2,511 research outputs found
The HATNet and HATSouth Exoplanet Surveys
The Hungarian-made Automated Telescope Network (HATNet) has been in operation
since 2003, with the key science goal being the discovery and accurate
characterization of transiting extrasolar planets (TEPs) around bright stars.
Using six small, 11\,cm\ aperture, fully automated telescopes in Arizona and
Hawaii, as of 2017 March, it has discovered and accurately characterized 67
such objects. The HATSouth network of telescopes has been in operation since
2009, using slightly larger, 18\,cm diameter optical tubes. It was the first
global network of telescopes using identical instrumentation. With three
premier sites spread out in longitude (Chile, Namibia, Australia), the HATSouth
network permits round-the-clock observations of a 128 square arcdegree swath of
the sky at any given time, weather permitting. As of this writing, HATSouth has
discovered 36 transiting exoplanets. Many of the altogether ~100 HAT and
HATSouth exoplanets were the first of their kind. They have been important
contributors to the rapidly developing field of exoplanets, motivating and
influencing observational techniques, theoretical studies, and also actively
shaping future instrumentation for the detection and characterization of such
objects.Comment: Invited review chapter, accepted for publication in "Handbook of
Exoplanets", edited by H.J. Deeg and J.A. Belmonte, Springer Reference Work
Detection of the evolutionary stages of variables in M3
The large number of variables in M3 provides a unique opportunity to study an
extensive sample of variables with the same apparent distance modulus. Recent,
high accuracy CCD time series of the variables show that according to their
mean magnitudes and light curve shapes, the variables belong to four separate
groups. Comparing the properties of these groups (magnitudes and periods) with
horizontal branch evolutionary models, we conclude that these samples can be
unambiguously identified with different stages of the horizontal branch stellar
evolution. Stars close to the zero age horizontal branch (ZAHB) show Oosterhoff
I type properties, while the brightest stars have Oosterhoff II type statistics
regarding their mean periods and RRab/RRc number ratios. This finding
strengthens the earlier suggestion of Lee et al. (1990) connecting the
Oosterhoff dichotomy to evolutionary effects, however, it is unexpected to find
large samples of both of the Oosterhoff type within a single cluster, which is,
moreover, the prototype of the Oosterhoff I class globular clusters. The very
slight difference between the Fourier parameters of the stars (at a given
period) in the three fainter samples spanning over about 0.15 mag range in M_V
points to the limitations of any empirical methods which aim to determine
accurate absolute magnitudes of RR Lyrae stars solely from the Fourier
parameters of the light curves.Comment: 4 pages, 4 figures. Submitted to Astrophys. J. Letter
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
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-10b: A light and moderately hot Jupiter transiting a K dwarf
We report on the discovery of HAT-P-10b, the lowest mass (0.46 +/- 0.03 MJ)
transiting extrasolar planet (TEP) discovered to date by transit searches.
HAT-P-10b orbits the moderately bright V=11.89 K dwarf GSC 02340-01714, with a
period P = 3.7224690 +/- 0.0000067 d, transit epoch Tc = 2454729.90631 +/-
0.00030 (BJD) and duration 0.1100 +/- 0.0015 d. HAT-P-10b has a radius of 1.05
+(0.05)-(0.03) RJ yielding a mean density of 0.498+/-0.064 g cm^-3 . Comparing
these observations with recent theoretical models we find that HAT-P-10 is
consistent with a ~4.5 Gyr, coreless, pure hydrogen and helium gas giant
planet. With an equilibrium temperature of Teq = 1030 +(26)-(19)K, HAT-P-10b is
one of the coldest TEPs. Curiously, its Safronov number Theta = 0.047 +/- 0.003
falls close to the dividing line between the two suggested TEP populations.Comment: 6 pages, 5 figures, submitted to ApJ. V2: added cross-reference to
WASP-11
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
THE IMPRINT of RADIAL MIGRATION on the VERTICAL STRUCTURE of GALAXY DISKS
We use numerical simulations to examine the effects of radial migration on the vertical structure of galaxy disks. The simulations follow three exponential disks of different mass but similar circular velocity, radial scalelength, and (constant) scale height. The disks develop different non-axisymmetric patterns, ranging from feeble, long-lived multiple arms to strong, rapidly evolving few-armed spirals. These fluctuations induce radial migration through secular changes in the angular momentum of disk particles, mixing the disk radially and blurring pre-existing gradients. Migration primarily affects stars with small vertical excursions, regardless of spiral pattern. This "provenance bias" largely determines the vertical structure of migrating stars: inward migrators thin down as they move in, whereas outward migrators do not thicken up but rather preserve the disk scale height at their destination. Migrators of equal birth radius thus develop a strong scale-height gradient, not by flaring out as commonly assumed, but by thinning down as they spread inward. Similar gradients have been observed for low-[α/Fe] mono-abundance populations (MAPs) in the Galaxy, but our results argue against interpreting them as a consequence of radial migration. This is because outward migration does not lead to thickening, implying that the maximum scale height of any population should reflect its value at birth. In contrast, Galactic MAPs have scale heights that increase monotonically outward, reaching values that greatly exceed those at their presumed birth radii. Given the strong vertical bias affecting migration, a proper assessment of the importance of radial migration in the Galaxy should take carefully into account the strong radial dependence of the scale heights of the various stellar populations. © 2016. The American Astronomical Society. All rights reserved
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
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