Progenitor stars of supernovae Poonam Chandra Royal Military College of Canada

SUPERNOVAE  Energetic explosions in the universe  Energy emitted ergs (10 29 times more than an atmospheric nuclear explosion)  One SN explosion shines brighter than the host Galaxy  In universe few supernovae explosions every second  Energetic explosions in the universe  Energy emitted ergs (10 29 times more than an atmospheric nuclear explosion)  One SN explosion shines brighter than the host Galaxy  In universe few supernovae explosions every second

Core collapse Supernovae Type II, Ib, Ic Neutron star or Black hole remains Found only in Spiral arms of the galaxy (Young population of stars) Thermonuclear Supernovae Type Ia No remnant remaining Found in elliptical and Spiral galaxies Two kinds of supernova explosions

Supernovae Core collapse supernovae: explosion of a massive star in a red supergiant phase. – Progenitor star > 8 M sun. Thermonuclear supernovae: explosion of a carbon-oxygen white dwarf in a binary system. – Progenitor star 4-8 M sun in a binary.

Progenitors of supernovae Very few are known. Require pre-explosion images. The progenitor stars are much fainter than the supernovae. Most supernovae at far away distances.

Circumstellar interaction The most reliable way to get indirect information about the mass of the progenitor star and the conditions of the surrounding medium.

SN explosion centre Photosphere Outgoing ejecta Reverse shock shell Contact discontinuity Forward shock shell Radius Density Circumstellar matter Not to scale

Circumstellar Interaction Shock velocity of typical SNe are ~1000 times the velocity of the (red supergiant) wind. Hence, SNe observed few years after explosion can probe the history of the progenitor star thousands of years back.

Radio emission from Supernovae: Synchrotron non-thermal emission of relativistic electrons in the presence of high magnetic field. X-ray emission from Supernovae: Both thermal and non-thermal emission from the region lying between optical and radio photospheres. Interaction of SN ejecta with CSM gives rise to radio and X-ray emission

SN 1995N A type IIn supernova Discovered on 1995 May 5 Parent Galaxy MCG (Distance=24 Mpc )

Excellent Case: SN 1995N Chandra et al. 2009, ApJ, Chandra et al. 2005, ApJ Radio and X-ray observations: Radio observations: for 11 years -Very Large Array (VLA) -Giant Meterwave radio telescope (GMRT) X-ray observations: -ROSAT HRI: Aug 1996, ASCA: Jan ChandraXO: March XMM-Newton: 2005

Bremsstrahlung (kT=2.21 keV, N H =1.51 x /cm 2. ) Gaussians at 1.02 keV (N=0.34 +/ x ) and 0.87 keV (N=0.36 +/ x ) NeX NeIX

Mass of the progenitor star If most of the Ne is in the Helium zone, close to C+O boundary then f is the fraction of Ne IX to Ne

Mass of the progenitor For f = 0.1, n e = 2 x 10 6 cm -3, n Ne = 600 cm -3 Corresponding Neon mass ~ M sun. Compatible with M sun progenitor star.

Radio light curves of SN 1995N

How fast ejecta is decelerating? R~t -0.8, this also implies n=8 (m=(n-3)/(n-2) in R~t -m ) What is the mass loss rate of the progenitor star? Mass loss rate = ~10 -4 M sun yr -1 Red supergiant star on 15 M sun in a superwind phase Density and temperature of the reverse shock Forward shock: T=2.4 x 10 8 K, Density=3.3 x 10 5 cm -3 Reverse shock: T=0.9 x 10 7 K, Density= 2 x 10 6 cm -3 How fast ejecta is decelerating? R~t -0.8, this also implies n=8 (m=(n-3)/(n-2) in R~t -m ) What is the mass loss rate of the progenitor star? Mass loss rate = ~10 -4 M sun yr -1 Red supergiant star on 15 M sun in a superwind phase Density and temperature of the reverse shock Forward shock: T=2.4 x 10 8 K, Density=3.3 x 10 5 cm -3 Reverse shock: T=0.9 x 10 7 K, Density= 2 x 10 6 cm -3

Presence of a cool shell Presence of a cool shell between the forward and the reverse shock responsible for excessive absorption of the X-rays. N H α Mass loss rate N H ~ 1.5 x cm -2 If reverse shock is in He layers close to C-O boundary (Fransson et al. 2002), then this implies reverse shock mass of ~0.002M-0.8M .

SN 2006X, Patat, Chandra, P. et al and 2007, Science In Virgo cluster spiral Galaxy M100 Feb 4, 2006, 70 million light years away Type Ia supernova

Type Ia supernova (Thermonuclear supernova) True nature of progenitor star system? What serves as a companion star? How to detect signatures of the binary system? Single degenerate or double degenerate system? Type Ia supernova (Thermonuclear supernova) True nature of progenitor star system? What serves as a companion star? How to detect signatures of the binary system? Single degenerate or double degenerate system? SN 2006X- Nature of progenitor?

How to investigate? Search for signatures of the material tranferred to the accreting white dwarf. Narrow emission lines Radio emission X-ray emission Till date no detection. ABSORPTION OF THE RADIATIONS COMING FROM SUPERNOVA DUE TO THE CIRCUMSTELLAR MEDIUM SURROUNDING SUPERNOVA. How to investigate? Search for signatures of the material tranferred to the accreting white dwarf. Narrow emission lines Radio emission X-ray emission Till date no detection. ABSORPTION OF THE RADIATIONS COMING FROM SUPERNOVA DUE TO THE CIRCUMSTELLAR MEDIUM SURROUNDING SUPERNOVA.

Observations of SN 2006X: Observations with 8.2m VLT on day -2, +14, +61, +121 Observations with Keck on day +105 Observations with VLA on day ∼ 400 (Chandra et al. ATel 2007). Observations with VLA on day ∼ 2 (Stockdale, ATel 729, 2006). Observations with ChandraXO on day ∼ 10 (Immler, ATel 751, 2006).

Na I D 2 line

Na vs Ca

RESULTS Variability not due to line-of-sight geometric effects. Associated with the progenitor system. Ionization timescale τ i < Recombination timescale τ r. Increase in ionization fraction till maximum light. Recombination starts, t s. Variability not due to line-of-sight geometric effects. Associated with the progenitor system. Ionization timescale τ i < Recombination timescale τ r. Increase in ionization fraction till maximum light. Recombination starts, t s.

Results Estimate of Na I ionizing UV flux: S UV ∼ 5 × photons s − 1 This flux can ionize Na I up to r i ∼ cm. This and recombination time scale of ~10 days implies n e ∼ 10 5 cm − 3 ( ONLY PARTIALLY IONIZED HYDROGEN CAN PRODUCE SUCH HIGH NUMBER DENSITY OF ELECTRONS ) Confinement: r H ≈ cm When all Na II recombined, no evolution. Agree with results. Estimate of Na I ionizing UV flux: S UV ∼ 5 × photons s − 1 This flux can ionize Na I up to r i ∼ cm. This and recombination time scale of ~10 days implies n e ∼ 10 5 cm − 3 ( ONLY PARTIALLY IONIZED HYDROGEN CAN PRODUCE SUCH HIGH NUMBER DENSITY OF ELECTRONS ) Confinement: r H ≈ cm When all Na II recombined, no evolution. Agree with results.

Mass estimation

CSM expansion velocity ∼ 50 − 100 km s − 1. For R ∼ cm, material ejected ∼ 50 year before! Double-degenerate system not possible. Not enough mass. Single degenerate. Favorable. Not main sequence stars or compact Helium stars. High velocity required. Compatible with Early red giant phase stars. CSM expansion velocity ∼ 50 − 100 km s − 1. For R ∼ cm, material ejected ∼ 50 year before! Double-degenerate system not possible. Not enough mass. Single degenerate. Favorable. Not main sequence stars or compact Helium stars. High velocity required. Compatible with Early red giant phase stars. Nature of the progenitor star