A reddening-free method to
estimate the 56Ni mass of Type
Ia supernovae
Suhail Dhawan (ESO)
Supervisor: Bruno Leibundgut
Collaborators: J. Spyromilio (ESO),
S. Blondin (LAM, Marseille)
Outline
•
•
•
•
Motivation for the study
NIR diversity at late times
Results
Interpretation
Motivation
• 56Ni drives intrinsic brightness
• Find a reddening independent
parameter
• Test correlation with 56Ni mass
• Apply to a sample of SN Ia
• Distinguish explosion scenarios
NIR light curves
Well Sampled
SNe
Visible increase
of scatter with
phase
Uniform late
decline
Fig: Objects with well
Sampled NIR light curves
from the CSP
Correlation with optical
properties
• Strong
correlation
• Seen,
previously in
i-band
(Hamuy et al.
1996, Folatelli
et al. 2010)
• Scatter ~2
days Y, J; ~3
Fig: t (YJH) versus m15 in
inetH
bandsdays
(Dhawan
al. 2015)
2
Emerging Physical Picture
• Ionization
transition
• Increased
NIR
emissivity
• t2 depends
on
synthesized
nickel mass
Fig: Model light curves
for different
radioactive nickel
How
56
Ni mass has been
measured
• Luminosity at
peak ==
instantaneous
rate of deposition
from decay
• Requires distance
and reddening
correction
Figure: Bolometric light curves
from Scalzo et al. [2014]
Correlation with t2
• Low reddening SNe
• Ultraviolet to NIR
flux
• Peak corresponds to
Nickel synthesized
(Arnett 1982)
• Bolometric
luminosity
correlates with t2
Fig: Bolometric luminosity versus
timing of second maximum
56
Ni mass estimates
• Comparing rise
time
assumptions
• Inferred from
model
relations
• Errors ~ 0.15
solar mass
• Differences
Figure: comparison of Ni mass estimates for
well
within
different
assumptions
on the rise time (Dhawan
56
SN2014J: Inferring Nickel
Mass
• Use t2 to get Lmax
• Derive Nickel mass
(Arnett’s rule)
Fig: SN2014J in M82.(ref: astrobob) Table: Different estimates for nickel
mass (Dhawan et al. 2016)
Comparison for reddened
SN Ia
•
Ni mass for SN2014J 0.60 +/- 0.12
solar mass
• Estimated value for SN2006X from
Wang+2008 of 0.5 +/- 0.05 solar
mass
56
Inferred 56Ni mass
distribution
•
Ni mass
range from ~
0.25 – 0.75
solar mass
• Peaks at 0.50.6 solar mass
• Doesn’t include
91bg-like SN Ia
Figure: The resulting distribution
56
for Lmax and
Ni mass
56
Super-Chandra SN Ia
• Very bright at
peak
• NIR t2 ~ 32d
• Implied 56Ni
mass ~ 0.65 –
0.8 solar
mass
• Implies
possibly
additional
energy source
Figure: Filtered light curves (left) and bolometric light curve (right) of
super-Chandra SN 2007if (Scalzo et al. 2010). t0 is the transparency
Distinguishing Explosion
Scenarios
• RM = Mej/MNi
• Compare with
model prediction
• MNi can be
reddening
independent
• Shorter rise for fast
decliners
• Fast-declining SNe
appear distinct
Conclusions
• t2 correlates with 56Ni mass
• Relation independent of reddening
• Compares well with independent
methods
• Factor of ~ 3 variation in 56Ni mass
• Super-Chandra SN 56Ni < 1 solar
mass
Why is
56
Ni important?
– Abundant radioactive
isotope
– Main energy source
– Drives observed
diversity
– Distinguishing model
scenarios
– Correlations important
for cosmology
Figure: Artist’s
impression of
progenitor scenarios
for SN Ia
The Promise of the NIR
• Lower dust
extinction
• Uniform peak
luminosity ~
0.15 mag
• Weak
dependence on
m15. No
correction
needed
Fig: peak magnitude versus
m15(Krisciunas et al. [2009])
Calibrate Peak Luminosity
Fig: (Left) Corrections
after applying the
Phillips relation
• Reduced scatter =>
better cosmology
• Width-luminosity
relation(Phillips 1993)
Fig: (left) CTIO/CfA SN sample. (Top): Decline rate
parameter (M.Phillips circa 1995 )
Nickel Mass Studies
• Well-observed SNe
• Studies require reddening correction
• Large diversity in Nickel mass values
Lira law epoch
• Uniform late
colour
evolution
• Optically faint
objects redden
earlier
• Models show
early Fe/Co
line
appearance
(Kasen
& for
Fig: B-V
colour curves
objects
Woosley 2007)
observed in CSP (Folatelli et
Relation to NIR second
maximum
• tL correlates
with t2
• Y, J identical
• H: 3 days
earlier
Fig:t2 versus t, the
epoch of entering
constant colour
evolution (Dhawan et
Correlation with NIR
properties
• Low
reddening
SNe
• Ultraviolet
to NIR flux
• Correlates
with t2
Fig: (Left): Bolometric luminosity
versus timing of second maximum
(Dhawan et al. 2016). (Right): NIR
light curves showing t2 (Dhawan et
Nickel Mass Distribution
• Range of 56Ni mass
• Estimated from t2
Fig:
Distribution
of Ni mass
from t2
(Dhawan et
al.
submitted)
This Study
• Y (1  m) J (1.2  m ) H (1.6  m) light
curves
• Near-maximum properties
• Late-time behaviour
• Based on literature data
• Mostly Carnegie Supernova Project
(CSP) data
– Dedicated NIR follow-up
– Observations at late epochs
– Uniform photometric system
Outline
• Background on Type Ia supernovae
(SNIa)
• Advantage of Near Infrared (NIR)
wavelengths
• Describe the study
• Results
• Interpretation
Complete sample
• Uniform at first
peak
• Uniform near
minimum
• Diverse at late
phases
Fig: light curves for the SN in
our sample. CSP objects are
in blue and non-CSP objects
in green. (plotted J band only
for visibility)
Timing parameters
t1 (~1d )
t0 (~2.5d)
t2 (~5d)
Late Decline
•
•
Slope between
+40 and +90 days
Late Decline
uniform
Top:  ray escape fraction (Woosley et
al. 2007)
Right: Late time decline rates for SNIa
Comparison of late time
properties
• Y brightest;
followed by
H and J
• Strong
correlation
(Far right): M|55 versus
t2 in YJH bands.
(Right): Light curves
showing M|55
Conclusions
•
•
•
•
Confirm low luminosity scatter
Diverse second maximum
Uniform late decline slope
Nickel mass driving optical/NIR
appearance of SNIa
(t2, m15, tL, M|55)
Fig: Matrix
representing
important
correlations
Studies so far
• Scatter of peak
luminosity < 0.2
mag
• Large, uniform
samples
• Distances to <
6% (Kattner et
al. 2012)
Fig: H band peak distribution for
different samples (Weyant et al.
IR correlations
• Weak trend
between t0
and t2
• Trend
between M0
and M2
• Strong interfilter
correlations
Fig:t2 and M2 in
different IR filters
M2 versus m15
in YJH bands
Improving Distances Further
• Colour correlations (Tripp 1998)
• Spectral features (Wang et al. 2009,
Bailey et al. 2009, Blondin et al.
2011)
• Host galaxy properties (Sullivan et al.
2006, 2010)
• Others: Late decline rate (Wang et al.
2008)
• Scatter ~ 0.15 mag (reduced from
~0.5 mag)
The Connection
Improved Distances?
• Uniformity in first peak
• Weak correlation with
t2
• Only slight
improvement in J and
H, none in Y
Fig: M1 versus t2 in YJH bands. (Top):
Table with scatter values for the
Infrared Colours
• Interpolat
ed with
SN(oo)Py
• Uniform
near first
max
• Trough in
J-H
Fig: IR colour
curves (left) Y-J
(right) J-H