6 research outputs found
Simultaneous TESS and NGTS Transit Observations of WASP-166b
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 and
. We find to be consistent to within 0.25 of the result
from the TESS data, and the difference between the TESS and NGTS measured
values is 0.9. 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
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
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 M and radius of R. The system has a reasonably long period of 17.84
days, and a high degree of eccentricity of . The
mass and radius of the brown dwarf imply an age of 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
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 (d) planets orbiting G-type main sequence stars, with radii
and masses between and . By considering the
host star luminosities and the planets' small orbital separations
( 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
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 (d) planets orbiting G-type main sequence stars, with radii
and masses between and . By considering the
host star luminosities and the planets' small orbital separations
( 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
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