43 research outputs found
HAT-P-17b,c: A Transiting, Eccentric, Hot Saturn and a Long-period, Cold Jupiter
We report the discovery of HAT-P-17b,c, a multi-planet system with an inner
transiting planet in a short-period, eccentric orbit and an outer planet in a
4.8 yr, nearly circular orbit. The inner planet, HAT-P-17b, transits the bright
V = 10.54 early K dwarf star GSC 2717-00417, with an orbital period P =
10.338523 +/- 0.000009 d, orbital eccentricity e = 0.346 +/- 0.007, transit
epoch T_c = 2454801.16945 +/- 0.00020, and transit duration 0.1691 +/- 0.0009
d. HAT-P-17b has a mass of 0.530 +/- 0.018 M_J and radius of 1.010 +/- 0.029
R_J yielding a mean density of 0.64 +/- 0.05 g cm^-3. This planet has a
relatively low equilibrium temperature in the range 780-927 K, making it an
attractive target for follow-up spectroscopic studies. The outer planet,
HAT-P-17c, has a significantly longer orbital period P_2 = 1797^+58_-89 d and a
minimum mass m_2 sin i_2 = 1.4^+1.1_-0.4 M_J. The orbital inclination of
HAT-P-17c is unknown as transits have not been observed and may not be present.
The host star has a mass of 0.86 +/- 0.04 M_Sun, radius of 0.84 +/- 0.02,
effective temperature 5246 +/- 80 K, and metallicity [Fe/H] = 0.00 +/- 0.08.
HAT-P-17 is the second multi-planet system detected from ground-based transit
surveys.Comment: Submitted to ApJ, 13 pages, 6 figures, 6 table
Hat-P-25b: A Hot-Jupiter Transiting a Moderately Faint G Star
We report the discovery of HAT-P-25b, a transiting extrasolar planet orbiting the V = 13.19 G5 dwarf star GSC 1788-01237, with a period P = 3.652836 ± 0.000019 days, transit epoch T_c = 2455176.85173 ± 0.00047 (BJD—barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time, UTC), and transit duration 0.1174 ± 0.0017 days. The host star has a mass of 1.01 ± 0.03 M_☉, radius of 0.96^(+0.05)_(– 0.04) R_☉, effective temperature 5500 ± 80 K, and metallicity [Fe/H] = +0.31 ± 0.08. The planetary companion has a mass of 0.567 ± 0.022 M_J and radius of 1.190^(+0.081)_(–0.056) R_J yielding a mean density of 0.42 ± 0.07 g cm^(–3)
HAT-P-18b and HAT-P-19b: Two Low-Density Saturn-Mass Planets Transiting Metal-Rich K Stars
We report the discovery of two new transiting extrasolar planets. HAT-P-18b
orbits the V=12.759 K2 dwarf star GSC 2594-00646, with a period
P=5.508023+-0.000006 d, transit epoch Tc=2454715.02174+-0.00020 (BJD), and
transit duration 0.1131+-0.0009 d. The host star has a mass of 0.77+-0.03 Msun,
radius of 0.75+-0.04 Rsun, effective temperature 4803+-80 K, and metallicity
[Fe/H]=+0.10+-0.08. The planetary companion has a mass of 0.197+-0.013 Mjup,
and radius of 0.995+-0.052 Rjup yielding a mean density of 0.25+-0.04 g cm-3.
HAT-P-19b orbits the V=12.901 K1 dwarf star GSC 2283-00589, with a period
P=4.008778+-0.000006 d, transit epoch Tc=2455091.53417+-0.00034 (BJD), and
transit duration 0.1182+-0.0014 d. The host star has a mass of 0.84+-0.04 Msun,
radius of 0.82+-0.05 Rsun, effective temperature 4990+-130 K, and metallicity
[Fe/H]=+0.23+-0.08. The planetary companion has a mass of 0.292+-0.018 Mjup,
and radius of 1.132+-0.072 Rjup yielding a mean density of 0.25+-0.04 g cm-3.
The radial velocity residuals for HAT-P-19 exhibit a linear trend in time,
which indicates the presence of a third body in the system. Comparing these
observations with theoretical models, we find that HAT-P-18b and HAT-P-19b are
each consistent with a hydrogen-helium dominated gas giant planet with
negligible core mass. HAT-P-18b and HAT-P-19b join HAT-P-12b and WASP-21b in an
emerging group of low-density Saturn-mass planets, with negligible inferred
core masses. However, unlike HAT-P-12b and WASP-21b, both HAT-P-18b and
HAT-P-19b orbit stars with super-solar metallicity. This calls into question
the heretofore suggestive correlation between the inferred core mass and host
star metallicity for Saturn-mass planets.Comment: 18 pages, 11 figures, 9 tables. Replaced with version accepted for
publication in Ap
Hat-P-20b-Hat-p-23b: Four Massive Transiting Extrasolar Planets
We report the discovery of four relatively massive (2-7 M J) transiting extrasolar planets. HAT-P-20b orbits the moderately bright V = 11.339 K3 dwarf star GSC 1910-00239 on a circular orbit, with a period P = 2.875317 ± 0.000004 days, transit epoch T_c = 2455080.92661 ± 0.00021 (BJD_(UTC)), and transit duration 0.0770 ± 0.0008 days. The host star has a mass of 0.76 ± 0.03 M_☉, radius of 0.69 ± 0.02 R_☉, effective temperature 4595 ± 80 K, and metallicity [Fe/H] = +0.35 ± 0.08. The planetary companion has a mass of 7.246 ± 0.187 M_J and a radius of 0.867 ± 0.033 R_J yielding a mean density of 13.78 ± 1.50 g cm^(–3). HAT-P-21b orbits the V = 11.685 G3 dwarf star GSC 3013-01229 on an eccentric (e = 0.228 ± 0.016) orbit, with a period P = 4.124481 ± 0.000007 days, transit epoch T_c = 2454996.41312 ± 0.00069, and transit duration 0.1530 ± 0.0027 days. The host star has a mass of 0.95 ± 0.04 M_☉, radius of 1.10 ± 0.08 R_☉, effective temperature 5588 ± 80 K, and metallicity [Fe/H] = +0.01 ± 0.08. The planetary companion has a mass of 4.063 ± 0.161 M_J and a radius of 1.024 ± 0.092 R_J yielding a mean density of 4.68^(+1.59)_(–0.99) g cm^(-3). HAT-P-21b is a borderline object between the pM and pL class planets, and the transits occur near apastron. HAT-P-22b orbits the bright V = 9.732 G5 dwarf star HD 233731 on a circular orbit, with a period P = 3.212220 ± 0.000009 days, transit epoch T_c = 2454930.22001 ± 0.00025, and transit duration 0.1196 ± 0.0014 days. The host star has a mass of 0.92 ± 0.03 M_☉, radius of 1.04 ± 0.04 R_☉, effective temperature 5302 ± 80 K, and metallicity [Fe/H] = +0.24 ± 0.08. The planet has a mass of 2.147 ± 0.061 M_J and a compact radius of 1.080 ± 0.058 R_J yielding a mean density of 2.11^(+0.40)_(–0.29) g cm^(–3). The host star also harbors an M-dwarf companion at a wide separation. Finally, HAT-P-23b orbits the V = 12.432 G0 dwarf star GSC 1632-01396 on a close to circular orbit, with a period P = 1.212884 ± 0.000002 days, transit epoch T_c = 2454852.26464 ± 0.00018, and transit duration 0.0908 ± 0.0007 days. The host star has a mass of 1.13 ± 0.04 M_☉, radius of 1.20 ± 0.07 R_☉, effective temperature 5905 ± 80 K, and metallicity [Fe/H] = +0.15 ± 0.04. The planetary companion has a mass of 2.090 ± 0.111 M_J and a radius of 1.368 ± 0.090 R_J yielding a mean density of 1.01 ± 0.18 g cm^(–3). HAT-P-23b is an inflated and massive hot Jupiter on a very short period orbit, and has one of the shortest characteristic infall times (7.5^(+2.9)_(–1.8) Myr) before it gets engulfed by the star
HAT-P-26b: A Low-Density Neptune-Mass Planet Transiting a K Star
We report the discovery of HAT-P-26b, a transiting extrasolar planet orbiting
the moderately bright V=11.744 K1 dwarf star GSC 0320-01027, with a period P =
4.234516 +- 0.000015 d, transit epoch Tc = 2455304.65122 +- 0.00035 (BJD), and
transit duration 0.1023 +- 0.0010 d. The host star has a mass of 0.82 +- 0.03
Msun, radius of 0.79 + 0.10 - 0.04 Rsun, effective temperature 5079 +- 88 K,
and metallicity [Fe/H] = -0.04 +- 0.08. The planetary companion has a mass of
0.059 +- 0.007 MJ, and radius of 0.565 + 0.072 - 0.032 RJ yielding a mean
density of 0.40 +- 0.10 g cm-3. HAT-P-26b is the fourth Neptune-mass transiting
planet discovered to date. It has a mass that is comparable to those of Neptune
and Uranus, and slightly smaller than those of the other transiting
Super-Neptunes, but a radius that is ~65% larger than those of Neptune and
Uranus, and also larger than those of the other transiting Super-Neptunes.
HAT-P-26b is consistent with theoretical models of an irradiated Neptune-mass
planet with a 10 Mearth heavy element core that comprises >~ 50% of its mass
with the remainder contained in a significant hydrogen-helium envelope, though
the exact composition is uncertain as there are significant differences between
various theoretical models at the Neptune-mass regime. The equatorial
declination of the star makes it easily accessible to both Northern and
Southern ground-based facilities for follow-up observations.Comment: 16 pages, 9 figures, 5 tables, submitted to Ap
HAT-P-16b: A 4 Mj Planet Transiting A Bright Star On An Eccentric Orbit
We report the discovery of HAT-P-16b, a transiting extrasolar planet orbiting
the V = 10.8 mag F8 dwarf GSC 2792-01700, with a period P = 2.775960 +-
0.000003 d, transit epoch Tc = 2455027.59293 +- 0.00031 (BJD), and transit
duration 0.1276 +- 0.0013 d. The host star has a mass of 1.22 +- 0.04 Msun,
radius of 1.24 +- 0.05 Rsun, effective temperature 6158 +-80 K, and metallicity
[Fe/H] = +0.17 +- 0.08. The planetary companion has a mass of 4.193 +- 0.094
MJ, and radius of 1.289 +- 0.066 RJ yielding a mean density of 2.42 +- 0.35
g/cm3. Comparing these observed characteristics with recent theoretical models,
we find that HAT-P-16b is consistent with a 1 Gyr H/He-dominated gas giant
planet. HAT-P-16b resides in a sparsely populated region of the mass{radius
diagram and has a non-zero eccentricity of e = 0.036 with a significance of 10
sigma.Comment: Submitted to Ap
HAT-P-24b: An inflated hot-Jupiter on a 3.36d period transiting a hot, metal-poor star
We report the discovery of HAT-P-24b, a transiting extrasolar planet orbiting
the moderately bright V=11.818 F8 dwarf star GSC 0774-01441, with a period P =
3.3552464 +/- 0.0000071 d, transit epoch Tc = 2455216.97669 +/- 0.00024
(BJD_UTC), and transit duration 3.653 +/- 0.025 hours. The host star has a mass
of 1.191 +/- 0.042 Msun, radius of 1.317 +/- 0.068 Rsun, effective temperature
6373 +/- 80 K, and a low metallicity of [Fe/H] = -0.16 +/- 0.08. The planetary
companion has a mass of 0.681 +/- 0.031 MJ, and radius of 1.243 +/- 0.072 RJ
yielding a mean density of 0.439 +/- 0.069 g cm-3 . By repeating our global
fits with different parameter sets, we have performed a critical investigation
of the fitting techniques used for previous HAT planetary discoveries. We find
that the system properties are robust against the choice of priors. The effects
of fixed versus fitted limb darkening are also examined. HAT-P-24b probably
maintains a small eccentricity of e = 0.052 +0.022 -0.017, which is accepted
over the circular orbit model with false alarm probability 5.8%. In the absence
of eccentricity pumping, this result suggests HAT-P-24b experiences less tidal
dissipation than Jupiter. Due to relatively rapid stellar rotation, we estimate
that HAT-P-24b should exhibit one of the largest known Rossiter-McLaughlin
effect amplitudes for an exoplanet (deltaVRM ~ 95 m/s) and thus a precise
measurement of the sky-projected spin-orbit alignment should be possible.Comment: 13 pages with 4 figures and 8 tables in emulateapj format. Minor
changes. Accepted in The Astrophysical Journa
HAT-P-25b: a Hot-Jupiter Transiting a Moderately Faint G Star
We report the discovery of HAT-P-25b, a transiting extrasolar planet orbiting
the V = 13.19 G5 dwarf star GSC 1788-01237, with a period P = 3.652836 +/-
0.000019 days, transit epoch Tc = 2455176.85173 +/- 0.00047 (BJD), and transit
duration 0.1174 +/- 0.0017 days. The host star has mass of 1.01 +/- 0.03
M(Sun), radius of 0.96 +(0.05)-(0.04) R(Sun), effective temperature 5500 +/- 80
K, and metallicity [Fe/H] = +0.31 +/- 0.08. The planetary companion has a mass
of 0.567 +/- 0.022 M(Jup), and radius of 1.190 +(0.081)-(0.056) R(Jup) yielding
a mean density of 0.42 +/- 0.07 g cm-3. Comparing these observations with
recent theoretical models, we find that HAT-P-25b is consistent with a
hydrogen-helium dominated gas giant planet with negligible core mass and age
3.2 +/- 2.3 Gyr. The properties of HAT-P-25b support several previously
observed correlations for planets in the mass range 0.4 < M < 0.7 M(Jup),
including those of core mass vs. metallicity, planet radius vs. equilibrium
temperature, and orbital period vs. planet mass. We also note that HAT-P-25b
orbits the faintest star found by HATNet to have a transiting planet to date,
and is one of only a very few number of planets discovered from the ground
orbiting a star fainter than V = 13.0.Comment: 11 pages, 8 figures, 5 tables, submitted to Ap
HAT-P-27b: A hot Jupiter transiting a G star on a 3 day orbit
We report the discovery of HAT-P-27b, an exoplanet transiting the moderately
bright G8 dwarf star GSC 0333-00351 (V=12.214). The orbital period is 3.039586
+/- 0.000012 d, the reference epoch of transit is 2455186.01879 +/- 0.00054
(BJD), and the transit duration is 0.0705 +/- 0.0019 d. The host star with its
effective temperature 5300 +/- 90 K is somewhat cooler than the Sun, and is
more metal-rich with a metallicity of +0.29 +/- 0.10. Its mass is 0.94 +/- 0.04
Msun and radius is 0.90 +/- 0.04 Rsun. For the planetary companion we determine
a mass of 0.660 +/- 0.033 MJ and radius of 1.038 +0.077 -0.058 RJ. For the 30
known transiting exoplanets between 0.3 MJ and 0.8 MJ, a negative correlation
between host star metallicity and planetary radius, and an additional
dependence of planetary radius on equilibrium temperature are confirmed at a
high level of statistical significance.Comment: Submitted to ApJ on 2011-01-18. 12 pages, 7 figures, 7 table