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TESS Weekly Bulletin: October 22nd

News article posted on by Rebekah Hounsell

STATUS UPDATE: There will be a TESS splinter session at AAS #239 see here for details.

Welcome TESS followers! This week we are looking at three papers from the archive,

TKS V. Twin sub-Neptunes Transiting the Nearby G Star HD 63935 (Scarsdale et. al., 2021) :

Two almost identically size sub-Neptune transiting planets were discovered using data from TESS, Keck HIRES, and Lick APF. The planets orbit the bright 8.6 V-band magnitude star HD 63935, which is Sun like in nature and has an effective temperature of 5560 K.

The first planet was identified by TESS in Sectors 7 and 34. Known as HD 63935 b (TOI-509.01), the planet has a period of 9.06 days, a radius of 2.99 R⊕, and a mass of 10.8 M⊕. The second planet was identified during the authors follow up campaign of the system using Keck HIRES and Lick APF radial velocity data. HD 63935 c has a period of 21.4 days, a radius of 2.9 R⊕, and a mass of 11.1 M⊕. This planet was also confirmed using TESS Sector 34 photometry.

The TESS-Keck Survey. VI. Two Eccentric sub-Neptunes Orbiting HIP-97166 (Mason et. al., 2021) :

While conducting a search of TESS Objects of Interest for planets with eccentric orbits, the authors of this paper discovered HIP-97166b (TOI-1255b), a sub-Neptune planet transiting its host star. The orbit of the planet is 10.3 days, with the host being a K0 dwarf located 68 pc from Earth.

HIP-97166b was confirmed using ground-based radial velocity measurements from which as mass of 20 M⨁ and radius of 2.7 R⨁ were derived. An additional non-transiting exoplanet, HIP-97166c, was also discovered with an orbit of 16.8 days and a mass of 10 M⨁.

Although the short transit duration of the inner planet might suggest a high eccentricity, a joint RV-photometry analysis revealed a high impact parameter b=0.84±0.03 and a moderate eccentricity. By modeling the dynamics of the system with the condition that it must remain stable over > 105 orbits, eccentricity constraints of 0.16 and <0.25 for planets b and c respectively. See this fascinating paper for more information about the system.

TOI-530b: A giant planet transiting an M dwarf detected by TESS (Gan et. al., 2021) :

TESS data was used to discover a giant planet transiting an M0.5V dwarf star know as TOI-530 which is located 147.7 pc away with a radius of 0.54 R⊙ and a mass of 0.53 M⊙.

The planet, TOI-530b, was verified using ground-based multi-wavelength photometry, high resolution spectroscopy from SPIRou, and high-angular-resolution imaging. The radius of the planet is 0.83 RJ, with a mass of 0.4 MJ, and an orbit of 6.39 days.

The host star has a V-band magnitude of 15.4, which means that TOI-530b orbits one of the faintest stars accessible by ground-based spectroscopy. TOI-530b is also one of only six known transiting giant planets hosted by an M-type star, which is predicted to be a rare occurrence according to core accretion theory.

Scarsdale

Fig. 1: Taken from Scarsdale et. al., (2021). Phase-folded transits of HD 63935 b and c. The normalized PDSCAP flux is shown in grey. Our best fit transit model is shown in red. Residuals from each fit are plotted in the lower panels.

Mason

Fig. 2: Taken from Mason et. al., (2021). Top: Transit models (orange; 50 samples) drawn from parameter posterior distributions fit from phase-folded TESS photometry of HIP-97166b. A simulated transit curve (blue) is shown for a theoretical circular orbit of HIP-97166b, modeled using median posterior distribution values for all other parameters. Details regarding fitting procedure are discussed in §2.2 of the paper. Bottom: Residuals to our maximum a posteriori model.

Gan

Fig. 3: Taken from Gan et. al., (2021). Top panels: The original TESS SAP light curves of TOI-530 from Sector 6 and 33. Middle panels: The PDCSAP light curves of TOI-530 along with the best-fit GP model shown as red solid lines. Bottom panels: The detrended PDCSAP light curves. The transits of TOI-530b are marked in blue ticks.