Examinando por Autor "Narita, N."

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Acceso Abierto
MuSCAT2 multicolour validation of TESS candidates: an ultra-short-period substellar object around an M dwarf
(EDP Sciences, 2020-01-03) Parviainen, H.; Pallé, E.; Zapatero Osorio, M. R.; Montañés Rodríguez, P.; Murgas Alcaino, F.; Narita, N.; Hidalgo Soto, D.; Béjar, V. J. S.; Korth, J.; Monelli, M.; Casasayas Barris, N.; Crouzet, N.; De Leon, J. P.; Fukui, A.; Klagyivik, P.; Kusakabe, N.; Luque, R.; Mori, M.; Nishiumi, T.; Prieto Arranz, J.; Tamura, M.; Watanabe, N.; Burke, C. J.; Charbonneau, D.; Collins, K. A.; Collins, K. I.; Conti, D.; García Soto, A.; Jenkins, J. S.; Jenkins, J. M.; Levine, A.; Li, J.; Rinehart, S.; Seager, S.; Tenenbaum, P.; Ting, E. B.; Vanderspek, R.; Vezie, M.; Winn, J. N.; HERRERA HERNÁNDEZ, ALEJANDRO; Ministerio de Economía y Competitividad (MINECO); Deutsche Forschungsgemeinschaft (DFG); Agencia Estatal de Investigación (AEI); Japan Society for the Promotion of Science (JSPS); Japan Science and Technology Agency (JST); Parvianen, H. [0000-0001-5519-1391]; Monelli, M. [0000-0001-5292-6380]; Korth, J. [0000-0002-0076-6239]; Zapatero Osorio, M. R. [0000-0001-5664-2852]; Luque, R. [0000-0002-4671-2957]; Kusakabe, N. [0000-0001-9194-1268]; Collins, K. [0000-0003-2781-3207]; García Soto, A. [0000-0001-9828-3229]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
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.
Acceso Abierto
TOI-519 b: A short-period substellar object around an M dwarf validated using multicolour photometry and phase curve analysis
(EDP Sciences, 2021-01-15) Parviainen, H.; Pallé, E.; Zapatero Osorio, M. R.; Nowak, G.; Fukui, A.; Murgas Alcaino, F.; Narita, N.; Stassun, K. G.; Livingston, J. H.; Collins, K. A.; Hidalgo Soto, D.; Béjar, V. J. S.; Korth, J.; Monelli, M.; Montañés Rodríguez, P.; Casasayas Barris, N.; Chen, G.; Crouzet, N.; De Leon, J. P.; Kawauchi, K.; Klagyivik, P.; Kusakabe, N.; Luque, R.; Mori, M.; Nishiumi, T.; Prieto Arranz, J.; Tamura, M.; Watanabe, N.; Gan, T.; Collins, K. I.; Jensen, E. L. N.; Barclay, T.; Doty, J. P.; Jenkins, J. M.; Latham, D. W.; Paegert, M.; Ricker, G.; Rodríguez, D. R.; Seager, S.; Shporer, A.; Vanderspek, R.; Villaseñor, J. N.; Winn, J. N.; Wohler, B.; Wong, I.; HERRERA HERNÁNDEZ, ALEJANDRO; Ministerio de Economía y Competitividad (MINECO); Agencia Estatal de Investigación (AEI); Japan Society for the Promotion of Science (JSPS); Deutsche Forschungsgemeinschaft (DFG); Monelli, M. [0000-0001-5292-6380]; Collins, K. [0000-0003-2781-3207]; Paegert, M. [0000-0001-8120-7457]; Luque, R. [0000-0002-4671-2957]
Context. We report the discovery of TOI-519 b (TIC 218795833), a transiting substellar object (R = 1.07 RJup) orbiting a faint M dwarf (V = 17.35) on a 1.26 d orbit. Brown dwarfs and massive planets orbiting M dwarfs on short-period orbits are rare, but more have already been discovered than expected from planet formation models. TOI-519 is a valuable addition to this group of unlikely systems, and it adds towards our understanding of the boundaries of planet formation. Aims. We set out to determine the nature of the Transiting Exoplanet Survey Satellite (TESS) object of interest TOI-519 b. Methods. Our analysis uses a SPOC-pipeline TESS light curve from Sector 7, multicolour transit photometry observed with MuSCAT2 and MuSCAT, and transit photometry observed with the LCOGT telescopes. We estimated the radius of the transiting object using multicolour transit modelling, and we set upper limits for its mass, effective temperature, and Bond albedo using a phase curve model that includes Doppler boosting, ellipsoidal variations, thermal emission, and reflected light components. Results. TOI-519 b is a substellar object with a radius posterior median of 1.07 RJup and 5th and 95th percentiles of 0.66 and 1.20 RJup, respectively, where most of the uncertainty comes from the uncertainty in the stellar radius. The phase curve analysis sets an upper effective temperature limit of 1800 K, an upper Bond albedo limit of 0.49, and a companion mass upper limit of 14 MJup. The companion radius estimate combined with the Teff and mass limits suggests that the companion is more likely a planet than a brown dwarf, but a brown-dwarf scenario is a priori more likely given the lack of known massive planets in ≈ 1 day orbits around M dwarfs with Teff < 3800 K, and given the existence of some (but few) brown dwarfs.