X-Ray Emission from SNe
SN 1987A - The Circumstellar Medium , SN Shock Interaction and Associated Emission
Dwarkadas, Vikram
American Astronomical Society, AAS Meeting #211, #105.22; Bulletin of the American Astronomical Society, Vol. 39, p.932
Abstract
We model the circumstellar medium surrounding SN 1987A in the equatorial region, using 1 and 2 dimensional numerical simulations. Data from X-ray, radio and optical observations gathered over the past 20 years is used to compute the structure of the surrounding medium as carved out by winds from the progenitor star. We then compute the evolution of the SN shock wave within this medium, and the emission resulting from the interaction of this shock with the circumstellar medium. We discuss our results in the context of the observations, and make predictions for the future evolution of the shock wave.
This research is supported by award AST-0319261 from the National Science Foundation, and by NASA through grant HST-AR-10649 awarded by STScI.
Circumstellar Interaction, X-ray And Radio Emission, And The Ambient Medium In Young Supernovae
Dwarkadas, Vikram
American Astronomical Society, AAS Meeting #213, #438.04; Bulletin of the American Astronomical Society, Vol. 41, p.311
01/2009
Abstract
Using numerical hydrodynamic simulations, we study the interaction of the supernova (SN) shock wave with the surrounding medium in young SNe. Comparison of the X-ray and radio emission resulting from this interaction with the observed data allows for a determination of the structural properties and density profile of the circumstellar medium. Using this we delineate the ambient medium in some well studied SNe such as SN 1993J and SN 1996cr.
Acknowledgements: Several collaborators have contributed to data used in this work and are appropriately listed on the poster. This work is partly supported by Chandra, NSF and STScI grants to VVD at U Chicago.
X-rays from the Explosion Site: 15 Years of Light Curves of SN 1993J
Chandra, Poonam; Dwarkadas, Vikram V.; Ray, Alak; Immler, Stefan; Pooley, David
The Astrophysical Journal, Volume 699, Issue 1, pp. 388-399 (2009).
Abstract
We present a comprehensive analysis of the X-ray light curves of supernova (SN) 1993J in a nearby galaxy M81. This is the only SN other than SN 1987A, which is so extensively followed in the X-ray bands. Here, we report on SN 1993J observations with Chandra in the year 2005 and 2008, and Swift observations in 2005, 2006, and 2008. We combined these observations with all available archival data of SN 1993J, which includes ROSAT, ASCA, Chandra, and XMM-Newton observations from 1993 April to 2006 August. In this paper, we report the X-ray light curves of SN 1993J, extending up to 15 years, in the soft (0.3-2.4 keV), hard (2-8 keV), and combined (0.3-8 keV) bands. The hard- and soft-band fluxes decline at different rates initially, but after about 5 years they both undergo a t -1 decline. The soft X-rays, which are initially low, start dominating after a few hundred days. We interpret that most of the emission below 8 keV is coming from the reverse shock which is radiative initially for around first 1000-2000 days and then turn into adiabatic shock. Our hydrodynamic simulation also confirms the reverse shock origin of the observed light curves. We also compare the Hα line luminosity of SN 1993J with its X-ray light curve and note that the Hα line luminosity has a fairly high fraction of the X-ray emission, indicating presence of clumps in the emitting plasma.
SNR 1987A: Ten Years of Chandra Monitoring
Park, Sangwook; Burrows, David; Racusin, Judith; Zhekov, Svetozar; McCray, Richard; Dewey, Daniel; Dwarkadas, Vikram; Garmire, Gordon
Chandra's First Decade of Discovery, Proceedings of the conference held 22-25 September, 2009 in Boston, MA. Edited by Scott Wolk, Antonella Fruscione, and Douglas Swartz, abstract #22
Abstract
We have been observing the dynamical and spectral evolution of SNR 1987A with Chandra since 1999. As of 2009 July, we have performed 20 monitoring observations of SNR 1987A. We have also performed 4 deep grating spectroscopic observations. We here review the X-ray evolution of SNR 1987A over the last 10 yr, including updates from the recent observations. The current X-ray emission of SNR 1987A originates primarily from the shock interaction with complex density structures along the inner circumstellar ring, which results in a range of the shock velocities and plasma conditions. We find no evidence for the much-anticipated central point source. The latest data show that SNR 1987A continues to brighten, but probably at a lower rate than 5 yr ago. The radial expansion of the SNR has significantly slowed since ˜2004, supporting the interpretation that the blast wave is entering the main body of the inner ring. Recently we transitioned from using the ACIS to using the HETG in our monitoring program. The upcoming X-ray light curves combined with high resolution spectroscopy will help us further study the details of the shock evolution in the context of the density/chemical structures of the equatorial stellar winds and the late-stage evolution history of SN 1987A's massive progenitor.
Modeling the deep HETG observation of SN 1996cr
Dewey, Daniel; Bauer, F. E.; Dwarkadas, V. V.
Chandra's First Decade of Discovery, Proceedings of the conference held 22-25 September, 2009 in Boston, MA. Edited by Scott Wolk, Antonella Fruscione, and Douglas Swartz, abstract #85
Abstract
SN 1996cr appears to have exploded into a wind-blown bubble structure giving rise to an increasing X-ray flux as late as a decade after explosion. This behavior is rare among SNe and similar to that of SN 1987A. However, SN 1996cr's X-ray luminosity is several orders of magnitude greater than '87A's. Comparing simple 1D hydrodynamic models to the HETG spectra support a model where '96cr is exploding into a more compact and extensive circumstellar bubble-and-shell structure than '87A's.
Chandra High-Resolution Spectroscopy of SN 1996cr
Bauer, Franz E.; Dewey, D.; Dwarkadas, V.; Brandt, W. N.
American Astronomical Society, HEAD meeting #11, #18.11; Bulletin of the American Astronomical Society, Vol. 41, p.688
Abstract
SN1996cr is among the closest SNe to explode in the past 30 years, yet went undiscovered for many years. Due to its fortuitous location in the Circinus Galaxy at 3.7 Mpc, however, we have a wealth of serendipitous archival data available to piece together its early evolution. Like SN1987A, it appears to have exploded into a shell-like structure formed by the progenitor, sparking a unique temporal evolution. I will describe our current multi-wavelength constraints on SN1996cr, focusing on a new 485ks Chandra HETG spectrum, and discuss physical interpretations of the system with the aid of hydrodynamical simulations by our team.
Bursting SN 1996cr's bubble: hydrodynamic and X-ray modelling of its circumstellar medium
Dwarkadas, V. V.; Dewey, D.; Bauer, F.
Monthly Notices of the Royal Astronomical Society, Volume 407, Issue 2, pp. 812-829. 09/2010
Abstract
SN1996cr is one of the five closest supernovae (SNe) to explode in the past 30 yr. Due to its fortuitous location in the Circinus galaxy at ~3.7 Mpc, there is a wealth of recently acquired and serendipitous archival data available to piece together its evolution over the past decade, including a recent 485-ks Chandra high-energy transmission grating spectrum. In order to interpret these data, we have explored hydrodynamic simulations, followed by computations of simulated spectra and light curves under non-equilibrium ionization conditions, and directly compared them to the observations. Our simulated spectra manage to fit both the X-ray continuum and lines at four epochs satisfactorily, while our computed light curves are in good agreement with additional flux-monitoring data sets. These calculations allow us to infer the nature and structure of the circumstellar medium (CSM), the evolution of the SN shock wave, and the abundances of the ejecta and surrounding medium. The data imply that SN 1996cr exploded in a low-density medium before interacting with a dense shell of material about 0.03 pc away from the progenitor star. We speculate that the shell could be due to the interaction of a blue supergiant or Wolf-Rayet wind with a previously existing red supergiant (RSG) wind. The shock wave has now exited the shell and is expanding in the medium exterior to it, possibly the undisturbed continuation of the dense RSG wind. The narrow lines that earned SN 1996cr its IIn designation possibly arise from dense, shocked clumps in the CSM. Although the possibility for a luminous blue variable progenitor for this Type IIn SN cannot be completely excluded, it is inconsistent with much of the data. These calculations allow us to probe the stellar mass-loss in the very last phases (<104 yr) of a massive star's life (>106 yr), and provide another means to deducing the progenitor of the SN.
Evolution of the High Velocity X-Ray Emission in SN 1987A
Dewey, Daniel; Haberl, F.; Dwarkadas, V. V.; Burrows, D. N.; Park, S.
AA(MIT Kavli Institute), AB(MPE, Germany), AC(U Chicago), AD(Penn State), AE(U Texas)
American Astronomical Society, AAS Meeting #217, #256.28 01/2011
Abstract
Chandra HETG observations of SN 1987A in late 1999 showed very broad lines with observed FWHM of order 7000 km/s (Michael et al. 2002). At this time (SN day 4600) the blastwave was already interacting with the HII region around the progenitor and optical spots had recently appeared. High-resolution spectra taken from May 2003 ( day 5900) to the present by XMM-Newton and Chandra have been well fit by models with FWHM less than 2000 km/s (Zhekov et al. 2005; Dewey et al. 2008; Sturm et al 2010). The emission is increasingly dominated by these narrower components as the blastwave encounters more of the dense equatorial ring. However emission from the HII region out of the ring plane is still expected at late times and would contribute a high-velocity component to the spectra.
We analyze 6 epochs of SN 1987A grating data and include an additional very broad component in the spectral model. We find that deep HETG 2007 data are better fit when one quarter of the flux comes from a component with FWHM 8500 km/s, and that RGS 2003 data show an improved fit with a very-broad fraction that is between the 1999 and 2007 values. Later data continue a progression to lower, but still significant, very-broad fractions. The measurements are discussed in terms of the density and extent of the out-of-plane HII region, hydrodynamical simulations, and 3D models of SN 1987A's emission.
Support for this work was provided by NASA/USA through contract NAS8-03060 to the Smithsonian Astrophysical Observatory (SAO) and further SAO sub-contracts TM9-0004X to VVD (U Chicago) and SV3-73016 to MIT for support of the CXC.
Modeling The Morphology Of SN 1996cr From X-ray Lines At High Resolution
Bauer, Franz E.; Dewey, D.; Dwarkadas, V
AA(Space Science Institute), AB(MIT Kavli Institute), AC(University of Chicago)
American Astronomical Society, AAS Meeting #217, #434.26 01/2011
Abstract
SN1996cr ( 3.7 Mpc) was X-ray "dim" up to 1000 days yet brightened to 4e39 erg/s (0.5-8 keV) after 10 years (Bauer et al. 2008). A 1-D hydro model of the ejecta-CSM interaction produces good agreement with the measured X-ray light curves and spectra at multiple epochs, suggesting that SN 1996cr was most likely a massive star, M > 30 solar masses, which went from an RSG to a brief W-R phase before exploding within its r 0.04 pc wind-blown shell (Dwarkadas et al. 2010). Further analysis of a 485ks Chandra HETG observation allows velocity-profile fitting to a handful of bright emission lines in the spectrum (e.g., Si and Fe). The line shapes are well fit with axisymmetric emission models that put the higher temperature Fe XXVI emission at high latitudes. The axis orientation is well constrained to be 55 degrees from our line-of-sight. The latitude variation may be explained either by higher CSM densities near the equator, or by the ejecta having greater velocity along the poles. SN1996cr demonstrates how X-ray emission lines can provide important diagnostics of SN shock structure.