Radio studies of mysterious Type IIn supernovae

Poonam ChandraNational Centre for Radio AstrophysicsTata Institute of Fundamental Research

Collaborators: Roger Chevalier, Nikolai Chugai, Claes Fransson, A. Soderberg

Supernova Classification(based on optical spectra and light curve)

Supernovae

HydrogenType II

Narrow H linesType IIn

No narrow H lines

Type IIP/IIL

No HydrogenType I

SiliconType Ia

No SiliconType Ib/c

PlateauType IIP

LinearType IIL

HeliumType Ib

No HeliumType Ic

Type IIn supernovae

• Very diverse stellar evolution and mass loss history.• SN 1988z, extremely bright even after 20 years• SN 1994w faded only in 130 days.• SN 2005gl: LBV progenitor?• SN 2006gy, extremely bright: PISN progenitor?• SN 2002ic, SN 2005gj: Hybrid between Ia/IIN.• SNe 2001em, 1995N, 2008fz: Type Ib/c properties• SN 2009ip: episodic ejections before turning into

true supernova

Type IIn supernovae

• Explosion in very dense environments• Very high mass loss rates ~ 10-3-0.1 Msun/Yr• Very high bolometric and Ha luminosities-

indicative of high circumstellar interaction

• INDICATIVE OF HIGH RADIO LUMINOSITY

Circumstellar interaction

Circumstellar wind (1E-5 Msun/Yr, v=10 km/s)

Explosion center

Reverse Shock~1000 km/s

Forward Shock~10,000 km/s

Ejecta

Circumstellar medium density ~1/r2

SN IIn Radio Statistics

• Around ~180 Type IIn supernovae• So far only 81 observed in radio bands• Out of 81, only 11 detected in radio bands

Poonam Chandra

Poonam Chandra

Peak radio and X-ray luminosities

2009ip

Radio light curves- SN 2006jdChandra et al. ApJ 2012, 755, 110

Poonam Chandra 11

Frequency

Free-free absorption: absorption by external medium

Information about mass loss rate.

Synchrotron self absorption: absorption by internal medium

Information about magnetic field and the size.

NB relssa

5.15.2

Radio SpectraChandra et al. ApJ 2012, 755, 110

Radio model of SN 2006jd (Chandra et al. 2012)

• Internal free-free absorption. • Seen in SN 1986J and SN 1988Z too.• Density of emitting gas r=6x106 cm-3.• Mass of absorbing gas required to do the observed

absorption is 2x10-8T45/2 Msun.

• Modest amount of cool gas mixed into radio emitting region can do the required absorption.

• Source of the cool gas is radiative cooling of the dense gas in the shocked region.

SN 2006jd: Main Results

• Radio and X-ray both give s~1.6-1.7 (density~1/rs).

• Mass loss rate ~ 5x10-3 Msun/yr.• Shocked gas density 6x106 cm-3.

SN 2010jl Chandra X-ray Spectra Comparison

November 2010 October 2011 June 2012

Chandra et al. 2012, ApJ Letters 2012, 750, L2

Mass loss rate 8E-3 Msun/yr

Observations November 2010 October 2011 June 2012

Duration 39.6 ks 41.0ks 39.5ks

Counts 468 1342 1484

Count Rate 1.13E-2 cts 3.29E-2 cts 3.68E-2 cts

Column Density 9.7E23 cm-2 2.67E23 cm-2 6.6E22 cm-2

Temperature >10 keV > 10 keV > 10 keV

Causes of radio non-detections

• Some Type IIn supernovae are thermonuclear explosions.

• Extremely high absorption.

TWO SEPARATE KINDS OF

TYPE IIN SUPERNOVAE!!!!

Summary

• Type IIN supernovae: diverse behaviour.• Extremely high circumstellar interaction.• Trend emerging: late radio emission.• Only 5% supernovae are radio bright.• Extremely high absorption supressing radio

emission?• Two classes of Type IIn supernovae?

Poonam Chandra 20

Evolution of stars

11-09-13

One example: SN 1995N, Type IINChandra et al. 2009, 2005

• Observed for many years with the GMRT (Chandra, Ray etc.)

• Radio observations for long time with the VLA (Weiler, Stockdale, van Dyk etc.)

• Chandra observations in 2004 (Chandra, Ray, Schlegel, Sutaria etc.)

• Archival ROSAT and ASCA observations (Fox et al).

• Many optical spectroscopic and photometric observations (Fransson et al.)

Radio studies

• Hb luminosity: free-free absorption dominant.• Fastest ejecta decelerating with R α t0.84.• Ejecta density gradient r = r-n, n=8.3.• Mass loss rate: 6x10-5-6x10-4 Msun/yr for wind

speeds of 10-100 km/s (Use ~10-4 Msun/yr).• Reverse shock X-ray luminosity and mass-loss

rate gives: n≈8, Tcs≈0.3x10-9 K, Trev≈0.9x10-7 K, rcs≈2x106 cm-3, rrev≈3x105 cm-3.

Core Collapse Supernovae

Thermonuclear Supernovae

Type IIn Supernovae• Suggested by Schlegel 1990.• Most diverse class of supernovae.• Unusual optical characteristics:–Very high bolometric and Ha luminosities–Ha emission, a narrow peak sitting atop of

broad emission–Slow evolution and blue spectral continuum

• Late infrared excess• Indicative of dense circumstellar medium.

Type IIn spectra

Circumstellar Interaction

SN IIn Radio Statistics

• Around ~180 Type IIn supernovae• So far only 81 observed in radio bands• 43 SN IIn observed by us in radio• Out of 81, only 11 detected in radio bands• 4 detected by us (SN 2005kd, 2006jd, 2008iy,

2009ip)• In X-rays detected by us: SN 2006jd, 2010jl,

2009ip

Poonam Chandra

SN Days Detection Distance ATel2005kd 640-1173 Y 64 11822006jd 404-1030 Y 79 12972008iy 300-1300 Y2009ip 30-90 Y 242010jl 30-1000 N 50

2007gy 72-418 N - -2007nx 22-372 N - -2007pk 2-342 N 71 12712007rt 49-329 N 96 13592008B 21 N 78 13662008J 254-336 N 66 -2008S 8-308 N 5.6 13822008X 12 N 27 14102008aj 6-300 N 108 1409

2008am 40-337 N - 14082008be 27-268 N 123 14702008bk 4-13 N 4 1452,55,652008bm 252 N - 1865,692008cg 39-222 N - 15942008cu 156 N 152 -2008en 132 N 160 -2008es 130 N - 17762008gm 52 N 50 -2008ip 5-124 N 65 18912009ay 15 N 95 -2009dn 55 N - -2009fs 7 N - 2070

VLA

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SN 2006jdChandra et al. ApJ 2012, 755, 110

• Discovered October 12, 2006 in UGC 4179 • Redshift z=0.0186• Initial spectrum shows Type Ib and later

spectrum shows IIn• Radio Observations: VLA(EVLA), GMRT• X-ray Observations: Swift-XRT, ChandraXO,

XMM-Newton

SN 2006jd- radio observations

• With VLA starting from 2007, Nov 21.28 UT• Epoch: Day 400 until Day 2000.• Frequency bands: 22.5 (K), 8.5 (X), 4.9 (C) and

1.4 (L) GHz bands• With GMRT at three epochs, between 1104

day to 1290 days.• Frequency bands: 1.4 GHz and 0.61 GHz

bands. Not detected yet in 0.61 GHz bands.

SN 2006jd: Main Results

• Column density is a factor 50 smaller (1.3E21) than needed to produce the X-ray luminosity (4E22). Indicate towards global asymmetry.

• Lower column density also works against external FFA model. The derived external FFA optical depth from X-ray data is ~8E-4 at 5 GHz on day 1000.

• EW of Fe line much higher than expected. Possible region is mixing of cool gas could enhance the width of the line.

SN 2010jlChandra et al. 2012, ApJ Letters 2012, 750, L2

• Discovered on 2010 Nov 3.5 UT in UGC 5189A (z=0.011)

• Discovered magnitude 13.5. Brightened to 12.9.• One of the brightest apparent magnitude.

(Absolute visual magnitude Mv=-20)• Archival HST image show progenitor star

>30Msun.• Low metallicity host galaxy, Z~0.3Msun.• Circumstellar expansion speed 40-120 km/s.

SN 2010jl

• Radio Observations: EVLA : 10 observations from November 2010 until Now. No detection.

• X-ray observations: At 3 epochs with Chandra– Novemeber 2010– October 2011– June 2012

• Detection at all three epochs in X-ray bands

SN 2010jl Main results

• Column density ~1024 cm-2 (1000 times higher than Galactic absorption).

• High temperature >10 keV• High temp indicates forward shock emission• High absorbing column density not accompanied by high

extinction of the SN.• This indicates column near forward shock, due to mass loss,

where dust has been evaporated.• First time X-ray absorption by external medium, that is not

fully ionized by the energetic medium.• Fe 6.4 keV line also points to partially unionized medium.

SN 2010jl Main results• Fe 6.4 keV (narrow k-alpha iron line) in the first epoch and not in the

second epoch explains that ejecta has moved past the closeby partially unionized gas.

• The equivalent width (EW=0.2 keV) consistent with that expected for this line.

• Low temperature component fit by powerlaw of ~1.7 or ~1-2 keV temperature and column density is that of Galactic. Luminosity ~4x1039 erg/s.

• Flux change between the two epochs is 20-30%. Consistent with a background contaminating ULX source.

• Also looked at the possibility that enhanced 1 kev emission is by the CNO elements. Not possible as this gives too little absorption in 1.5-3 keV range.

• Origin of additional component (NH~8E22, kT~1keV) is not known.

SN 2010jl Main results

• Luminosity (0.2-10 keV) ~7x1041 erg/s, amongst most luminous X-ray supernovae.

• Since most emission > 10 keV, this is spectral luminosity

• Ejecta speed (v=sqrt(16 kT/3m) > 2700 km/s.• Mass loss rate > 4x10-3 Msun/year

Circumstellar Interaction: Absorption Processes

• Trace back the history of the progenitor star since wind velocity ~10 km/s and ejecta speeds ~10,000 km/s.

•Supernova observed one year after explosion gives information about the progenitor star 1000 years before explosion!!!

Circumstellar interaction