Composite colliding winds (CWo - orbiting; CWc - concentric; CWb - binary) and Seaquist,

1. Kenny, 1995. PhD Thesis, University of Calgary • Composite colliding winds (CWo - orbiting; CWc - concentric; CWb - binary) and Seaquist, • Taylor and Button (STB) model of HM Sge (open circle - hot component; filled circle - Mira). • rotation of stars leads to rotation of p.a. of nebular features. • projection effects due to orbital inclination may lead to changes in apparent separation of features

2. Richards et al. 1999. MNRAS 305, 380 5GHz (MERLIN) radio maps at several epochs Northern and Southern components separated by ~ 150 m.a.s. at 5GHz (~120 m.a.s. at 22GHz with VLA) • Apparent “rotation” of radio components at ~ 2.5 arcsec p.a. • In line with Kenny et al. models • Suggests P ~ 90 20 yrs ±

3. Eyres et al, 2001. ApJ, 551, 512 [OIII]4959/5007 [OIII]4363 • HST GO observations with WFPC2 and selected narrow • and broad band filters (diagnostic lines, location of continuum • sources) - 1999 October 22 • VLA A-array 8.56 and 23GHz observations - • 1999 September 26 • North, South and Central components are indicated • Line ratio indicates cooler “wedge” of material to SW, • extending ~ 0.5arcsec from the central binary

4. Hb VLA 23GHz EB-V • Comparison of Hb and thermal radio emission allows • estimation of variation of extinction across nebula (left) • Peak of extinction (EB-V~1) to S • Interstellar extinction estimated as EB-V~0.35 (d >700pc)

5. Cartoon showing main nebular components and positions of hot (WD) and cool (RG) stellar components (derived from HST WFPC2 F218W and F547M observations respectively). Implies: binary separation = 40 ± 9 m.a.s. at p.a. = 1300 ±100 (cf. Schmid et al. 2000, p.a. = 1230) Thus d = 625± 140 pc if a = 25AU (P = 90yrs; M = 2M¤) Also shown are centroids from narrow band filters

6. CH Cygni Crocker et al., 2001. MNRAS 326, 781 U and V light curves Hb [OIII]4959/5007 VLA (1999 September 26 - lower panel) • HST WFPC2, 1999 August 13 • during primary eclipse • no significant offset of hot and cool component centroids

7. Crocker et al. 2002. MNRAS • Variation in p.a. of central region CH Cyg • from radio and HST observations with simple • fit • Precession due to interaction of inner regions • of accretion disk with WD magnetic field • favoured by Crocker et al. Ballistic ejection model overlaid on 5GHz maps from 1986 -2000. Fitted Parameters: P = 6519 ± 153 days To = JD2444038 ± 128 qmid = 140 ± 10 qo = 35 ± 10 vo = 1263 ± 18 km s-1 i = 88 ± 10

8. The shape of things to come: COAST results for CH Cyg - resolution 9 m.a.s. (2.4 AU), 920 nm Persistent elongation of primary stellar disk with possible rotation consistent with ~14.5yr period (Young et al 2002, to be submitted)

9. The Liverpool Telescope • 2m Robotic Telescope • New, UK National Facility • Sited on La Palma • CCD and NIR cameras • (spectrograph soon) • Studies of variability from • seconds to years • First light 21st July Application Round likely deadline 30th September (see telescope.livjm.ac.uk)