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MuSCAT2 multicolour validation of TESS candidates : An ultra-short-period substellar object around an M dwarf

Parviainen, H. ; Palle, E. ; Zapatero-Osorio, M. R. ; Montanes Rodriguez, P. ; Murgas, F. ; Narita, N. ; Hidalgo Soto, D. ; Béjar, V. J.S. ; Korth, J. LU and Monelli, M. , et al. (2020) In Astronomy and Astrophysics 633.
Abstract

Context. We report the discovery of TOI 263.01 (TIC 120916706), a transiting substellar object (R = 0.87 RJup) orbiting a faint M3.5 V dwarf (V = 18.97) on a 0.56 d orbit. Aims. We setout to determine the nature of the Transiting Exoplanet Survey Satellite (TESS) planet candidate TOI 263.01 using ground-based multicolour transit photometry. The host star is faint, which makes radial-velocity confirmation challenging, but the large transit depth makes the candidate suitable for validation through multicolour photometry. Methods. Our analysis combines three transits observed simultaneously in r′, i′, and zs bands usingthe MuSCAT2 multicolour imager, three LCOGT-observed transit light curves in g′, r′, and i′ bands, a TESS light curve from... (More)

Context. We report the discovery of TOI 263.01 (TIC 120916706), a transiting substellar object (R = 0.87 RJup) orbiting a faint M3.5 V dwarf (V = 18.97) on a 0.56 d orbit. Aims. We setout to determine the nature of the Transiting Exoplanet Survey Satellite (TESS) planet candidate TOI 263.01 using ground-based multicolour transit photometry. The host star is faint, which makes radial-velocity confirmation challenging, but the large transit depth makes the candidate suitable for validation through multicolour photometry. Methods. Our analysis combines three transits observed simultaneously in r′, i′, and zs bands usingthe MuSCAT2 multicolour imager, three LCOGT-observed transit light curves in g′, r′, and i′ bands, a TESS light curve from Sector 3, and a low-resolution spectrum for stellar characterisation observed with the ALFOSC spectrograph. We modelled the light curves with PYTRANSIT using a transit model that includes a physics-based light contamination component, allowing us to estimate the contamination from unresolved sources from the multicolour photometry. Using this information we were able to derive the true planet-star radius ratio marginalised over the contamination allowed by the photometry.Combining this with the stellar radius, we were able to make a reliable estimate of the absolute radius of the object. Results. The ground-based photometry strongly excludes contamination from unresolved sources with a significant colour difference to TOI 263. Furthermore, contamination from sources of the same stellar type as the host is constrained to levels where the true radius ratio posterior has a median of 0.217 and a 99 percentile of0.286. The median and maximum radius ratios correspond to absolute planet radii of 0.87 and 1.41 RJup, respectively,which confirms the substellar nature of the planet candidate. The object is either a giant planetor a brown dwarf (BD) located deep inside the so-called "brown dwarf desert". Both possibilities offer a challenge to current planet/BD formation models and make TOI 263.01 an object that merits in-depth follow-up studies.

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publishing date
type
Contribution to journal
publication status
published
keywords
Methods: statistical, Planets and satellites: general, Stars: individual: TIC 120916706, Techniques: photometric
in
Astronomy and Astrophysics
volume
633
article number
A28
publisher
EDP Sciences
external identifiers
  • scopus:85088113636
ISSN
0004-6361
DOI
10.1051/0004-6361/201935958
language
English
LU publication?
no
additional info
Publisher Copyright: © ESO 2019.
id
c490b270-70af-4ab5-89ef-898bd3a10fe8
date added to LUP
2023-02-02 09:31:16
date last changed
2023-02-21 10:04:35
@article{c490b270-70af-4ab5-89ef-898bd3a10fe8,
  abstract     = {{<p>Context. We report the discovery of TOI 263.01 (TIC 120916706), a transiting substellar object (R = 0.87 RJup) orbiting a faint M3.5 V dwarf (V = 18.97) on a 0.56 d orbit. Aims. We setout to determine the nature of the Transiting Exoplanet Survey Satellite (TESS) planet candidate TOI 263.01 using ground-based multicolour transit photometry. The host star is faint, which makes radial-velocity confirmation challenging, but the large transit depth makes the candidate suitable for validation through multicolour photometry. Methods. Our analysis combines three transits observed simultaneously in r′, i′, and zs bands usingthe MuSCAT2 multicolour imager, three LCOGT-observed transit light curves in g′, r′, and i′ bands, a TESS light curve from Sector 3, and a low-resolution spectrum for stellar characterisation observed with the ALFOSC spectrograph. We modelled the light curves with PYTRANSIT using a transit model that includes a physics-based light contamination component, allowing us to estimate the contamination from unresolved sources from the multicolour photometry. Using this information we were able to derive the true planet-star radius ratio marginalised over the contamination allowed by the photometry.Combining this with the stellar radius, we were able to make a reliable estimate of the absolute radius of the object. Results. The ground-based photometry strongly excludes contamination from unresolved sources with a significant colour difference to TOI 263. Furthermore, contamination from sources of the same stellar type as the host is constrained to levels where the true radius ratio posterior has a median of 0.217 and a 99 percentile of0.286. The median and maximum radius ratios correspond to absolute planet radii of 0.87 and 1.41 RJup, respectively,which confirms the substellar nature of the planet candidate. The object is either a giant planetor a brown dwarf (BD) located deep inside the so-called "brown dwarf desert". Both possibilities offer a challenge to current planet/BD formation models and make TOI 263.01 an object that merits in-depth follow-up studies.</p>}},
  author       = {{Parviainen, H. and Palle, E. and Zapatero-Osorio, M. R. and Montanes Rodriguez, P. and Murgas, F. and Narita, N. and Hidalgo Soto, D. and Béjar, V. J.S. and Korth, J. and Monelli, M. and Casasayas Barris, N. and Crouzet, N. and De Leon, J. P. and Fukui, A. and Hernandez, A. and Klagyivik, P. and Kusakabe, N. and Luque, R. and Mori, M. and Nishiumi, T. and Prieto-Arranz, J. and Tamura, M. and Watanabe, N. and Burke, C. and Charbonneau, D. and Collins, K. A. and Collins, K. I. and Conti, D. and Garcia Soto, A. and Jenkins, J. S. and Jenkins, J. M. and Levine, A. and Li, J. and Rinehart, S. and Seager, S. and Tenenbaum, P. and Ting, E. B. and Vanderspek, R. and Vezie, M. and Winn, J. N.}},
  issn         = {{0004-6361}},
  keywords     = {{Methods: statistical; Planets and satellites: general; Stars: individual: TIC 120916706; Techniques: photometric}},
  language     = {{eng}},
  month        = {{01}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{MuSCAT2 multicolour validation of TESS candidates : An ultra-short-period substellar object around an M dwarf}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/201935958}},
  doi          = {{10.1051/0004-6361/201935958}},
  volume       = {{633}},
  year         = {{2020}},
}