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 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.