1,203 research outputs found
HATS-5b: A Transiting hot-Saturn from the HATSouth Survey
We report the discovery of HATS-5b, a transiting hot-Saturn orbiting a G type
star, by the HAT-South survey. HATS-5b has a mass of Mp=0.24 Mj, radius of
Rp=0.91 Rj, and transits its host star with a period of P=4.7634d. The radius
of HATS-5b is consistent with both theoretical and empirical models. The host
star has a V band magnitude of 12.6, mass of 0.94 Msun, and radius of 0.87
Rsun. The relatively high scale height of HATS-5b, and the bright,
photometrically quiet host star, make this planet a favourable target for
future transmission spectroscopy follow-up observations. We reexamine the
correlations in radius, equilibrium temperature, and metallicity of the
close-in gas-giants, and find hot Jupiter-mass planets to exhibit the strongest
dependence between radius and equilibrium temperature. We find no significant
dependence in radius and metallicity for the close-in gas-giant population.Comment: 10 pages, submitted to A
HATS-6b: A Warm Saturn Transiting an Early M Dwarf Star, and a Set of Empirical Relations for Characterizing K and M Dwarf Planet Hosts
We report the discovery by the HATSouth survey of HATS-6b, an extrasolar
planet transiting a V=15.2 mag, i=13.7 mag M1V star with a mass of 0.57 Msun
and a radius of 0.57 Rsun. HATS-6b has a period of P = 3.3253 d, mass of
Mp=0.32 Mjup, radius of Rp=1.00 Rjup, and zero-albedo equilibrium temperature
of Teq=712.8+-5.1 K. HATS-6 is one of the lowest mass stars known to host a
close-in gas giant planet, and its transits are among the deepest of any known
transiting planet system. We discuss the follow-up opportunities afforded by
this system, noting that despite the faintness of the host star, it is expected
to have the highest K-band S/N transmission spectrum among known gas giant
planets with Teq < 750 K. In order to characterize the star we present a new
set of empirical relations between the density, radius, mass, bolometric
magnitude, and V, J, H and K-band bolometric corrections for main sequence
stars with M < 0.80 Msun, or spectral types later than K5. These relations are
calibrated using eclipsing binary components as well as members of resolved
binary systems. We account for intrinsic scatter in the relations in a
self-consistent manner. We show that from the transit-based stellar density
alone it is possible to measure the mass and radius of a ~0.6 Msun star to ~7%
and ~2% precision, respectively. Incorporating additional information, such as
the V-K color, or an absolute magnitude, allows the precision to be improved by
up to a factor of two.Comment: 21 pages, 11 figures, 10 tables. Submitted to AJ. Data available at
http://hatsouth.org Code implementing empirical model available at
http://www.astro.princeton.edu/~jhartman/kmdwarfparam.htm
A Finite Element Computation of the Gravitational Radiation emitted by a Point-like object orbiting a Non-rotating Black Hole
The description of extreme-mass-ratio binary systems in the inspiral phase is
a challenging problem in gravitational wave physics with significant relevance
for the space interferometer LISA. The main difficulty lies in the evaluation
of the effects of the small body's gravitational field on itself. To that end,
an accurate computation of the perturbations produced by the small body with
respect the background geometry of the large object, a massive black hole, is
required. In this paper we present a new computational approach based on Finite
Element Methods to solve the master equations describing perturbations of
non-rotating black holes due to an orbiting point-like object. The numerical
computations are carried out in the time domain by using evolution algorithms
for wave-type equations. We show the accuracy of the method by comparing our
calculations with previous results in the literature. Finally, we discuss the
relevance of this method for achieving accurate descriptions of
extreme-mass-ratio binaries.Comment: RevTeX 4. 18 pages, 8 figure
Baryon Content of Massive Galaxy Clusters (0.57 < z < 1.33)
We study the stellar, Brightest Cluster Galaxy (BCG) and intracluster medium
(ICM) masses of 14 South Pole Telescope (SPT) selected galaxy clusters with
median redshift and median mass . We
estimate stellar masses for each cluster and BCG using six photometric bands
spanning the range from the ultraviolet to the near-infrared observed with the
VLT, HST and Spitzer. The ICM masses are derived from Chandra and XMM-Newton
X-ray observations, and the virial masses are derived from the SPT
Sunyaev-Zel'dovich Effect signature.
At the BCG mass constitutes %
of the halo mass for a cluster, and this fraction
falls as . The cluster stellar mass function has a
characteristic mass , and the number of
galaxies per unit mass in clusters is larger than in the field by a factor
. Both results are consistent with measurements on group scales and
at lower redshift. We combine our SPT sample with previously published samples
at low redshift that we correct to a common initial mass function and for
systematic differences in virial masses. We then explore mass and redshift
trends in the stellar fraction (fstar), the ICM fraction (fICM), the cold
baryon fraction (fc) and the baryon fraction (fb). At a pivot mass of
and redshift , the characteristic values are
fstar=%, fICM=%, fc=% and fb=%.
These fractions all vary with cluster mass at high significance, indicating
that higher mass clusters have lower fstar and fc and higher fICM and fb. When
accounting for a 15% systematic virial mass uncertainty, there is no
statistically significant redshift trend at fixed mass in these baryon
fractions.
(abridged)Comment: Accepted for publication in MNRA
Recommended from our members
Fiber optic calorimetry
A twin-bridge calorimeter using optical fiber as the sensor element was constructed and tested. This system demonstrates the principle and capability of using optical fibers for heat-flow measurements of special nuclear material. This calorimeter uses piezoelectric-generated phase-carrier modulation with subsequent electronic signal processing to allow phase shifts as small as 1 {micro}rad to be measured. The sensing element consists of 21-m lengths of single-mode optical fiber wrapped around sample and reference chambers. The sensitivity of the calorimeter was determined to be 74 rad of phase shift per mW of thermal power. One milliwatt of thermal power is equivalent to 400 mg of plutonium (6% {sup 240}Pu). The system noise base was about 0.2 rad, equivalent to about 1 mg of plutonium
HATS-15 b and HATS-16 b: Two massive planets transiting old G dwarf stars
We report the discovery of HATS-15 b and HATS-16 b, two massive transiting
extrasolar planets orbiting evolved ( Gyr) main-sequence stars. The
planet HATS-15 b, which is hosted by a G9V star ( mag), is a hot
Jupiter with mass of and radius of
, and completes its orbit in nearly 1.7 days.
HATS-16 b is a very massive hot Jupiter with mass of and radius of ; it orbits around
its G3 V parent star ( mag) in days. HATS-16 is slightly
active and shows a periodic photometric modulation, implying a rotational
period of 12 days which is unexpectedly short given its isochronal age. This
fast rotation might be the result of the tidal interaction between the star and
its planet.Comment: 16 pages, 8 figures, submitted to PAS
HATS-11b and HATS-12b: Two transiting Hot Jupiters orbiting sub-solar metallicity stars selected for the K2 Campaign 7
We report the discovery of two transiting extrasolar planets from the
HATSouth survey. HATS-11, a V=14.1 G0-star shows a periodic 12.9 mmag dip in
its light curve every 3.6192 days and a radial velocity variation consistent
with a Keplerian orbit. HATS-11 has a mass of 1.000 0.060 M, a
radius of 1.444 0.057 M and an effective temperature of 6060
150 K, while its companion is a 0.85 0.12 M, 1.510 0.078
R planet in a circular orbit. HATS-12 shows a periodic 5.1 mmag flux
decrease every 3.1428 days and Keplerian RV variations around a V=12.8 F-star.
HATS-12 has a mass of 1.489 0.071 M, a radius of 2.21
0.21 R, and an effective temperature of 6408 75 K. For HATS-12,
our measurements indicate that this is a 2.38 0.11 M, 1.35 0.17
R planet in a circular orbit. Both host stars show sub-solar metallicity of
-0.390 0.060 dex and -0.100 0.040 dex, respectively and are
(slightly) evolved stars. In fact, HATS-11 is amongst the most metal-poor and,
HATS-12 is amongst the most evolved stars hosting a hot Jupiter planet.
Importantly, HATS-11 and HATS-12 have been observed in long cadence by Kepler
as part of K2 campaign 7 (EPIC216414930 and EPIC218131080 respectively).Comment: 14 pages, 7 figures, 6 tables, submitted to A
HATS-7b: A Hot Super Neptune Transiting a Quiet K Dwarf Star
IW ../submit_V2/abstract.txt ( Row 1 Col 1 6:48 Ctrl-K H for help We report
the discovery by the HATSouth network of HATS-7b, a transiting Super-Neptune
with a mass of 0.120+/-0.012MJ, a radius of 0.563+/-(0.046,0.034)RJ, and an
orbital period of 3.1853days. The host star is a moderately bright
(V=13.340+/-0.010mag, K_S=10.976+/-0.026mag) K dwarf star with a mass of
0.849+/-0.027Msun , a radius of 0.815+/-(0.049,-0.035)Rsun, and a metallicity
of [Fe/H]=+0.250+/-0.080. The star is photometrically quiet to within the
precision of the HATSouth measurements and has low RV jitter. HATS-7b is the
second smallest radius planet discovered by a wide-field ground-based transit
survey, and one of only a handful of Neptune-size planets with mass and radius
determined to 10% precision. Theoretical modeling of HATS-7b yields a
hydrogen-helium fraction of 18+/-4% (rock-iron core and H2-He envelope), or
9+/-4% (ice core and H2-He envelope), i.e.it has a composition broadly similar
to that of Uranus and Neptune, and very different from that of Saturn, which
has 75% of its mass in H2-He. Based on a sample of transiting exoplanets with
accurately (<20%) determined parameters, we establish approximate power-law
relations for the envelopes of the mass-density distribution of exoplanets.
HATS-7b, which, together with the recently discovered HATS-8b, is one of the
first two transiting super-Neptunes discovered in the Southern sky, is a prime
target for additional follow-up observations with Southern hemisphere
facilities to characterize the atmospheres of Super-Neptunes (which we define
as objects with mass greater than that of Neptune, and smaller than halfway
between that of Neptune and Saturn, i.e. 0.054 MJ<Mp<0.18 MJ).Comment: 11 pages, accepted for publication by Ap
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