Supernova Remnant 1987A: Opening the Future by Reaching the Past

We report an up-turn in the soft X-ray light curve of supernova remnant (SNR) 1987A in late 2003 (~6200 days after the explosion), as observed with the Chandra X-ray Observatory. Since early 2004, the rapid increase of the 0.5-2 keV band X-ray light curve can no longer be described by the exponential density distribution model with which we successfully fitted the data between 1990 and 2003. Around day ~6200, we also find that the fractional contribution to the observed soft X-ray flux from the decelerated shock begins to exceed that of the fast shock and that the X-ray brightening becomes "global" rather than "spotty". We interpret these results as evidence that the blast wave has reached the main body of the dense circumstellar material all around the inner ring. This interpretation is supported by other recent observations, including a deceleration of the radial expansion of the X-ray remnant, a significant up-turn in the mid-IR intensities, and the prevalence of the optical hot spots around the entire inner ring, all of which occur at around day 6000. In contrast to the soft X-ray light curve, the hard band (3-10 keV) X-ray light curve increases at a much lower rate which is rather similar to the radio light curve. The hard X-ray emission may thus originate from the reverse shock where the radio emission is likely produced. Alternatively, the low increase rate of the hard X-rays may simply be a result of the continuous softening of the overall X-ray spectrum.Comment: AASTex preprint style 12 pages including 1 table and 4 figures, Accepted by ApJ

High-Resolution X-ray Spectroscopy of SNR 1987A: Chandra LETG and HETG Observations in 2007

We present an extended analysis of the deep Chandra LETG and HETG observations of the supernova remnant 1987A (SNR 1987A) carried out in 2007. The global fits to the grating spectra show that the temperature of the X-ray emitting plasma in the slower shocks in this system has remained stable for the last three years, while that in the faster shocks has decreased. This temperature evolution is confirmed by the first light curves of strong X-ray emission lines and their ratios. On the other hand, bulk gas velocities inferred from the X-ray line profiles are too low to account for the post-shock plasma temperatures inferred from spectral fits. This suggests that the X-ray emission comes from gas that has been shocked twice, first by the blast wave and again by shocks reflected from the inner ring of SNR 1987A. A new model that takes these considerations into account gives support to this physical picture.Comment: 36 pages, 10 figures, Accepted for publication in Ap

Chandra observations of SN 1987A: the soft X-ray light curve revisited

We report on the present stage of SN 1987A as observed by the Chandra X-ray Observatory. We reanalyze published Chandra observations and add three more epochs of Chandra data to get a consistent picture of the evolution of the X-ray fluxes in several energy bands. We discuss the implications of several calibration issues for Chandra data. Using the most recent Chandra calibration files, we find that the 0.5-2.0 keV band fluxes of SN 1987A have increased by ~6 x 10 ^-13 erg s^-1 cm^-2 per year since 2009. This is in contrast with our previous result that the 0.5-2.0 keV light curve showed a sudden flattening in 2009. Based on our new analysis, we conclude that the forward shock is still in full interaction with the equatorial ring.Comment: Accepted for publication by ApJ, 7 pages, 5 figure

Observing Supernova 1987A with the Refurbished Hubble Space Telescope

Observations with the Hubble Space Telescope (HST), conducted since 1990, now offer an unprecedented glimpse into fast astrophysical shocks in the young remnant of supernova 1987A. Comparing observations taken in 2010 using the refurbished instruments on HST with data taken in 2004, just before the Space Telescope Imaging Spectrograph failed, we find that the Ly-a and H-a lines from shock emission continue to brighten, while their maximum velocities continue to decrease. We observe broad blueshifted Ly-a, which we attribute to resonant scattering of photons emitted from hotspots on the equatorial ring. We also detect NV~\lambda\lambda 1239,1243 A line emission, but only to the red of Ly-A. The profiles of the NV lines differ markedly from that of H-a, suggesting that the N^{4+} ions are scattered and accelerated by turbulent electromagnetic fields that isotropize the ions in the collisionless shock.Comment: Science, accepted. Science Express, 02 Sept 2010. 5 figures. Supporting online material can be found at http://www.sciencemag.org/cgi/content/full/sci;science.1192134/DC

Chandra Observations of Shock Kinematics in Supernova Remnant 1987A

We report the first results from deep X-ray observations of the SNR 1987A with the Chandra LETG. Temperatures inferred from line ratios range from 0.1 - 2 keV and increase with ionization potential. Expansion velocities inferred from X-ray line profiles range from 300 - 1700 km/s, much less than the velocities inferred from the radial expansion of the radio and X-ray images. We can account for these observations with a scenario in which the X-rays are emitted by shocks produced where the supernova blast wave strikes dense protrusions of the inner circumstellar ring, which are also responsible for the optical hot spots.Comment: 12 pages, 3 figures, accepted for publication in ApJ

A Chandra View of The Morphological And Spectral Evolution of Supernova Remnant 1987A

We present an update on the results of our monitoring observations of the X-ray remnant of supernova (SN) 1987A with the {\it Chandra X-Ray Observatory}. As of 2002 December, we have performed a total of seven observations of SN 1987A. The high angular resolution images from the latest data reveal developments of new X-ray bright spots in the northwestern and the southwestern portions of the remnant as well as changes on the eastern side. The latest 0.5-2 keV band flux ($f_X$ $\sim$ 6 $\times$ 10$^{-13}$ ergs cm$^{-2}$ s$^{-1}$) is four times brighter than three years earlier. The overall X-ray emission is primarily from the blast wave shock with $kT$ $\sim$ 2.4 keV. As the blast wave approaches the dense circumstellar material, the contribution from the decelerated slow shock ($kT$ $\sim$ 0.22 keV) to the observed X-ray emission is becoming significant. The increase of this slow shock contribution over the last two years is particularly noticeable in the western half of the remnant. These results indicate that the shock front is now reaching the main body of the inner circumstellar ring. Based on the best-fit two-shock spectral model, we derive approximate densities of the X-ray-emitting regions ($n_e$ $\sim$ 235 cm$^{-3}$ for the fast shock and $n_e$ $\sim$ 7500 cm$^{-3}$ for the slow shock). We obtain an upper limit on the observed X-ray luminosity of any embedded point source ($L_X$ $\le$ 1.5 $\times$ 10$^{34}$ ergs s$^{-1}$) in the 2$-$10 keV band. The X-ray remnant continues to expand linearly at a rate of 4167 km s$^{-1}$.Comment: 22 pages (ApJ preprint style), 7 Figures, Accepted by ApJ (scheduled on July 20, 2004), for high-quality Fig 1 and Fig 2, please contact [email protected]

The X-ray Remnant of SN1987A

We present high resolution Chandra observations of the remnant of SN1987A in the Large Magellanic Cloud. The high angular resolution of the Chandra X-ray Observatory (CXO) permits us to resolve the X-ray remnant. We find that the remnant is shell-like in morphology, with X-ray peaks associated with some of the optical hot spots seen in HST images. The X-ray light curve has departed from the linear flux increase observed by ROSAT, with a 0.5-2.0 keV luminosity of 1.5 x 10^35 erg/s in January 2000. We set an upper limit of 2.3 x 10^34 ergs/s on the luminosity of any embedded central source (0.5 - 2 keV). We also present a high resolution spectrum, showing that the X-ray emission is thermal in origin and is dominated by highly ionized species of O, Ne, Mg, and Si.Comment: 16 pages, 3 figures, Accepted for publication in ApJ Letter

Optimization of Cutaneous Electrically Mediated Plasmid DNA Delivery Using Novel Electrode

The easy accessibility of skin makes it an excellent target for gene transfer protocols. To take advantage of skin as a target for gene transfer, it is important to establish an efficient and reproducible delivery system. Electroporation is an established technique for enhancing plasmid delivery to many tissues in vivo. A critical component of this technique is the electrode configuration. Electroporation parameters were optimized for transgene expression with minimal tissue damage with a novel electrode. The highest transgene expression and efficiency of individual cell transformation with minimal damage was produced with eight 150 ms pulses at field strength of 100 V/cm. This electrode design offers the potential for easier and more reproducible electrically mediated cutaneous plasmid delivery than the simple electrodes currently commercially available. This electrode can be a valuable tool in determining the applicability of electrically mediated cutaneous gene transfer