# Presentation: 940918

##        Toward an Understanding of the Progenitors of  GRBs and SNe Ibc

**       ****Toward an Understanding of the Progenitors of  GRBs and SNe Ibc**

**Alicia M. Soderberg** (*Caltech*)
*Aspen - February 23, 2007*

## Introduction:  The Death of Massive Stars

- Final phase of stellar evolution
- 	- mass loss history
- 	- binary evolution
- Galaxy enrichment and ISM dynamics
- Observed diversity of compact objects
- Mapping between progenitors and explosions

**Type Ibc supernovae (SNe Ibc)**
**long-duration ********-ray bursts (GRBs)**

- }

- Massive stellar death (> 10 M)

**An unhampered view of the explosion **

## Type Ibc supernovae: 15% of local SNe                                                          (Cappellaro et al. 1999)

*(Heger et al. 2003)*

**Progenitors: **
-  Isolated Wolf-Rayet stars (>20 M)
- (Woosley et al., 1995)
-  Helium star binaries (8-20 M)
*(Podsiadlowski et al., 1992)*

**“****Naked” core-collapse explosions **
-                                                           (Wheeler & Levreault, 1985)
-  lack Hydrogen, Silicon in optical spectra
*                                                   **(Elias et al 1985; Filippenko 1997)*
-  weak or absent Helium *(Matheson et al., 2001)*
-  associated with star-forming regions
*                                                                       **(Van Dyk et al. 1996)*
-  often strong radio emission from CSI
*                                               **(Weiler et al., 1998; Chevalier 1998)*

## Type Ibc (or Ib and Ic?) supernovae                                                        

*(Heger et al. 2003)*

**“****Naked” core-collapse explosions **
-                                                           (Wheeler & Levreault, 1985)
-  lack Hydrogen, Silicon in optical spectra
*                                                   **(Elias et al 1985; Filippenko 1997)*
-  weak or absent Helium *(Matheson et al., 2001)*
-  associated with star-forming regions
*                                                                       **(Van Dyk et al. 1996)*
-  often strong radio emission from CSI
*                                               **(Weiler et al., 1998; Chevalier 1998)*

**Progenitors: **
-  Isolated Wolf-Rayet stars (>20 M)
- (Woosley et al., 1995)
-  Helium star binaries (8-20 M)
*(Podsiadlowski et al., 1992, Kobulnicky et al. 2006)*

**Based on amount of Helium in ejecta**

**Notes:**
Draw analogy between Ia’s and Ibc’s in terms of progenitors

## A GRB/SN Connection 0.1 to 1% of S_x000e_Ne Ibc produce gamma-ray bursts

-     GRB 980425 (40 Mpc)    GRB 030329 (z=0.17)   GRB 031203 (z=0.1)    _x0007__x0012__x0002_GRB 060218 (150 Mpc)

*(Galama et al. 1998, Matheson et al. 2003, Malesani et al. 2004, Pian et al. 2006) *

**Notes:**
High-light that XRFs seem to be related to GRBs, we know now that there is a XRF-GRB connection.

## Gamma-ray Burst Progenitors

- dramatic variability, t/t << 1
- ultra-relativistic outflow, ~100
-  Compact accreting source                     **       ****“central engine”**
- highly collimated jets, ~5 deg
**Rapidly rotating star**
- Located in star-forming hosts
- No Hydrogen in SN spectra
**Progenitors:**
- Isolated Wolf-Rayet
*(MacFadyen et al. 2001)*
- 2.  Helium Star Binary
*(Izzard et al. 2003; Podsiadlowski et al 2004)*

- ?

- Despite similar progenitor models, still an open question:
***What is the relation between ordinary SNe Ibc and GRBs?***

**Notes:**
Given that there’s an obvious distinction : gamma-rays 
Are there a lot of Ibc’s that also produce relativistic ejecta?

## We Need: a Multi-Wavelength, Detailed Study:The nearest (z < 0.1)  SNe Ibc and GRBs 

- 	- mass of Nickel synthesized (**optical**)
- 	- mass of Helium in the ejecta (**optical**)
-            - velocity, geometry, kinetic energy
-                 (**radio**, **X-ray**, **optical**)
- 		 GRBs
- II. **Local Environment ( < 1 pc) **
- 	- mass loss history (**radio**, **X-ray**)
- 	- binarity (**radio**, **X-ray**, **optical**)
- III. **Large-Scale Environment (> 10 pc)**
- 	- host galaxy metallicity (**optical**)
- 	- nearby stellar populations (**optical)**
- 	- host galaxy star-formation rate (**optical**, **radio**, **X-ray**)

**We Need: a Multi-Wavelength, Detailed Study:***The nearest (z < 0.1)  SNe Ibc and GRBs*

*(Bjornsson & Fransson, 2004)*

## An Optical Study of SNe Ibc and GRBs

*Soderberg et al. 2005b, 2006a                                                                                    Pian et al. 2006)*

-  GRB-SNe are** not **clearly** **distinguished from ordinary SNe Ibc either by optical luminosity or photospheric velocities.
-  May indicate similar Nickel-56 production and stellar explosion mechanisms

**“****broad-lined” (BL): ~5% of SNe Ibc**

**GRBs**

**SNe Ibc**

**Notes:**
This similar may indicate similar Nickel-56 production mechanisms and explosion mechanism .  Optical gives a lot of diagnostics, given that optical properties are not
That differeremt, observations at other wavelengths may help us to understand what the difference is.  Mention 060614.

## Radio/X-ray provide unique diagnostics:An Example

*(Mazzali et al 2002)*

*(Kulkarni et al 1998, Berger 2002)*

-  Spectra* identical****   *****      but             **Radio Lum 104 : 1

## ?

**?**

**   ****Optical Photosphere**
**v ~ 0.03c to 0.1c    E ~10****51 ****erg**

**Radio and X-rays Trace the *****Fastest *****Ejecta**

**Fastest Ejecta**
**v ~ 0.1c** to ****** ~ few**
**E ~ 10****45** to **10****51**** erg**

**GRB-SN**

**SN**

**Central “engine” **(accreting BH or NS)

**Energy**

**Velocity**

**No engine?**

**engine**

## The Most Luminous Radio SN:BeppoSAX discovery of SN1998bw and GRB 980425

- EK ~ 1049 erg coupled to
-  ~3 ejecta  Central Engine
*(Kulkarni et al., 1998; Li & Chevalier 1999)*
**Sub-energetic explosion**
- E ~ 1048 erg
-  Only detectable to z ~ 0.1

**A GRB-SN connection**
- d ~ 40 Mpc *(Galama et al. 1998)*
- Most radio luminous local SN

**The Most Luminous Radio SN:***BeppoSAX* discovery of SN1998bw and GRB 980425

## The Most Luminous Radio SN:BeppoSAX discovery of SN1998bw and GRB 980425

**Radio ****(Synchrotron)**** Requires:**
- EK ~ 1049 erg coupled to
-  ~3 ejecta  Central Engine
*(Kulkarni et al., 1998; Li & Chevalier 1999)*
**Sub-energetic explosion**
- E ~ 1048 erg
-  Only detectable to z ~ 0.1

**A GRB-SN connection**
- d ~ 40 Mpc *(Galama et al. 1998)*
- Most radio luminous local SN

-  98bw

*(Bloom et al., 2003)*

- z~1

## Rough Numbers: 170 SNe Ibc (since 1980’s), 2 GRB-SNe

*(Weiler 1986; Kulkarni 1998; Berger 2002,2003; Soderberg 2004,2005a,2006b,c,d & in prep**)*

- _Rough Numbers_: 170 SNe Ibc (since 1980’s), 2 GRB-SNe
-  60% Ic (5% BL), 20% Ib, 20% Ib/c
-  19 detections - roughly equal between Ib vs Ic, 2 BLs,2 GRB-SNe
-  detection rate: 30% Ib, 10% Ic, 25% BL, 100% GRB-SNe
-  Similar fraction of massive stars in close binaries *(Podsiadlowski)*
-  What fraction of non-detections (esp. BL)  are like 2002ap?  EVLA

**A Search for Engine-Driven Sne Ibc **(d < 150 Mpc)
**   **

**Notes:**
Motivated by these science goals we began a large radio survey of Type Ibc supernovae in 1999.  We’ve observed 150 optically-selected SNe each within a few weeks of explosion, all within ~150 Mpc.  To date, ~we’ve detected radio emision from 12 Sne Ibc, bringing the total number of positive detections to about 17, including several older events from the literature.
Of these, about a dozen have well-sampled light-cures, shown here.  
First thing to take away, 1998bw remains the most luminous local SN ever observed.

## The Caltech/NRAO Radio Survey (z < 0.1)Since 2002, we’ve increased the sample by 10x

*(Kulkarni et al. 1998, Weiler et al. 2001, Berger et al 2003, Soderberg et al. 2004a, 2005a, 2006d, in prep)  *

- A dispersion in light-curves
- - peak time
- - luminosity
-  decay rate
- Progenitor
- parameters:
-  mass
-  metallicity
-  binarity

## I. Extracting the Physical Parameters

**I. Extracting the Physical Parameters**
- (velocity, energy, geometry, circumstellar density)

**   ****Type Ic**** ****SN2003bg**

- SNe Ibc dominated by** ****SSA** *(Chevalier,1998)*
-  Expect (and observe) 2.5 spectrum
*    *(external FFA   steeper spectrum)
-  For sources dominated by SSA,
- TB < 5 x 1010 K *(Readhead 1994)*
-  Assuming **equipartition** of energy
- r  Lp8/17 p-33/34
- Etot  Lp20/17 p-40/34

*(Soderberg et al, 2006d)*

*(Kulkarni,et al 1998; Li & Chevalier 1999)*

## Searching for “Engine-driven” SNe

*NONE** of the SNe in our survey show evidence for relativistic ejecta.*

**Searching for “Engine-driven” SNe**

- v ~ Lp8/17 p-33/34 tp-1
** ****Ib’s** ~ 0.1c
-  **Ic’s** ~ 0.03 - 0.3c
-  Similar dispersion in Ic
- optical spectral properties *(Matheson,01)*
-  **GRB-SNe:**  ~ few
-  NOT true for all BL SNe      e.g. SN 2002ap *(Berger, 02)*

## I. Searching for Engine-driven SNe:Constraining Off-Axis GRBs

- When  *M*sw* **≈ E*0 /*c*2  the blast-wave becomes non-relativistic and nearly spherical:
-  Observed Flattening
* **t*NR ~ 65 (*E*iso,52 / *n*0)1/3 days

*(Soderberg et al 2006b; Soderberg, Frail & Wieringa 2004)                        (Frail,Soderberg et al.,2005)*

**I. Searching for Engine-driven SNe:**Constraining Off-Axis GRBs

**030329**

**Less than 10%** of SNe Ibc host CLASSICAL off-axis GRBs
- We **rule out** a scenario where every BL Ibc has a CLASSICAL GRB (85% conf)
- 3.    GRB-SN 1998bw was **intrinsically** sub-energetic (not off-axis).

**Notes:**
Again, late-time radio data constrain off-axis ejecta components.  In particular, the signature of an off-axis GRB is rising OPTICALLY THIN emission and most easy to detect in the radio.  Here the light-curve peak is caused by the jet coming into our line-of-sight rather than the passage of a the synchrotron self-absorption frequency.   Shown in red and blue are the model predictions for a typical GRB jet spreading into our line of sight for wind and constrant density profiles.  Just to reiterate, 
The early limits constrain ejecta within 30 degrees of our line-of-sight.  Focusing now
On the late time limits, with the exception of 1 event (2001em which I will discuss late, ALL  of the 68 Sne are fainter than even the most extreme viewing angle of 90 degrees.  We place a limit that <10% of Sne Ibc host off-axis Jets.  This holds in particular for the broad-lined Sne and empahsizes (again) that broad-lines are not a reliable proxy for a GRB explosion.

## I. A study of the nearest GRBs (z < 0.1) The discovery of a NEW class of sub-energetic bursts

**GRB031203 / SN 2003aw (z=0.1)**

**GRB 060218 / SN 2006aj (150 Mpc)**

*(Soderberg et al., 2004b, Nature)*

*(Soderberg et al., 2006c, Nature)*

- Radio/X-ray luminosities 100-1000 x lower than typical GRBs  Sub-energetic explosions like GRB-SN 1998bw

**Notes:**
We know the distribution of the GRB energetics and we now know the distribution of Sne -- bimodal vs continuum.  Is It all or nothing?  Only 98bw.  The hope was that Swift would
Find additional bursts

## I. Searching for Engine-driven SNeThe Discovery of a New Class of Sub-energetic GRBs

-  Nearest (***z < 0.1***) GRBs are:
**- outliers**
**- sub-energetic**
**- uncollimated**
-  Sub-energetic GRBs are more **common **by a factor of a few (up to 10)
-  undetected at > 200 Mpc
-  need optical SN trigger

***                       ****Adapted from Soderberg et al., Nature, 2004*

**I. Searching for Engine-driven SNe**The Discovery of a New Class of Sub-energetic GRBs

**SNe Ibc**
**     ******

*Soderberg et al., Nature 2006*

**Notes:**
Put in context of cosmological GRBs.  Dominate the local rate.  The importance of this result  
Emphasize two things: this result was not expected and it has important implications for other nearby events (aka Sne).

## I. Searching for Engine-driven SNeThe Discovery of a New Class of Sub-energetic GRBs

**E-v space:**
- 3 populations or 2?
**Flatter profiles:**
- Difficult to explain with hydrodynamic collapse
*(Tan, Matzner & McKee 2001)*
**Progenitor sample:**
- One model or 2?

*(Soderberg, 2006, Nature)*

**Optical**

**Radio**

**I. Searching for Engine-driven SNe**The Discovery of a New Class of Sub-energetic GRBs

**Notes:**
We know the distribution of the GRB energetics and we now know the distribution of Sne -- bimodal vs continuum.  Is It all or nothing?  Only 98bw.  The hope was that Swift would
Find additional bursts

**II. The Local Environment (< 1 pc) **

*The temporal evolution of SN Ibc radio light-curves allows us to measure the circumstellar density profile:*

- 

- In nearly every case, we find evidence for a **WIND** density profile.       Note that this is not true for most **GRB-SNe**.
*(Li & Chevalier, 99; Berger et al 03, Soderberg et al 04a, Soderberg et al 04b, Soderberg et al 06c)*

*Soderberg et al, 2005a*

## II. Progenitor Mass Loss Rates

**Type Ic        ****Type Ib**

- M  Lp-4/17 p59/34 tp2
** ****Ib’s** ~ 10-5 M/yr
-  **Ic’s** ~ 10-7 - 10-3 M/yr
-  **GRB-SNe** < 10-6 M/yr
*(Li & Chevalier 99,Soderberg,06)*
-  GRBs afterglows:
-    n ~ 10-3 - 102 cm-3
-     ~ 10-8 - 10-3 M/yr
*(Panaiescu &Kumar,02,Yost,03)*
- _For Comparison:_
-  WRs > 10-6 M/yr
*(Cappa,Goss,van der Hucht,04)*

**II. Progenitor Mass Loss Rates**

**.**

## ~ 40% of ALL well-studied Radio SNe show abrupt variability 

- ~ 40% of ALL well-studied Radio SNe show abrupt variability** **

*But clearly plagued by observational selection effects:*

-  cadence
- weeks to months
-  frequency
- 5 or 8 GHz
-  sensitivity
- > 0.1 mJy

**Notes:**
In fact, this continuity is supported by a compilation of well studied radio SNe shows that ~40% also show evidence for unusual radio variability (abrupt variations), in all cases adequately described by abrupt variations in the CSM density.  But before we  start making statistical conclusions regarding binary progenitors, or off-axis gamma-ray bursts it must be understood that this result is seriously plagued by observational selection effects.  

##  III. Large-Scale Environments ( > 10 pc)

** ****III. Large-Scale Environments ( > 10 pc)**
*** **GRBs favor low-luminosity, low-metallicity (Z~0.5 Z****) hosts*
* **But SNe Ibc (including BL) from “targeted” optical searches ****(biased)***
***	*** low-metallicity is not a requirement for broad lines (Modjaz 2007)

**z < 0.25**

**d < 150 Mpc**

*(Stanek 2006, Fruchter 2006, but see Wolf & Podsaidlowski 2006)                      Soderberg in prep                                                                                                                                                                    *

**Fortunately, a new sample of SNe from “blind” searches (e.g. SDSS).**

## Conclusions: 

- Need a multi-wavelength study (radio,X-ray,optical)
-  optical data do not enable distinction between SNe Ibc and GRBs
-  < 3% of SNe Ibc produce relativistic ejecta
-  Discovery of new population of sub-energetic GRBs
-  Broad dispersion in radio/X-ray light-curves

**VLA+EVLA**

**Future:**
- “Blind” SNe Ibc (e.g. SDSS)
- Unbiased sample
- Most efficient way to discover
- sub-energetic GRBs (radio follow-up)
- NIR spectra: are Ibc 1 class of 2?

**PI Soderberg**

## The Future: Helium in SNe IbcOne class or two? (Ibc vs Ib and Ic)

**The Future: Helium in SNe Ibc**One class or two?** **(Ibc vs Ib and Ic)

-    Gemini NIR spectra of 10 SNe Ibc with GNIRS/NIRI **(PI Soderberg**)

-  weak, blended optical He I lines prevent clear classification
-  Instead, use two strongest He I lines  (at 1 and 2 micron)

*(Hamuy et al.  2002)*

**To date, NIR spectra of just a few SNe Ibc**

*(Taubenberger 2006)*

## The Future: I. Helium in SNe IbcOne class or two? (Ibc vs Ib and Ic)

**The Future: I. Helium in SNe Ibc**One class or two?** **(Ibc vs Ib and Ic)

- ToO NIR spectra of SNe Ibc with **Gemini **GNIRS/NIRI (PI Soderberg, *Submitted*)
*Looking forward:* well-matched to the capability of FIRE on **Magellan** in 2008

-  weak, blended optical He I lines prevent clear classification
-  Instead, use two strongest He I lines  (at 1 and 2 micron)

*(Hamuy et al.  2002)*

**To date, NIR spectra of just a few SNe Ibc**