X-ray & radio observations of type II
Plateau SNe & Equipartition Factors
Alak Ray
Tata Institute of Fundamental Research, Mumbai, India
with Naveen Yadav, Sayan Chakraborti, Randall Smith, Keiichi Maeda (Kyoto Univ!) et al
Submitted 2013, N. Yadav et al+ 2013, 2012 ApJ, S. Chakraborti et al

November 6, 2013, Long Term Program On SNe & GRBs, Yukawa Institute For Theoretical Physics, Kyoto University
1

Ongoing Program
to observe type II
Plateau type SN
with Chandra and EVLA & GMRT thatprobes X-ray and radio bands (high and lowfrequencies) to detect the nature of thermal
and non thermal radiation from SNIIP
Examples: SN 2004dj, SN 2011ja, SN 2012aw, SN 2013ej

Images courtesy of:
Chandra X-ray Observatory; NRAO/AUI & GMRT/NCRA-TIFR

2

Radio and X-ray nearcontemporaneous observations✤Can constrain equipartition
factors εB & εe within a narrow
range.

✤Since IC requires γmin ~ 30-100,
for X-ray band this allows thedetermination of εe.

✤If X-ray bright objects (e.g. SN2004dj) can be detected andfollowed, we may quantify theInverse Compton (IC) vsthermal emission mechanisms✤

For thermal X-ray emission, Xray observations can constrain
mass loss rate in wind set up by
the progenitor star.

✤From the mass loss rate, withthe help of model evolution ofstars, can constrain theprogenitor star mass main seq.

✤If IC is detected then εeγmin aredetermined by comparing Xray and OIR luminosities

3How are Supernovae
distributed amongdifferent types?
Nathan Smith et al, MNRAS 2011✤

Volume limited sample of 80 Core
Collapse Supernovae up to 60 Mpc
discovered and followed up by the UC
Berkeley group.

4Sampling the IMF consistently w.
observed fractions of CCSN types✤

Higher initial mass leads to higher mass loss rates in asingle star evolution, and a greater stripping of the H &He envelopes.

✤In close binary evolution & Roche Lobe overflow leads
to loss of H-envelope.

✤The fraction of all massive stars that lose their H
envelopes as type Ibc (26%) and and with IIBs the total
fraction is 36.5%✤Roughly half of SN Ic (8.8% of all CCSNe to match thefraction of SN IIn) away from the RLOF population andmixed them with single star population. SN Ic that arise
from single stars are below the dashed line.

✤Half of all single stars above ~ 23 Msun are able to shed
their H-envelopes via winds or eruptions while theother half retain their H-envelopes until just before corecollapse producing SNe IIn.

Fig 7 from: Nathan Smith et al, MN 2011:
one example
5

A red supergiant problem?
✤Type IIP progenitors were redsupergiants (RSG) when they
exploded✤

There are massive RSG stars (M> 17 Msun) seen in the Local
Group of galaxies (MW, LMC..).

✤But no high mass RSG
progenitors above about 17
Msun ( & < 25 M for W-R starprogenitors) have been foundfor IIP SNe.

✤Smartt et al (2009) used a
volume limited search for SN
progenitor stars in direct
detection efforts.

✤RSG “Problem” may indicate:more massive stars could havehigh core masses to form black
holes instead of neutron stars.
SNe of higher M stars too faint.

✤

But: Walmswell & Eldridge(2012): circumstellar dust
6

Ugliano, Janka, et al 2012

Compactness parameter ξ2.5 = (M/MSUN)/(R(M)/1000 km) has to be > 0.45(threshold value of O’Connor & Ott 2011) for BH formation7

Electron synchrotron radiation
and Inverse Compton loss for eShock
X-ray photon

electron Magnetic field
Acceleration ofelectrons by shock

Synchrotron radiation

Inverse Compton Boostingof low energy photons
8

0B.$9#/(#/.,A&"''"/.

;+8.)("$,<")*=>&7*"?"$+("/.

-.:)#'),!/&7(/.

@)*+(":"'("$,A*)$(#/.
>$$*)#+("/.
67("$+*,*"89(,$%#:)

Type IIP SNe!"#$%&'()**+#,-.()#+$("/.

!

01,23445+
SN 2012aw!

Chakraborti et al 2013 ApJ 774, 30
Yadav et al 2013 submitted9

10

“supernova impostor”
SN 1954J: a highly
luminous (MV = -8.0),very massive (Minitial > 25
Msun, eruptive star now
surrounded by a dusty(AV = 4 mag) nebula: S.
van Dyk , PASP 2005.

X-ray bright
SN 2004djin NGC2403

11

What type of stars exploded?

✤Red Supergiant stars✤

In recent star-forming regions of spiral galaxies✤

Progenitor stars are short lived & explode from massive stars (M > 8Msun)

12

SN2004dj: Chandra Observation
summary13

Chandra X-ray spectra of SN 2004dj
2004 Dec 22

10-510-6

APEC thermalcomponent

5x10-30-5x10-3

12Energy (keV)

5Flux (ph cm-2s-1keV-1)

Inverse Compton
powerlaw component

6 (cts s-1keV-1)

6 (cts s-1keV-1)

Flux (ph cm-2s-1keV-1)

2004 Aug 09
10-510-6

Inverse Compton
powerlaw component
APEC thermal
component

10-7

2x10-301

2Energy (keV)

5at two epochs: 1) 2004 Aug 09 and 2) 2004 Dec 22✤Extracted spectra (into XSPEC 12.7.1) jointly fitted w. power law & thermal APECmodels (Randall Smith et al 2011) with photoelectric absorbing column.

Date: SN Discovered 31.76 July 2004 (UT) : This Could Be 50 +/- 21 Days After Core Collapse
14

Time evolution of IC & Thermalcomponents
3e-05

1.4e-05

Chandra Obs
1/t

1.2e-05

APEC Normalization

Powerlaw Normalization

2.5e-05
2e-05
1.5e-05
1e-05
5e-06
0

Chandra Obs
1/t

1e-05
8e-06
6e-06
4e-06
2e-06

60

80

100120140160t (Days since explosion)

18020006080

100120140160

180200t (Days since explosion)158  .2+

11.5

Power Law Photon Index

2×10ï
1.×10ïPower Law Normalization+2.5Levels = 68%, 95%, 99.7%

2.×10ï

LeYelV

3X-ray emission uniquely separable
in IC & Thermal components

02×10ï

4×10ï

×10ï
8×10ï
10ï
APEC normalization

1.2×10ï

1.4×10ïConfidence contours for normalization of the thermal flux (inthe APEC model) vs. the normalization of the non-thermal flux
(in the power-law model). They are anticorrelated and the sumof two fluxes must add up to explain the total observed flux.

0.6

0.8

11.2

1.4

Temperature (keV)
Chandra data successfully breaks the degeneracy between
the two components and determine their most importantparameters, namely, the temperature and the photon index.

16NASA's Astronomy Picture of the Day for March 22, 2012:
SN 2012aw

SN 2012aw (arrow) lighting up in spiral galaxy M95; Photo: Adam Block, Mt. Lemmon Center171.0CSX
KKa

SFν (t) (mJy)

CX
0.1
KKa
10100
Time (Days from explosion)

Date of explosion used in this work: March 16.1 2012 UTFirst detection: March 16.9, 2012 UT (Fagotti et al). Last non-detection: March 15.27 2012 UT (Poznanski et al)18

Evolution of radio spectral indices21.5-α~ν

1Spectral Index (α)

Fν

"
f1log
f! 2"
α=
ν1log
ν2!

CBand
SBand

0.5

XBand
CBand

0-0.5
-1-1.5

0

20

40

60

80

100

120140Time (Days after explosion)
19

Radio frequencies affected byInverse Compton Cooling
103

Cooling frequency (GHz)

Bolometric Light Curve

2Luminosity (1042 ergs/sec)

102

νmin (GHz)

Ka-Band101

C-Band100

10−110−21001.51Plateau

0.5

101
Time (Days from explosion)102

5.0 × 1041 ergs/sec

020

4060

80

100

Time (Days after explosion)
20

4

7.5
7.4

3.5

7.3
3
7.2log 10(α̃)

2.5

7.1

2

7
6.9

1.5

6.8
1
6.7
0.5
0
0.1

6.6
0.2

0.3

0.4

0.5

0.6

0.7

0.8t̃acc (day)21Summary for radio observationsof SN 2012aw✤Radio observations (JVLA & GMRT) of SN 2012aw span 184 days tomake it one of the best observed IIP SNe✤Radio spectral index curve at high frequencies shows a dip at earlytimes (t < 60 days) & goes below -1, usual for optically thin case✤

We show that this is a signature of electron cooling at a young age✤

Inverse Compton cooling dominates over Synchrotron coolingbecause of the abundant seed (optical) photons over the long plateau
phase (the long lasting “light bulb”)✤Radiating plasma is far from equipartition => relativistic electrons
carry a larger fraction of the thermal energy of the shocked plasma
than the post-shock magnetic field.

22

SN 2013ej: B= 13.8 V=14.0 R=14.3
on 2013 Jul 24.80- 24.83 UT

23

SN 2013ej inspiral galaxy M74✤M74 is at a distance of 9.1 +/1.0 Mpc (Fraser et al 2013).

✤From the HST image, Fraser etal (2013) estimate a progenitor
mass range of 8 - 15.5 Msun.
HST ACS image of the site ofSN 2013ej prior to explosion(Fraser et al 2013)24

Chandra detects SN 2013ej

S. Chakraborti, A.R., Keiichi Maeda et al (in prep)25

Another Type IIP SN 2011ja
Host galaxy NGC4945 is close by at 3.36 Mpc away (Mouchine et al 2005)
Discovery Magnitude: 14 (unfiltered CCD) On 2011 December 18.1 UT (Monard 2011); Type IIP Classification From Spectra
Taken On Dec 19.1 UT (Milisavljevic 2011): Like SN 2004et A Week After Max Light)

26

Chandra ToO observed SN 2011ja
on Jan 10, 2012 & Apr 3, 2012
“Target of Opportunity”

Quick-look image of Jan 10, 2012:detection !
27

There is another source close-by !

✤✤The contaminating source waspresent in a pre-SN exposure of
the galaxy NGC 4945 on
2000Jan 27.

1.35”

It is only 1.35” away from SN2011ja28

X-ray flux of SN & XB in two epochs29

Chandra X-ray spectra ofSN 2011ja at two epochs
Flux (photons cm-2s-1keV-1)

5×10−6

Second epoch (~84 days after SN)
2×10−610−6

5×10−7First epoch (~41 days after SN)

Δ (counts s-1 keV-1)

2×10−74×10−42×10−40−2×10−4
0.5

12
Energy (keV)

530

ATCA Radio spectrum:2011 Dec 19✤✤

Radio emission due to Synchrotron radiation.
Assuming Synchrotron self absorption modelat late times:

2001 Dec 19
Optically thin part to the right ~ ν-1
optically thick part to the left ~ ν5/2✤

Under equipartition, Rs = 1.8 x 1015 cm✤Expansion velocity from Halpha absorption
minimum: 11,000 km/s (Milisavljevic 2011)=> age 19.4 days at time of radio obs (Dec 19).

✤Explosion date: 2011 Nov 30 UT (+/- 2 days)

31

Mass loss rate (Solar masses / year)

Varying mass loss rate of the progenitorof SN 2011ja: complex circumstellar
medium set up by a non-steady wind?
1e-05

SN2001ja (2nd epoch)
Mesa

ND90SN2004dj

1e-06

SN2001ja (1st epoch)
1e-07

10121416

ZAMS Mass (Solar masses)

182032

Summary & Conclusions✤X-rays in SN 2004dj: a combination of thermal and non-thermal processes. At early
spectra dominated by Inverse Compton scattering by relativistic electrons of optical SN
photons at the forward shock. X-ray luminosity falls off as Lbol/t. At late time dominantemission is from reverse shock heated thermal plasma which falls off as 1/t✤

Radio observations (JVLA & GMRT) of SN 2012aw show its radio spectral index curveat high frequencies has a dip at early times (t < 60 days). This is an indication ofelectron cooling. Inverse Compton cooling dominates over Synchrotron coolingbecause of the abundant seed (optical) photons over the long plateau phase (the longlasting “light bulb”)✤Radiating plasma in SN 2012aw is far from equipartition => relativistic electrons carry alarger fraction of the thermal energy of the shocked plasma than the post-shockmagnetic field. However, for SN 2004dj, around a third of the energy thermalized by
the collision of the ejecta with circumstellar matter is used to accelerate electrons torelativistic velocities and about a tenth of the thermal energy available is used in theturbulent amplification of magnetic fields. εB and εe are determined separately by theuse of X-ray, radio and optical data.
33

Thank You34

1.0Fν (t) (mJy)

3.0 GHz dataFν (t)|ν=3.0 GHz

SSA model

tp,3.0 =50.90 days

23d

Fp,3.0 =0.58 mJy

0.1100Time (Days after explosion)

Chevalier (1998) model gives R0 = 3.9 x 1015 cm & B0 = 0.48 G at t ~50.9 d35

IC cooling & radio frequency
turnoverElectrons affected by cooling (tIC < tAd) have energy greater than:With νC ~ const x B E2 , minimum radio frequency above which Compton cooling present:

Electron energy distribution has a truncation point depending upon the loss and gain terms
affecting individual electron energy:

36Radio light curve from electron
distribution and model calculation
Radio flux density calculated in terms of the source function Sν = εν/κν with free-freeabsorption (Chevalier 1998):

tff is the time at which optical depth to FFA becomes unity at radio frequency ν1Compute the radio fluxes as a function of time, with:
1. For a given explosion date (tex) fit the 3 GHz light curve with an SSA model todetermine peak values of Fp, tp and m (where R(t) = R0(t) (t/t0)m).
2.

Calculate the radius Rp & Bp from SSA model expressions using Fp, tp .

3. Use Rp, Bp & tp in the cooling model to calculate the best fit values of tff , tacc & log (α)
based on χ2 minimization.
4.

Use optical light curves referenced to explosion dates to compute the cooling model

The best fit from radio data gives:37

Another method to obtain theequipartition factor α:
Integrate the spectral distribution of the X-ray luminosity expected from IC (Chakrabortiet al 2012) for 0.5-2.0 keV; relate the observed X-ray luminosity & radio emission measure:

Chandra observed SN 2012aw on 2012 Apr 11. Luminosity: (6 +/- 1.4) x 1037 erg/s/keV.
This value implies an equipartition factor from above:38

Electron energy distribution:
Electron distribution function at time t (Pacholczyk 1970) is:Electrons are accelerated by SN shock and gain energy and lose energy by radiativeprocesses, e.g. IC. The maximum electron energy Emax is dependent upon the shock
radius and bolometric luminosity (supply of seed photons):

Normalization N0 is related to the equipartition factor α:39Electron energy & Inverse
Compton scattering✤

Rates at which an electron loses energy:
Adiabatic loss
Inverse Compton cooling
Synchrotron✤

Timescales:

Radiation density at the radiosphere40

IC & radio emission measures
Ejecta with density profile runs into a steady (s=2) wind of the presupernova star:

Chevalier &Fransson 2006:
in terms of the radioemission measure

41

Ugliano, Janka et al 2012 ApJ

42

Ugliano, Janka, et al 201243