Supernova 1987A at 25 years. 1.Highlights of the past 25 years 2.Outstanding mysteries and surprises...

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.