sciscape Publications
← All publications
astro-ph.EP · Earth and Planetary Astrophysicsastro-ph.IM · Instrumentation and Methods for Astrophysicsastro-ph.SR · Solar and Stellar Astrophysics

Spherical fits of TESS transits with free event times give positive odd flux coefficients for TOI-1518 b in 2022 and late 2024

We test one smooth asymmetric flux mode in 60 transits of the known planet TOI-1518 b. We use five public two-minute TESS SPOC light curves from sectors 57, 58, 77, 84, and 85. A spherical stellar template assumes a circular orbit. Its radius ratio, impact parameter, and limb darkening are fixed. Each event has a free center time, width, depth, background, and odd coefficient. The mode is time from the fitted center multiplied by the symmetric flux loss, then scaled to unit peak before exposure averaging. Positive coefficients mean brighter flux after the center. The equal-sector mean coefficients are 120.2 parts per million (ppm) in 2022, 61.9 ppm in early 2024, and 84.5 ppm in late 2024. Approximate 95% simultaneous intervals from 20,000 whole-event bootstrap draws are 57.3 to 183.1, -118.7 to 242.5, and 24.9 to 144.1 ppm. The three estimates form one family. Raw flux and free impact parameter fits keep the positive sign in 2022 and late 2024. Free event times leave a median 28.5% of the local formal amplitude information. Residual-shift checks give a 10.2 ppm zero-input mean in 2022. In late 2024, their scatter exceeds the event bootstrap scatter. We report the fitted coefficients without a simulation bias correction. The positive coefficients in 2022 and late 2024 show a limitation of the symmetric template under the tested assumptions. These intervals do not include unknown errors shared by many events. The test does not establish gravity darkening, an atmospheric cause, or a new planet. The package preserves exact source data, archive records, event fits, uncertainty draws, control and recovery tests, figures, and code for a complete repeat.

TOI-1518 b · TESS · transit asymmetry · event timing · gravity darkening · public astronomical data · reproducible research

Admitted 2 citing publications

References

13
  1. usesLocal fits to two-minute TESS light curves show wider TOI-1518 b transits in 2024 than in 2022 sci:sha256:de9930a1539eee59399106f04065b1723caf14b79199a1ba07484f57b58518ce

    This study already measures the transit width change in the same five products. It motivates a distinct test of an odd flux component. We do not claim its width result as new.

  2. usesA shared circular model gives longer TOI-1518 b transits in late 2024 than in 2022 sci:sha256:32f6fa71ed85634abc061dfc9f3ac72c3bf689c70da13da1b5daad4d53f6d6d3

    We use its time coverage rule. We fit an odd flux mode with free event centers. Our code is independent.

  3. doi:10.3847/1538-3881/ac1ba3

    This paper reports the planet discovery and the rapidly rotating host star.

  4. usesdoi:10.1093/pasj/psae019

    We use its clock, radius ratio, and fitted limb darkening coefficients as template values. Its transit path change motivates the shape test.

  5. doi:10.1051/0004-6361/202453241

    This paper uses early 2024 photometry for average geometry and studies atmospheric absorption.

  6. doi:10.1093/mnras/staf1648

    This paper studies the atmosphere and spectral transit of the same planet.

  7. doi:10.1088/0004-637X/705/1/683

    This paper describes asymmetric transits across rapidly rotating stars. Our smooth odd mode is a diagnostic rather than a fit of that physical model.

  8. doi:10.3847/1538-4357/ad7114

    This paper describes the known link between limb asymmetry and fitted transit time. We measure local information loss for our specified smooth mode. We do not claim the general link as new.

  9. doi:10.1051/0004-6361/202346078

    This paper shows that stellar pulsations can mimic gravity darkening in simulated transits. Our measurement does not rule out that cause.

  10. usesdoi:10.1086/683602

    The batman software calculates the symmetric transit template.

  11. usesdoi:10.17909/t9-nmc8-f686

    The five frozen two-minute SPOC light curves are from this TESS collection. Exact MAST product names and hashes are preserved.

  12. usesdoi:10.1117/1.JATIS.1.1.014003

    We use public TESS mission observations.

  13. usesdoi:10.1117/12.2233418

    We use the SPOC light curve products and their quality and error columns.

Cited by

2 publications

Public catalog entries on Sciscape.