1,272 research outputs found
WASP-4b Arrived Early for the TESS Mission
The Transiting Exoplanet Survey Satellite (TESS) recently observed 18
transits of the hot Jupiter WASP-4b. The sequence of transits occurred 81.6
11.7 seconds earlier than had been predicted, based on data stretching
back to 2007. This is unlikely to be the result of a clock error, because TESS
observations of other hot Jupiters (WASP-6b, 18b, and 46b) are compatible with
a constant period, ruling out an 81.6-second offset at the 6.4 level.
The 1.3-day orbital period of WASP-4b appears to be decreasing at a rate of
milliseconds per year. The apparent period change
might be caused by tidal orbital decay or apsidal precession, although both
interpretations have shortcomings. The gravitational influence of a third body
is another possibility, though at present there is minimal evidence for such a
body. Further observations are needed to confirm and understand the timing
variation.Comment: AJ accepte
GJ 1252 b: A 1.2 R\u3csub\u3eâ\u3c/sub\u3e Planet Transiting An M3 Dwarf At 20.4 pc
We report the discovery of GJ 1252 b, a planet with a radius of 1.193 ± 0.074 Râ and an orbital period of 0.52 days around an M3-type star (0.381 ± 0.019 Mâ, 0.391 ± 0.020 Râ) located 20.385 ± 0.019 pc away. We use Transiting Exoplanet Survey Satellite (TESS) data, ground-based photometry and spectroscopy, Gaia astrometry, and high angular resolution imaging to show that the transit signal seen in the TESS data must originate from a transiting planet. We do so by ruling out all false-positive scenarios that attempt to explain the transit signal as originating from an eclipsing stellar binary. Precise Doppler monitoring also leads to a tentative mass measurement of 2.09 ± 0.56 Mâ. The host star proximity, brightness (V = 12.19 mag, K = 7.92 mag), low stellar activity, and the system\u27s short orbital period make this planet an attractive target for detailed characterization, including precise mass measurement, looking for other objects in the system, and planet atmosphere characterization
HETE Observations of the Gamma-Ray Burst GRB030329: Evidence for an Underlying Soft X-ray Component
An exceptionally intense gamma-ray burst, GRB030329, was detected and
localized by the instruments on board the High Energy Transient Explorer
satellite (HETE) at 11:37:14 UT on 29 March 2003. The burst consisted of two
\~10s pulses of roughly equal brightness and an X-ray tail lasting >100s. The
energy fluence in the 30-400 keV energy band was 1.08e-4 erg/cm2, making
GRB030329 one of the brightest GRBs ever detected. Communication of a 2 arcmin
error box 73 minutes after the burst allowed the rapid detection of a
counterpart in the optical, X-ray, radio and the ensuing discovery of a
supernova with most unusual characteristics. Analyses of the burst lightcurves
reveal the presence of a distinct, bright, soft X-ray component underlying the
main GRB: the 2-10 keV fluence of this component is ~7e-6 erg/cm2. The main
pulses of GRB030329 were preceded by two soft, faint, non-thermal bumps. We
present details of the HETE observations of GRB030329.Comment: 22 pages, 5 figures, to be published in ApJ 617, no. 2 (10 December
2004). Referee comments have been incorporated; results of improved spectral
analysis are include
Short Gamma Ray Bursts: marking the birth of black holes from coalescing compact binaries
This contribution summarizes, as of early 2008, the observational and
theoretical understanding of the origin, physics, and emission properties of
short gamma-ray bursts in both electromagnetic and gravitational waves.Comment: 19 pages, appeared in the book "Physics of Relativistic Objects in
Compact Binaries: From Birth to Coalescence", Astrophysics and Space Science
Library, edited by M. Colpi, P. Casella, V. Gorini, U. Moschella, and A.
Possent
Global Characteristics of X-Ray Flashes and X-Ray-Rich GRBs Observed by HETE-2
We describe and discuss the global properties of 45 gamma-ray bursts (GRBs)
observed by HETE-2 during the first three years of its mission, focusing on the
properties of X-Ray Flashes (XRFs) and X-ray-rich GRBs (XRRs). We find that the
numbers of XRFs, XRRs, and GRBs are comparable. We find that the durations and
the sky distributions of XRFs and XRRs are similar to those of GRBs. We also
find that the spectral properties of XRFs and XRRs are similar to those of
GRBs, except that the values of the peak energy of the
burst spectrum in , the peak energy flux \Fp, and the energy
fluence of XRFs are much smaller -- and those of XRRs are smaller -- than
those of GRBs. Finally, we find that the distributions of all three kinds of
bursts form a continuum in the [(2-30 keV),(30-400) keV]-plane, the
[(2-400 keV), ]-plane, and the [(50-300 keV),
]-plane. These results provide strong evidence that all three
kinds of bursts arise from the same phenomenon.Comment: 33 pages, 15 figures, submitted to Ap
HETE-2 Observation of two gamma-ray bursts at z > 3
GRB 020124 and GRB 030323 constitute half the sample of gamma-ray bursts with
a measured redshift greater than 3. This paper presents the temporal and
spectral properties of these two gamma-ray bursts detected and localized with
HETE-2. While they have nearly identical redshifts (z=3.20 for GRB 020124, and
z=3.37 for GRB 030323), these two GRBs span about an order of magnitude in
fluence, thus sampling distinct regions of the GRB luminosity function. The
properties of these two bursts are compared with those of the bulk of the GRB
population detected by HETE-2. We also discuss the energetics of GRB 020124 and
GRB 030323 and show that they are compatible with the Epeak - Eiso relation
discovered by Amati et al. (2002). Finally, we compute the maximum redshifts at
which these bursts could have been detected by HETE-2 and we address various
issues connected with the detection and localization of high-z GRBs.Comment: 19 pages, 4 figures, submitted to Ap
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