Abstract
We report the discovery of the unusually bright long-duration gamma-ray burst (GRB), GRB 221009A, as observed by the Neil Gehrels Swift Observatory (Swift), Monitor of All-sky X-ray Image, ...and Neutron Star Interior Composition Explorer Mission. This energetic GRB was located relatively nearby (
z
= 0.151), allowing for sustained observations of the afterglow. The large X-ray luminosity and low Galactic latitude (
b
= 4.°3) make GRB 221009A a powerful probe of dust in the Milky Way. Using echo tomography, we map the line-of-sight dust distribution and find evidence for significant column densities at large distances (≳10 kpc). We present analysis of the light curves and spectra at X-ray and UV–optical wavelengths, and find that the X-ray afterglow of GRB 221009A is more than an order of magnitude brighter at
T
0
+ 4.5 ks than that from any previous GRB observed by Swift. In its rest frame, GRB 221009A is at the high end of the afterglow luminosity distribution, but not uniquely so. In a simulation of randomly generated bursts, only 1 in 10
4
long GRBs were as energetic as GRB 221009A; such a large
E
γ
,iso
implies a narrow jet structure, but the afterglow light curve is inconsistent with simple top-hat jet models. Using the sample of Swift GRBs with redshifts, we estimate that GRBs as energetic and nearby as GRB 221009A occur at a rate of ≲1 per 1000 yr—making this a truly remarkable opportunity unlikely to be repeated in our lifetime.
We present the earliest ultraviolet (UV) observations of the bright Type Ia supernova SN 2011fe/PTF11kly in the nearby galaxy M101 at a distance of only 6.4 Mpc. It was discovered shortly after ...explosion by the Palomar Transient Factory and first observed by Swift/UVOT about a day after explosion. The early UV light is well defined, with ~20 data points per filter in the five days after explosion. These early and well-sampled UV observations form new template light curves for comparison with observations of other SNe Ia at low and high redshift. We report fits from semiempirical models of the explosion and find the time evolution of the early UV flux to be well fitted by the superposition of two parabolic curves. Finally, we use the early UV flux measurements to examine a possible shock interaction with a non-degenerate companion. From models predicting the measurable shock emission, we find that even a solar mass companion at a distance of a few solar radii is unlikely at more than 95% confidence.
This work is part of a systematic re-analysis program of all the data of gamma-ray burst (GRB) X-ray afterglows observed so far, in order to constrain the GRB models. We present here a systematic ...analysis of those afterglows observed by XMM-Newton between January 2000 and March 2004. This dataset includes GRB 011211 and GRB 030329. We have obtained spectra, light curves and colors for these afterglows. In this paper we focus on the continuum spectral and temporal behavior. We compare these values with the theoretical ones expected from the fireball model. We derive constraints about the burst environment (absorption, density profile) and put constraints on their beaming angle.
Among Type Ia supernovae (SNe Ia), a class of overluminous objects exist whose ejecta mass is inferred to be larger than the canonical Chandrasekhar mass. We present and discuss the UV/optical ...photometric light curves, colors, absolute magnitudes, and spectra of three candidate Super-Chandrasekhar mass SNe-2009dc, 2011aa, and 2012dn-observed with the Swift Ultraviolet/Optical Telescope. The light curves are at the broad end for SNe Ia, with the light curves of SN 2011aa being among the broadest ever observed. We find all three to have very blue colors which may provide a means of excluding these overluminous SNe from cosmological analysis, though there is some overlap with the bluest of "normal" SNe Ia. All three are overluminous in their UV absolute magnitudes compared to normal and broad SNe Ia, but SNe 2011aa and 2012dn are not optically overluminous compared to normal SNe Ia. The integrated luminosity curves of SNe 2011aa and 2012dn in the UVOT range (1600-6000 A) are only half as bright as SN 2009dc, implying a smaller super(56)Ni yield. While it is not enough to strongly affect the bolometric flux, the early time mid-UV flux makes a significant contribution at early times. The strong spectral features in the mid-UV spectra of SNe 2009dc and 2012dn suggest a higher temperature and lower opacity to be the cause of the UV excess rather than a hot, smooth blackbody from shock interaction. Further work is needed to determine the ejecta and super(56)Ni masses of SNe 2011aa and 2012dn and to fully explain their high UV luminosities.
ABSTRACT We present optical and ultraviolet (UV) photometry and spectra of the very nearby and highly reddened supernova (SN) 2014J in M82 obtained with the Swift Ultra-Violet/Optical Telescope ...(UVOT). Comparison of the UVOT grism spectra of SN 2014J with Hubble Space Telescope observations of SN2011fe or UVOT grism spectra of SN 2012fr are consistent with an extinction law with a low value of RV ∼1.4. The high reddening causes the detected photon distribution in the broadband UV filters to have a much longer effective wavelength than for an unreddened SN. The light curve evolution is consistent with this shift and does not show a flattening due to photons being scattered back into the line of sight (LOS). The light curve shapes and color evolution are inconsistent with a contribution scattered into the LOS by circumstellar dust. We conclude that most or all of the high reddening must come from interstellar dust. We show that even for a single dust composition, there is not a unique reddening law caused by circumstellar scattering. Rather, when considering scattering from a time-variable source, we confirm earlier studies that the reddening law is a function of the dust geometry, column density, and epoch. We also show how an assumed geometry of dust as a foreground sheet in mixed stellar/dust systems will lead to a higher inferred RV. Rather than assuming the dust around SNe is peculiar, SNe may be useful probes of the interstellar reddening laws in other galaxies.
Very early observations with the Swift satellite of g-ray burst (GRB) afterglows reveal that the optical component is not detected in a large number of cases. This is in contrast to the bright ...optical flashes previously discovered in some GRBs (e.g., GRB 990123 and GRB 021211). Comparisons of the X-ray afterglow flux to the optical afterglow flux and prompt g-ray fluence is used to quantify the seemingly deficient optical, and in some cases X-ray, light at these early epochs. This comparison reveals that some of these bursts appear to have higher than normal g-ray efficiencies. We discuss possible mechanisms and their feasibility for explaining the apparent lack of early optical emission. The mechanisms considered include, foreground extinction, circumburst absorption, Lya blanketing and absorption due to high-redshift, low-density environments, rapid temporal decay, and intrinsic weakness of the reverse shock. Of these, foreground extinction, circumburst absorption, and high redshift provide the best explanations for most of the nondetections in our sample. There is tentative evidence of suppression of the strong reverse shock emission. This could be because of a Poynting flux-dominated flow or a pure nonrelativistic hydrodynamic reverse shock.
We present results of Swift optical, ultraviolet (UV) and X-ray observations of the afterglow of GRB 050801. The source is visible over the full optical, UV and X-ray energy range of the Swift ...Ultraviolet and Optical Telescope and X-ray telescope instruments. Both optical and X-ray light curves exhibit a broad plateau (Δt/t∼ 1) during the first few hundred seconds after the γ-ray event. We investigate the multiwavelength spectral and timing properties of the afterglow, and we suggest that the behaviour at early times is compatible with an energy injection by a newly born magnetar with a period of a few tenths of a millisecond, which keeps the forward shock refreshed over this short interval by irradiation. Reverse shock emission is not observed. Its suppression might be due to GRB ejecta being permeated by high magnetic fields, as expected for outflows powered by a magnetar. Finally, the multiwavelength study allows a determination of the burst redshift, z= 1.56.
Gama-ışın patlamaları (GIP) evrendeki en enerjik olaylardır. Bu patlamalar, ana ışınım ve ardıl ışınım olarak iki bileşen halinde gözlenirler. Ardıl ışınım fiziksel parametreleri kullanılarak ...afterglowpy yazılımı aracılığıyla sentetik ışık eğrileri üretilebilir. Bu çalışmada, farklı jet modelleri kullanarak (Silindir şapka jet modeli (Top hat jet model), Gaussyan jet modeli (Gaussian jet model) ve Güç kanunu jet modeli (Power law jet model)) afterglowpy ile Swift - XRT ile gözlenmiş X-ışın ardıl ışınımları modellendi. Afterglowpy jet modellerini veriye doğrudan uygulanabilen ve ekibimizce geliştirilen Ciao-Sherpa versiyonu kullanılarak ardıl ışınım fiziksel paremeterleri belirlendi. Bu çalışmada, örnek olarak bir uzun GIP ve bir kısa GIP ardıl ışınım fiziksel parametreleri elde edildi. Ardıl ışınım fiziksel parametreleri yani, Kinetik enerji, jet yarı açıklık açısı ve çevresel yoğunluk değerleri literatürle uyumlu şekilde bulundu.
Gamma-ray bursts (GRBs) are the most energetic events in the Universe. These bursts are observed as two components, prompt emission and afterglow emission. By using afterglow physical parameters synthetic light curves can be produced via afterglowpy software. In this study, Swift - XRT X-ray afterglows were modeled with afterglowpy by using different jet models (Top hat jet model, Gaussian jet model and Power law jet model). Afterglow emission physical parameters were determined by using the Ciao-Sherpa version of the afterglowpy jet models developed by our team, which can be applied directly to the data. In this study, one long GRB and one short GRB afterglow emission physical parameters were obtained as an example. Afterglow physical parameters namely kinetic energy, jet half-opening angle and circumburst density values were found consistently with the literature.
Swift and optical observations of GRB 050401 De Pasquale, Massimiliano; Beardmore, Andy P.; Barthelmy, S. D. ...
Monthly notices of the Royal Astronomical Society,
January 2006, Letnik:
365, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We present the results of the analysis of γ-ray and X-ray data of GRB 050401 taken with the Swift satellite, together with a series of ground-based follow-up optical observations. The Swift X-ray ...light curve shows a clear break at about 4900 s after the γ-ray burst (GRB). The decay indices before and after the break are consistent with a scenario of continuous injection of radiation from the ‘central engine’ of the GRB to the fireball. Alternatively, this behaviour could result if ejecta are released with a range of Lorentz factors, with the slower shells catching up the faster at the afterglow shock position. The two scenarios are observationally indistinguishable. The GRB 050401 afterglow is quite bright in the X-ray band, but weak in the optical, with an optical to X-ray flux ratio similar to those of ‘dark bursts’. We detect a significant amount of absorption in the X-ray spectrum, with NH= (1.7 ± 0.2) × 1022cm−2 at a redshift of z= 2.9, which is typical of a dense circumburst medium. Such high column density implies an unrealistic optical extinction of 30 mag if we adopt a Galactic extinction law, which would not be consistent with the optical detection of the afterglow. This suggests that the extinction law is different from the Galactic one.
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