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Register a new userKELT-24b: A 5M$_{rm J}$ Planet on a 5.6 day Well-Aligned Orbit around the Young V=8.3 F-star HD 93148
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Added by
Joseph Rodriguez Jr.
Publication date
2019
fields
Physics
and research's language is
English
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We present the discovery of KELT-24 b, a massive hot Jupiter orbiting a bright (V=8.3 mag, K=7.2 mag) young F-star with a period of 5.6 days. The host star, KELT-24 (HD 93148), has a $T_{rm eff}$ =$6509^{+50}_{-49}$ K, a mass of $M_{*}$ = $1.460^{+0.055}_{-0.059}$ $M_{odot}$, radius of $R_{*}$ = $1.506pm0.022$ $R_{odot}$, and an age of $0.78^{+0.61}_{-0.42}$ Gyr. Its planetary companion (KELT-24 b) has a radius of $R_{rm P}$ = $1.272pm0.021$ $R_{rm J}$, a mass of $M_{rm P}$ = $5.18^{+0.21}_{-0.22}$ $M_{rm J}$, and from Doppler tomographic observations, we find that the planets orbit is well-aligned to its host stars projected spin axis ($lambda$ = $2.6^{+5.1}_{-3.6}$). The young age estimated for KELT-24 suggests that it only recently started to evolve from the zero-age main sequence. KELT-24 is the brightest star known to host a transiting giant planet with a period between 5 and 10 days. Although the circularization timescale is much longer than the age of the system, we do not detect a large eccentricity or significant misalignment that is expected from dynamical migration. The brightness of its host star and its moderate surface gravity make KELT-24b an intriguing target for detailed atmospheric characterization through spectroscopic emission measurements since it would bridge the current literature results that have primarily focused on lower mass hot Jupiters and a few brown dwarfs.
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We report the independent discovery and characterisation of a hot Jupiter in a 4.5-d, transiting orbit around the star TYC 7282-1298-1 ($V$ = 10.8, F5V). The planet has been pursued by the NGTS team as NGTS-2b and by ourselves as WASP-179b. We characterised the system using a combination of photometry from WASP-South and TRAPPIST-South, and spectra from CORALIE (around the orbit) and HARPS (through the transit). We find the planets orbit to be nearly aligned with its stars spin. From a detection of the Rossiter-McLaughlin effect, we measure a projected stellar obliquity of $lambda = -19 pm 6^circ$. From line-profile tomography of the same spectra, we measure $lambda = -11 pm 5^circ$. We find the planet to have a low density ($M_{rm P}$ = 0.67 $pm$ 0.09 $M_{rm Jup}$, $R_{rm P}$ = 1.54 $pm$ 0.06 $R_{rm Jup}$), which, along with its moderately bright host star, makes it a good target for transmission spectroscopy. We find a lower stellar mass ($M_*$ = $1.30 pm 0.07$ $M_odot$) than reported by the NGTS team ($M_*$ = $1.64 pm 0.21$ $M_odot$), though the difference is only $1.5$ $sigma$.
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