Photometric analysis ofSupernovae 2008gj

By- Rakesh Bisht

Collaborators Komal Kabara ( S.R.T.M University Nanden, Chennai) ManiKandan K. ( Bombay University)

CONTENTS

INTRODUCTIONSUPERNOVAE FORMATIONSNe TYPESARIES TELESCOPES CCDsPHOTOMETRYRESULT

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What is a supernova ?

Stars which undergo a tremendous explosion, or sudden brightening. During this time their luminosity becomes comparable to that of the entire galaxy (which can be ~1011 stars)

SN1998bu in M96: left DSS reference image (made by O.Trondal), right BVI colour image from 0.9m at CTIO (N. Suntzeff)

Supernovae

In the 1930’s supernovae were recognised as a separate class of objects to novae (meaning new stars).

These are violent explosions in universe, releasing enormous amount of energy (1051 erg).

• Supernovae outbursts last for short periods: typically months to a few years.

• Typical galaxies like the Milky Way appear to have a rate of 1-2 SNe per 100 years.

• But as they are extremely bright - even small telescopes can detect the, a large cosmic distances.

• Historical accounts of supernovae in our galaxy are coincident with supernovae remnants now visible.

Pathways of Stellar Evolution

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Supernovae in the Milky Way

European and far eastern written records of the following Galactic events:

Supernova Remnant Year Peak Visual mag

CasA 1680 ?

Kepler 1604 -3

Tycho 1572 -4

3C58 1181 -1

Crab 1054 -4

SN1006 1006 -9

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The Crab nebula - optical (red) and X-ray (lilac) composite Death of a massive star

Tycho’s supernova remnant in X-raysExplosion of a white dwarf

Coordinate Systems

There are at least 5 types of spherical coordinate systems that Are commonly used in astronomy. 1) Horizon Coordinates (altitude-azimuth): defined by the place And time of observation (a, A) 2) Equatorial Coordinates (right ascension – declination): defined by the Earth’s rotation axis (α, δ) 3) Ecliptic Coordinates: defined by Earth’s ecliptic plane (λ, β) 4) Galactic Coordinates: defined by the plane of the Milky Way (ℓ, b)

5) Supergalactic Coordinates: defined by the large scale structure

Of the local universe (L, B)

Equatorial Coordinate System

The Equatorial System

An object’s declination (δ) is equivalent to its latitude: +90° is over the north pole, -90° is over the south pole, and 0° is over the equator.

Right ascension (α) is equivalent to longitude, but is measured over 24 hours, rather than 360°.

The zero point of right ascension is the location of the Sun on the vernal equinox, i.e., the intersection of the ecliptic plane with the celestial equator, on the side where the Sun is ascending from the south to the north.

Type I: White dwarf supernova

White dwarf near 1.4 Msun accretes matter from red giant companion, causing supernova explosion.

Type II: Massive star supernova

Massive star builds up 1.4 Msun core and collapses into a neutron star, gravitational PE released in explosion.

Classification of SNe

Classification of SNe

On basis of light curve and spectra they are mainly grouped in two classes (Type I & II). Type-I: No hydrogen, further classified as Ia, Ib & Ic

In Ia-silicon present (thermonuclear), In Ib He is present & Ic less silicon is present (core collapse).

Type-II: Yes –Hydrogen, (core collapse).

Type II supernovae are created by the deaths of massive stars.

1.04 m SAMPURNANAND TELESCOPE

The 104 c.m.(40 –inch telescope) ST-optical telescope located at Manora peak, Nainital .

It was installed in 1972 by Carl Zeiss, Germany.

Observatory- Aryabhatta Research Institute of Observational Sciences (ARIES)

Location: Manora Peak Nanital

Latitude: +29035’(North) Longitude: +280054’(East) Altitude: 1951m Primary diameter- 104 c.m.

Primary focal length - 416(f/4) c.m.

Effective focal length - 1330(f/13) c.m.  Filter - UVBRI       

CHARGE COUPLED DEVICES (CCDs)

A CCD is most simply described as an electronic photon detector.

When photon hit the detector surface of the CCD sensor, electrons are Liberated and stored in the detector element are pixel.

Motive

Stellar Object Telescope CCD Software

Raw Image

Learning Data AnalysisFor this we select an object called SN2008gjwhich has been determined as a supernovae type Ic.

It has been observed from 104-cm “Sampurnand” Telescope at ARIES, Nainital using 2k X 2k CCD in the ‘V’ , ‘I’ filter for several nights.

Image processing

1. Preprocessing -Master bias -Flat fielding -Flat bias combining -Cosmic rays removal We get cleaned image.

2. Photometry -Align -Combine -Photometry

WHAT WE HAVE TO DO ?

The raw images from the telescope have been “bias subtracted” and “flat fielded” using the ZEROCOMBINE, FLATCOMBINE and CCDPROC tasks in IRAF.

They have also been corrected for any presence of cosmic rays using the COSMICRAYS task in the package CRUTIL.

FOR MASTER BIAS

Bias Correction (MASTER BIAS )

Flat fielding

To subtract master bias from all flat frames

FLAT FRAME

Bias corrected and Flat fielded frame

For removing cosmic rays

After this we get a image which is clean image:

For alignment & photometry• Differential Photometry has been performed after image alignment and image combine. • Digiphot ---> Apphot ----> epar center• Imalign• Imcombine ------> Final image (for photometry)•Photometry•Imexam ---> fwhm, sigma (sky)•For photometry we selected 4 stars including SN.•Digiphot ---> Daophot -

FINAL IMAGE OF SN2008gj

Light curve

Thank You !