HAT-P-12b: A Low-Density Sub-Saturn Mass Planet Transiting a Metal-Poor K Dwarf

We report on the discovery of HAT-P-12b, a transiting extrasolar planet orbiting the moderately bright V=12.8 K4 dwarf GSC 03033-00706, with a period P = 3.2130598 +- 0.0000021 d, transit epoch Tc = 2454419.19556 +- 0.00020 (BJD) and transit duration 0.0974 +- 0.0006 d. The host star has a mass of 0.73 +- 0.02 Msun, radius of 0.70 +- ^0.02_0.01 Rsun, effective temperature 4650 +- 60 K and metallicity [Fe/H] = -0.29 +- 0.05. We find a slight correlation between the observed spectral line bisector spans and the radial velocity, so we consider, and rule out, various blend configurations including a blend with a background eclipsing binary, and hierarchical triple systems where the eclipsing body is a star or a planet. We conclude that a model consisting of a single star with a transiting planet best fits the observations, and show that a likely explanation for the apparent correlation is contamination from scattered moonlight. Based on this model, the planetary companion has a mass of 0.211 +- 0.012 MJup, and a radius of 0.959 +- ^0.029_0.021 RJup yielding a mean density of 0.295 +- 0.025 g cm^-3. Comparing these observations with recent theoretical models we find that HAT-P-12b is consistent with a ~ 1-4.5 Gyr, mildly irradiated, H/He dominated planet with a core mass Mc <~ 10 Mearth. HAT-P-12b is thus the least massive H/He dominated gas giant planet found to date. This record was previously held by Saturn.Comment: Accepted for publication in ApJ, 13 pages, 9 figures, 5 table

HATNet Field G205: Follow-Up Observations of 28 Transiting-Planet candidates and Confirmation of the Planet HAT-P-8b

We report the identification of 32 transiting-planet candidates in HATNet field G205. We describe the procedures that we have used to follow up these candidates with spectroscopic and photometric observations, and we present a status report on our interpretation of the 28 candidates for which we have follow-up observations. Eight are eclipsing binaries with orbital solutions whose periods are consistent with their photometric ephemerides; two of these spectroscopic orbits are singled-lined and six are double-lined. For one of the candidates, a nearby but fainter eclipsing binary proved to be the source for the HATNet light curve, due to blending in the HATNet images. Four of the candidates were found to be rotating more rapidly than vsini = 50 km/s and were not pursued further. Thirteen of the candidates showed no significant velocity variation at the level of 0.5 to 1.0 km/s . Seven of these were eventually withdrawn as photometric false alarms based on an independent reanalysis using more sophisticated tools. Of the remaining six, one was put aside because a close visual companion proved to be a spectroscopic binary, and two were not followed up because the host stars were judged to be too large. Two of the remaining candidates are members of a visual binary, one of which was previously confirmed as the first HATNet transiting planet, HAT-P-1b. In this paper we confirm that the last of this set of candidates is also a a transiting planet, which we designate HAT-P-8b, with mass Mp = 1.52 +/- 0.18/0.16 Mjup, radius Rp = 1.50 +/- 0.08/0.06 Rjup, and photometric period P = 3.076320 +/- 0.000004 days. HAT-P-8b has an inflated radius for its mass, and a large mass for its period. The host star is a solar-metallicity F dwarf, with mass M* = 1.28 +/- 0.04 Msun and Rp = 1.58 +/- 0.08/0.06 Rsun.Comment: 16 pages, 6 figures, 13 table

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

Characterization and Compensation of the Residual Chirp in a Mach-Zehnder-Type Electro-Optical Intensity Modulator

We utilize various techniques to characterize the residual phase modulation of a fiber-based Mach-Zehnder electro-optical intensity modulator. A heterodyne technique is used to directly measure the phase change due to a given change in intensity, thereby determining the chirp parameter of the device. This chirp parameter is also measured by examining the ratio of sidebands for sinusoidal amplitude modulation. Finally, the frequency chirp caused by an intensity pulse on the nanosecond time scale is measured via the heterodyne signal. We show that this chirp can be largely compensated with a separate phase modulator. The various measurements of the chirp parameter are in reasonable agreement.Comment: 11 pages, 6 figure

Ground-based NIR emission spectroscopy of HD189733b

We investigate the K and L band dayside emission of the hot-Jupiter HD 189733b with three nights of secondary eclipse data obtained with the SpeX instrument on the NASA IRTF. The observations for each of these three nights use equivalent instrument settings and the data from one of the nights has previously reported by Swain et al (2010). We describe an improved data analysis method that, in conjunction with the multi-night data set, allows increased spectral resolution (R~175) leading to high-confidence identification of spectral features. We confirm the previously reported strong emission at ~3.3 microns and, by assuming a 5% vibrational temperature excess for methane, we show that non-LTE emission from the methane nu3 branch is a physically plausible source of this emission. We consider two possible energy sources that could power non-LTE emission and additional modelling is needed to obtain a detailed understanding of the physics of the emission mechanism. The validity of the data analysis method and the presence of strong 3.3 microns emission is independently confirmed by simultaneous, long-slit, L band spectroscopy of HD 189733b and a comparison star.Comment: ApJ accepte

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

HATS-1b: The First Transiting Planet Discovered by the HATSouth Survey

We report the discovery of HATS-1b, a transiting extrasolar planet orbiting the moderately bright V=12.05 G dwarf star GSC 6652-00186, and the first planet discovered by HATSouth, a global network of autonomous wide-field telescopes. HATS-1b has a period P~3.4465 d, mass Mp~1.86MJ, and radius Rp~1.30RJ. The host star has a mass of 0.99Msun, and radius of 1.04Rsun. The discovery light curve of HATS-1b has near continuous coverage over several multi-day periods, demonstrating the power of using a global network of telescopes to discover transiting planets.Comment: Submitted to AJ 10 pages, 5 figures, 6 table

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-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