Evidence for a Magnetically driven wind from the Black Hole Transient GRO 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 67-85º Inclination 3.2 kpc Distance

HETG April 1, x10 37 erg/s kT=1.34 keV disk Steep power law Constant for 64 ksec 90 Absorption lines! (typically 2)

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

km/s blue shifts: Wind

Very Highly Ionized

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

Fe XXII and 11.92Å lines give the populations of 2p 2 P 1/2 and 2p 2 P 3/2 states of ground level Density diagnostic (Mauche et al. for emission lines) Radiative excitation negligible at relevant r

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

How to drive a disk wind? 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 Radiative Driving-Opacity in UV lines (O stars, CVs, AGN) Thermal Pressure – Compton heating XRBs Magnetic processes – MRI or Blandford-Payne

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

Thermally Driven Wind? Begelman, McKee, Shields Woods et al. T IC = 1.4x10 7 K R IC where c s = v esc R IC = cm Wind at r > 0.1 to 0.2 R IC r > cm

Woods et al.

Where is the absorbing gas? ξ = L/nr 2 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 < cm < 0.01 R IC and concluded Not Thermally Driven Wind

BUT Netzer (astro-ph/ ) constructed models with n ~ 1/r 2 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. r min = cm = 0.1 R IC Concluded Thermally Driven Wind OK

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 but not as large as cm Check n e Netzer’s maximum density is ¼ Fe XXII value. Average is 1/10 n 2 /n 1 = 0.05 vs 0.5 to 0.7 measured r = cm or 0.02 R IC

Woods et al predict a peak mass loss rate of 6x10 –6 g/(cm 2 s) Divide by v=500 km/s (Vertical wind makes it worse.) n max = 6x10 10 cm -3 THERMAL WIND PREDICTS A DENSITY TOO LOW BY ORDERS OF MAGNITUDE

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

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 R IC seems plausible Other systems may show thermally driven winds, but this spectrum of GRO1655 seems to require magnetic wind.