A Wind Analysis of an Evolved Giant

Cool Stars 13 - 2004 - Hamburg A Wind Analysis of an Evolved Giant Phase Resolved FUSE and HST/STIS Observations of an Eclipsing Symbiotic Binary Cian Crowley Dr. Brian Espey Trinity College Dublin Collaborators: McCandliss, Ferland, Lamers, Hauschildt, Barman, Keenan, Young

What are symbiotic binaries? Binary nature confirmed by IUE • Red giant continuum with emission lines requiring photoionisation by UV source • Closest separation detached binaries red giant primary white dwarf secondary line emission from ionised portion of RG wind

Composite symbiotic spectrum Need multiwavelength data

System parameters • EG And has a number of important properties: • Eclipsing binary • Non-dusty, low extinction • Bright from optical into far-UV • Low luminosity WD secondary • Never observed to undergo outburst • Well determined orbit ~ 481 days

EG And…..some numbers: • Separation ~ 4.5 RRG • Inclination > 70º (from eclipses)

Dataset • Ground-based high resolution echelle spectra (R ~ 35,000) • Far-Ultraviolet Spectroscopic Explorer (FUSE) data for 912 – 1180 Ångstrom region (R ~ 15,000 – 20,000) • Hubble Space Telescope (HST) medium resolution echelle spectra for 1150 – 3180 Ångstrom region (R ~ 48,000)

HST data covering 1150 – 5600 Å

Absorption lines in the UV / FUV • Absorption data provides tomographic information on the chromosphere / low wind of the giant star • Incorrect or incomplete atomic data in FUV • HI columns well defined by Lyman alpha damping profile But complications as always…. • Spectral region extremely feature rich – blending and saturated lines complicate analysis

Flux Observed wavelength Phi=0.80 Phi=0.90 Phi=0.04 Phi=0.15

Wind conditions • Absorption lines from species such as CI, CII, NI, NII, OI, OII, MgII, AlII, SiII, PII, ArI, CaII, MnII, FeII, CoII, NiII…. • Transitions observed from range of lower energy levels: absorption from 0 to 4.5ev above ground • However no CO or H2 absorption in chromosphere H2/Htot < 10–8 • Populations of FeII levels reveal temp ~ 8,000K • Ionisation levelconstant through ingress and egress

Wind velocity profiles……

Standard wind model • The standard parameterisation of winds from both hot and cool stars is a beta law model: v(r) = v(1– R/r) • The following ranges of  are found: 0.5    1 hot stars (Lamers & Morton 1981) 2.5    3.5 K supergiants (Schroeder 1985)

Onset of ionisation  Observed column densities (red points) and smooth polynomial model fit (black line)

Determination of wind parameters • Solving the velocity / column density equation is a form of Abel inverse problem to which a solution has been found by Knill, Dgani and Vogel (1993) • Data fit with a low order polynomial and this function is inverted

SY Mus Hot stars  EG And

Further wind determinations… • We have additional new FUSE data for BF Cyg (M5 III) • The spectra show similarities to the EG And data, but with stronger P-Cygni profiles • Clues to wind driving mechanism?

Summary • Determination of wind conditions and acceleration for EG And • Stellar models being generated for giant • Further data for other stars under analysis • Improved treatment of absorption lines (including improved atomic data) underway • Improved treatment of matter distribution (hydro code + photoionisation) planned

See poster:Brian Espey et al. : (Section F.1) ‘Multiwavelength observations of giant mass loss and interaction in eclipsing symbiotic binaries’ We acknowledge support from Enterprise Ireland Basic Research grant SC/2002/370 from EU funded NDP

A Wind Analysis of an Evolved Giant