RADIO EMISSION FROM SNe & GRBs, AND THE NEED FOR SKA Kurt W. Weiler (NRL) Collaborators: Schuyler D. Van Dyk (IPAC/Caltech) Christina K. Lacey (NRC/NRL) Nino Panagia (STScI/ESA) Richard A. Sramek (NRAO/VLA) Marcos Montes (NRL) http://rsd-www.nrl.navy.mil/7214/weiler/

Supernovae (SNe) Play a vital role in galactic evolution: Nucleosynthesis, chemical enrichment, energy input into ISM production of stellar remnants, production of cosmic rays A primary goal of SN research: Understanding progenitor stars and explosion mechanisms for different SNe types SNe types: Ia, Ib/c, II (also IIn, IIb) SNe Ia not radio sources to limit of VLA sensitivity

Radio Supernovae (RSNe) 27 RSNe detected by in the radio; 17 objects extensively studied Analysis of radio emission provides vital insight into SN shock/CSM interaction Nature of pre-SN evolution Nature of the progenitor All RSNe have in common: Nonthermal synchrotron with high TB Decrease in (l - dependent) absorption with time Power­law flux density decline after max Final approach to optically, thin constant a

Radio Supernovae (RSNe) Interesting variations: Clumpiness in CSM; variations in Mdot; early time synchrotron self-absorption

“Standard” Light Curves Type Ib/c Type II

CSM Sampling ‘

More Recent Examples SN1994I (Ic) SN1993J (II)

SN1993J VLBI Expansion of SN 1993J from age 5 months to age 31 months

SN1987A -- Radio

SN1987A -- Optical

SN1979C -- Radio

SN1980K -- Radio

Luminosity vs. Time to 6 cm Peak

Evolution of RSNe into SNRs

SUMMARY (1 of 2) SNe classes are distinct in radio emission properties (thus distinct in CSM environments): SNe Ia are undetectable at VLA’s limiting sensitivity SNe Ib/c turn on and off quickly SNe II show a wide range of properties RSNe are sensitive to Mdot/wwind (~ pre-SN mass loss rate) RSNe sample the CSM => properties of the pre-SN wind density & structure -- unique stellar evolution probe

SUMMARY (2 of 2) Now, what about 1998bw and GRBs? SN 1978K shows evidence for a (possibly associated) HII region along the line of sight. SN 1979C & SN 1980K show evidence for very rapid stellar evolution in the presupernova phase SN 1993J shows evidence for a change in mass loss rate in the last ~10,000 years before explosion RSNe may be distance indicators Now, what about 1998bw and GRBs?

http://cossc.gsfc.gov/cossc/batse/counterparts/GRB_table.html

SN 1998bw Radio Light Curves

GRB 980508 -- Early

GRB 980508 -- Late

GRB 980519

Radio Observations of GRBs If present, radio observations of the GRB afterglow can yield: Size and expansion velocity of the fireball Through IS scattering Through changing spectral shape with time Density & structure of the CSM As for RSNe VLBI observations confirming size & shape Providing lower distance limits

Schematic of Fireball + Relativistic Blast Wave

RSN Luminosity at Peak

GRB Radio Luminosity at Peak

The Sensitivity Problem

Conclusions SKA could: Current VLA is severely sensitivity limited for SN studies Can only detect SNe with mvmax ~ 12 -- 14 (out to ~Virgo cluster) ~1300 SNe known; ~ 25 radio detections ~150 new discoveries/year; only 1-2 radio detections No Type Ia SN ever detected No VLA on­line mapping precludes RSN searches SKA could: Extend RSN detections to mvmax ~ 19 ~50 radio detections/year Discover ``hidden'' SNe Improve SN statistics not limited by absorption/dust Improve knowledge of Type Ia progenitors Provide a new cosmological distance probe

Conclusions SKA could: Current VLA is severely sensitivity limited for GRB studies Can only detect a few GRBs Thousands of GRBs known; ~ dozen radio detections >300 new discoveries/year; only 1-2 radio detections Not enough radio to distinguish types (fast-hard, slow-soft) SKA could: Extend GRB searches tens of detections/year Establish GRB CSM properties (Possibly) distinguish GRB classes Increase knowledge of relativistic jet/fireball physics

Recommendations One would like to see: Sensitivity of 1 mJy (preferably 0.1 Jy) in 30 minutes Resolution <1” @ 1.4 GHz (prefer @ 327 MHz) Simultaneous, multi­frequency observations Real­time, on­line editing, calibration & snapshot mapping Near circular snapshot beam

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