The Evolution of Nova Ejecta

1. The Evolution of Nova Ejecta Michael F. Bode Astrophysics Research Institute Liverpool John Moores University with grateful thanks particularly to Tim O’Brien, Huw Lloyd, John Porter, Sean Dougherty, Andy Newsam

2. Overview • Classical Nova basics • Observations of expanding ejecta • Remnant shaping • An idiosyncratic remnant (help wanted!) • Concluding remarks

3. Observations of the Explosion Visual Light Curve “Speed Class”: Correlations with ejection velocities, peak absolute mag. (From nova search in M31 Using POINT-AGAPE data. Darnley, Bode, Kerins & Newsam 2003, in prep)

4. CNe Characteristics Central System: • WD + late-type MS, P ~ 3-10 hrs • Lqu ~ L¤ At Outburst (TNR on WD): • L ~ 105 L¤ ( ~ LEdd) • Mej ~ 10-5 – 10-4 M¤ • vej~ 1000 km/s • Inter-outburst period: 104 –105 yrs (~ 1000 o/b’s?)

5. Observations of Expanding Ejecta (e.g. V705 Cas 1993) Day 585 1086 0.5¢¢ 1140 1539-1544 MERLIN WHT WHT optical spectra taken on day 963 imply ordered structure (consistent with expanding equatorial and tropical rings in a remnant with i = 600). Difficult to reconcile with radio observations (MERLIN 5GHz – Eyres et al. 2000, MNRAS).

6. Optical imagery (WHT, AAT, HST) (Slavin, O’Brien & Dunlop, 1995.Gill & O’Brien, 1998; 1999.2000, Harman & O’Brien 2003) Blueshifted Ha rest frame Redshifted HR Del (1967, VS) in Ha (left), [OIII] (right). Major axis ~ 12 arcsec (HST). + WHT spectra gives i = 350±50, vpolar= 560±50 km/s, axial ratio = 1.75±0.15 and d = 970±70pc (HO 03 – also thesis by Hillwig) RR Pic (1925, S) in Ha/[NII]. Note equatorial ring (diameter 21 arcsec) and “tails” of emission (AAT - GO 98) DQ Her (1934, MF) in Ha (WHT), ~23x17 arcsec with halo ~ 47x29 arcsec, equatorial and tropical bands (i ~ 90) plus “tails” extending ~ 20 arcsec from points of origin. GK Per (1901, VF, WHT – see later)

7. .3 Relationship of remnant shape to speed class .21 .inclination-corrected (Bode, 2002) 10. .14 .11 .15 .12 Downes & Duerbeck 2000

8. Remnant Shaping • Initial Common Envelope Phase (first explored by Livio et al., 1990) • Model in terms of: • ejecta in form of wind, secularly increasing v, decreasing M • evidence for faster wind later from optical/ir spectra, x-rays, images • flows past secondary which imparts energy and angular momentum • ejection velocities linked to speed class • (Lloyd, O’Brien & Bode, 1997. MN, 284, 137) • Produces rings, blobs and caps, plus a correlation of speed class and • axial ratio in the sense required, but oblate shells • Modified to include effects of WD envelope rotation on variation of • local luminous flux with latitude driving the outburst • Produces prolate shells as required • (Porter, O’Brien & Bode (1998, MN, 296, 943) Ÿ + + **See also poster by Wareing et al.**

9. Results for Run 2 Lloyd et al. (1997 - MF nova) and f = 0: [ANIMATION] [ANIMATION] and f = 0.7 (fast rotation of accreted envelope - Porter et al. 1998): [ANIMATION] [ANIMATION]

10. GK Persei: Vital Statistics • Very fast “neon” nova (Feb 22nd 1901) • d = 470 pc (expansion parallax) • Lmax ~ 5x1038ergs/s; Lqu = 1034ergs/s • Mej ~ 10-4 M¤, vej = 1200 km/s Central System: • P = 1.904 d; WD (intermediate polar) + K2IV • Primary Mass ~ 1 M¤; Secondary Mass ~ 0.2 M¤ • Dwarf nova outbursts

11. The Light Echoes 1901 Sep 1902 Jan • J.C. Kapteyn (1902, AN, 157, 201) concluded v > c • Heroic (34 hr) spectrum of nebulosity by Perrine in 1902 showed it to • be very similar to that of the nova a few days after outburst • Apparent expansion velocity ~ 4c (feature marked in 1901 is 5´ from nova. Also note persistent “bar” to SW in 1902 image)

12. Multi-frequency imaging of the Central Remnant Optical images from (a) 1917 (Ritchey 1918) and (b) 1993 (Slavin et al. 1995) (All images 4x4 arcmin approx) (c) VLA 5GHz image (synchrotron emission – courtesy E.R. Seaquist) (d) CHANDRA images: 0.4-0.6 keV (red); 0.8-1 keV (blue – see also Balman 2002)

13. Form of the Ambient Medium? • IRAS 100mm and HI (21cm) emission • (Bode et al. 1987, Seaquist et al 1989) • Re-analysed by Dougherty et al. (1996 • HIRAS data) • Td= 23 ± 1K, Md = 0.04 M¤ (MHI ~ M¤) IRAS/HI “cloud” ejecta from previous phase of binary evolution? If v = 20 km s-1: t ~ 105 yrs; last major ejection ~ 3x104 yrs ago • Suggest ejection from “born again” AGB star • Current secondary mass and spectral type + luminosity class consistent with ~ 1 M¤ lost

14. Large scale optical nebula discovered by Tweedy (1995) • INT WFC images (1999, 2000 – Bode, O’Brien & Summers • 2003 - submitted) [OIII]5007 (blue), Ha (red) But – what is the cause of the asymmetries? Have measured proper motion of central binary from 1917 – 1993, results:

15. p.m. = 0.015 ± 0.002 arcsec/yrp.a. = 191o ± 5o (thru E from N)vs = 45 ± 4 km/s What is this “cat o’ nine tails”? [OIII] image plus IRAS 100mm contours Ha image plus contours of the light echoes from 1902

16. Concluding Remarks • CNe have reasonably well defined physical parameters (cf. pPNe) • Ejecta show large scale order, but clumpy at small spatial scales • Degree of shaping correlated with “speed class” • Now relatively well modelled, but still improvements to be made • GK Persei is a highly unusual object in many respects • Many phenomena may be explained by interaction of ejecta from • 1901 (first?) outburst with matter from previous evolutionary phase • New observational tools: • e-MERLIN (and EVLA) will give higher spatial resolution, higher • sensitivity and simultaneous multi-frequency mapping of ejecta • AO on 8m-class telescopes and optical interferometry with e.g. • VLTI, Keck outriggers, CHARA, MRO, Large Optical Array • (the latter would resolve structure in the ejecta ~hrs after outburst!)