2,369 research outputs found
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withdrawn as photometric false alarms based on an independent reanalysis using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-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
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-39b--HAT-P-41b: Three Highly Inflated Transiting Hot Jupiters
We report the discovery of three new transiting extrasolar planets orbiting
moderately bright (V=11.1 to 12.4) F stars. The planets have periods of P =
2.6940 d to 4.4572 d, masses of 0.60 M_J to 0.80 M_J, and radii of 1.57 R_J to
1.73 R_J. They orbit stars with masses between 1.40 M_sun and 1.51 M_sun. The
three planets are members of an emerging population of highly inflated Jupiters
with 0.4 M_J 1.5 R_J.Comment: Submitted to AJ. 16 pages, 11 figures, 12 table
HAT-P-5b: A Jupiter-like hot Jupiter Transiting a Bright Star
We report the discovery of a planet transiting a moderately bright (V =
12.00) G star, with an orbital period of 2.788491 +/-0.000025 days. From the
transit light curve we determine that the radius of the planet is Rp = 1.257
+/- 0.053 RJup. HAT-P-5b has a mass of Mp = 1.06 +/- 0.11 MJup, similar to the
average mass of previously-known transiting exoplanets, and a density of rho =
0.66 +/- 0.11 g cm^-3 . We find that the center of transit is Tc =
2,454,241.77663 +/- 0.00022 (HJD), and the total transit duration is 0.1217 +/-
0.0012 days.Comment: 5 pages, submitted to APJ
Refined parameters of the planet orbiting HD 189733
We report on the BVRI multi-band follow-up photometry of the transiting
extrasolar planet HD 189733b. We revise the transit parameters and find
planetary radius RP = 1.154+/- 0.032RJ and inclination i_P = 85.79+/-0.24deg.
The new density (~ 1g cm-3) is significantly higher than the former estimate (~
0.75g cm-3); this shows that from the current sample of 9 transiting planets,
only HD 209458 (and possibly OGLE-10b) have anomalously large radii and low
densities. We note that due to the proximity of the parent star, HD 189733b
currently has one of the most precise radius determinations among extrasolar
planets. We calculate new ephemerides: P = 2.218573+/-0.000020 days, T0 =
2453629.39420+/-0.00024 (HJD), and estimate the timing offsets of the 11
distinct transits with respect to the predictions of a constant orbital period,
which can be used to reveal the presence of additional planets in the system.Comment: 10 pages, 4 figures, submitted to Ap
The Mass-Radius Relationship for Very Low Mass Stars: Four New Discoveries from the HATSouth Survey
We report the discovery of four transiting F-M binary systems with companions
between 0.1-0.2 Msun in mass by the HATSouth survey. These systems have been
characterised via a global analysis of the HATSouth discovery data, combined
with high-resolution radial velocities and accurate transit photometry
observations. We determined the masses and radii of the component stars using a
combination of two methods: isochrone fitting of spectroscopic primary star
parameters, and equating spectroscopic primary star rotation velocity with
spin-orbit synchronisation. These new very low mass companions are HATS550-016B
(0.110 -0.006/+0.005 Msun, 0.147 -0.004/+0.003 Rsun), HATS551-019B (0.17
-0.01/+0.01 Msun, 0.18 -0.01/+0.01 Rsun), HATS551-021B (0.132 -0.005/+0.014
Msun, 0.154 -0.008/+0.006 Rsun), HATS553-001B (0.20 -0.02/+0.01 Msun, 0.22
-0.01/+0.01 Rsun). We examine our sample in the context of the radius anomaly
for fully-convective low mass stars. Combining our sample with the 13 other
well-studied very low mass stars, we find a tentative 5% systematic deviation
between the measured radii and theoretical isochrone models.Comment: 17 pages, 8 figures, accepted for publication in MNRA
Qatar-1b: a hot Jupiter orbiting a metal-rich K dwarf star
We report the discovery and initial characterisation of Qatar-1b, a hot
Jupiter orbiting a metal-rich K dwarf star, the first planet discovered by the
Alsubai Project exoplanet transit survey. We describe the strategy used to
select candidate transiting planets from photometry generated by the Alsubai
Project instrument. We examine the rate of astrophysical and other false
positives found during the spectroscopic reconnaissance of the initial batch of
candidates. A simultaneous fit to the follow-up radial velocities and
photometry of Qatar-1b yield a planetary mass of 1.09+/-0.08 Mjup and a radius
of 1.16+/-0.05 Rjup. The orbital period and separation are 1.420033 days and
0.0234 AU for an orbit assumed to be circular. The stellar density, effective
temperature and rotation rate indicate an age greater than 4 Gyr for the
system.Comment: 8 pages, 5 figures, submitted to Monthly Notices of the Royal
Astronomical Societ
HAT-P-32b and HAT-P-33b: Two Highly Inflated Hot Jupiters Transiting High-jitter Stars
We report the discovery of two exoplanets transiting high-jitter stars. HAT-P-32b orbits the bright V = 11.289 late-F-early-G dwarf star GSC 3281-00800, with a period P = 2.150008 ± 0.000001 d. The stellar and planetary masses and radii depend on the eccentricity of the system, which is poorly constrained due to the high-velocity jitter (~80 m s^(–1)). Assuming a circular orbit, the star has a mass of 1.16 ± 0.04 M_☉ and radius of 1.22 ± 0.02 R_☉, while the planet has a mass of 0.860 ± 0.164 M_J and a radius of 1.789 ± 0.025 R_J. The second planet, HAT-P-33b, orbits the bright V = 11.188 late-F dwarf star GSC 2461-00988, with a period P = 3.474474 ± 0.000001 d. As for HAT-P-32, the stellar and planetary masses and radii of HAT-P-33 depend on the eccentricity, which is poorly constrained due to the high jitter (~50 m s^(–1)). In this case, spectral line bisector spans (BSs) are significantly anti-correlated with the radial velocity residuals, and we are able to use this correlation to reduce the residual rms to ~35 m s^(–1). We find that the star has a mass of 1.38 ± 0.04 M_☉ and a radius of 1.64 ± 0.03 R_☉ while the planet has a mass of 0.762 ± 0.101 M_J and a radius of 1.686 ± 0.045 R_J for an assumed circular orbit. Due to the large BS variations exhibited by both stars we rely on detailed modeling of the photometric light curves to rule out blend scenarios. Both planets are among the largest radii transiting planets discovered to date
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