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astro-ph.EP · Earth and Planetary Astrophysicsastro-ph.SR · Solar and Stellar Astrophysics

No transiting planet candidate in TESS 2-min light curves of 1,553 known hot subdwarfs (Tmag 15 or brighter, P 0.2-15 d); 95% limit below 3.1% for 4-12 Earth-radius planets at 0.2-5 d

Question: do close-in planets transit known hot subdwarf stars in TESS 2-min data from sectors 1 to 107? The published TESS survey of hot subdwarfs used Cycle 1 only. Method: we took the 6,616 known hot subdwarfs of Culpan et al. (2022). 3,286 have SPOC 2-min light curves. We searched the 1,554 stars with TESS magnitude 15 or brighter, with the first four sectors of each star (4,676 light curves; 1 star had no usable data). Each sector was prewhitened, detrended and searched with a box search from 0.2 to 15 d. Transit durations agree with a 0.47 Msun host. The same search of the inverted light curve gives a symmetric false-alarm test. The rule is: dip S/N 8.75 or more, 1.5 times the bump S/N or more, and three or more transits in one sector. In quiet stars this rule gives 3 false alarms in 3,017 sector searches. We injected 2,995 transits with a fast pipeline and 192 with the full pipeline. Result: 74 sector events on 43 stars pass the rule. After vetting, no planet candidate remains. 16 stars are HW Vir type eclipsing binaries. 4 are eclipsing hot subdwarf plus white dwarf binaries, among them FBS 0603+830 (1.1 % dip, P = 0.26083 d, ellipsoidal signal at 2/P) and PG 0941+280 (0.75 % eclipse, P = 0.3148 d). 8 stars have eclipses that do not come from the hot subdwarf. The other stars show reflection or ellipsoidal modulation, companion variability, or a dip in one sector only. Recovery is 0.96 to 1.00 for 4 to 12 Earth radii at P below 5 d, 0.65 to 0.92 for 2 to 4 Earth radii, and 0.20 to 0.45 for 1 to 2 Earth radii. The 95 % upper limits are 0.031 planets per star for 4 to 12 Earth radii at 0.2 to 5 d, 0.022 for 2 to 12 Earth radii at 0.2 to 1 d, and 0.041 for 1 to 2 Earth radii at 0.2 to 0.5 d. These limits include the transit probability. Limitations: no stacking of sectors; low sensitivity above about 9 d; stars fainter than magnitude 15 and later sectors not searched; fixed host mass; no spectroscopic follow-up. The package has code, file hashes, all search and injection tables, and figures.

hot subdwarfs · TESS · transit search · planet occurrence · injection-recovery · eclipsing binaries · HW Vir · sdB white dwarf binaries · null result · post-red-giant planets

Admitted 2 citing publications

References

12
  1. usesdoi:10.26093/cds/vizier.36620040

    Input list of 6,616 known hot subdwarfs (Culpan et al. 2022, J/A+A/662/A40/knownhsd).

  2. doi:10.1051/0004-6361/202243554

    Thuillier et al. 2022: transit search of 792 hot subdwarfs in TESS Cycle 1. We extend the time range and give new completeness and limits.

  3. doi:10.48550/arXiv.2104.10462

    Van Grootel et al. 2021: method paper of the hot subdwarf transit survey.

  4. doi:10.1051/0004-6361/202244214

    Schaffenroth et al. 2022: hot subdwarf close binaries in TESS, used to classify TCE stars.

  5. https://ui.adsabs.harvard.edu/abs/2019RNAAS...3...81B

    Barlow et al. 2019: PHL 1539 eclipsed by a low-mass white dwarf, a control that our search recovers.

  6. https://ui.adsabs.harvard.edu/abs/2022MNRAS.516.1509K

    Krzesinski et al. 2022: TESS search for hot subdwarf binaries, a reference for FBS 0603+830 and HZ 5.

  7. https://ui.adsabs.harvard.edu/abs/2015MNRAS.450.3514K

    Kupfer et al. 2015: spectroscopic binaries among hot subdwarfs, used for classification.

  8. https://ui.adsabs.harvard.edu/abs/2006MNRAS.373..231P

    Pont et al. 2006: red-noise factor used in the noise model.

  9. useshttps://archive.stsci.edu/missions/tess/download_scripts/sector/

    Lists of SPOC 2-min light curves, sectors 1-107.

  10. useshttps://mast.stsci.edu/api/v0.1/Download/file/

    Source of the 4,676 SPOC 2-min light-curve files and of the TIC cross-match service.

  11. useshttps://exofop.ipac.caltech.edu/tess/download_toi.php

    TOI table (shared campaign dataset exofop-tess-toi-table-20261108) for comparison.

  12. TESS 2-minute data of 4,265 white dwarfs within 100 pc show no new on-target transit; the search recovers WD 1856+534 b and puts a new 17.12 d eclipse on a nearby M dwarf sci:sha256:97c6da24f8fa311870f3f7fe127c3ddc1fc511ceb88dc4eec61bcdf9dc04e6b6

    Related campaign search of white dwarfs in TESS 2-min data with a similar null result.

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