a 500 ks chandra/hetg observation of ex hya

A 500 ks Chandra/HETG observation of EX Hya

Gerardo J. M. Luna (SAO)Nancy Brickhouse (SAO)

John Raymond (SAO)Chris Mauche (LLNL)Daniel Proga (UNLV)

Danny Steeghs (University of Warwick)

Tucson, 2009

EX Hya-X-rays observations:

50 ks Chandra/HETG in 2000

Tucson, 2009

Cooling-flow spectrum

non-magnetic CVs, except EX Hya

Photoionized spectrum

Magnetic CVs

Mukai et al (2003)

Comparison with Capella

Calibration uncertainty? Chandra Line Profile Function?

EX Hya line profiles

Tucson, 2009

EX Hya line profiles

Tucson, 2009

Si XIIIFe XVII

Mg XII Fe XVII

EX Hya lines density diagnostic

•We measure the density using 3 different line ratios (f/i), Fe XXII, Fe XVII and Si XIII. The values agree with previous measurements (Mauche et al 2005).

Tucson, 2009

EX Hya line-based light curves

Tucson, 2009

EX Hya line-based light curves

Allan et al. (1998)

Tall shock, ~ 1RWD

EX Hya line-based light curves

Photoionization model

•We assume a dipole field and the density just above the shock as a parameter, n

0=n14 1014

cm-3

•As n0 goes from 1 to 10, the area of the

accretion spot goes from 0.143-0.045 RWD

and

the height of the shock goes from 0.459 to

0.046 RWD

.

•For scales near the accretion spot size, the

dilution factor of the X-ray radiation drops

rapidly as (rspot

/(r-1))2. The ionization

parameters drops quickly close to the

accretion spot.

•For large height it drops as r-2 and the

ionization parameter rise slowly as r1/2.

Tucson, 2009

Photoionization model

Tucson, 2009

ϴ α

φ

Photoionization model

•Add compressional heating

•Escape probabilities and collisional quenching

•Continuum radiative transfer along the column

•Line radiative transfer along the column

•Accurate Hα and UV fluxes.

Tucson, 2009

Synthesis

•A long exposure in X-rays has allowed us to observe for the first

time new features in the accretion column of EX Hya.

•High signal-to-noise line profiles revealed a photoionization

component with FWHM~1600 km/s.

•Preliminary photoionization models show that OVIII, Si XIV, Mg

XII are formed close to the shock, and this is confirmed by their

modulation at the spin period.

•We measure more accurately density diagnostic lines ratios

with the unprecedented quality of this dataset.

Tucson, 2009