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

HETGApril 1, 2005

3x1037 erg/skT=1.34 keV diskSteep 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

ne diagnostic ratios

300-1600 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 11.77 and 11.92Å lines give the populations of2p 2P1/2 and 2p 2P3/2 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 scatteredseveral times, converting to 4p 3s and 3s 2p photons.

Upper limit to 3s 2p EW places limit on coveringfactor. (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-Opacityin UV lines(O stars, CVs, AGN)

Thermal Pressure – Comptonheating XRBs

Magnetic processes – MRIor Blandford-Payne

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

Thermally Driven Wind?

Begelman, McKee, ShieldsWoods 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

Woods et al.

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

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 notimplausible

Nearly constant ionization parameter, unlike constant densityModels of Miller et al.

rmin = 10 10.7 cm = 0.1 RIC

Concluded Thermally Driven Wind OK

Check ξ

Our models, CLOUDY and XSTAR allow lower ξ than we hadthought, 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

Woods et al predicta peak mass loss rateof 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

MRI disk wind simulations (Proga 2003)

equatorial

v = few*10^(2-3) km/s

high m-dot

Magnetic Disk Wind ModelsProga 2003

Equatorial

Few hundred km/s

High M-dot

CONCLUSION

It still appears that neither radiation pressure nor thermalpressure is capable of driving a wind at the density seen.

Other, more typical X-ray spectra of BH systems showonly Fe XXVI and Fe XXV:

Much lower column density, much higher ξr > 0.1 RIC seems plausible

Other systems may show thermally driven winds, butthis spectrum of GRO1655 seems to require magnetic wind.