The 2006 Explosion of the Recurrent Nova RS Ophiuchi Tim O’Brien Jodrell 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 Statistics Recurrent Nova – previous outbursts 1898, (1907), 1933, 1958, 1967, 1985 Recurrent Nova – previous outbursts 1898, (1907), 1933, 1958, 1967, 1985 Brightens from ~11 th mag to ~4 th mag in less than a day. Before & after 2006

High-mass white dwarf ( M ๏ ) + Red Giant (M2III), P = 455 days Outbursts due to thermonuclear runaway (TNR) on WD surface

1985 Outburst – First multi-wavelength campaign X-rays: EXOSAT, 6 epochs from t = 55d. Indicative of gas at several million degrees. Mason et al (1987) X-rays: EXOSAT, 6 epochs from t = 55d. Indicative of gas at several million degrees. Mason et al (1987) Radio: Jodrell BBI from t = 18d, VLA, EVN Padin et al (1985), Hjellming et al (1986), Porcas et al (1987), Taylor et al (1989) Radio: Jodrell BBI from t = 18d, VLA, EVN Padin et al (1985), Hjellming et al (1986), Porcas et al (1987), Taylor et al (1989) Models of shock interaction similar to SNR. Bode & Kahn (1985), O ’ Brien & Kahn (1987), O ’ Brien, Bode & Kahn (1992) Models of shock interaction similar to SNR. Bode & Kahn (1985), O ’ Brien & Kahn (1987), O ’ Brien, Bode & Kahn (1992) Led to estimates of various parameters: d = 1.6  0.3 kpc, N H = 2.4  0.6 cm -2, M ej = 1.1 x M , M W = 2 x M  yr -1, E = 1.1 x erg Led to estimates of various parameters: d = 1.6  0.3 kpc, N H = 2.4  0.6 cm -2, M ej = 1.1 x M , M W = 2 x M  yr -1, E = 1.1 x erg EVN 1985 Effelsberg, Jodrell, Westerbork, No fringes on JB-Wb

2006 Outburst Discovered Feb UT (t = 0) Discovered Feb UT (t = 0) Within a few days, ToO’s granted on Swift, XMM, Chandra, MERLIN, VLA, VLBA, EVN, Liv Tel, UKIRT, plus HST, GMRT, OCRA and Spitzer later. Within a few days, ToO’s granted on Swift, XMM, Chandra, MERLIN, VLA, VLBA, EVN, Liv Tel, UKIRT, plus HST, GMRT, OCRA and Spitzer later. Thanks! Thanks!

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

L/C-Band Lightcurve Eyres et al (2006)

L/C-Band Lightcurve 1985 New component

VLBI Imaging VLBA EVN

First VLBI image – Day 13.8 VLBA image reveals the shock wave for the first time. Earliest resolution of structure in any such explosion. Res’n ~ 3 mas Peak T b ~ 5x10 7 K Significant contribution from synchrotron. O’Brien et al (2006) 6 cm

Three epochs of VLBI imaging 6 cm 18 cm Day 13.8 Day 20.5Day 28.7 Day 21.5 Expanding ring VLBAEVN VLBA

Expansion velocity 0.63 mas day km s -1 at 1600 pc. Consistent with Swift X-ray temperatures.

Three epochs of VLBI imaging 6 cm 18 cm Day 13.8 Day 20.5Day 28.7 Day 21.5 ? The “second” component

MERLIN imaging Second component clearly visible from day 21 onwards. Second component clearly visible from day 21 onwards. Third component to west visible around day 50. Third component to west visible around day 50. Source evolves into E-W structure. Source evolves into E-W structure.

VLBI Sequence VLBA 14d EVN 22d VLBA 29d VLBA 49d VLBA 63d 6 cm 18 cm

Swift X-ray Observations Two 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 model Bipolar shell viewed at the (known) inclination of the binary orbit and partially obscured by the overlying red giant wind. Binary orbit

A model Early Late Synthetic images As the source expands the overlying free-free absorption is reduced and it becomes symmetrical.

Summary Direct imaging of shock wave for first time. Properties consistent with X-ray emission. Direct imaging of shock wave for first time. Properties consistent with X-ray emission. Develops into E-W structure similar to the 1985 image of Porcas et al despite doubters! Develops into E-W structure similar to the 1985 image of Porcas et al despite doubters! Radio monitoring reveals double-peaked light curve related to these multiple components. Radio monitoring reveals double-peaked light curve related to these multiple components. X-rays reveal shock and nuclear burning (BTW proving part of my own PhD thesis wrong!). X-rays reveal shock and nuclear burning (BTW proving part of my own PhD thesis wrong!). Hydro modelling in progress to determine whether ejection in form of jets. Hydro modelling in progress to determine whether ejection in form of jets. Will RS Oph explode as a Type Ia SN? Will RS Oph explode as a Type Ia SN?