Constraints on X-ray polarization of synchrotron jets from stellar-mass BHs Dave Russell niversity...
-
date post
22-Dec-2015 -
Category
Documents
-
view
213 -
download
0
Transcript of Constraints on X-ray polarization of synchrotron jets from stellar-mass BHs Dave Russell niversity...
Constraints on X-ray polarization of synchrotron jets from stellar-mass
BHs
Dave Russell
niversity of Amsterdam
In collaboration with:
Dipankar Maitra, Robert Dunn, Sera Markoff, Rob Fender, Fraser Lewis,
Piergiorgio Casella, Peter Curran... and some results from a larger collaboration
28th June 2011
Let’s start with the conclusions
Future spaceborne X-ray polarimeters will* detect variable X-ray polarization from synchrotron emission from the jets
released from accreting Galactic black holes
X-ray binary – microquasar system
I will show:
• Sometimes, synchrotron emission from jets can dominate the X-ray flux of a black hole X-ray binary• This synchrotron emission is polarized at a low, and variable level• The polarization properties can help us understand jet physics
*probably
Optical & infrared data published in Jain et al. 2001; radio in Corbel et al. 2001
X-ray analysis as in Dunn et al. 2010
Introducing the 2000 outburst of XTE J1550-564
Well monitored in X-ray, optical and near-infrared (NIR)
We can separate disc and jet emission
Assumes continuation of the exponential decay of disc flux
Jet has optically thin spectrum
Russell, Maitra, Dunn & Fender 2011, MNRAS, in press
Hardness-intensity vs colour-magnitude diagrams
Could it be a synchrotron jet dominating X-ray?
NIR jet flux is proportional to X-ray flux variability amplitude
increases here(Kalemci et al. 2001)
Russell, Maitra, Dunn & Markoff 2010, MNRAS, 405, 1759
α (NIR optical) ~ -0.7α (optical X-ray) = -0.7α (X-ray power law) = -0.7 (photon index = 1.7)α (X-ray power law before) = -0.6
A single power law decreasing in flux by a factor of ten
Jet origin of X-ray emission predicted by Markoff, Falcke & Fender 2001(modelling of multiwavelength SED of XTE J1118+480)
Fender, Gallo & Jonker 2003:
Energetics are jet dominated at low luminosities in the hard state
A p
ossib
le r
evis
ed
pic
ture
fo
r B
H o
utb
urs
ts
Jet could dominate X-ray flux in the hard state between
News flash: XTE J1752-223 late X-ray + optical flare
2009-2010 outburst of this new BH transient:
Faulkes Telescope monitoring in 4 optical filtersα (optical excess) = -0.16 +- 0.29No change in X-ray PL propertiesRussell et al. in prep.
Polarization of optically thin synchrotron emission
Shahbaz et al. 2008
• In NIR, the observed emission can be highly polarized
• Depends on magnetic field configuration
• Ordered field up to 70% polarized
Russell & Fender 2008
• Tangled field ~ no net polarization
We infer a predominantly tangled, variable magnetic field near the jet base
The PA of polarization is ~ perpendicular to the PA of the resolved radio jet
The magnetic field is approximately parallel to the jet axis (Russell et al. in prep.)
We infer a predominantly tangled, variable magnetic field near the jet base
The PA of polarization is ~ perpendicular to the PA of the resolved radio jet
The magnetic field is approximately parallel to the jet axis (Russell et al. in prep.)
We observed GX 339-4 in September 2008 during a hard state with VLT+ISAAC
We detect significant, variable linear polarization in the near-infrared (when the jet dominated)
Resolved radio jet of GX 339-4 (Gallo et al. 2004) Resolved radio jet of GX 339-4 (Gallo et al. 2004)
New VLT observations of GX 339-4 in 2008
News flash: Polarized γ-ray emission from Cygnus X-1 might be from the jet (Laurent et al. 2011, Science)
Polarization strength is very high: 67 +- 30 % !! (0.4-2 MeV)Derived from 58 days of exposure time
This would imply a very highly ordered, constant B field at the base of the jet of Cyg X-1
PA is offset from jet axis
Conclusions revisited• NIR synchrotron emission from jets in BH X-ray binaries is polarized
• The results so far suggest:
• Near the jet base of GX 339-4, the magnetic field is: generally turbulent (only partially ordered) and rapidly changing parallel to the jet axis
• Near the jet base of Cygnus X-1 (Laurent et al. 2011), the magnetic field is possibly:
extremely ordered and not rapidly changing offset from the jet axis
• These magnetic geometry/variability properties are useful for jet models
• This polarized synchrotron emission can occasionally dominate the X-ray flux (This is probably true XTE J1550-564, and possibly XTE J1752-223)
• Regular X-ray & optical/NIR monitoring is beneficial, such as SMARTS & Faulkes
Future spaceborne X-ray polarimeters like GEMS and NHXM may be able to detect variable X-ray polarization from
synchrotron emission from the jets released from accreting Galactic black holes