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
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 – First multi-wavelength campaign
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)
EVN 1985 Models of shock interaction similar to SNR. Effelsberg, Jodrell, Westerbork,
Bode & Kahn (1985), O’Brien & Kahn (1987), O’Brien, Bode & Kahn No fringes on JB-Wb (1992)
Led to estimates of various parameters:
d = 1.6 ± 0.3 kpc, NH = 2.4 ± 0.6 cm-2 , Mej = 1.1 x 10-6 M, MW = 2 x 10-7 M yr-1 , E = 1.1 x 1043 erg
2006 Outburst
Discovered Feb 12.83 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.
Thanks!
Radio Observations
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 VLBA 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 Tb ~ 5x107K
6 cm O’Brien et al (2006)
Significant contribution from synchrotron.
VLBA
6 cm
EVN Expanding ring
VLBA
Three epochs of VLBI imaging
Day 13.8
Day 21.5
Day 28.7
18 cm
Day 13.8
Day 20.5
Day 28.7
Expansion velocity
0.63 mas day-1
1750 km s-1 at 1600 pc. Consistent with Swift X-ray temperatures.
6 cm
Three epochs of VLBI imaging
The “second” component
Day 13.8
Day 21.5
Day 28.7
18 cm
?
Day 13.8 Day 20.5 Day 28.7
MERLIN imaging
Second component clearly visible from day 21 onwards. Third component to west visible around day 50. Source evolves into E-W structure.
VLBI Sequence
VLBA 14d VLBA 63d
6 cm
EVN 22d
VLBA 49d
18 cm
VLBA 29d
6 cm 18 cm
6 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
Binary orbit
Bipolar shell viewed at the (known) inclination of the binary orbit and partially obscured by the overlying red giant wind.
A model
Synthetic images
Early
Late
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. 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. 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. Will RS Oph explode as a Type Ia SN?