The X-Ray Universe 2008, Granada, Spain, May 28, 2008 Chandra Monitoring of X-Ray Evolution of SNR 1987A Sangwook Park Department of Astronomy & Astrophysics The Pennsylvania State University with D. N. Burrows, J. L. Racusin (Penn State), S. A. Zhekov, R. McCray (Colorado), B. M. Gaensler, C.-Y. Ng (Sydney), & L. Staveley-Smith (Western Australia)

SN 1987A in Her Uniqueness Brightest supernova observed by mankind since 1604 (J. Kepler) Distance: 50 kpc, in the LMC Age: 21 years old as of Jan 2008 Type II SN Progenitor: Blue supergiant (Sk , B3 I) Neutrino burst => Core-collapse explosion => neutron star? Most intensively studied SN of all time: – – Optical/UV: HST and many ground-based – – Radio: initial detection, turned on again in ~1990 – – X-ray: no initial detection, turned on in ~1990 – – Gamma-ray: detected decay lines from 56 Co  decay of 56 Ni, confirming explosive nucleosynthesis => ADS: ~1000 (~1/week) refereed papers (since 1987)   Chandra observations since 1999: - Monitoring: ACIS, twice a year, separated by ~6 months - Spectroscopy: HETG/LETG - - As of , 21 Chandra observations performed: 16 ACIS monitoring ( Penn State/Colorado ) 4 HETG/LETG deep spectroscopy ( Penn State/Colorado/MIT ) 1 HRC imaging ( CfA/Sydney/Penn State/Colorado )

SNR 1987A: Physical Picture Cf. Michael et al Artistic presentation of SN 1987A (SAO/CXC) Optical/Soft X-rays Hard X-rays Radio ? NS/BH

N E (7626) SNR 1987A: ACIS Images 2000– arcsec

SNR 1987A: X-Ray & Radio Light Curves

(Zhekov+ 06,08) (Haberl+ 06; Heng+ 08) (Haberl+ 06; Heng+ 08)

SNR 1987A: X-Ray & Radio Light Curves - Soft X-ray light curve continues a rapid increase (f ~ t 7 ): a current (last 2 yr) rate of ~35% /yr. As of , f (0.5-2 keV) = 4.1 x erg/cm 2 /s, L x = 2.7 x erg/s. - Hard X-ray light curve increases with a lower rate of ~20% /yr (f ~ t 4 ). As of , f (3-10 keV) = 5.2 x erg/cm 2 /s, L x = 1.6 x erg/s. - Cross-comparisons among different X-ray instruments are consistent. - Radio emission shows an evolution of the spectral index: currently S ~  Radio light curves are flatter than X-rays: ~ t 2.6 (9 GHz), ~ t 2.2 (1.4 GHz). An upper limit (~50% of the 3-10 keV flux) for the contribution from synchrotron emission in the observed hard X-ray flux is estimated based on a simple extrapolation of the radio fluxes (assuming S ~  -0.8 and no spectral break), and SRCUT/PL model fits of the latest ACIS spectrum.

SNR 1987A: X-ray Radial Expansion Racusin et al X-ray radius vs time. Broadband deconvolved image for each epoch is deprojected (43 deg) and fitted to a model (a torus + 4 lobes) in order to estimate the radius of the SNR as a function of time. Estimated overall expansion velocity is ~3500 km/s (w/ poor fit). The expansion slows down to ~1700 km/s since d ~ 6000.

SNR 1987A: X-Ray Spectral Evolution 2008 Jan Soft component: kT s ~ 0.3 keV n e t ~ cm -3 s Hard component: kT h ~ 1.9 keV n e t ~ 2 x cm -3 s   n s /n h ~ 100 Overall softening of spectrum. Abundances fixed at values obtained from the LETG/HETG data (Zhekov et al. 2008): N = 0.56 O = 0.08 Ne = Mg = 0.28 Si = 0.33 Si = 0.30 Fe = 0.19 Dewey+ 2008, Zhekov+ 2008Park+ 2006

SNR 1987A: Dispersed Spectrum (2007) Dewey+ 2008; Zhekov Deep HETG (355 ks) & LETG (285 ks) observations in Two characteristic shock model fit: kT ~ 0.5 and 2 keV. - Soft kT is constant (~0.5 keV). - Hard kT decreases (2.7 -> 1.9 keV). Bulk gas velocities measured by the line widths are v ~ km/s, while v ~ km/s as derived from the fitted electron temperatures. Do lower bulk motion velocities imply a contribution from the reflecte shock? kT ~ 1.9 keV kT ~ 0.5 keV

SUMMARY Ring-like morphology with asymmetric intensity Developments of X-ray spots => becomes a complete ring as the blast wave arrives the inner ring Steep brightening in soft X-rays => Now ~24 x brighter than 2000: L x (0.5-2keV) = 2.7 x ergs/s A rapid brightening (~ t 7 ): The shock continues interacting w/ a steep density increase. Radial expansion: v ~ 7800 km/s to 1700 km/s at day ~6000 Slower brightening in hard X-rays: ~6 x brighter than Synchrotron emission? But, steeper than radio light curves (f ~ t 4 vs t 2.6 ). Shock-CSM interaction: spectral softening and distribution of shock velocity Soft comp kT ~ keV (constant) Hard comp kT ~ 1.9 keV (decreasing) Low bulk velocities: reflected shock? Little changes in metal abundances. The complex shock structure by interacting with inner ring: Careful analysis with more data is required with upcoming Chandra monitoring with the HETG. The origin of hard X-ray emission: hot gas vs synchrotron? We need to watch continuous evolution in both X-ray and radio emission. Searching for the embedded neutron star