10 research outputs found
The positional probability and true host star identification of TESS exoplanet candidates
We present a method for deriving a probabilistic estimate of the true source
of a detected TESS transiting event. Our method relies on comparing the
observed photometric centroid offset for the target star with models of the
offset that would occur if the event was either on the target or any of the
Gaia identified nearby sources. The comparison is done probabilistically,
allowing us to incorporate the uncertainties of the observed and modelled
offsets in our result. The method was developed for TESS Full Frame Image
lightcurves produced from the SPOC pipeline, but could be easily adapted to
lightcurves from other sources. We applied the method on 3226 TESS Objects of
Interest (TOIs), with a released lightcurve from SPOC. The method correctly
identified 96.5% of 655 known exoplanet hosts as the most likely source of the
eclipse. For 142 confirmed Nearby Eclipsing Binaries (NEBs) and Nearby Planet
Candidates (NPCs), a nearby source was found to be the most likely in 96.5% of
the cases. For 40 NEBs and NPCs where the true source is known, it was
correctly designated as the most likely in 38 of those. Finally, for 2365
active planet candidates, the method suggests that 2072 are most likely
on-target and 293 on a nearby source. The method forms a part of an
in-development vetting and validation pipeline, called RAVEN, and is released
as a standalone tool.Comment: Accepted for publication in MNRA
The positional probability and true host star identification of TESS exoplanet candidates
We present a method for deriving a probabilistic estimate of the true source of a detected TESS transiting event. Our method relies on comparing the observed photometric centroid offset for the target star with models of the offset that would occur if the event was either on the target or any of the Gaia identified nearby sources. The comparison is done probabilistically, allowing us to incorporate the uncertainties of the observed and modelled offsets in our result. The method was developed for TESS Full Frame Image lightcurves produced from the SPOC pipeline, but could be easily adapted to lightcurves from other sources. We applied the method on 3226 TESS Objects of Interest (TOIs), with a released lightcurve from SPOC. The method correctly identified 96.5% of 655 known exoplanet hosts as the most likely source of the eclipse. For 142 confirmed Nearby Eclipsing Binaries (NEBs) and Nearby Planet Candidates (NPCs), a nearby source was found to be the most likely in 96.5% of the cases. For 40 NEBs and NPCs where the true source is known, it was correctly designated as the most likely in 38 of those. Finally, for 2365 active planet candidates, the method suggests that 2072 are most likely on-target and 293 on a nearby source. The method forms a part of an in-development vetting and validation pipeline, called RAVEN, and is released as a standalone tool
Discovery and characterisation of two Neptune-mass planets orbiting HD 212729 with TESS
We report the discovery of two exoplanets orbiting around HD 212729
(TOI\,1052, TIC 317060587), a K star with V=9.51 observed by
TESS in Sectors 1 and 13. One exoplanet, TOI-1052b, is Neptune-mass and
transits the star, and an additional planet TOI-1052c is observed in radial
velocities but not seen to transit. We confirm the planetary nature of
TOI-1052b using precise radial velocity observations from HARPS and determined
its parameters in a joint RV and photometry analysis. TOI-1052b has a radius of
R, a mass of M, and
an orbital period of 9.14 days. TOI-1052c does not show any transits in the
TESS data, and has a minimum mass of M and an
orbital period of 35.8 days, placing it just interior to the 4:1 mean motion
resonance. Both planets are best fit by relatively high but only marginally
significant eccentricities of for planet b and
for planet c. We perform a dynamical analysis and
internal structure model of the planets as well as deriving stellar parameters
and chemical abundances. The mean density of TOI-1052b is g
cm consistent with an internal structure similar to Neptune. A nearby
star is observed in Gaia DR3 with the same distance and proper motion as
TOI-1052, at a sky projected separation of ~1500AU, making this a potential
wide binary star system.Comment: Accepted to MNRAS. 11 page
TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf
We present the discovery of two exoplanets transiting TOI-836 (TIC 440887364)
using data from TESS Sector 11 and Sector 38. TOI-836 is a bright (
mag), high proper motion ( mas yr), low metallicity
([Fe/H]) K-dwarf with a mass of M and a
radius of R. We obtain photometric follow-up
observations with a variety of facilities, and we use these data-sets to
determine that the inner planet, TOI-836 b, is a R
super-Earth in a 3.82 day orbit, placing it directly within the so-called
'radius valley'. The outer planet, TOI-836 c, is a R
mini-Neptune in an 8.60 day orbit. Radial velocity measurements reveal that
TOI-836 b has a mass of M , while TOI-836 c has a mass
of M. Photometric observations show Transit Timing
Variations (TTVs) on the order of 20 minutes for TOI-836 c, although there are
no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by
an undetected exterior planet
TOI-836 : a super-Earth and mini-Neptune transiting a nearby K-dwarf
Funding: TGW, ACC, and KH acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant ST/R003203/1.We present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data from TESS Sector 11 and Sector 38. TOI-836 is a bright (T = 8.5 mag), high proper motion (∼200 mas yr−1), low metallicity ([Fe/H]≈−0.28) K-dwarf with a mass of 0.68 ± 0.05 M⊙ and a radius of 0.67 ± 0.01 R⊙. We obtain photometric follow-up observations with a variety of facilities, and we use these data-sets to determine that the inner planet, TOI-836 b, is a 1.70 ± 0.07 R⊕ super-Earth in a 3.82 day orbit, placing it directly within the so-called ‘radius valley’. The outer planet, TOI-836 c, is a 2.59 ± 0.09 R⊕ mini-Neptune in an 8.60 day orbit. Radial velocity measurements reveal that TOI-836 b has a mass of 4.5 ± 0.9 M⊕, while TOI-836 c has a mass of 9.6 ± 2.6 M⊕. Photometric observations show Transit Timing Variations (TTVs) on the order of 20 minutes for TOI-836 c, although there are no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by an undetected exterior planet.Publisher PDFPeer reviewe
TOI-332 b : a super dense Neptune found deep within the Neptunian desert
To date, thousands of planets have been discovered, but there are regions of the orbital parameter space that are still bare. An example is the short period and intermediate mass/radius space known as the “Neptunian desert”, where planets should be easy to find but discoveries remain few. This suggests unusual formation and evolution processes are responsible for the planets residing here. We present the discovery of TOI-332 b, a planet with an ultra-short period of 0.78 d that sits firmly within the desert. It orbits a K0 dwarf with an effective temperature of 5251 ± 71 K. TOI-332 b has a radius of 3.20+ 0.16 −0.12 R⊕, smaller than that of Neptune, but an unusually large mass of 57.2 ± 1.6 M⊕. It has one of the highest densities of any Neptune-sized planet discovered thus far at 9.6+ 1.1 −1.3 g cm−3 . A 4-layer internal structure model indicates it likely has a negligible hydrogen-helium envelope, something only found for a small handful of planets this massive, and so TOI-332 b presents an interesting challenge to planetary formation theories. We find that photoevaporation cannot account for the mass loss required to strip this planet of the Jupiter-like envelope it would have been expected to accrete. We need to look towards other scenarios, such as high-eccentricity migration, giant impacts, or gap opening in the protoplanetary disc, to try and explain this unusual discovery
TOI-332 b: A super dense Neptune found deep within the Neptunian desert
To date, thousands of planets have been discovered, but there are regions of the orbital parameter space that are still bare. An example is the short period and intermediate mass/radius space known as the ‘Neptunian desert’, where planets should be easy to find but discoveries remain few. This suggests unusual formation and evolution processes are responsible for the planets residing here. We present the discovery of TOI-332 b, a planet with an ultra-short period of 0.78 d that sits firmly within the desert. It orbits a K0 dwarf with an effective temperature of 5251 ± 71 K. TOI-332 b has a radius of R⊕, smaller than that of Neptune, but an unusually large mass of 57.2 ± 1.6 M⊕. It has one of the highest densities of any Neptune-sized planet discovered thus far at g cm−3. A 4-layer internal structure model indicates it likely has a negligible hydrogen-helium envelope, something only found for a small handful of planets this massive, and so TOI-332 b presents an interesting challenge to planetary formation theories. We find that photoevaporation cannot account for the mass loss required to strip this planet of the Jupiter-like envelope it would have been expected to accrete. We need to look towards other scenarios, such as high-eccentricity migration, giant impacts, or gap opening in the protoplanetary disc, to try and explain this unusual discovery