# Presentation: 227597

## 15 Years of High Resolution Radio Imaging of SN 1987A

**15 Years of ****High Resolution Radio Imaging ****of SN 1987A**

**Bryan Gaensler (U. Sydney / ****CfA****);**
**Lister Staveley-Smith (UWA);**
**Dick Manchester, Mike Kesteven, Lewis Ball, Tasso Tzioumis (ATNF)**

## Circumstellar Structure

**Circumstellar Structure**

-  Dense slow RSG wind, concentrated into equatorial plane
-  High-velocity low-density isotropic BSG wind for final ~20 000 yr
-  BSG photoionizes RSG wind   (Chevalier & Dwarkadas 1996)

*HST* WFPC2 (Pete Challis / SAINTS)

- Hydro simulation (Michael et al. 2003)

**BSG wind**

**RSG**
**wind**

## Prompt Phase

-  Core collapse on 23 Feb 1987
-  Burst of radio emission seen by MOST on day 2; peaked on day 4  (Turtle et al. 1987)
-  Power law decay; faded by day 150
-  Synchrotron in BSG wind (ρ  *r** *–2)  (Storey & Manchester 1987; Chevalier & Fransson 1987)
-  Hα, VLBI: V ~ 19000 – 30000 km/s   (Hanuschik & Dachs 1987; Jauncey et al.1988)

- Optical (Malin/AAO)

- 843 MHz light curve (Ball et al. 1995)

## Birth of a Supernova Remnant

-  MOST & ATCA redetected radio emission in Jul 1990 (day ~ 1200)
-   9 GHz ATCA data (  0.9 ̋) showed source was extended
-       (Staveley-Smith et al. 1992, 1993)
-   Since 1992, deep 9 GHz ATCA observation every ~ 6 months
-   High flux  self-calibration  high fidelity reconstruction
-  Track size vs. time in *u-v* plane: first-order fit to thin spherical shell
-    (Staveley-Smith et al. 1993; Gaensler et al. 1997)

- ATCA (ATNF/CSIRO)

- MOST (Douglas Bock)

## Expansion

-  Shell was ~1.3 ̋ (0.3 pc)
-    across at day ~1800
-    → mean expansion
-   ~ 38 000 km/s (1987-1992)
-  Since day 1800,
-    approx. constant
-    expansion at
-    V = 4700 ± 100 km/s
-  → rapid deceleration
-  → slightly better fit:
-       break at 5000 days from
-       V1 = 3600 km/s to V2 = 4900 km/s
-  Source now same size as optical ring
-  Radius, velocity & acceleration all discrepant with X-rays  (Park et al. 2002, 2004, 2006)

## Imaging & Super-Resolution

**Imaging & Super-Resolution**

-  Limb brightened
-  Bright lobes to
-   east and west
-  Eastern lobe
-   brighter than
-   western lobe, &
-   brightening faster

- ATCA 9 GHz diffraction limited (0.9 arcsec)

## Spatial Modeling

-  Spherical shell not
-   ideal fit to data
-  Are other simple
-   models better?
-  Thin shell, thick shell,
-   thick ring, all agree to 5%
-  Radio, X-ray agree to < 1%
-  X-ray deceleration tracing
-    forward shock?
-  Vr  Vrev  4700 300 km/s ;
-  cf. 4100 km/s  (Borkowski et al. 1997) ,
-       3700  900 km/s  (Michael et al. 2003)
-  Now at point where Rradio   Rring

**Spatial Modeling**

- ATCA 9 GHz epoch 1998.0 (Manchester et al. 2002)

**ATCA 9 GHz**

**ATCA 18 GHz**

**CXO 1.2-8 keV **

- 18 GHz  ATCA (Manchester et al. 2005)

## Multi-Wavelength Comparison

**Multi-Wavelength Comparison**

-  Two-lobed structures
-    seen in radio, hard
-    X-rays, optical
-  Radio lobes not related
-    to optical hotspots in
-    position or in timing
-   Lobes align with
-    major axis of ring
- → True morphology is
-       likely a tilted ring
-       (not easy to fit!)
-  Brighter lobe is at
-   larger radius
- → Asymmetry in
-      explosion/ejecta

- STIS Ly α (Michael et al. 1998)

**ATCA**** / *****Chandra***** / *****HST***  (day 6300)

## Conclusions

-  Turn-on & deceleration of radio source due to impact with dense RSG wind
-  Radio remnant of SN 1987A continues to steadily expand & brighten
-  Consistent multi-wavelength picture of reverse-shock emitting region:
-     - limb-brightened shell expanding at V ~ 4700 km/s
-     - interaction is with dense gas in equatorial plane
-     - collision of ejecta piston with optical ring now upon us!
-   The Future (I): Fourier modeling of axisymmetric structures
-    The Future (II): ALMA, MIRA, SKA

- 9 GHz images of SN 1987A, 1992 to 2007

- SN 1993J (Bietenholz et al. 2003)

- Cas A (L. Rudnick / T. Rector)

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