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Evidence for a Magnetically driven wind from the Black Hole Transient GRO1655-40

Evidence for a Magnetically driven wind from the Black Hole Transient GRO1655-40 John Raymond, Jon Miller , A. Fabian, D. Steeghs, J. Homan, C. Reynolds, M. van der Klis, R. Wijnands 7 M S Black Hole 2.3 M S Companion 2.6 Day Period

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Evidence for a Magnetically driven wind from the Black Hole Transient GRO1655-40

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  1. Evidence for a Magnetically driven wind from the Black Hole Transient GRO1655-40 John Raymond, Jon Miller, A. Fabian, D. Steeghs, J. Homan, C. Reynolds, M. van der Klis, R. Wijnands 7 M S Black Hole 2.3 MS Companion 2.6 Day Period 67-85º Inclination 3.2 kpc Distance

  2. HETG April 1, 2005 3x1037 erg/s kT=1.34 keV disk Steep power law Constant for 64 ksec 90 Absorption lines! (typically 2)

  3. Lines of Na, Al, P, Cl, K, Ti, Cr, Mn, Co Fe XXII – XXVI Fe XXIV 2-3 up to 2-10 ne diagnostic ratios

  4. 300-1600 km/s blue shifts: Wind

  5. Very Highly Ionized

  6. Need to use Voigt profiles to model EW (saturation) Double Abundances of O, Ne and Ca-Ni to match (Does not agree with optical abundances of Israelian) Some trouble for low Z He-like ions

  7. Fe XXII 11.77 and 11.92Å lines give the populations of 2p 2P1/2 and 2p 2P3/2 states of ground level Density diagnostic (Mauche et al. for emission lines) Radiative excitation negligible at relevant r

  8. Low Covering Factor:Fe XXIV 2s 4p photons are absorbed and scattered several times, converting to 4p 3s and 3s 2p photons. Upper limit to 3s 2p EW places limit on covering factor. (Lack of P Cygni profiles probably similar) Gas less than 12º above disk Lack of eclipse implies at least 6º above disk Lack of change implies uniform over 1/3 of azimuth

  9. How to drive a disk wind? Radiative Driving-Opacity in UV lines (O stars, CVs, AGN) Thermal Pressure – Compton heating XRBs Magnetic processes – MRI or Blandford-Payne • Radiative driving - pressure due to opacity in UV lines (O stars, CVs, AGN) • Thermal driving - Compton heating (Begelman et al. 83) • Magnetic processes - magnetocentrifugal driving or pressure from MRI in the accetion disk Ionization parameter: xi = L_x / n r^2

  10. Radiation Pressure Driven Wind? Popular for AGN Works for O stars No Measure Prad in X-rays Comparable amount in EUV Fe XXII, XXIII, XXIV Too Highly Ionized to absorb

  11. Thermally Driven Wind? Begelman, McKee, Shields Woods et al. TIC = 1.4x107 K RIC where cs = vesc RIC= 10 11.7 cm Wind at r > 0.1 to 0.2 RIC r > 10 10.7 cm

  12. Woods et al.

  13. Where is the absorbing gas? ξ = L/nr2 N = nr = L/ξr r < L/N ξ (L from continuum, N and ξ from lines) OR r = (L/nξ)1/2 (n from Fe XXII) We found r < 10 9.5 cm < 0.01 RIC and concluded Not Thermally Driven Wind

  14. BUT Netzer (astro-ph/0610231) constructed models with n ~ 1/r2 or 1/r 2.3 Spherical wind, constant v or modest acceleration Not necessarily right for vertical wind from disk, but not implausible Nearly constant ionization parameter, unlike constant density Models of Miller et al. rmin = 10 10.7 cm = 0.1 RIC Concluded Thermally Driven Wind OK

  15. Check ξ Our models, CLOUDY and XSTAR allow lower ξ than we had thought, but not as low as Netzer’s parameters; Too little Fe XXVI, too much Fe XXII Allows r larger than 10 9.5 but not as large as 10 10.7 cm Check ne Netzer’s maximum density is ¼ Fe XXII value. Average is 1/10 n2/n1 = 0.05 vs 0.5 to 0.7 measured r = 10 10 cm or 0.02 RIC

  16. Woods et al predict a peak mass loss rate of 6x10–6 g/(cm2 s) Divide by v=500 km/s (Vertical wind makes it worse.) nmax = 6x1010 cm-3 THERMAL WIND PREDICTS A DENSITY TOO LOW BYORDERS OF MAGNITUDE

  17. MRI disk wind simulations (Proga 2003) equatorial v = few*10^(2-3) km/s high m-dot Magnetic Disk Wind Models Proga 2003 Equatorial Few hundred km/s High M-dot

  18. CONCLUSION It still appears that neither radiation pressure nor thermal pressure is capable of driving a wind at the density seen. Other, more typical X-ray spectra of BH systems show only Fe XXVI and Fe XXV: Much lower column density, much higher ξ r > 0.1 RIC seems plausible Other systems may show thermally driven winds, but this spectrum of GRO1655 seems to require magnetic wind.

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