Optical study of type II event SN 2008gz

Many Faces of GRB Phenomena- Optics vs High EnergyOctober 12 – 16, 2009

SAO, RAS, Russia

Rupak Roy

Aryabhatta Research Institute of Observational Sciences (ARIES) Nainital, India

Locations of Indian Optical Facilities

Starting from IAO, Hanle (Latitude : 32d 46m 46s N, Longitude : 78d 57m 51s E)

Up-to VBO, Kavalor (Latitude : 12d 34m N, Longitude : 78d 50m E)

More than 50 GRB fields since 1999

More than 30 optical afterglows

Earliest optical Observations GRB 000301C GRB 020405 GRB 060124

Recently observed GRB afterglows GRB 090424 GRB 080430 GRB 071010A GRB 071003

Observations of Transient Events From ARIES

More than 15 SNe have been monitored.

ARIES(~ 29d N, 79d E)

Chevalier

Discovered on 5th November 2008, in the spiral galaxy NGC 3672.

We have carried out optical broadband (BVRI) photometric and low resolution spectroscopic observations of this event since 10th November 2008.

Host Galaxy Information (From NASA/IPAC Extragalactic Database) :

Nomenclature : NGC 3672

Coordinate (J2000) : = 11h 25m 02.5s

= -

09d 47m 43s

Radial Velocity : 1862 4 km/s

Redshift : 0.006211 0.000013

Luminosity Distance : 30.8 Mpc

SN 2008gz

SN 2008gzPhotometric Observations were mainly

carried out from 1.04-m ST, Nainital

Spectroscopic Observations were

performedfrom 2.00-m IGO, Pune,

Observations from India

1.04-m, ST, ARIES2.00-m, IGO, Girawali

3.58-m NTT, La Silla 6-m BTA, SAO

0.61-m, Perth-Lowell

3.58-m TNG, La Palma

Over The Globe

SN 2008gz SN 2007bm

Template Subtraction : Measurement of true flux

After Template Subtraction

According to Benetti et al, 2008 (CBET 1568 ), SN 2008gz was discovered nearly 62 days after Burst.

We compare the BVRI light curves of SN 2008gz with type IIP SN 2004et under the constrain imposed through spectroscopy and found it as a type IIP SN, which just completed its Plateau phase

Optical Light Curve

Bolometric Light Curve & Ni mass estimation

BVRI Bolometric Light Curve is derived for this SN over the span of observation and compared with that of two well studied type II events SN2004et & SN1987A. BVRI Bolometric Luminosity for SN 2008gz is ~ 3.1 x 1048 ergs : similar to SN 2004et & SN 1987A

Estimated Ni mass ejected over the time span (following Hamuy, 2003) is around 0.05 M_sun. This is well inside the range specified by Hamuy, 2003. (between 0.0016 and 0.26 M_sun).

Contributions from different bands

+62 day

+90 day

+115 day

+146 day+207 day

Spectroscopic Observations of SN 2008gz

+250 day

SYNOW modelling of spectrum

From 1st Spectrum, Benetti, et al. (CBET 1568) determined the velocity of expanding photosphere near about 6600 km/sec. This velocity is comparable with that of well studied type IIp (like SN 2004et) at the end of its plateau. They determined this velocitythrough the tool GELATO.

The SYNOW modelling of 2nd and 3rd spectra shows that the velocity of photosphere around 100 days after the burst is ~ 4000 km/sec, which is the typical velocity of photosphere at very beginning of nebular phase. Minimum velocity of the shell where lines are formed is ~ 3,500 km/sec.

The best fit of the model correspond to effective black body temperature of the photosphere ~ 4000 K.

08.12.2008

11.11.2008

02.02.2009 03.04.2009

17.05.2009

Late time Spectra

Velocity Profile

Host Galaxy Spectrum

Spectrum-090201 IGO, Pune, India

Comparison with Other Galaxy Spectrum

Nature of Host Galaxy

NGC 3672 is plausibly a spiral galaxy of type Sb.

NGC 3672 is at a redshift ~ 0.006172 which corresponds to the luminosity distance ~ 26.2 Mpc

Preliminary Results The event was discovered nearly two months after the explosion

Comparison of photometric and spectroscopic characteristic of this event with other type II events suggests that this event is of type IIP.

The event was as energetic as type IIP event SN 2004et and SN

1987A.

The region of the envelope producing H_alpha emission moves much faster than the regions which contain heavy elements and attached with the photosphere. So, probably the outer shell producing H_alpha is detached from the shells containing higher elements like iron and other.