The final chapter in the long-standing mystery of the gamma-ray bursts (GRBs) centres on the origin of the short-hard class of bursts, which are suspected on theoretical grounds to result from the ...coalescence of neutron-star or black-hole binary systems. Numerous searches for the afterglows of short-hard bursts have been made, galvanized by the revolution in our understanding of long-duration GRBs that followed the discovery in 1997 of their broadband (X-ray, optical and radio) afterglow emission. Here we present the discovery of the X-ray afterglow of a short-hard burst, GRB 050709, whose accurate position allows us to associate it unambiguously with a star-forming galaxy at redshift z = 0.160, and whose optical lightcurve definitively excludes a supernova association. Together with results from three other recent short-hard bursts, this suggests that short-hard bursts release much less energy than the long-duration GRBs. Models requiring young stellar populations, such as magnetars and collapsars, are ruled out, while coalescing degenerate binaries remain the most promising progenitor candidates.
Abstract
We investigated the doping and temperature evolutions of the optical response of Sr
3
(Ir
1−
x
Mn
x
)
2
O
7
single crystals with 0 ≤
x
≤ 0.36 by utilizing infrared spectroscopy. ...Substitution of 3
d
transition metal Mn ions into Sr
3
Ir
2
O
7
is expected to induce an insulator-to-metal transition via the decrease in the magnitude of the spin–orbit coupling and the hole doping. In sharp contrast, our data reveal the resilience of the spin–orbit coupling and the incoherent character of the charge transport. Upon Mn substitution, an incoherent in-gap excitation at about 0.25 eV appeared with the decrease in the strength of the optical transitions between the effective total angular momentum
J
eff
bands of the Ir ions. The resonance energies of the optical transitions between the
J
eff
bands which are directly proportional to the magnitude of the spin–orbit coupling hardly varied. In addition to these evolutions of the low-energy response, Mn substitution led to the emergence of a distinct high-energy optical excitation at about 1.2 eV which is larger than the resonance energies of the optical transitions between the
J
eff
bands. This observation indicates that the Mn 3
d
states are located away from the Ir 5
d
states in energy and that the large difference in the on-site energies of the transition metal ions is responsible for the incoherent charge transport and the robustness of the spin–orbit coupling. The effect of Mn substitution was also registered in the temperature dependence of the electronic response. The anomaly in the optical response of the parent compound observed at the antiferromagnetic transition temperature is notably suppressed in the Mn-doped compounds despite the persistence of the long-range antiferromagnetic ordering. The suppression of the spin-charge coupling could be related to charge disproportionation of the Ir ions.
Abstract
We present the results of our continued systematic search for near-infrared (NIR) candidate counterparts to ultraluminous X-ray sources (ULXs) within 10 Mpc. We observed 42 ULXs in 24 nearby ...galaxies and detected NIR candidate counterparts to 15 ULXs. Fourteen of these ULXs appear to have a single candidate counterpart in our images and the remaining ULX has two candidate counterparts. Seven ULXs have candidate counterparts with absolute magnitudes in the range between −9.26 and −11.18 mag, consistent with them being red supergiants (RSGs). The other eight ULXs have candidate counterparts with absolute magnitudes too bright to be a single stellar source. Some of these NIR sources show extended morphology or colours expected for active galactic nuclei (AGNs), strongly suggesting that they are likely stellar clusters or background galaxies. The RSG candidate counterparts form a valuable sample for follow-up spectroscopic observations to confirm their nature, with the ultimate goal of directly measuring the mass of the compact accretor that powers the ULX using binary Doppler shifts.
We present multicolor optical observations of long-duration g-ray bursts (GRBs) made over a three-year period with the robotic Palomar 60 inch telescope (P60). Our sample consists of all 29 events ...discovered by Swift for which P60 began observations less than 1 hr after the burst trigger. We were able to recover 80% of the optical afterglows from this prompt sample, and we attribute this high efficiency to our red coverage. Like Melandri et al. (2008), we find that a significant fraction (50%) of Swift events show a suppression of the optical flux with regard to the X-ray emission (the so-called 'dark' bursts). Our multicolor photometry demonstrates this is likely due in large part to extinction in the host galaxy. We argue that previous studies, by selecting only the brightest and best-sampled optical afterglows, have significantly underestimated the amount of dust present in typical GRB environments.
We present a monitoring study of SN 2004A and probable discovery of a progenitor star in pre-explosion Hubble Space Telescope (HST) images. The photometric and spectroscopic monitoring of SN 2004A ...show that it was a normal Type II-P which was discovered in NGC 6207 about two weeks after explosion. We compare SN 2004A to the similar Type II-P SN 1999em and estimate an explosion epoch of 2004 January 6. We also calculate three new distances to NGC 6207 of 21.0 ± 4.3,-21.4 ± 3.5 and 25.1 ± 1.7-Mpc. The former was calculated using the Standard Candle Method (SCM) for SNe-II-P, and the latter two from the brightest supergiants method (BSM). We combine these three distances with existing kinematic distances, to derive a mean value of 20.3 ± 3.4-Mpc. Using this distance, we estimate that the ejected nickel mass in the explosion is 0.046+0.031−0.017-M⊙. The progenitor of SN 2004A is identified in pre-explosion WFPC2 F814W images with a magnitude of mF814W= 24.3 ± 0.3, but is below the detection limit of the F606W images. We show that this was likely a red supergiant (RSG) with a mass of 9+3−2-M⊙. The object is detected at 4.7σ above the background noise. Even if this detection is spurious, the 5σ upper limit would give a robust upper mass limit of 12-M⊙ for a RSG progenitor. These initial masses are very similar to those of two previously identified RSG progenitors of the Type II-P SNe 2004gd (8+4−2-M⊙) and 2005cs (9+3−2-M⊙).
Context. Supernova (SN) 1987A was a peculiar hydrogen-rich event with a long-rising (~84 d) light curve, stemming from the explosion of a compact blue supergiant star. Only a few similar events have ...been presented in the literature in recent decades. Aims. We present new data for a sample of six long-rising Type II SNe (SNe II), three of which were discovered and observed by the Palomar Transient Factory (PTF) and three observed by the Caltech Core-Collapse Project (CCCP). Our aim is to enlarge this small family of long-rising SNe II, characterizing their differences in terms of progenitor and explosion parameters. We also study the metallicity of their environments. Methods. Optical light curves, spectra, and host-galaxy properties of these SNe are presented and analyzed. Detailed comparisons with known SN 1987A-like events in the literature are shown, with particular emphasis on the absolute magnitudes, colors, expansion velocities, and host-galaxy metallicities. Bolometric properties are derived from the multiband light curves. By modeling the early-time emission with scaling relations derived from the SuperNova Explosion Code (SNEC) models of MESA progenitor stars, we estimate the progenitor radii of these transients. The modeling of the bolometric light curves also allows us to estimate other progenitor and explosion parameters, such as the ejected 56Ni mass, the explosion energy, and the ejecta mass. Results. We present PTF12kso, a long-rising SN II that is estimated to have the largest amount of ejected 56Ni mass measured for this class. PTF09gpn and PTF12kso are found at the lowest host metallicities observed for this SN group. The variety of early light-curve luminosities depends on the wide range of progenitor radii of these SNe, from a few tens of R⊙ (SN 2005ci) up to thousands (SN 2004ek) with some intermediate cases between 100 R⊙ (PTF09gpn) and 300 R⊙ (SN 2004em). Conclusions. We confirm that long-rising SNe II with light-curve shapes closely resembling that of SN 1987A generally arise from blue supergiant (BSG) stars. However, some of them, such as SN 2004em, likely have progenitors with larger radii (~300 R⊙, typical of yellow supergiants) and can thus be regarded as intermediate cases between normal SNe IIP and SN 1987A-like SNe. Some extended red supergiant (RSG) stars such as the progenitor of SN 2004ek can also produce long-rising SNe II if they synthesized a large amount of 56Ni in the explosion. Low host metallicity is confirmed as a characteristic of the SNe arising from compact BSG stars.
Objective
The present study aimed to analyse the Korean National Health Insurance Service (NHIS) cohort data to examine the safety of acupuncture therapy during pregnancy.
Design
Retrospective ...cohort.
Setting
Korea.
Population or sample
Women with confirmed pregnancy between 2003 and 2012 from the 2002–13 NHIS sample cohort (n = 20 799).
Methods
Women with confirmed pregnancy were identified and divided into acupuncture or control group for comparison of their outcomes. Differences in other factors such as age, and rate of high‐risk pregnancy and multiple pregnancy were examined. In the acupuncture group, the most frequent acupuncture diagnosis codes and the timing of treatment were also investigated.
Main outcome measures
Incidence of full‐term delivery, preterm delivery and stillbirth by pregnancy duration and among the high‐risk and multiple pregnancy groups.
Results
Of 20 799 pregnant women analysed, 1030 (4.95%) and 19 749 were in the acupuncture and control groups, respectively. Both overall (odds ratio OR 1.23; 95% CI 0.98–1.54), and in the stratified analysis of high‐risk pregnancies (OR 1.09; 95% CI 0.73–1.64), there was no significant difference between acupuncture and control groups in preterm deliveries. No stillbirths occurred in the acupuncture group and 0.035% of pregnancies resulted in stillbirths in the control group.
Conclusion
No significant difference in delivery outcomes (preterm delivery and stillbirth) was observed between confirmed pregnancies in the acupuncture and control groups. Therefore, in pregnancy, acupuncture therapy may be a safe therapeutic modality for relieving discomfort without an adverse delivery outcome.
Tweetable
In pregnancy, acupuncture therapy may be a safe therapeutic modality for relieving discomfort without an adverse outcome.
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In pregnancy, acupuncture therapy may be a safe therapeutic modality for relieving discomfort without an adverse outcome.
We present observations of the unusually bright and long g-ray burst GRB 050820A, one of the best sampled broadband data sets in the Swift era. The g-ray light curve is marked by a soft precursor ...pulse some 200 s before the main event; the lack of any intervening emission suggests that it is due to a physical mechanism distinct from the GRB itself. The large time lag between the precursor and the main emission enabled simultaneous observations in the g-ray, X-ray, and optical bandpasses, something only achieved for a handful of events to date. While the contemporaneous X-rays are the low-energy tail of the prompt emission, the optical does not directly track the g-ray flux. Instead, the early-time optical data appear consistent with the forward shock synchrotron peak passing through the optical and are therefore likely the beginning of the afterglow. On hour timescales after the burst, the X-ray and optical light curves are inconsistent with an adiabatic expansion of the shock into the surrounding region, but rather indicate that there is a period of energy injection. Observations at late times allow us to constrain the collimation angle of the relativistic outflow to 6:8 f 9:3. Our estimates of both the kinetic energy of the afterglow (E sub(KE) = 5.2 super(+7.9-4.1) x 10 super(51) ergs) and the prompt g-ray energy release (E sub(g) = 7.5 super(+6.7-2.4) x 10 super(51) ergs) make GRB 050820A one of the most energetic events for which such values could be determined.
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