6 research outputs found

    Simultaneous TESS and NGTS Transit Observations of WASP-166b

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    We observed a transit of WASP-166 b using nine NGTS telescopes simultaneously with TESS observations of the same transit. We achieved a photometric precision of 152 ppm per 30 minutes with the nine NGTS telescopes combined, matching the precision reached by TESS for the transit event around this bright (T=8.87) star. The individual NGTS light curve noise is found to be dominated by scintillation noise and appears free from any time-correlated noise or any correlation between telescope systems. We fit the NGTS data for TCT_C and Rp/R∗R_p/R_*. We find TCT_C to be consistent to within 0.25σ\sigma of the result from the TESS data, and the difference between the TESS and NGTS measured Rp/R∗R_p/R_* values is 0.9σ\sigma. This experiment shows that multi-telescope NGTS photometry can match the precision of TESS for bright stars, and will be a valuable tool in refining the radii and ephemerides for bright TESS candidates and planets. The transit timing achieved will also enable NGTS to measure significant transit timing variations in multi-planet systems

    TIC-320687387 B: a long-period eclipsing M-dwarf close to the hydrogen burning limit

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    We are using precise radial velocities from CORALIE together with precision photometry from the Next Generation Transit Survey (NGTS) to follow-up stars with single-transit events detected with the Transiting Exoplanet Survey Satellite (TESS). As part of this survey, we identified a single transit on the star TIC-320687387, a bright (T = 11.6) G-dwarf observed by TESS in Sectors 13 and 27. From subsequent monitoring of TIC-320687387 with CORALIE, NGTS, and Lesedi we determined that the companion, TIC-320687387 B, is a very low-mass star with a mass of 96.2±1.92.0 MJ and radius of 1.14±0.020.02 RJ placing it close to the hydrogen burning limit (∼80 MJ). TIC-320687387 B is tidally decoupled and has an eccentric orbit, with a period of 29.77381 d and an eccentricity of 0.366 ± 0.003. Eclipsing systems such as TIC-320687387 AB allow us to test stellar evolution models for low-mass stars, which in turn are needed to calculate accurate masses and radii for exoplanets orbiting single low-mass stars. The sizeable orbital period of TIC-320687387 B makes it particularly valuable as its evolution can be assumed to be free from perturbations caused by tidal interactions with its G-type host star.</p

    NGTS-19b: a high-mass transiting brown dwarf in a 17-d eccentric orbit

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    We present the discovery of NGTS-19b, a high mass transiting brown dwarf discovered by the Next Generation Transit Survey (NGTS). We investigate the system using follow up photometry from the South African Astronomical Observatory, as well as sector 11 TESS data, in combination with radial velocity measurements from the CORALIE spectrograph to precisely characterise the system. We find that NGTS-19b is a brown dwarf companion to a K-star, with a mass of 69.5−5.4+5.769.5 ^{+5.7}_{-5.4} MJup_{Jup} and radius of 1.034−0.053+0.0551.034 ^{+0.055}_{-0.053} RJup_{Jup}. The system has a reasonably long period of 17.84 days, and a high degree of eccentricity of 0.3767−0.0061+0.00610.3767 ^{+0.0061}_{-0.0061}. The mass and radius of the brown dwarf imply an age of 0.46−0.15+0.260.46 ^{+0.26}_{-0.15} Gyr, however this is inconsistent with the age determined from the host star SED, suggesting that the brown dwarf may be inflated. This is unusual given that its large mass and relatively low levels of irradiation would make it much harder to inflate. NGTS-19b adds to the small, but growing number of brown dwarfs transiting main sequence stars, and is a valuable addition as we begin to populate the so called brown dwarf desert

    NGTS 15b, 16b, 17b and 18b: four hot Jupiters from the Next Generation Transit Survey

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    We report the discovery of four new hot Jupiters with the Next Generation Transit Survey (NGTS). NGTS-15b, NGTS-16b, NGTS-17b, and NGTS-18b are short-period (P<5P<5d) planets orbiting G-type main sequence stars, with radii and masses between 1.10−1.301.10-1.30 RJR_J and 0.41−0.760.41-0.76 MJM_J. By considering the host star luminosities and the planets' small orbital separations (0.039−0.0520.039-0.052 AU), we find that all four hot Jupiters are highly irradiated and therefore occupy a region of parameter space in which planetary inflation mechanisms become effective. Comparison with statistical studies and a consideration of the planets' high incident fluxes reveals that NGTS-16b, NGTS-17b, and NGTS-18b are indeed likely inflated, although some disparities arise upon analysis with current Bayesian inflationary models. However, the underlying relationships which govern radius inflation remain poorly understood. We postulate that the inclusion of additional hyperparameters to describe latent factors such as heavy element fraction, as well as the addition of an updated catalogue of hot Jupiters, would refine inflationary models, thus furthering our understanding of the physical processes which give rise to inflated planets

    NGTS 15b, 16b, 17b and 18b: four hot Jupiters from the Next Generation Transit Survey

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    We report the discovery of four new hot Jupiters with the Next Generation Transit Survey (NGTS). NGTS-15b, NGTS-16b, NGTS-17b, and NGTS-18b are short-period (P<5P<5d) planets orbiting G-type main sequence stars, with radii and masses between 1.10−1.301.10-1.30 RJR_J and 0.41−0.760.41-0.76 MJM_J. By considering the host star luminosities and the planets' small orbital separations (0.039−0.0520.039-0.052 AU), we find that all four hot Jupiters are highly irradiated and therefore occupy a region of parameter space in which planetary inflation mechanisms become effective. Comparison with statistical studies and a consideration of the planets' high incident fluxes reveals that NGTS-16b, NGTS-17b, and NGTS-18b are indeed likely inflated, although some disparities arise upon analysis with current Bayesian inflationary models. However, the underlying relationships which govern radius inflation remain poorly understood. We postulate that the inclusion of additional hyperparameters to describe latent factors such as heavy element fraction, as well as the addition of an updated catalogue of hot Jupiters, would refine inflationary models, thus furthering our understanding of the physical processes which give rise to inflated planets

    NGTS-11 b / TIC-54002556 b: A transiting warm Saturn recovered from a TESS single-transit event

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    We report the discovery of NGTS-11 b (=TIC-54002556 b), a transiting Saturn in a 35.46-day orbit around a mid K-type star (Teff=5050+-80 K). The system was initially identified from a single-transit event in our TESS full-frame image light-curves. Following seventy-nine nights of photometric monitoring with an NGTS telescope, we observed a second full transit of NGTS-11 b approximately one year after the TESS single-transit event. The NGTS transit confirmed the parameters of the transit signal and restricted the orbital period to a set of 13 discrete periods. We combined our transit detections with precise radial velocity measurements to determine the true orbital period and measure the mass of the planet. We find NGTS-11 b has a radius of 0.823+-0.035 RJup, a mass of 0.37+-0.14 MJup, and an equilibrium temperature of just 440+-40 K, making it one of the coolest known transiting gas giants. NGTS-11 b is the first exoplanet to be discovered after being initially identified as a TESS single transit event, and its discovery highlights the power of intense photometric monitoring in recovering longer-period transiting exoplanets from single-transit events
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