Dipartimento di Astronomia, Università degli Studi di Padova
INAF – Osservatorio Astronomico di Padova
Studio fotometrico e spettroscopico di
SN 1994Z, rara supernova IIP dal
plateau brillante
Irene Agnoletto
Geremeas (CA), 20-26 maggio 2007
Modern classification
Turatto, 2003
Geremeas, 22 maggio 2007
2
Core collapse supernovae:
basic properties

originate from the energy liberated by the gravitational collapse
of the nucleus of massive stars (> 8 M  )

show H (typeII), He (except for type Ic), Ca, O, Mg, Fe

from small to huge radio to X-ray emissions

leave collapsed remnant (NS or BH)

emit neutrinos and gravitational waves

occur only in late type galaxies and are associated with star
forming regions

are very heterogeneous: large spread in luminosity, ejected Ni
masses, light curves evolution…
Geremeas, 22 maggio 2007

3
Presentation

Discovered on October,
2.51 UT in the irregular
galaxy NGC 87 (Wassilief, IAUC
n. 6087)

NGC 87
First mag. estimation:
V ~ 16, (B-V)~0.1 (on
October 4th, by P. Philips at CTIO)

SN 1994Z
Spectra analysis =>
typical features of a
II-P SN 2-3 weeks after
explosion (on October 4th, by S.
Benetti and G. Hasinger on ESO 2.2m
telescope spectra)
Geremeas, 22 maggio 2007
RA 00h,21m,16.6s
DEC -48d,37m,49s
H vel 3546
4
Dataset
~ 500 days photometric coverage
~ 380 days spectroscopic coverage
Geremeas, 22 maggio 2007
5
Basic Estimates for Photometry




Milky Way Reddening: AB,MW=0.084 (Schlegel et al. 1998)
AB,pg=0 No Host Galaxy reddening (no NaID, Turatto et al. 2003)
Distance through Hubble’s law
vinfall=3371km/s (LEDA), H0=72±4 km/s/Mpc
d= 46.81 Mpc
= 33.35
(Freedman, 2001):
Explosion Date through comparison with similar objects:
Dexpl=13 September 1994
Geremeas, 22 maggio 2007
6
Photometric data reduction
and results



Both aperture and PSF photometry
with SNOoPY (Cappellaro & Patat)
Calibration through Landolt (1992)
standard stars
Calibration of SN in not photometric
nights through local sequence stars
Geremeas, 22 maggio 2007
7
Plateau luminosity not perfectly
constant for V, R, I bands
V=1.07mag/100d
Geremeas, 22 maggio 2007
8
Absolute UBVRI light curves
For comparison:
U
B
V
R
I
Geremeas, 22 maggio 2007
9
Absolute magnitudes



Mmax,B ≤ -17.29
<M>V,plat.~ -17.05,
<M>R,plat.~ -17.32,
<M>I,plat.~ -17.62
Similar evolution to SN 1996W and
SN 1992H (photosferic phase) but …
standard luminosity tail!!
Geremeas, 22 maggio 2007
94Z
96W
92H
V band
96W
92H
87A
69L
94Z
V band
10
Colour…
M(56Ni)~0.07 M
(as for SN 1987A!)

SN 2004et
…And
bolometric
light curve
Geremeas, 22 maggio 2007
Pastorello (private communication)
11
Photosferic phase
Spectroscopy
ScII
H FeII FeII ScII NaID
FeII
H
CaII]
[FeII]
Nebular phase



Tcont~6200K
procedure
vph~2300km/s
Standard IRAF reduction
Wavelength calibration through HeNe or HeAr
lamps spectra
CaII-IR
H
SN flux
calibration through instrument sensitivity
H
functions
Tcont~13000K
HeI
vph~9000km/s
RESULT: THE WHOLE SPECTROSCOPIC
EVOLUTION IS…
H



CaII]
[OI]
Geremeas, 22 maggio 2007
12
Comparisons:
SN 1992H
…therefore:
H Velocity
Geremeas, 22 maggio 2007
Similar kinematics
and structure of the
nebulae
13
But…
H line luminosity
OI line luminosity
6300-6364
Different line luminosities
Different Envelope masses,
less massive for 94Z CaII line luminosity
7291-7332
Less massive progenitor for SN 1994Z!
MHenv ~10M 
Geremeas, 22 maggio 2007
14
Modelling


Comparison between obervational
data (light curves, evolution of the line
velocity and continuum temperature) and
numerical simulations (Zampieri et al. 2003)
Automatic data fitting
initial radius of the envelope
envelope mass
ejected 56Ni mass
velocity of the env. at the outer shell
explosion energy
luminosity at recombination

Output parameters:
Geremeas, 22 maggio 2007
15
Best fit
Progenitor mass: ~9.5M 
Geremeas, 22 maggio 2007
16
Correlation among II-P SNe
physical parameters
See Hamuy et al (2003)
Zampieri et al (2003)
Zampieri (2006)
Geremeas, 22 maggio 2007
17
Conclusions:


SN 1994Z belongs to the poor populated class of bright IIP SNe
Similar to SN 1996W and SN 1992H in brightness and
kinematics at first stages, but with smaller amount of 56Ni
ejected (maybe because of fallback??)

No evidence of Luminosity-Ni mass correlation!! (Hamuy, 2003)

High luminosity IIP supernovae can be associated with low mass
progenitors

Standard physical parameters except for velocity

progenitor mass of ~9.5M  => consistent with the recent
progenitor identifications!! (see Li et al., 2006 for SN 2005cs, Li et al., 2005b for
SN 2004et, Hendry & Smartt 2006 for SN 2004A);
Geremeas, 22 maggio 2007
18
Geremeas, 22 maggio 2007
19
Observational data
 physical parameters (progenitor mass and
radius, energetics and velocity of the
explosion etc.)  nature, evolution
Bright II-P supernovae are rare
 More information are important, more data
are necessary!
Geremeas, 22 maggio 2007
20
Geremeas, 22 maggio 2007
21
Geremeas, 22 maggio 2007
22
Geremeas, 22 maggio 2007
23
Geremeas, 22 maggio 2007
24