Constraints on SNIa from Their Remnants: X-ray studies of the Tycho SNR John P. Hughes

1. Constraints on SNIa from Their Remnants: X-ray studies of the Tycho SNR John P. Hughes Rutgers University Collaborators: Jessica Warren, Carles Badenes, Gamil Cassam-Chenai JD09 IAU GA Prague

2. Discovery of SN 1572 Cassiopeia SN 1572 was first sighted in Korea and (probably) Spain on 6 November, 1572, then shortly thereafter in China and elsewhere in Europe. It was brighter than Venus (visible at noon for “those gifted with keen sight”). Tycho Brahe noted the new star on the evening of 11 November, carefully measured its position (his value is within ~2’ of the center of the remnant) and recorded its brightness until Mar 1574 when it became too faint to see. The remnant was discovered as a radio source in 1952 (also 3C10), then as a faint set of Ha filaments, and lastly as an X-ray source in 1967. JD09 IAU GA Prague

3. A Modern View: Tycho’s SNR Across Wavebands VLA 1.4 GHz Optical Ha Spitzer 24 mm Chandra 0.5-7 keV Current size ~ 8’ diameter Only Balmer line optical emission X-ray spectrum dominated by ejecta Fe (red), Si (green), 4-6 keV (blue) Square root scale JD09 IAU GA Prague

4. What we knew prior to Chandra • Consistent with a Type Ia SN if most of the Fe remains unshocked in the interior (i.e., ejecta stratified) (Hamilton, Sarazin, & Szymkowiak 1986) • There are Fe-rich blobs in SE (Vancura, Hughes, & Gorenstein 1995) • Fe-K emission peaks interior to Fe-L/Si-K (Hwang & Gotthelf 1997) • Fe-K emission requires a distinct spectral component with higher kT and lower net than Si & S (Hwang, Hughes & Petre 1998) • X-ray expansion rate is ~0.124% yr-1, somewhat higher than radio (Hughes 2000) JD09 IAU GA Prague

5. New Insights from Modeling I • Radial variation in the X-ray spectrum due to kT gradient through ejecta • Invoke modest amount of collisionless electron heating (b~0.01-0.1) at the reverse shock (Badenes, Borkowski, & Bravo 2005) Si-S C-O Fe b=0.1 b=0.01 b=bmin JD09 IAU GA Prague

6. New Insights from Modeling II • X-ray spectral modeling of SN Ia remnants can constrain explosion mechanism (Badenes et al. 2006) • 1D hydro with realistic ejecta models evolved to age of Tycho (430 yrs) in uniform ambient medium • Use XMM spectrum from west (avoid Fe blobs) • Only 3 parameters: rAM, b, NH Delayed detonation – GOOD fit Mixed 3D model – BAD fit JD09 IAU GA Prague

7. New Results from Chandra • Forward shock in Tycho shows geometrically thin, spectrally featureless rims (Hwang et al. 2002, Warren et al. 2005) 4-6 keV continuum band linear display sqrt display JD09 IAU GA Prague

8. Why Featureless? • Thermal interpretation untenable (Warren et al. 2005) • Low abundance • Would require < 3% solar composition • Low ionization timescale (Hwang et al. 2002) • Requires net < 108 cm-3 s or ne ~ 0.05 cm-3 • Inconsistent with ne ~ 10 cm-3 from intensity • Nonthermal (synchrotron) • Photon index (ap = 2.7) consistent with Ginga 10-20 keV spectrum • Evidence for TeV energy electrons • Similar to SN1006 only more intense! JD09 IAU GA Prague

9. Rim Morphology: Further Evidence for Relativistic Electrons at the Blast Wave • Extract surface brightness profiles and fit with thin shell models (include Chandra PSF) • Thickness < 5” • B ~ 30-450 mG Thermal model only • Final nail: morphology of rim inconsistent with thermal emission from shocked ambient medium (from Badenes’ 1D hydro and ionization model) • Limits on thermal emission imply ambient density < 0.3 cm-3 (Cassam-Chenai et al 2006) Thermal model plus thin rim JD09 IAU GA Prague

10. Locating the BW, CD, RS in Tycho Continuum-subtracted Fe-K Broadband 0.5-7 keV Map of Thermal vs. nonthermal • Green contour defines contact discontinuity (CD), as boundary between thermal and nonthermal emission • Outermost edge of X-ray emission defines blast wave (BW) • Reverse shock (RS) from shell fits to Fe K image JD09 IAU GA Prague

11. Locating the BW, CD, RS in Tycho • Mean radii: • BW: 251” 1.0 (black) • CD: 241” 0.93 (green) • RS: 183” 0.72 (purple) • Relative positions constrain dynamical state: inconsistent with shock hydro-models Problem: CD too close to BW Solution: CR acceleration Insufficient pressure in relativistic electrons – large hadronic component required Blondin & Ellison 2001 JD09 IAU GA Prague

12. Chandra View of Si/Fe in Tycho Broadband Chandra image Si-rich emission Examine spectra of six knots at breakout on rim Si-rich Fe-rich 1.8 keV (Si) to 0.8 keV (Fe) emission ratio “Fe-rich” emission Hughes et al. 2006, in prep. JD09 IAU GA Prague

13. Chandra Spectra of Tycho Knots Fe-rich Si-rich [Si/Fe] [Si/Fe] 20 0.32 15 0.35 6 0.64 Single component fits, kT ~ 1-3 keV, net ~ 3x1010 cm-3 s Si abundances all > 2 x solar (confirmed ejecta knots) Factor of >60 range in [Si/Fe], but no pure Fe or Si knots JD09 IAU GA Prague

14. Origin of SN Ia Ejecta Clumps I Clumps may originate in the region between Si+S and Fe rich zones A consequence of the nickel bubble effect? BUT WHY ONLY A SINGLE SUCH FE-RICH CLUMP? JD09 IAU GA Prague

15. Origin of SN Ia Ejecta Clumps II Ignition of the thermonuclear flame occurs near the star’s center The resulting hot bubble of Fe-rich “ash” is buoyant Not yet clear how many such bubbles are involved High velocity, asymmetric Ca emission from Ia SNe (e.g., SN2001el) Is this a spark from the ignition of the SN Ia explosion that formed the Tycho SNR? Simulation of a buoyant bubble being sheared by Rayleigh-Taylor instabilities (from Flash Center at Chicago) Would be a unique view of the SNIa ignition process!! JD09 IAU GA Prague

16. Tycho Scorecard • Previous results confirmed/explained • Tycho is the remnant of a SN Ia • Realistic SN Ia explosion models (~1051 ergs, 1.4 Msun of compositionally-stratified ejecta, density & velocity profiles) describe the X-ray spectra, size, and age of Tycho. • Fe-K peaks interior to Fe-L/Si-K • Requires some collisionless electron heating at reverse shock JD09 IAU GA Prague

17. Tycho Scorecard • New findings (explained) • Spectrally featureless, geometrically-thin rims • Synchrotron emission from relativistic electrons – evidence for diffusive shock acceleration • Also present in Cas A, Kepler, SN1006, RCW 86, … • Closeness of contact discontinuity to forward shock • Cosmic-ray modified dynamics – requires relativistic protons – strong evidence for the hadronic component of cosmic rays • Consequences: • No measurements of forward shock temperature or ambient medium density from X-rays • Dynamical models that ignore CR acceleration (e.g., Truelove & McKee 1999) now inadequate JD09 IAU GA Prague

18. Tycho Scorecard • New findings (not yet fully explained) • Single Fe-rich clump at rim • A “spark” from the SN Ia ignition process ?? • Spatial variation in emission from low-Z (O, Ne, Mg) vs. high-Z (Si, S, Ar, Ca) species (Warren 2006, PhD thesis; Warren & Hughes 2006) • Compositional inhomogeneity in SN Ia or an excitation effect ?? Spectra contain less (rim, west) or more (interior, east) emission below 0.7 keV Low-Z (O, Ne, Mg)/High-Z (S, Ar, Ca) [O/S] ~ 0.13 to 0.33 JD09 IAU GA Prague

19. Carles Badenes Cefalú 14/06/06 SN1006 SNR: Also a DDT? Si Heα O Heα O Heb Ne Heα S Heα Mg Heα Ar Heα SN 1006 SNR. Top: Chandra image [Hughes et al. in prep.]. Left: Chandra spectrum [Badenes et al. in prep.] • The thermal X-ray emission in SN1006 is also dominated by ejecta. • Model DDTe (ρAM=2x10-25 g.cm-3, β=0.1) + powerlaw + absorption. • Work in progress, but DDT models are the only ones that work well so far... JD09 IAU GA Prague 19

20. THE END JD09 IAU GA Prague

21. What Type Of Explosion? • Evidence for Type Ia origin • Pure Balmer spectra (Kirshner & Chevalier 1978) • Partially neutral ambient medium • No compact remnant • X-ray spectrum (Hwang et al. 1998) • X-ray structure • Uniform ISM, “smoother” ejecta, modest spectral variations • 1.4 solar masses of ejecta (Hamilton et al. 1986) • Evidence for Type Ia origin • Light curve • Based on historical records (Baade 1945, Ruiz-Lapuenta 2004) JD09 IAU GA Prague

22. Principal Component Analysis (Warren 2006, PhD thesis, Warren & Hughes 2006) Spectra vary from Line-dominated to Featureless Thermal/Synchrotron Spectra vary from Strong Fe-L (e.g., eastern blob) to Strong Si-K Fe-rich/Si-rich Spectra contain less (rim, west) or more (interior, east) emission below 0.7 keV Low-Z (O, Ne, Mg)/High-Z (S, Ar, Ca) JD09 IAU GA Prague

23. Fin JD09 IAU GA Prague