The 2006 Explosion of the The 2006 Explosion of the Recurrent Nova RS OphiuchiRecurrent Nova RS OphiuchiTim O’BrienTim O’BrienJodrell Bank Observatory, University of ManchesterJodrell Bank Observatory, University of Manchester

Bode, , Harman (Liverpool), Porcas (MPIfR), Muxlow, Beswick, Garrington, Vaytet, Davis (Manchester),Eyres, Rushton (Central Lancs), Gawronski, Feiler (Torun),Anupama (Bangalore), Kantharia (Pune),Osborne, Page, Beardmore, Goad (Leicester),Evans (Keele), Starrfield, Ness (Arizona State), Burrows (Penn State), Schwarz (West Chester), Krautter (Heidelberg), Drake (Harvard CfA), Gehrels (Goddard)…

Vital StatisticsVital Statistics Recurrent Nova – previous outbursts Recurrent Nova – previous outbursts

1898, (1907), 1933, 1958, 1967, 1898, (1907), 1933, 1958, 1967, 19851985

Brightens from ~11th mag to ~4th mag in less than a day.

Before & after 2006

High-mass white dwarf (1.2-1.4 M๏) + Red Giant (M2III), P = 455 days

Outbursts due to thermonuclear runaway (TNR) on WD surface

1985 Outburst – 1985 Outburst – First multi-wavelength First multi-wavelength

campaigncampaign X-rays: EXOSAT, 6 epochs from X-rays: EXOSAT, 6 epochs from t t = 55d. = 55d.

Indicative of gas at several million degrees. Indicative of gas at several million degrees. Mason et al (1987)Mason et al (1987)

Radio: Jodrell BBI from Radio: Jodrell BBI from tt = 18d, VLA, EVN = 18d, VLA, EVNPadin et al (1985), Hjellming et al (1986), Porcas et al (1987), Padin et al (1985), Hjellming et al (1986), Porcas et al (1987), Taylor et al (1989) Taylor et al (1989)

Models of shock interaction similar to SNR. Models of shock interaction similar to SNR. Bode & Kahn (1985), O’Brien & Kahn (1987), O’Brien, Bode & Bode & Kahn (1985), O’Brien & Kahn (1987), O’Brien, Bode & Kahn (1992)Kahn (1992)

Led to estimates of various parameters:Led to estimates of various parameters:dd = 1.6 = 1.6 0.3 kpc, 0.3 kpc, NNHH = = 2.4 2.4 0.6 cm0.6 cm-2 -2 ,, MMejej = = 1.1 1.1 x 10x 10-6-6 M M, , MMWW = 2 x 10 = 2 x 10-7 -7 MM yr yr-1 -1 ,, E = E = 1.1 x 101.1 x 1043 43 ergerg

EVN 1985Effelsberg, Jodrell, Westerbork,No fringes on JB-Wb

2006 Outburst2006 Outburst

Discovered Feb 12.83 UT (Discovered Feb 12.83 UT (t = t = 0)0)

Within a few days, ToO’s granted on Within a few days, ToO’s granted on Swift, XMM, Chandra, MERLIN, VLA, Swift, XMM, Chandra, MERLIN, VLA, VLBA, EVN, Liv Tel, UKIRT,VLBA, EVN, Liv Tel, UKIRT, plus plus HSTHST, , GMRT, OCRA GMRT, OCRA and and SpitzerSpitzer later. later.

Thanks!Thanks!

Radio ObservationsRadio Observations

Monitoring from day 4.5 onwards Monitoring from day 4.5 onwards with MERLIN, VLA, GMRT, OCRA, with MERLIN, VLA, GMRT, OCRA, VLBA and EVN.VLBA and EVN.

L/C-Band LightcurveL/C-Band Lightcurve

Eyres et al (2006)

L/C-Band LightcurveL/C-Band Lightcurve

1985

New component

VLBI ImagingVLBI Imaging

VLBA VLBA VLBAEVN EVN

First VLBI image – Day 13.8First VLBI image – Day 13.8

VLBA image revealsthe shock wave for thefirst time. Earliest resolution of structure in any such explosion.

Res’n ~ 3 mas

Peak Tb ~ 5x107K

Significant contribution from synchrotron.

O’Brien et al (2006)6 cm

Three epochs of VLBI Three epochs of VLBI imagingimaging

6 cm

18 cm

Day 13.8

Day 13.8 Day 20.5 Day 28.7

Day 28.7Day 21.5

Expanding ring

VLBA EVN VLBA

Expansion velocityExpansion velocity

0.63 mas day0.63 mas day-1-1

1750 km s1750 km s-1-1 at 1600 pc.at 1600 pc.

Consistent withConsistent withSwift X-raySwift X-raytemperatures.temperatures.

Three epochs of VLBI Three epochs of VLBI imagingimaging

6 cm

18 cm

Day 13.8

Day 13.8 Day 20.5 Day 28.7

Day 28.7Day 21.5

?

The “second” component

MERLIN imagingMERLIN imaging

Second component Second component clearly visible from clearly visible from day 21 onwards.day 21 onwards.

Third component Third component to west visible to west visible around day 50. around day 50.

Source evolves into Source evolves into

E-W structure.E-W structure.

VLBI SequenceVLBI SequenceVLBA 14d

EVN 22d

VLBA 29d

VLBA 49d

VLBA 63d

6 cm

6 cm

6 cm

18 cm

18 cm

Swift Swift X-ray ObservationsX-ray ObservationsTwo components:

1. Shock providing higher-energy emission visible at early and late times.

2. Bright soft component from nuclear burning on white dwarf.

Bode et al (2006), Osborne et al (2006)

A modelA model

Bipolar shell viewed at the (known) inclination of the binary orbit and partially obscured by the overlying red giant wind.

Binary orbit

A modelA model

Early

Late

Synthetic images

As the source expands the overlying free-free absorption is reduced and it becomes symmetrical.

SummarySummary Direct imaging of shock wave for first time. Direct imaging of shock wave for first time.

Properties consistent with X-ray emission.Properties consistent with X-ray emission. Develops into E-W structure similar to the Develops into E-W structure similar to the

1985 image of Porcas et al despite doubters!1985 image of Porcas et al despite doubters! Radio monitoring reveals double-peaked light Radio monitoring reveals double-peaked light

curve related to these multiple components.curve related to these multiple components. X-rays reveal shock and nuclear burning (BTW X-rays reveal shock and nuclear burning (BTW

proving part of my own PhD thesis wrong!).proving part of my own PhD thesis wrong!). Hydro modelling in progress to determine Hydro modelling in progress to determine

whether ejection in form of jets.whether ejection in form of jets. Will RS Oph explode as a Type Ia SN?Will RS Oph explode as a Type Ia SN?