Supernova study with BATC Sky Survey Wang Xiao-feng Physics Department and Tsinghua Center for Astrophysics, Tsinghua University 2005, 8, 12, Weihai

What is supernova SN in M51! (SN 2005cs) Stellar explosion with giant energy release Supernovae might be the brightest objects in the universe, and can outshine a whole galaxy (for a few weeks) One of the endpoints of stellar evolution Energy of the visible explosion~10 51 ergs Luminosity~ L ⊙

To measure the universe with supernovae Extremely bright stellar explosions Important for the production of the heavy elements Best distance indicators in the universe The only reliable way of determining extragalactic distances is through supernova investigations. F. Zwicky

Supernovae Big Bang Stars Supernovae

Type II (core-collapse) supernovae H He C O Si Fe Non- burning H Massive star: Fe is fusion endpoint electron capture  pressure drop collapse density increases core bounces back shockwave  heating  expansion

core collapse supernova mechanism Fe core inner core pre SN star 1. infalling outer core outgoing shock from rebounce proto neutron star 2. infalling outer core proto neutron star stalled shock 3. revived shock proto neutron star matter flow gets reversed - explosion 4. neutrinos neutrino heated layer

Type Ia supernovae white dwarf in binary stellar system high H accretion rates growing C/O white dwarf ~Chandrasekhar mass (1.4 M solar )  contraction high central density  C fusion thermonuclear explosion

SN Ia Differences SN Ia are not all the same. Variations occur in their light curves and spectra.

SN Ia correlations Phillips relation or  m 15 relation

Luminosity and Light Curve shape  m15 relation Phillips (1993), Hamuy et al. (1996), Phillips et al. (1999) MLCS Riess et al. (1996, 1998), Jha et al. (2003) Stretch Perlmutter et al. (1997, 1999), Goldhaber et al. (2001)

Nearby SN Ia sample Evidence for good distances –distance accuracy around 10%

Wang et al 2005a More precise cosmology- A Novel Color Parameter Wang et al 2005a

SN Luminosity vs.  C 12

Precise Hubble diagram of SNe Ia (Wang et al. 2005c, ApJ, submitted)

The discovery of supernovae 2004 年底已发现 3031 颗 /year since 1998

Multicolor SN study with BATC Sky Survey Multicolor photometry of bright supernovae(Ia, II, Ib, Ic) SN 1993J: Circumstellar Interaction around SN 1993J(Wang et al. 2004a) Late-time photometry of SN 1993J -- heroic observation compaign (Zhang, Wang, Zhou et al. AJ, 2004, 128, 1857) SN 2004dj: Progenitor and Light curves (Wang et al. 2005b; Zhang, Wang, Zhou et al. 2005) SN 2004et: An atypical type II supernpovae in NGC 6946 (in preparation) SN 2005cs in M51 (on minitoring) Ia: SNe 2002er, 2002fk, 2003kf, 2003cg (Wang et al. 2004b) SN survey plan in Nearby clusters of galaxies interrupted but contributes to BATC’s image reduction

Progenitor identifications SN Ia ?? SN II (SN 1987A, SN 1993J, SN 2003gd) To confirm stellar evolution models and SN theories Smart et al (2004,Science)

Progenitor of SN 2004dj in NGC 2403 SN Position: R.A. = 7h 37m 17.02s, Decl. = +65 。 35 ’ 57 ”.8 offset from the nucleus of NGC 2403: E160 ” and N10 ” Discovery epoch: July UT NGC 2403: R.A. = 7h 36m54s, Decl. = +65 。 35 ’ 8” Type: Scd 20’X20’ in the sky m-M = mag D=3.2Mpc

Spectrum of SN 2004dj

Progenitors for Type II-P Supernovae Theory predicts: SNe II P arise from the core collapse of red supergiant with initial masses > 8Msun Observations for II P: SN 1987A -- blue supergiant ~25Msun SN 2003gd -- red supergiant~8- 9Msun (Smartt et al. 2004) SN 2004et -- yellow supergiant~15Msun? (Li et al. 2005) SN 2004dj…?

BATC Images of Pre- and post-explosion of SN 2004dj Pre- and post-explosion images of SN 2004dj by 60/90cm Schmidt telescope of NAOC

Positional Coincidence of the Supernova Position of SN 2004dj at difference wavelengths optical: R.A. = 7h 37m 17.01s, Decl. = +65 。 35 ’ 58 ” X-ray: R.A. = 7h 37m 17.05s, Decl. = +65 。 35 ’ 57 ”.9 Radio: R.A. = 7h 37m 16.92s, Decl. = +65 。 35 ’ 56 ”.97 Position of ‘star’96 (Sandage 1984) R.A. = 7h 37m 16.96s, Decl. = +65 。 35 ’ 58 ”.2 SN 2004dj coincides with ‘star’ 96 to within 0.”7

The light variation of star96?

Stellar population of Star96 Stellar model: the spectral flux library (Pickles 1998, PASP) Cluster model: a simple stellar population of Galaxy Isochrone Synthesis spectra Evolution library (Bruzual & Charlot 2003) To test with Chi-square minimization

Reddening and Metallicity Reddening Na ID interstellar absorption lines can provide clues to the line-of-sight reddening E(B – V) ~ EW: large uncertainty! As a fitting parameter along with the T or log t Metallicity Garnett et al. (1997) measured the metallity and its radial distribution in NGC 2403 log(O/H)+12 ~8.45 Z~0.008

Fitting results for single star A highly reddened E(B-V)=0.78 B2IV star  2 =24 for 14 BATC points. Reasons why this fit does not work S96: 1) the corrected intrinsic B – V color is too blue to be consistent with a B-type star; 2) Such an extremely blue and bright star is most likely to be a luminous blue variable, but it did not show significant light variations on a time scale of few years; 3) The high reddening would imply an unrealistic high luminosity for a SN 2004dj as a type II-P SN.

Fitting results for clusters

Wang et al 2005c, ApJ, 626, L89

Optical Photometry of type II-P SN 2004dj (Zhang, Wang, & Zhou et al. 2005)

Color Evolution of SN 2004dj comparison with SN 1999em

Explosion date of SN 2004dj ~ 60 days after explosion

SED of SN 2004dj

Bolometric light curve of SN 2004dj M(Ni56)~0.02Msun

The Explosion Parameters of SN 2004dj Litvinova & Nadyozhin (1985) calculated a grid of supernova models for E, M and R for SN II P. Mv(plateau) = mag (our light curves) Δt = 80 days (comparison with SN 1999em) Vp = 3900 km/s (Patat etal. 2004) M ej,, E, R 10Msun 0.7X10^51ergs 265Rsun Zhang, Wang, Zhou et al. 2005, AJ, submitted

Future SN work Publishing a series of multicolor light curve data obtained by BATC observations (~20 SNe Ia) Late-time photometry of some bright SNe II,Ib,Ic Simultaneous observations of some bright SNe (TNT UBVRI+BATC intermediate-band filters) Progenitor work