# Presentation: 702626

## Chandra Observations of Supernova 1987A

**Chandra Observations of ****Supernova 1987A**

***SN 1987A: 20 Years after SNe and GRBs, Aspen, February 19, 2007***

**Sangwook Park**

- Department of Astronomy and Astrophysics

- The Pennsylvania State University

-                     With
- David Burrows (Penn State)
- Judith Racusin (Penn State)
- Gordon Garmire (Penn State)
- Richard McCray (Colorado)
- Svetozar Zhekov (Colorado, SRI)

## SN 1987A in Her Uniqueness

- Brightest supernova observed by mankind since 1604 (J. Kepler)
- Distance: 50 kpc, in the LMC
- Age: 20 years old as of Feb 2007
- Type II SN
- Progenitor: Blue supergiant (Sk -69 202, B3 I)
- Neutrino burst** **
**    ****=> Core****-****collapse**** explosion => neutron star?**
- Most intensively studied SN of all time:
- Optical/UV: HST and many ground-based
- Radio: initial detection, turned on again in ~1990
- X-ray: no initial detection, turned on in ~1990
- Gamma-ray: detected decay lines from 56Co  decay of 56Ni,
-       confirming explosive nucleosynthesis
- => ADS: ~1000 (~1/week) refereed papers (since 1987)

** **Chandra monitoring since 1999:
-  Twice a year, separated by ~6 months
-  As of 2007-01, 16 observations performed

## SN 1987A: Chandra Observations

**      **Date                Instruments        Exp.
-       (since SN)                                    (ks)
- 1999-10-6 (4609)    ACIS-S+HETG  116
- 2000-1-17 (4711)         ACIS-S3           9
- 2000-12-7 (5038)        ACIS-S3          99
- 2001-4-25 (5176)        ACIS-S3          18
- 2001-12-12 (5407)      ACIS-S3          49
- 2002-5-15 (5561)        ACIS-S3          44
- 2002-12-31 (5791)      ACIS-S3          49
- 2003-7-8 (5980)          ACIS-S3          45
- 2004-1-2 (6157)          ACIS-S3          46
- 2004-7-22 (6359)        ACIS-S3          49
- 2004-8-26 (6393)    ACIS-S+LETG   289
-  ~ 2004-9-5 (6404)
- 2005-1-9/13 (6533)     ACIS-S3          48
- 2005-7-11/16 (6716)   ACIS-S3          44
- 2006-1-28 (6914)       ACIS-S3          42
- 2006-7-27 (7095)        ACIS-S3          40
- 2007-1-19 (7271)        ACIS-S3          38
*2007-3                            HETG             370*
*2007-7?                         ACIS-S3           31*
*2007-9?                          LETG              300*

- - Publications:
- Burrows et al. 2000, ApJ, 543, L149 (Obs 1-2)
- Park et al. 2002, ApJ, 567, 314 (Obs 1-4)
- Michael et al. 2002, 574, 166 (Obs 1 & 3)
- Park et al. 2004, AdSpR, 33, 386 (Obs 1-6)
- Park et al. 2004, ApJ, 610, 275 (Obs 1-7)
- Park et al. 2005, AdSpR, 35, 991 (Obs 1-9)
- Zhekov et al. 2005, ApJ, 628, L127 (Obs 11)
- Park et al. 2005, ApJ, 634, L73 (Obs 2-10, 12-13)
- Zhekov et al. 2006, ApJ, 645, 293 (Obs 2-10, 12-13)
- Park et al. 2006, ApJ, 646, 1001 (Obs 2-10, 12-13)
*Racusin et al. 2007, in preparation: HEAD 2006-10*
*        **(X-ray radial expansion: Obs 1-15)*

- Current presentation:
- A review and the latest results.

**Notes:**
Racusin et al. in HEAD

## SN 1987A: Physical Picture

**SN 1987A: Physical Picture**

- Cf. Michael et al. 1998

*Artistic presentation of SN 1987A (SAO/CXC)*

- Optical/Soft X-rays

- Hard X-rays

- Radio

**?**

**NS/BH**

## SN 1987A: First X-ray Images

**SN 1987A: First X-ray Images**

- N

- E

- ROSAT/HRI
-       (5” pixels)
- HEASARC/SkyView

- 1 arcsecond

- ACIS (1999-10): Burrows et al. 2000

- Green-Blue: ACIS
- Red: HST
- Contour: ATCA

## SN 1987A: ACIS Images 2000–2007

**SN 1987A: ACIS Images 2000–2007**

*1 arcsec*

- 2005-07-11

- 2005-01-09

- 2003-07-08

- 2002-12-31

- 2001-04-25

- 2000-12-07

- N

- E

- Ring-like, asymmetric intensity
- Developments of X-ray spots
-   => becoming a complete ring as the
-      blast wave arrives the inner ring!
- Surface brightness increase
-   => Now ~18 x brighter than 2000
-       Lx (0.5-2keV) = 2.1 x 1036 ergs/s
- No point source at the center

- Scheduled
-        on
- 2007-7-16

## SN 1987A: ACIS Subband Images (2000-2004)

**SN 1987A: ACIS Subband Images (2000-2004)**

- 0.3-0.8 keV

- 0.8-1.2  keV

- 1.2-8.0  keV

- 2000-12

*(HST: 2000-11)*

*(HST: 2001-12)*

*(HST: 2001-12)*

*(HST: 2001-12)*

*(ATCA: 1999-9)*

*(ATCA: 2001-11)*

*(ATCA: 2002-11)*

*(ATCA: 2002-11)*

*1 arcsec*

- 2001-12

- 2002-12

- 2004-01

## SN 1987A:  Soft X-Ray Intensity Ratio

- 2002-12 to 2000-12

- 2005-7 to 2002-12

- Contours: 2002-12

- (0.5 – 2 keV)

- (0.5 – 2 keV)

- Contours: 2005-7

- (5791)          (5038)

- (6716)          (5791)

## SN 1987A: ACIS Spectrum (“2-shock” model) 

- keV

- NH = 2.35 x 1021 cm-2
- Soft component:
-    kTs = 0.23 – 0.31 keV
-    ne t ~ 1013 cm-3 s
- Hard component:
-    kTh = 2.2 – 3.2 keV
-    ne t ~ 2 x 1011 cm-3 s
- => ns/nh ~ 20
- Abundances fixed at
- values obtained from
- the LETG data:
- N = 0.76     O = 0.09
- Ne = 0. 29  Mg = 0.24
- Si = 0.28    Si = 0.45
- Fe = 0.16
- (Zhekov et al. 2006)

- 2000 Jan – 2005 July

- 2004-8: LETG

**Notes:**
Abundances are LMC ISM.
Spectrum becomes softer.

## SN 1987A:  Soft X-Ray Light Curve

- Linear increase of X-ray flux  until day ~3000.
- Rate  jump in 1997 (day ~3700): coincident with emergence of optical spots.
- An exponential radial density profile can fit the lightcurve over a decade.
- An excess became
- evident since d ~ 6200.
- Forward shock enters a “wall”?

*f**x** **~ n**e**2**R**3**T**-0.6**(e.g., McKee & Cowie 1977)*
*      *Where T = const
*~ R**3**(n**0**+n**r **e**-(Rr-R)/s**)**2*

- d ~ 3700

- d ~ 6200

*f**x** **~ n**0**2**V**0**T**0**-0.6 **+ n**r**2**V**r**T**r**-0.6*
*   *Where V ~ R3
-               R ~ t2/3* **  *(*Chevalier 1982*)
-               Tr ~ T0 (n0/nr)  (e-i equilibrium)
-               Filling factor of nr  increases
-                                             ~ e-(Rr-R)/D

- Chandra/ACIS

- 0.5-2 keV fractional flux

- “Fast” shock

- “Slow” shock

- 0.5-2 keV
- 3-10 keV

- Day since SN

- d ~ 6200

- X-ray (2005-7) vs. Optical (2005-4)

- Image: ACIS 0.5-2 keV
- Contours: HST (Credit: Peter Challis)

-           ROSAT
- (Hasinger et al. 1996)

- X-ray Flux (10-13 ergs/cm2/s)

- 0.4-1.5/2-5 keV ratio

## SN 1987A X-Ray Light Curve Updates: 2007-1                   (Preliminary Results)

- 0.5-2 keV fractional flux

- 0.4-1.5/2-5 keV  ratio

## SN 1987A:  Hard X-Ray Light Curve

**SN 1987A:  Hard X-Ray Light Curve**

- ROSAT

- Chandra
- (0.5 – 2 keV)

- Chandra
- (3 – 10 keV)

- ATCA

- Similar rates of hard X-ray and radio
- => The same origin for them?
- => Simply due to softening of X-ray spectrum?

- X-ray (2005-7) vs.
-                 Radio (2005-6)

- Image: ACIS 3-8 keV
- Contours: ATCA 9 GHz

- Image: ACIS 0.4-0.5 keV
- Contours: ATCA 9 GHz

- X-ray Flux (10-13 ergs/cm2/s)

- Day since SN

- Radio image: B. Gaensler &
-                       L. Staveley-Smith

**Notes:**
New 3 data points continue linear increase.

## SN 1987A: X-ray Radial Expansion

**X-ray**** radius vs time. **
- The broadband deconvolved image for each observation
- is deprojected (43 deg) and fitted to 3 models (a ring + 4 spots) in order to estimate the radius of  the SNR as a function of time.
- Estimated overall expansion velocity is ~3900 km/s (with poor fit). However,  the expansion apparently decelerates to ~1400 km/s since d ~ 6200.

*Racusin et al. 2007*

**Notes:**
Work by Judy
Spot 1 proper motion 1500 km/s

## SN 1987A: Dispersed Spectrum (1999)                               Combined Line Profile (day 4609)

***                   ******(single Gaussian fit)***

**SN 1987A: Dispersed Spectrum (1999)****                               Combined Line Profil****e (day 4609)**

***V******s****** = ******3400****** ******± 700 km/s***
***(***consistent with radio measurements***)***
**   ****=> ****kT****i**** ****~ ****17 keV**
**Observed kT****e**** ****~ ****2.5 keV**

*Michael et al. 2002*

**Direct evidence for ****incomplete**** electron-ion thermal ****equilibration**** behind shock!**

- Dispersed Spectrum (HETG): 1999

## SN 1987A: Dispersed Spectrum (2004)

- N VII

- O VII

- Fe XVII

- O VIII

- Mg XII

- Si XIV

- Angstrom

**SN 1987A: Dispersed Spectrum (2004)**

- LETG/ACIS-S
- 289 ks in 2004-8/9
- (day ~6400)
- Detailed X-ray lines are resolved with good photon statistics.
**kT ~ 0.5 & 2.7 keV**
- Doppler widths of  individual lines are measured: v ~ 300-1700 km/s
- LMC-like abundances
- with N/O ~ 1.1

*Zhekov et al. 2005,2006*

- North (m = -1)

- V = 340 ~ 1700 km/s
- (Wherez

- South (m = +1)

- Angstrom

- FWHM (km/s)

- Si XIII

- Mg XI

- Ne X

- Ne IX

- Fe XVII

- O VIII

- OVIII

- LETG 1st-order
- LETG 0th-order

## SN 1987A: Blast Wave Arrives at Inner Ring!

-  HST images: optical spots dominate entire inner ring by
-   2003 (day ~6000).
-  Chandra images: western side brightening up since ~2003
-  (day ~6000) and now X-ray morphology is  a complete ring.
- - Soft X-ray light curve makes a turn-up at day ~6200.
-  Soft X-ray emission is now dominated by the decelerated
-   shock since day ~6000.
- - X-ray radial expansion rate reduces since day ~6200.
- - HETG/LETG: Shock velocity reduces to 1400 km/s.
- Mid-IR intensity turns up since day ~6000: dust emission
-  from the inner ring (Bouchet et al. 2006).

- mid-IR vs HST (2005-1)

##     SN 1987A Time-Lapse Movie:            (2000-01 to 2005-01)

**    ****SN 1987A Time-Lapse Movie:**** ****           **(2000-01 to 2005-01)

*PSU/SAO/CXC*

**To be continued...**

**Multi-wavelength collaboration: **
**      ****Chandra****/HST/Spitzer/Gemini/ATCA**
**Chandra AO8: ~740 ksec ACIS/LETG/HETG ***(PSU/Colorado/MIT)*** **
**                 ****observations ****accepted!**

## Comments on Harberl et al. (2006)

*ACIS pileup affects ~20-25% of X-ray fluxes. Chandra results are thus artifacts.*
**Generals**
-      - Corrections for days 4609, 6533 & 6716 are incorrect (HETG & 1/8 subarray).
-      - Basic assumptions are questionable.
-        * EPIC fluxes are “correct” or “true”: **???**
-        * Uncertainties on measurements for EPIC and ACIS are ~1%: **???**
-           (Harberl et al. determined their own ACIS fluxes and errors)
-        * Attribute discrepancy entire to the ACIS pileup: **???**
-          EPIC vs. ACIS cross-calibrations: several % at 1-8 keV.
-          ACIS CTI: 5-10% CR
-          ACIS QE: Time-dependent, invalid constant CR-to-e flux conversion (up to ~20%).
-          ACIS Pileup: NOTE: **SN 1987A is an EXTENDED source** with the ACIS!
**Specifics on ACIS pileup**
-       - Qualitative estimates: <10% overall. No significant effects on LC analysis.
-       - Quantitative estimates:
-          1. PIMMS/XSPEC simulations based on the XMM results: 4711, 5176, 5980.
-          2. ACIS grade branching distribution analysis: all epochs.
-          3. ACIS pileup modeling: 4711, 5176, 5980, 6157, 6533
-                                                  (Not suitable for extended, line-dominated sources).
-          Results: Self-consistent estimates of all several % or less, but ~15% on day 6153.

**                                   ****Conclusions:**
**The ACIS pileup does not affect our scientific results.**
- (Haberl et al. corrections are incorrect and/or statistically/physically insignificant.)