13 research outputs found
Stellar rotational periods in the planet hosting open cluster Praesepe
By using the dense coverage of the extrasolar planet survey project HATNet,
we Fourier analyze 381 high-probability members of the nearby open cluster
Praesepe (Beehive/M44/NGC 2632). In addition to the detection of 10 variables
(of \delta Scuti and other types), we identify 180 rotational variables
(including the two known planet hosts). This sample increases the number of
known rotational variables in this cluster for spectral classes earlier than M
by more than a factor of three. These stars closely follow a color/magnitude --
period relation from early F to late K stars. We approximate this relation by
polynomials for an easier reference to the rotational characteristics in
different colors. The total (peak-to-peak) amplitudes of the large majority
(94%) of these variables span the range of 0.005 to 0.04 mag. The periods cover
a range from 2.5 to 15 days. These data strongly confirm that Praesepe and the
Hyades have the same gyrochronological ages. Regarding the two planet hosts,
Pr0211 (the one with the shorter orbital period) has a rotational period that
is ~2 days shorter than the one expected from the main rotational pattern in
this cluster. This, together with other examples discussed in the paper, may
hint that star-planet interaction via tidal dissipation can be significant in
some cases in the rotational evolution of stars hosting Hot Jupiters.Comment: 17 pages, 13 figures, 5 tables; accepted for publication in MNRA
HATS-18 b: An Extreme Short--Period Massive Transiting Planet Spinning Up Its Star
We report the discovery by the HATSouth network of HATS-18 b: a 1.980 +/-
0.077 Mj, 1.337 +0.102 -0.049 Rj planet in a 0.8378 day orbit, around a solar
analog star (mass 1.037 +/- 0.047 Msun, and radius 1.020 +0.057 -0.031 Rsun)
with V=14.067 +/- 0.040 mag. The high planet mass, combined with its short
orbital period, implies strong tidal coupling between the planetary orbit and
the star. In fact, given its inferred age, HATS-18 shows evidence of
significant tidal spin up, which together with WASP-19 (a very similar system)
allows us to constrain the tidal quality factor for Sun-like stars to be in the
range 6.5 <= lg(Q*/k_2) <= 7 even after allowing for extremely pessimistic
model uncertainties. In addition, the HATS-18 system is among the best systems
(and often the best system) for testing a multitude of star--planet
interactions, be they gravitational, magnetic or radiative, as well as planet
formation and migration theories.Comment: Submitted. 12 pages, 9 figures, 5 table
No Conclusive Evidence for Transits of Proxima b in MOST photometry
The analysis of Proxima Centauri's radial velocities recently led
Anglada-Escud\'e et al. (2016) to claim the presence of a low mass planet
orbiting the Sun's nearest star once every 11.2 days. Although the a-priori
probability that Proxima b transits its parent star is just 1.5%, the potential
impact of such a discovery would be considerable. Independent of recent radial
velocity efforts, we observed Proxima Centauri for 12.5 days in 2014 and 31
days in 2015 with the MOST space telescope. We report here that we cannot make
a compelling case that Proxima b transits in our precise photometric time
series. Imposing an informative prior on the period and phase, we do detect a
candidate signal with the expected depth. However, perturbing the phase prior
across 100 evenly spaced intervals reveals one strong false-positive and one
weaker instance. We estimate a false-positive rate of at least a few percent
and a much higher false-negative rate of 20-40%, likely caused by the very high
flare rate of Proxima Centauri. Comparing our candidate signal to HATSouth
ground-based photometry reveals that the signal is somewhat, but not
conclusively, disfavored (1-2 sigmas) leading us to argue that the signal is
most likely spurious. We expect that infrared photometric follow-up could more
conclusively test the existence of this candidate signal, owing to the
suppression of flare activity and the impressive infrared brightness of the
parent star.Comment: Accepted to ApJ. Posterior samples, MOST photometry and HATSouth
photometry are all available at https://github.com/CoolWorlds/Proxim
HAT-P-50b, HAT-P-51b, HAT-P-52b, and HAT-P-53b: Three Transiting Hot Jupiters and a Transiting Hot Saturn From the HATNet Survey
We report the discovery and characterization of four transiting exoplanets by
the HATNet survey. The planet HAT-P-50b has a mass of 1.35 M_J and a radius of
1.29 R_J, and orbits a bright (V = 11.8 mag) M = 1.27 M_sun, R = 1.70 R_sun
star every P = 3.1220 days. The planet HAT-P-51b has a mass of 0.31 M_J and a
radius of 1.29 R_J, and orbits a V = 13.4 mag, M = 0.98 M_sun, R = 1.04 R_sun
star with a period of P = 4.2180 days. The planet HAT-P-52b has a mass of 0.82
M_J and a radius of 1.01 R_J, and orbits a V = 14.1 mag, M = 0.89 M_sun, R =
0.89 R_sun star with a period of P = 2.7536 days. The planet HAT-P-53b has a
mass of 1.48 M_J and a radius of 1.32 R_J, and orbits a V = 13.7 mag, M = 1.09
M_sun, R = 1.21 R_sun star with a period of P = 1.9616 days. All four planets
are consistent with having circular orbits and have masses and radii measured
to better than 10% precision. The low stellar jitter and favorable R_P/R_star
ratio for HAT-P-51 make it a promising target for measuring the
Rossiter-McLaughlin effect for a Saturn-mass planet.Comment: Submitted to AJ. 20 pages, 9 figures, 5 tables. Data available at
http://hatnet.org
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HAT-P-68b: A Transiting Hot Jupiter around a K5 Dwarf Star
We report the discovery by the ground-based HATNet survey of the transiting
exoplanet HAT-P-68b, which has a mass of 0.724 0.043 , and
radius of 1.072 0.012 . The planet is in a circular P =
2.2984-day orbit around a moderately bright V = 13.937 0.030 magnitude K
dwarf star of mass 0.673 0.020 0.014 , and radius 0.6726
0.0069 . The planetary nature of this system is confirmed
through follow-up transit photometry obtained with the FLWO~1.2m telescope,
high-precision RVs measured using Keck-I/HIRES, FLWO~1.5m/TRES, and
OHP~1.9m/Sophie, and high-spatial-resolution speckle imaging from
WIYN~3.5m/DSSI. HAT-P-68 is at an ecliptic latitude of and outside
the field of view of both the NASA TESS primary mission and the K2 mission. The
large transit depth of 0.036 mag (-band) makes HAT-P-68b a promising target
for atmospheric characterization via transmission spectroscopy.Comment: submitted to AJ on October 1, 2020; accepted on October 27. 15 pages,
8 figures, 6 table
TOI-150b and TOI-163b: two transiting hot Jupiters, one eccentric and one inflated, revealed by TESS near and at the edge of the JWST CVZ
peer reviewedWe present the discovery of TYC9191-519-1b (TOI-150b, TIC 271893367) and HD271181b (TOI-163b, TIC 179317684), two hot Jupiters initially detected using 30-min cadence Transiting Exoplanet Survey Satellite (TESS) photometry from Sector 1 and thoroughly characterized through follow-up photometry (CHAT, Hazelwood, LCO/CTIO, El Sauce, TRAPPIST-S), high- resolution spectroscopy (FEROS, CORALIE), and speckle imaging (Gemini/DSSI), confirming the planetary nature of the two signals. A simultaneous joint fit of photometry and radial velocity using a new fitting package JULIET reveals that TOI-150b is a 1.254± 0.016 {R}_ {J}, massive (2.61^{+0.19}_{-0.12} {M}_ {J}) hot Jupiter in a 5.857-d orbit, while TOI-163b is an inflated (R_ {P} = 1.478^{+0.022}_{-0.029} R_ {J}, M_ {P} = 1.219± 0.11 {M}_ {J}) hot Jupiter on a P = 4.231-d orbit; both planets orbit F-type stars. A particularly interesting result is that TOI-150b shows an eccentric orbit (e=0.262^{+0.045}_{-0.037}), which is quite uncommon among hot Jupiters. We estimate that this is consistent, however, with the circularization time-scale, which is slightly larger than the age of the system. These two hot Jupiters are both prime candidates for further characterization - in particular, both are excellent candidates for determining spin-orbit alignments via the Rossiter-McLaughlin (RM) effect and for characterizing atmospheric thermal structures using secondary eclipse observations considering they are both located closely to the James Webb Space Telescope (JWST) Continuous Viewing Zone (CVZ)