We present the first results from the Swift Ultraviolet Survey of the Magellanic Clouds (SUMaC), the highest resolution ultraviolet (UV) survey of the Magellanic Clouds yet completed. In this paper, we focus on the Small Magellanic Cloud (SMC). When combined with multi-wavelength optical and infrared observations, the three near-UV filters on the Swift Ultraviolet/Optical Telescope are conducive to measuring the shape of the dust extinction curve and the strength of the 2175A dust bump. We divide the SMC into UV-detected star-forming regions and large 200" (58~pc) pixels and then model the spectral energy distributions using a Markov Chain Monte Carlo method to constrain the ages, masses, and dust curve properties. We find that the majority of the SMC has a 2175A dust bump, which is larger to the northeast and smaller to the southwest, and that the extinction curve is universally steeper than the Galactic curve. We also derive a star formation history and find evidence for peaks in the star formation rate at 6-10 Myr, 30-80 Myr, and 400 Myr, the latter two of which are consistent with previous work.

ABSTRACT We present multi-epoch X-ray spectral observations of three Type IIn supernovae (SNe), SN 2005kd, SN 2006jd, and SN 2010jl, acquired with Chandra, XMM-Newton, Suzaku, and Swift. Previous extensive X-ray studies of SN 2010jl have revealed that X-ray spectra are dominated by thermal emission, which likely arises from a hot plasma heated by a forward shock propagating into a massive circumstellar medium (CSM). Interestingly, an additional soft X-ray component was required to reproduce the spectra at a period of ∼1–2 years after the SN explosion. Although this component is likely associated with the SN, its origin remained an open question. We find a similar, additional soft X-ray component from the other two SNe IIn as well. Given this finding, we present a new interpretation for the origin of this component; it is thermal emission from a forward shock essentially identical to the hard X-ray component, but directly reaches us from a void of the dense CSM. Namely, the hard and soft components are responsible for the heavily and moderately absorbed components, respectively. The co-existence of the two components with distinct absorptions as well as the delayed emergence of the moderately absorbed X-ray component could be evidence for asphericity of the CSM. We show that the X-ray spectral evolution can be qualitatively explained by considering a torus-like geometry for the dense CSM. Based on our X-ray spectral analyses, we estimate the radius of the torus-like CSM to be on the order of ∼5 × 1016 cm.

When measuring star formation rates using ultraviolet light, correcting for dust extinction is a critical step. However, with the variety of dust extinction curves to choose from, the extinction correction is quite uncertain. Here, we use Swift/UVOT to measure the extinction curve for star-forming regions in the SMC and M33. We find that both the slope of the curve and the strength of the 2175 Angstrom bump vary across both galaxies. In addition, as part of our modeling, we derive a detailed recent star formation history for each galaxy.

We report on the X-ray spectral evolution of the nearby Type IIn supernova (SN) 2005ip based on Chandra and Swift observations covering similar to 1-6 yr after explosion. X-ray spectra in all epochs are well fitted by a thermal emission model with kT greater than or similar to 7 keV. The somewhat high temperature suggests that the X-ray emission mainly arises from the circumstellar medium (CSM) heated by the forward shock. We find that the spectra taken two to three years after the explosion are heavily absorbed (N-H similar to 5 x 10(22) cm(-2)), but the absorption gradually decreases to the level of the Galactic absorption (N-H similar to 4 x 10(20) cm(-2)) at the final epoch. This indicates that the SN went off in a dense CSM and that the forward shock has overtaken it. The intrinsic X-ray luminosity stays constant until the final epoch, when it drops by a factor of similar to 2. The intrinsic 0.2-10 keV luminosity during the plateau phase is measured to be similar to 1.5 x 10(41) erg s(-1), ranking SN 2005ip as one of the brightest X-ray SNe. Based on the column density, we derive a lower limit of a mass-loss rate to be (M) over dot similar to 1.5 x 10(-2) (V-w/100 km s(-1)) M-circle dot yr(-1), which roughly agrees with that inferred from the X-ray luminosity, (M) over dot similar to 2 x 10(-2) (V-w/100 km s(-1)) M-circle dot yr(-1), where V-w is the circumstellar wind speed. Such a high mass-loss rate suggests that the progenitor star had eruptive mass ejections similar to a luminous blue variable star. The total mass ejected in the eruptive period is estimated to be similar to 15 M-circle dot, indicating that the progenitor mass is greater than or similar to 25 M-circle dot.

We report four years of radio and X-ray monitoring of the Type IIn supernova SN 2006jd at radio wavelengths with the Very Large Array, Giant Metrewave Radio Telescope and Expanded Very Large Array; at X-ray wavelengths with Chandra, XMM-Newton and Swift-XRT. We assume that the radio and X-ray emitting particles are produced by shock interaction with a dense circumstellar medium. The radio emission shows an initial rise that can be attributed to freefree absorption by cool gas mixed into the nonthermal emitting region; external free-free absorption is disfavored because of the shape of the rising light curves and the low gas column density inferred along the line of sight to the emission region. The X-ray luminosity implies a preshock circumstellar density ∼ 10 cm at a radius r ∼ 2 × 10 cm, but the column density inferred from the Department of Physics, Royal Military College of Canada, Kingston, ON, K7K 7B4, Canada; Poonam.Chandra@rmc.ca Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325. Institute of Astronomy of Russian Academy of Sciences, Pyatnitskaya St. 48, 109017 Moscow, Russia. Department of Astronomy, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden. Smithsonian Astrophysical Observatory, 60 Garden St., MS-20, Cambridge, MA 02138, USA. Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Colaba, Mumbai 400005, India. Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 Center for Research and Exploration in Space Science and Technology, NASA Goddard Space Flight Center, Greenbelt, MD 20771 Department of Astronomy, University of Maryland, College Park, MD 20742 https://ntrs.nasa.gov/search.jsp?R=20130012582 2018-08-07T21:14:31+00:00Z

Only a handful of supernovae (SNe) have been studied in multi-wavelength from radio to X-rays, starting a few days after explosion. The early detection and classification of the nearby type IIb SN2011dh/PTF11eon in M51 provides a unique opportunity to conduct such observations. We present detailed data obtained at the youngest phase ever of a core-collapse supernova (days 3 to 12 after explosion) in the radio, millimeter and X-rays; when combined with optical data, this allows us to explore the early evolution of the SN blast wave and its surroundings. Our analysis shows that the expanding supernova shockwave does not exhibit equipartition (e_e/e_B 1000), and is expanding into circumstellar material that is consistent with a density profile falling like R^-2. Within modeling uncertainties we find an average velocity of the fast parts of the ejecta of 15,000 +/- 1800 km/s, contrary to previous analysis. This velocity places SN 2011dh in an intermediate blast-wave regime between the previously defined compact and extended SN IIb subtypes. Our results highlight the importance of early ( 1 day) high-frequency observations of future events. Moreover, we show the importance of combined radio/X-ray observations for determining the microphysics ratio e_e/e_B.

We report four years of radio and X-ray monitoring of the Type IIn supernova SN 2006jd at radio wavelengths with the Very Large Array, Giant Metrewave Radio Telescope, and Expanded Very Large Array; at X-ray wavelengths with Chandra, XMM-Newton, and Swift-XRT. We assume that the radio and X-ray emitting particles are produced by shock interaction with a dense circumstellar medium. The radio emission shows an initial rise that can be attributed to free-free absorption by cool gas mixed into the nonthermal emitting region; external free-free absorption is disfavored because of the shape of the rising light curves and the low gas column density inferred along the line of sight to the emission region. The X-ray luminosity implies a preshock circumstellar density similar to 10(6) cm(-3) at a radius r similar to 2 x 10(16) cm, but the column density inferred from the photoabsorption of X-rays along the line of sight suggests a significantly lower density. The implication may be an asymmetry in the interaction. The X-ray spectrum shows Fe line emission at 6.9 keV that is stronger than is expected for the conditions in the X-ray emitting gas. We suggest that cool gas mixed into the hot gas plays a role in the line emission. Our radio and X-ray data both suggest the density profile is flatter than r(-2) because of the slow evolution of the unabsorbed emission.

We have considered 53 Type Ia supernovae (SNe Ia) observed by the Swift X-Ray Telescope. None of the SNe Ia are individually detected at any time or in stacked images. Using these data and assuming that the SNe Ia are a homogeneous class of objects, we have calculated upper limits to the X-ray luminosity (0.2-10 keV) and mass-loss rate of L0.2-10 < 1.7 x 10(38) erg s(-1) and (M) over dot < 1.1 x 10(-6) M-circle dot yr(-1) x (v(w))/(10 km s(-1)), respectively. The results exclude massive or evolved stars as the companion objects in SN Ia progenitor systems, but allow the possibility of main sequence or small stars, along with double degenerate systems consisting of two white dwarfs, consistent with results obtained at other wavelengths (e.g., UV, radio) in other studies.

We present an analysis of simultaneous X-Ray and UV observations ofcomet C/2007 N3 (Lulin) taken on three days between January 2009 and March 2009 using the Swift observatory. For our X-ray observations, we used basic transforms to account for the movement of the comet to allow the combination of all available data to produce an exposure-corrected image. We fit a simple model to the extracted spectrum and measured an X-ray flux of 4.3+/-1.3 * 10^-13 ergs cm-2 s-1 in the 0.3 to 1.0 keV band. In the UV, we acquired large-aperture photometry and used a coma model to derive water production rates given assumptions regarding the distribution of water and its dissociation into OH molecules about the comet's nucleus. We compare and discuss the X-ray and UV morphology of the comet. We show that the peak of the cometary X-ray emission is offset sunward of the UV peak emission, assumed to be the nucleus, by approximately 35,000 km. The offset observed, the shape of X-ray emission and the decrease of the X-ray emission comet-side of the peak, suggested that the comet was indeed collisionally thick to charge exchange, as expected from our measurements of the comet's water production rate (6–8 10^28 mol. s-1). The X-ray spectrum is consistent with solar wind charge exchange emission, and the comet most likely interacted with a solar wind depleted of very highly ionised oxygen. We show that the measured X-ray lightcurve can be very well explained by variations in the comet's gas production rates, the observing geometry and variations in the solar wind flux.

We present Swift Ultra-Violet Optical Telescope and X-Ray Telescope (XRT) observations, and visual wavelength spectroscopy of the Type IIb supernova (SN) 2009mg, discovered in the Sb galaxy ESO 121-G26. The observational properties of SN 2009mg are compared to the prototype Type IIb SNe 1993J and 2008ax, with which we find many similarities. However, minor differences are discernible including SN 2009mg not exhibiting an initial fast decline or u-band upturn as observed in the comparison objects, and its rise to maximum is somewhat slower leading to slightly broader light curves. The late-time temporal index of SN 2009mg, determined from 40 d post-explosion, is consistent with the decay rate of SN 1993J, but inconsistent with the decay of 56Co. This suggests leakage of ?-rays out of the ejecta and a stellar mass on the small side of the mass distribution. Our XRT non-detection provides an upper limit on the mass-loss rate of the progenitor of . Modelling of the SN light curve indicates a kinetic energy of , an ejecta mass of and a 56Ni mass of 0.10 +/- 0.01 M?.

AbstractWe present the results of over two decades of radio observations of type IIb Supernovae with the Very Large Array and the Australia Telescope Compact Array. These radio studies illustrate the need for multi-wavelength follow-up to determine the progenitor scenario for type IIb events.

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 semi-empirical models of the explosion and find the time evolution of the early UV flux to be well fit 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.