%). In the field, the 50 known transiting objects of interest (19 confirmed planets, 31 candidates) would all be recovered; a transiting HZ planet of 1.0 (1.5) Earth radii would be recovered as a candidate with ~40% (65%) probability, giving about 4 HZ Earths and 7 super-Earths over 16 929 field M dwarfs. The systematics arm shifts the 50% point by +0.54 (+0.27/-0.22) in S/N, a penalty localised on the transition, leaving the floor robust and negligible on the long-period injections that feed the HZ. Habitable-zone Earths around the PLATO M dwarfs sit at the measured detection frontier, where completeness and reliability, both measurable before launch, decide the yield.

astro-ph.EP↗

arXiv2026

A uniform transit survey of 461 ExoFOP M-dwarf TOI hosts: Follow-up prioritization and new transit candidates

Context. M dwarfs are favorable hosts for small transiting planets. A transit-detection and statistical-validation pipeline was previously developed and validated at the photometric noise frontier, on M3-M6 dwarfs observed in few sectors. Aims. That pipeline is applied uniformly to the full active ExoFOP M-dwarf TOI population, 461 hosts (M0-M6) each hosting a confirmed planet (CP) or planet candidate (PC), to test its recovery and classification of the cataloged signals and to prioritize the candidates for follow-up. Methods. The pipeline chains two complementary blind searches merged per host, a full-baseline transit-least-squares scan and a segmented, semi-coherent search across the gapped multiyear baseline. It adds an event-time-coherence test that rejects signals with incoherent per-transit timing (window-function aliases of stellar variability), all-sector TRICERATOPS false-positive probabilities, and Gaia DR3 background and aperture-localization analysis. Results. Of 193 in-range CP, 165 (85.5%) are re-detected, none rejected as a false positive, and 147 (76.2%) reach a Gaia-verified disposition. Of 286 in-range PC, 225 (78.7%) are re-detected, of which 11 are flagged as false positives and 87 ranked as planet candidates for follow-up. Beyond the catalog, 13 new transit candidates of 0.7-2.0 Earth radii emerge, including two new members of a compact, dynamically stable near-resonant three-planet candidate system; four cataloged single- or dual-transit TOIs have their orbital periods determined, two of them in the optimistic habitable zone. Conclusions. The recoveries and new candidates are released as a uniform, prioritized follow-up target list.

astro-ph.EP↗

arXiv2026

At the stellar noise frontier: A transit survey of 121 TESS M3--M6 dwarfs

M-dwarf stars are the most favorable hosts for detecting small transiting planets, yet mid-to-late M-dwarfs that acquired sufficient TESS multi-sector coverage only through recent Cycle 6+ observations represent a newly accessible discovery space. This paper presents a systematic transit survey of 121 M3-M6 dwarfs (Teff = 2700-3400 K) selected as "newly enabled" targets -- stars with <=2 archival TESS sectors that only recently crossed the multi-sector detection threshold, covering P = 0.5-100 d. The sample was selected from 498,312 TIC M-dwarfs via a 9-step funnel. The pipeline combines TLS with a signal validation cascade, TRICERATOPS vetting, Gaia DR3 verification, and three empirical signal reliability tests. Pipeline validation achieved 100% recovery (16/16 planets) on 10 known systems with zero false positives. The survey identifies 20 transit-like signals across 16 systems, none with prior TOI designations. The reliability framework classifies 2 as Tier 1 (High Robustness), 7 as Tier 2 (Moderate), and 10 as Tier 3 (Noise-Susceptible); one monotransit is excluded. No candidate SDE significantly exceeds its host star's noise floor. The global false alarm rate is 17.4% (21/121; Wilson 95% CI: [11.6%, 25.1%]).The 2 Tier 1 candidates are priorities for RV confirmation. The 10 Tier 3 candidates require additional TESS sectors to establish signal persistence; 9 systems need high-resolution imaging.

astro-ph.EP↗