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

Kenny, 1995. PhD Thesis, University of Calgary

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

Eyres et al, 2001. ApJ, 551, 512

• HST GO observations with WFPC2 and selected narrowand 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

[OIII]4959/5007 [OIII]4363

EB-V

Comparison of H and thermal radio emission allowsestimation 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)

H VLA 23GHz

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

CH Cygni

U and V light curvesCrocker et al., 2001. MNRAS 326, 781

HST WFPC2, 1999 August 13 • during primary eclipse • no significant offset of hot and cool component centroids

H [OIII]4959/5007

VLA (1999 September 26- lower panel)

Crocker et al. 2002. MNRAS

• Variation in p.a. of central region CH Cygfrom 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 modeloverlaid on 5GHz mapsfrom 1986 -2000.

Fitted Parameters:

P = 6519 153 daysTo = JD2444038 128mid = 140 10

o = 35 10

vo = 1263 18 km s-1

i = 88 10

The shape of things to come:COAST results for CH Cyg - resolution 9 m.a.s. (2.4 AU), 920 nm

Data-set Reduced2

Majoraxis/mas

Axial ratio Major axisPA /deg

1999 Aug/Sep 3.3 6.20.1 1.0 —2.0 6.70.1 0.750.04 1354

2000 Jun/Jul/Aug 3.6 6.10.1 1.0 —3.2 6.20.1 0.840.06 1617

2001 Jun/Jul/Aug/Sep 4.1 6.70.1 1.0 —3.1 7.10.1 0.870.03 17610

Persistent elongation of primary stellar disk with possible rotation consistent with ~14.5yr period (Young et al 2002, to be submitted)

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)