12 3-2014 atsoa.ppt

Photometric analysis of
Supernovae 2008gj
By- Rakesh Bisht
Collaborators
Komal Kabara ( S.R.T.M University Nanden, Chennai)
ManiKandan K. ( Bombay University)

CONTENTS
INTRODUCTION
SUPERNOVAE FORMATION
SNe TYPES
ARIES TELESCOPES
CCDs
PHOTOMETRY
RESULT

3
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.

7
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

8
The Crab nebula - optical (red)
and X-ray (lilac) composite
Death of a massive star
Tycho’s supernova remnant in X-
rays
Explosion 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)

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.

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

Learning Data Analysis
For this we select an object called SN2008gj
which 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.

Bias Correction (MASTER BIAS )

To subtract master bias from all flat frames

Bias corrected and Flat fielded frame

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 -

12 3-2014 atsoa.ppt

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12 3-2014 atsoa.ppt