Study of the type IIP supernova 2008gz

Roy et al. 2011, MNRAS accepted

Supernovae: Catastrophic cosmic explosions

Energy released ~10^46 J

Responsible for chemical enrichment of galaxies

Trigger new star formation

SNe link to neutron stars, black holes, GRBs, …..

Progenitors & Process

1. White dwarf binary: thermonuclear

Accretion

Chandrasekhar limit

Explosion

Image: scienceblogs.com

Progenitors & Process

2. Massive stars: Core collapse

Star >10M_sun

Iron core - Chandrasekhar limit

Radiation pressure reduces

Gravitational core collapse

Remnant: neutron star, black hole

Image: smithsonianscience.com

Supernova family (spectra and light curve) Type I Type II

Ia Silicon lines

no Hydrogen Ib no Si but rich He

Ic no Si, poor/or no He

Ibc_pec (no H but unusual LC and spectra)

IIP, show plateau in the light curve

with Hydrogen IIL, linear decay of light curve

IIn, narrow emission lines

IIb, early time dominant H (like II)

But later similar to Ib

Image: astro.rug.nl SNe light curves

Supernovae family: (early spectra and light curve)

SN type I > 55%

SN type II ~ 41%

Core collapse SNe

Ib, Ic, Ibc_pec,

IIL, IIP, IIb, IIn

Smith, N. et al. 2010

Type IIP SNe show variation in their luminosity, velocity and Ni production.

Supernova 2008gz

Host: Spiral galaxy NGC 3672

Explosion date (UT): 5.83 Nov 2008

RΑ (J2000): 11h 25m 3s

DEC (J2000): -09º 47' 51''

Observations:

BVRI data

1m, ST ARIES, India

2m, IGO IUCAA, India

3.6m, NTT ESO, Chile

Spectra

2m, IUCAA

3.5m, TNG

3.6m, NTT

6m, SAO Russia

Light curve in BVRI magnitudes

+87d to +275d since explosion

SN detected very close to end

of plateau phase

Time of inflection 115± 5 days

Bolometric light curve

Nebular phase governed by radioactive decay of Ni to Co to Fe

=> tail luminosity is proportional to Ni synthesized.

(Arnett 1980, 1996)

Derived tail luminosity

= 1.51± 0.29 * 10^41 erg/s

Comparison of absolute V mag to other IIP SNe

Unusual V dropping ~1.5mag

during plateau to nebular phase

SN 2008gz spectra (late plateau to deep nebular )

Late plateau

Nebular

Late nebular

Velocity profile of different elements

Photospheric velocity is a good indicator of explosion energy

(Dessart et al. 2010)

=>SN 2008gz has explosion energy 2.3*10^51erg similar to SN2004et

Summary Photometric and spectral nature of this event is similar to

normal type IIP SNe 2004et and 1999em. The plateau phase lasted about 115±5 days.

Photospheric velocity ~ 4000 km/s at similar epoch comparable to SN 2004et.

Explosion energy 2-3 * 10^51 erg/s. SN 2008gz exhibits rarely observed drop of 1.5 mag in V,

within 30 days from plateau to nebular phase. Synthesized Ni during the explosion 0.05± 0.01 M_sun.