Supernova 1987A at 25 years

1. Highlights of the past 25 years2. Outstanding mysteries and

surprises3. What we can expect to learn,

sooner and later

TOPICS

Supernova Energy Sources

• Core collapse: E ~ GM2/R ~ 0.1 Mc2 ~ 1053 ergs Neutrinos: t ~ 10s

• Radioactivity: 0.07 M8[56Ni g 56Co g 56Fe] ~ 1049 ergs. Light: t ~ 3 months

• Kinetic energy: ~ 10 M8, Vexpansion ~ 3000 km/s ~ 1051 ergs ~ 1% core collapse. X-rays: t ~ decades - centuries.

Neutrino signal (1053 ergs) a a neutron star formed (I think!)

Optical Light (1049 ergs): driven by radioactivity

56Co

57Co44Ti

X-rays (1051 ergs): from kinetic energy (crash)

What we have learned:the interior

RADIOACTIVE DEBRIS

IR nebular spectrum:

• CO bands a interior T < 3000 K @ 260 days; now < 300 K

• Strong, optically thick FIR lines of [FeII], [CoII] a newly synthesized Fe must occupy ~ 50% of volume of glowing interior: “nickel bubbles” due to foaming action driven by radioactive heating

Fe, Co, Ni

Dust

C, O, Si, S

H, He

Interior Dust Formation

• 400 – 700 d: bolometric luminosity shifted from optical to FIR;

• Red sides of nebular emission lines vanished

• Visible glow of interior comes mostly from near side. • Morphology determined largely by dust distribution. • Dust obscures central object.• Southern extension is in equatorial plane

What we have learned:the exterior

Crash: birth of SNR1987A

Time-lapse movie of HST images 1994 - 2006

HST - OpticalMarch 2011

ATCA 9 GHz 2009

Chandra 0.5 – 2 keV2009

Light Curves of CS Ring

Optical (HST)

Radio, IR, X-ray

RADIOACTIVE DEBRIS

Motion of optical (HST) hotspots

Expansion of X-ray ring (Racusin et al) and radio shell (Ng et al)

Heating of debris by external X-rays

Hubble observations of the reverse shock: an adventure in spectroscopy

Ha

H + p g H* + p

H + p g 2p + e

Line emission and impact ionization at reverse shock surface

/Dn n = v;/c

H* g H + hn Ha, Lya

Luminosities of Ha and Lya

Each hydrogen atom crossing RS will produce, on average:

Rexc(2p)/Rion = 1 Lya

Rexc(Ha)/Rion = 0.2 Ha

Integrated luminosity of Ha amass flux of H atoms across RS.

z

Dl

/Dl lo = v/cwhere v = H0z and H0 = 1/t

Surfaces of constantDoppler shift are planar sections of the supernova debris

To observer

STIS Ha Observations Jan 30, 2010

Doppler Mapping of Ha Emission from RS Surface

Lyman-a

Ha 2010/2004

Lya vs. Ha

• Reverse shock: photon emission ratio Lya/Ha should be 5/1• Ratio should be independent of Doppler velocity

• But actual ratio varies from 10/1 to 200/1 !• Line profiles completely different: unlike Ha, Lya is not confined

to surface; appears to come from interior

(We should have realized this in 2004): There must be another mechanism to account for most Ly a emission!

Two possiblities (maybe both):1. Resonant scattering of narrow Lya from the ring by HI in debris2. Heating of HI in debris by external X-rays

Resonance Scattering of Lya by Supernova Debris

Source of Lya is nearly stationary emission from hotspots in circumstellar ring

Model requires:aSufficient luminosity of Lya photons from hotspots to account for broad Lya;aSufficient optical depth of SN envelope in damping wings of Lya @ 5000 km/s.

New (March 2011) results fromCosmic Origins Spectrograph

COS compared to STIS:• UV only• Much (60x) better sensitivity & S/N• But poor spatial resolution

Ly a

NV 1240

CIV1550

He II 1640

H (2S a 1S) continuum from hotspots

Broad NV1239,1242 Emission from Reverse Shock

NV

Reverse shock excitation:

Ha/H = [Rexc(Ha) (12.1 eV)]/Rion(H) (13.6 eV) = 0.2

NV1240/N = [Rexc(1240) (10.1 eV)]/Rion(N+4) (98 eV) = 500!

Borkowski, Blondin, & McCray 1997

Carbon/Nitrogen Ratio

Standard cosmic abundance ratio: C/N = 4.1

Narrow UV emission lines from ring a C/N = 0.11

Broad UV emission lines from RS a C/N = 0.05

Interpretation: • nuclear burning (CNO bi-cycle) converts C, O into

N. This explains decreased C/N ratio in ring.

• Further decrease of C/N ratio seen in RS a either: (a) stratification of C/N ratio in outer envelope of progenitor; or (b) continued nucleosynthesis subsequent to ejection of ring.

The Future: what can we hope to learn?

• What is the compact object? • What made the triple ring system?• How (where) are the relativistic electrons

accelerated?• What is the distribution of newly-synthesized

elements in the SN interior

Compact object? – not a clue!

Bolometric luminosity < few hundred L8 < 10-3 Crab pulsar

The best hope: image compact FIR source with JWST (2018?)

How (where) are the relativistic electrons accelerated? Image non-thermal radio emission.

ALMA will do these things:Angular resolution <0.1 arcsec

Cycle 0 observations: April 2012

Mysteries

New Far Infrared Results from Herschel Telescope

250 mm emission has been interpreted as continuum emission from interior dust grains (Matsuura et al 2011). This requires ~ 0.6 solar masses of dust at 18K !!??.

Even if CO (2.6 mm) line emission is 1% of dust emission, ALMA will see it.

If so, ALMA will provide a 3-d map of the interior CO emitting region.

Simulated ALMA Cycle 0 images @ 0.8 mmL: 10 mJY central, 10 mJy ring; R: 3 mJy central, 17 mJy ring

HST Cycle 20 (we hope!)

STIS: 3-d map of interior debris + RS

WFC3 + filters: 2-d images of high-velocity Lya and Ha

Thanks to:

• Bob Kirshner and SAINTS team• Kevin France• Claes Fransson• Remy Indebetouw• Sangwook Park• and many others

VLT broad Ha profile: Fransson et al 2011

Inner debris

Reverse Shock

HeII 1640: analogue of Ha:

1640/Ha = [XHe/XH][Rexc/Rion(He)]/[Rexc/Rion(H)] = [XHe/XH] = 0.21 ✔

But line profiles are different, because He+ can be accelerated in shocked gas.