9,978 research outputs found
Independent confirmation and refined parameters of the hot Jupiter XO-5b
We present HATNet observations of XO-5b, confirming its planetary nature
based on evidence beyond that described in the announcement of Burke et al.
(2008), namely, the lack of significant correlation between spectral bisector
variations and orbital phase. In addition, using extensive spectroscopic
measurements spanning multiple seasons, we investigate the relatively large
scatter in the spectral line bisectors. We also examine possible blended
stellar configurations (hierarchical triples, chance alignments) that can mimic
the planet signals, and we are able to show that none are consistent with the
sum of all the data. The analysis of the S activity index shows no significant
stellar activity. Our results for the planet parameters are consistent with
values in Burke et al. (2008), and we refine both the stellar and planetary
parameters using our data. XO-5b orbits a slightly evolved, late G type star
with mass M_s = 0.88 +/- 0.03, radius R_s = 1.08 +/- 0.04, and metallicity
close to solar. The planetary mass and radius are M_p = 1.059 +/- 0.028 M_Jup
and R_p = 1.109 +/- 0.050 R_Jup, respectively, corresponding to a mean density
of 0.96 -0.11 +0.14 g/cm^3. The ephemeris for the orbit is P = 4.187757 +/-
0.000011, E= 2454552.67168 +/- 0.00029 (BJD) with transit duration of 0.1307
+/- 0.0013 d. By measuring four individual transit centers, we found no signs
for transit timing variations. The planet XO-5b is notable for its anomalously
high Safronov number, and has a high surface gravity when compared to other
transiting exoplanets with similar period.Comment: Accepted for publication in ApJ, 8 pages in emulateapj styl
International Courts and the Crime of Genocide
En este trabajo realizo un anĂĄlisis jurĂdico de los elementos constitutivos (tanto subjetivos como objetivos) del crimen de genocidio, tal y como han sido interpretados y aplicados por la jurisprudencia internacional. En concreto, se estudia la jurisprudencia de la Corte Internacional de Justicia, del Tribunal Internacional Penal para la antigua Yugoslavia y del Tribunal Internacional Penal para Ruanda sobre el crimen de genocidio
An Improved Method for Estimating the Masses of Stars with Transiting Planets
To determine the physical parameters of a transiting planet and its host star
from photometric and spectroscopic analysis, it is essential to independently
measure the stellar mass. This is often achieved by the use of evolutionary
tracks and isochrones, but the mass result is only as reliable as the models
used. The recent paper by Torres et al (2009) showed that accurate values for
stellar masses and radii could be obtained from a calibration using T_eff, log
g and [Fe/H]. We investigate whether a similarly good calibration can be
obtained by substituting log rho - the fundamental parameter measured for the
host star of a transiting planet - for log g, and apply this to star-exoplanet
systems. We perform a polynomial fit to stellar binary data provided in Torres
et al (2009) to obtain the stellar mass and radius as functions of T_eff, log
rho and [Fe/H], with uncertainties on the fit produced from a Monte Carlo
analysis. We apply the resulting equations to measurements for seventeen
SuperWASP host stars, and also demonstrate the application of the calibration
in a Markov Chain Monte Carlo analysis to obtain accurate system parameters
where spectroscopic estimates of effective stellar temperature and metallicity
are available. We show that the calibration using log rho produces accurate
values for the stellar masses and radii; we obtain masses and radii of the
SuperWASP stars in good agreement with isochrone analysis results. We ascertain
that the mass calibration is robust against uncertainties resulting from poor
photometry, although a good estimate of stellar radius requires good-quality
transit light curve to determine the duration of ingress and egress.Comment: 5 pages, 2 figures, accepted for publication in A&
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-15b: A 10.9-day Extrasolar Planet Transiting a Solar-type Star
We report the discovery of HAT-P-15b, a transiting extrasolar planet in the
`period valley', a relatively sparsely-populated period regime of the known
extrasolar planets. The host star, GSC 2883-01687, is a G5 dwarf with V=12.16.
It has a mass of 1.01+/-0.04 M(Sun), radius of 1.08+/-0.04 R(Sun), effective
temperature 5568+/-90 K, and metallicity [Fe/H] = +0.22+/-0.08. The planetary
companion orbits the star with a period 10.863502+/-0.000027 days, transit
epoch Tc = 2454638.56019+/-0.00048 (BJD), and transit duration 0.2285+/-0.0015
days. It has a mass of 1.946+/-0.066 M(Jup), and radius of 1.072+/-0.043 R(Jup)
yielding a mean density of 1.96+/-0.22 g/cm3. At an age of 6.8+/-2.1 Gyr, the
planet is H/He-dominated and theoretical models require about 2% (10 M(Earth))
worth of heavy elements to reproduce its measured radius. With an estimated
equilibrium temperature of 820 K during transit, and 1000 K at occultation,
HAT-P-15b is a potential candidate to study moderately cool planetary
atmospheres by transmission and occultation spectroscopy.Comment: 12 pages with 10 figures and 6 tables in emulateapj format. Submitted
to The Astrophysical Journa
Detection of an optical transient following the 13 March 2000 short/hard gamma-ray burst
We imaged the error box of a gamma-ray burst of the short (0.5 s), hard type
(GRB 000313), with the BOOTES-1 experiment in southern Spain, starting 4 min
after the gamma-ray event, in the I-band. A bright optical transient (OT
000313) with I = 9.4 +/- 0.1 was found in the BOOTES-1 image, close to the
error box (3-sigma) provided by BATSE. Late time VRIK'-band deep observations
failed to reveal an underlying host galaxy. If the OT 000313 is related to the
short, hard GRB 000313, this would be the first optical counterpart ever found
for this kind of events (all counterparts to date have been found for bursts of
the long, soft type). The fact that only prompt optical emission has been
detected (but no afterglow emission at all, as supported by theoretical models)
might explain why no optical counterparts have ever been found for short, hard
GRBs.This fact suggests that most short bursts might occur in a low-density
medium and favours the models that relate them to binary mergers in very
low-density enviroments.Comment: Revised version. Accepted for publication in Astronomy and
Astrophysics Letters, 5 pages, 3 figure
Search for low-mass WIMPs in a 0.6 kg day exposure of the DAMIC experiment at SNOLAB
We present results of a dark matter search performed with a 0.6 kg day
exposure of the DAMIC experiment at the SNOLAB underground laboratory. We
measure the energy spectrum of ionization events in the bulk silicon of
charge-coupled devices down to a signal of 60 eV electron equivalent. The data
are consistent with radiogenic backgrounds, and constraints on the
spin-independent WIMP-nucleon elastic-scattering cross section are accordingly
placed. A region of parameter space relevant to the potential signal from the
CDMS-II Si experiment is excluded using the same target for the first time.
This result obtained with a limited exposure demonstrates the potential to
explore the low-mass WIMP region (<10 GeV/) of the upcoming DAMIC100, a
100 g detector currently being installed in SNOLAB.Comment: 11 pages, 11 figure
A New Spectroscopic and Photometric Analysis of the Transiting Planet Systems TrES-3 and TrES-4
We report new spectroscopic and photometric observations of the parent stars of the recently discovered transiting planets TrES-3 and TrES-4. A detailed abundance analysis based on high-resolution spectra yields [Fe/H] = â0.19 ± 0.08, T_(eff) = 5650 ± 75 K, and log g = 4.4 ± 0.1 for TrES-3, and [Fe/H] = +0.14 ± 0.09, T_(eff) = 6200 ± 75 K, and log g = 4.0 ± 0.1 for TrES-4. The accuracy of the effective temperatures is supported by a number of independent consistency checks. The spectroscopic orbital solution for TrES-3 is improved with our new radial velocity measurements of that system, as are the light-curve parameters for both systems based on newly acquired photometry for TrES-3 and a reanalysis of existing photometry for TrES-4. We have redetermined the stellar parameters taking advantage of the strong constraint provided by the light curves in the form of the normalized separation a/R_* (related to the stellar density) in conjunction with our new temperatures and metallicities. The masses and radii we derive are M_* = 0.928^(+0.028)_(â0.048) M_â, R_* = 0.829^(+0.015)_(â0.022) R_â, and M_* = 1.404^(+0.066)_(â0.134) M_â, R_* = 1.846^(+0.096)_(â0.087) R_â for TrES-3 and TrES-4, respectively. With these revised stellar parameters, we obtain improved values for the planetary masses and radii. We find M_p = 1.910^(+0.075)_(â0.080) M_(Jup), R_p = 1.336^(+0.031)_(â0.036) R_(Jup) for TrES-3, and M_p = 0.925 ± 0.082 M_(Jup), R_p = 1.783^(+0.093)_(â0.086) R_(Jup) for TrES-4. We confirm TrES-4 as the planet with the largest radius among the currently known transiting hot Jupiters
A New Spectroscopic and Photometric Analysis of the Transiting Planet Systems TrES-3 and TrES-4
We report new spectroscopic and photometric observations of the parent stars
of the recently discovered transiting planets TrES-3 and TrES-4. A detailed
abundance analysis based on high-resolution spectra yields [Fe/H] , K, and for TrES-3,
and [Fe/H] , K, and for TrES-4. The accuracy of the effective temperatures is supported
by a number of independent consistency checks. The spectroscopic orbital
solution for TrES-3 is improved with our new radial-velocity measurements of
that system, as are the light-curve parameters for both systems based on newly
acquired photometry for TrES-3 and a reanalysis of existing photometry for
TrES-4. We have redetermined the stellar parameters taking advantage of the
strong constraint provided by the light curves in the form of the normalized
separation (related to the stellar density) in conjunction with our
new temperatures and metallicities. The masses and radii we derive are
M_\star=0.928_{-0.048}^{+0.028} M_{\sun},R_\star = 0.829_{-0.022}^{+0.015}
R_{\sun}, and M_\star = 1.404_{-0.134}^{+0.066} M_{\sun},
R_\star=1.846_{-0.087}^{+0.096} R_{\sun} for TrES-3 and TrES-4, respectively.
With these revised stellar parameters we obtain improved values for the
planetary masses and radii. We find , for TrES-3, and
, for TrES-4. We confirm TrES-4 as the planet with the largest
radius among the currently known transiting hot Jupiters.Comment: 42 pages, 10 tables, 8 figures. Accepted for publication in the
Astrophysical Journa
HAT-P-11b: A Super-Neptune Planet Transiting a Bright K Star in the Kepler Field
We report on the discovery of HAT-P-11b, the smallest radius transiting
extrasolar planet (TEP) discovered from the ground, and the first hot Neptune
discovered to date by transit searches. HAT-P-11b orbits the bright (V=9.587)
and metal rich ([Fe=H] = +0.31 +/- 0.05) K4 dwarf star GSC 03561-02092 with P =
4.8878162 +/- 0.0000071 days and produces a transit signal with depth of 4.2
mmag. We present a global analysis of the available photometric and
radial-velocity data that result in stellar and planetary parameters, with
simultaneous treatment of systematic variations. The planet, like its near-twin
GJ 436b, is somewhat larger than Neptune (17Mearth, 3.8Rearth) both in mass Mp
= 0.081 +/- 0.009 MJ (25.8 +/- 2.9 Mearth) and radius Rp = 0.422 +/- 0.014 RJ
(4.73 +/- 0.16 Rearth). HAT-P-11b orbits in an eccentric orbit with e = 0.198
+/- 0.046 and omega = 355.2 +/- 17.3, causing a reflex motion of its parent
star with amplitude 11.6 +/- 1.2 m/s, a challenging detection due to the high
level of chromospheric activity of the parent star. Our ephemeris for the
transit events is Tc = 2454605.89132 +/- 0.00032 (BJD), with duration 0.0957
+/- 0.0012 d, and secondary eclipse epoch of 2454608.96 +/- 0.15 d (BJD). The
basic stellar parameters of the host star are M* = 0.809+0.020-0.027 Msun, R* =
0.752 +/- 0.021 Rsun and Teff = 4780 +/- 50 K. Importantly, HAT-P-11 will lie
on one of the detectors of the forthcoming Kepler mission. We discuss an
interesting constraint on the eccentricity of the system by the transit light
curve and stellar parameters. We also present a blend analysis, that for the
first time treats the case of a blended transiting hot Jupiter mimicing a
transiting hot Neptune, and proves that HAT-P-11b is not such a blend.Comment: Accepted for publication in ApJ, 24 pages, 14 figures, 6 tables. All
RV data presented in this versio
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