Optical/infrared polarised emission in X-ray binaries
Dave Russell
New York University Abu Dhabi
[email protected]
In collaboration with Tariq Shahbaz (IAC, Tenerife)
I’d also like to thank Rob Fender, Elena Gallo, Poshak Gandhi, James Miller-Jones
Maria Cristina Baglio, Karri Koljonen, Marion Cadolle Bel, Richard Plotkin
Polarised Emission from Astrophysical Jets, Ierapetra, Crete, 14th June 2017
X-ray Binary Jets
Black hole XB: GRO J1655-40
Neutron star XB: Sco X-1
Radio emission:  is synchrotron in nature
 collimated outflows (2 types of jet)
The approximate spectrum of a steady, hard state jet:
Optically thick
log
Optically thin
F
Radio
X-ray?
log

• The power carried in the jets is uncertain
• Depends on the position of the “jet break”
• How does the jet spectrum evolve during outbursts?
 Time evolution (impossible for AGN)
• What are the conditions in the inner regions of the jets?  Polarisation
Can we see the jet in the optical/infrared?
In the last decade or so, evidence shows that:
 the jet is sometimes visible in optical and NIR
 the turnover in the jet spectrum probably lies somewhere in the IR
-------------------JET ON---------------------JET OFF—
-------------JET ON --------------------
Data from Homan et al. 2005, Jain et al. 2001, Buxton & Bailyn 2004
We need polarisation data in the hard state
 The radio and optical/infrared emission
drops when the source leaves the hard
state as jet is quenching
(Cadolle Bel et al. 2011)
2010 outburst:
Soft X-ray
Hard X-ray
Time resolution
typically ~100 sec
Faulkes Telescope South
 This happens in every outburst of
GX 339-4 in which there are state
transitions (Buxton et al. 2012)
 The infrared component is highly
variable (Casella et al. 2010, Kalamkar
et al. 2016)
Optical
Jet spectral breaks
Jet break found in the black hole XRB GX 339-4 in the mid-IR and varying rapidly:
WISE data
Gandhi et al. 2011 identify the jet break in GX 339-4:
In the mid-IR: moving between 4 and 22 microns (probably further)
See also Corbel & Fender (2002), Migliari et al. (2010), Russell et al. (2013)
Polarisation of optically thin synchrotron emission
Gliozzi et al. 1998
Some radio
data exist:
Some optical
data exist:
A few %
polarised
A few %
polarised due
to scattering
(James
Miller-Jones’
talk)
Very little opt/NIR data exist, but growing
field (Shahbaz, Russell, Baglio, Chaty)
Shahbaz et al. 2008
(e.g. Dolan,
Gliozzi, Baglio)
• In NIR, the observed emission of X-ray binaries can be highly polarised
• Depends on magnetic field configuration
• Ordered field  up to ~80% polarised
• Tangled field  ~ no net polarisation (low f)
VLT observations of GX 339-4 in the hard state
 We observed GX 339-4 during a hard state with VLT+ISAAC
 We detect significant, variable linear polarisation in the near-infrared (when the jet dominated)
 Polarisation variability timescale: < 60 sec
Resolved radio jet of GX 339-4 (Gallo et al. 2004)
We infer a predominantly tangled, variable magnetic field near the jet base: 1 – 3 % polarised
 The PA of polarisation is ~ perpendicular to the PA of the resolved radio jet
 The magnetic field is approximately parallel to the jet axis
 variability dampens pol.?
Time-resolved optical polarimetry of V404 Cyg
during its flaring state in 2015 (discrete ejections)
Shahbaz et al. 2016:
•
•
•
•
On 23 June 2015: time resolved optical
polarimetry with the Telescopio
Nazionale Galileo (TNG) telescope
2 sec exposure times in r'-band, for 2
hours
Intrinsic polarisation light curve
determined by subtracting the
interstellar quiescent polarisation level
Variable polarisation: 4.5 to 3.5 % in 20
mins PA is -9 degrees E of N
Time-resolved optical polarimetry of V404 Cyg
during its flaring state in 2015 (discrete ejections)
•
•
•
•
Outburst VLBI data show resolved radio
jet: PA between ~ -30 and +5 degrees
E of N (James Miller-Jones’ talk)
The optical PA implies that the E-field
vector near the base of the jet is parallel
to the jet axis
B-field is orthogonal to the jet axis
Evidence for magnetic field compression
in shocks within the jet, resulting in a
partially ordered transverse field
Time-resolved optical polarimetry of V404 Cyg
during its flaring state in 2015 (discrete ejections)
•
•
•
A huge X-ray flare was observed
with INTEGRAL JEM X-1 reaching
about 40 Crab
A prominent radio flare at 16 GHz
was observed with the AMI,
peaking just a few hours after the
optical polarisation flare
The optical polarisation flare occurs
during the initial stages of the rise
of the radio flux
Time-resolved optical polarimetry of V404 Cyg
during its flaring state in 2015 (discrete ejections)
•
•
•
•
The 16 GHz and 5 GHz flares
(Fender et al. in prep) peak at 2 h
and 4 h respectively after the
r’-band polarisation flare
We first observe the jet base in
polarised light at optical
wavelengths, and then the radio
flares, which arise from emission
along the jet downstream
The three flares describe a
classically evolving synchrotron flare
from an ejection
It appears we are witnessing an
individual ejection evolving from
optical to radio wavelengths, over a
frequency range spanning 4.5
orders of magnitude
Time-resolved optical polarimetry of V404 Cyg
during its flaring state in 2015 (discrete ejections)
Lupinov et al. 2016:
•
•
•
Found 2 flares of optical
polarisation in V404 Cyg
Changes by ~ 4-6 % in
polarisation in 1 hour
Seen when the optical flux
was faint, before an optical
flare
Polarisation of neutron star XRBs
4U 0614+09: M.C. Baglio’s
talk
Cyg X-2 and Sco X-1
NIR spectropolarimetry
(Shahbaz et al. 2008)
All detections are
stronger at low
frequencies
The results imply a predominantly tangled, likely
variable magnetic field near the jet base
Cyg X-2 has an infrared
excess (Wang & Wang
2014)
Sco X-1
NIR (Russell & Fender 2008)
and optical (Schultz et al.
2004) polarisation
The radio jet of Cyg X-2
has now been resolved
(Spencer et al. 2013)
A multiwavelength campaign on Cyg X-2
We took time-resolved NIR polarisation observations with WHT + LIRIS of
Cyg X-2, simultaneously with X-ray (Swift and RXTE) in 2010
4.2 m William Herschel Telescope
LIRIS
A multiwavelength campaign on Cyg X-2
We took time-resolved NIR polarisation observations with WHT + LIRIS of
Cyg X-2, simultaneously with X-ray (Swift and RXTE) in 2010
A multiwavelength campaign on Cyg X-2
We took time-resolved NIR polarisation observations with WHT + LIRIS of
Cyg X-2, simultaneously with X-ray (Swift and RXTE) in 2010
BH XRBs in quiescence have jets
Radio
IR optical
V404 Cyg has flat radio spectrum
(Gallo et al. 2005, 2007) with
instabilities (Rana et al. 2015)
Jets exist in quiescence
Swift J1357.2–0933 has a steep IR–optical
spectrum, high rms variability (20 – 30%)
Optical, NIR, WISE mid-IR (3.4 to 22 mu)
power-law with index -1.4 (Shahbaz et al. 2013)
Could be a thermal, possibly Maxwellian
distribution of electrons in a weaker jet
Jet break is seen by Plotkin et al. 2016
New results from quiescent jets
We took NIR polarisation observations with WHT + LIRIS of
Swift J1357.2–0933 in quiescence
4.2 m William Herschel Telescope
LIRIS
• The synchrotron emission is polarised at a level of 8.0 ± 2.5 % (J to K)
(a detection of intrinsic polarisation at the 3.2σ level)
• The mean magnitude and rms variability of the flux agree with previous
observations (fractional rms of 15–21 per cent)
• These properties imply a continuously launched (stable on long timescales),
highly variable (on short timescales) jet, which has a moderately tangled
magnetic field close to the jet base
Comparing to polarisation in AGN jets
• We need to compare to polarisation measurements from the core in AGN jets
• For example:
• Lopez-Rodriguez et al. (2014) report polarisation of 12 +- 3 % at 12 μm
and 11 +- 3 % at 9 μm in Cyg A
• This is from the steep spectrum originating near the base of the jet
• Above broadband spectrum from Koljonen et al. 2015
• Similar levels of polarisation in M87 at these size scales (~103 Rg)
Source
Intrinsic polarisation
Band
HARD STATE BLACK
HOLE X-RAY
BINARIES:
XTE J1550-564
~2.4 %
K
GRO J1655-40
GX 339-4
5 –/ CSS
6 % sources
GPS
0 – 3% flickering
H and1998)
K
(O’Dea
J-K
Reference
Chaty et al. 2011
Russell & Fender 2008
Russell et al. 2011
QUIESCENT BLACK
HOLE X-RAY
BINARIES:
Swift J1357.2–0933
8.0 ± 2.5 %
J-K
Russell et al. 2016
A0620-00
~0.5 – 1 %
K
Russell et al. 2016
NEUTRON STAR
X-RAY
BINARIES:
Sco X-1
0.2 – 1 % flickering
J-K
Russell & Fender 2008
Cyg X-2
2 – 10 %
K
Shahbaz et al. 2008
4U 0614+09
2.85 ± 0.96 %
r
Baglio et al. 2014
1–7%
Radio
O’Dea 1998
Radio
eg.Lister&Homan 2005
NON-COMPACT JETS
(DISCRETE EJECT I ONS):
Curran; Brocksopp, etc
X-ray binaries
1 – 50 %
Radio, opt.
James’ talk +V404 Cyg
AGN
10 – 50 %
Opt,radio
e.g.Perlman et al. 2006
AGN CORES:
GPS / CSS sources
Flat-spectrum AGN,XRBs 0 – 10 %
Conclusions
• NIR-optical synchrotron emission from jets in X-ray binaries is polarised
• The results so
far suggest:
X-RAY
POLARISATION:
•
COULD BE UP
TO A FEW % FROM THE JET?
Near the jet base the magnetic field is probably:
 generally turbulent (only partially ordered) and rapidly changing
 (this seems to be similar to AGN jet cores)
 parallel
to the
axis (exceptwith
in V404
Cyg: perpendicular: shocks?)
May
be jet
detectable
experiments:
POGOLITE, X-CALIBUR, IXPE
• Open questions:
 What are the timing properties of the variable polarisation?
 Does polarisation correlate with anything in the inflow?
 What drivesNEED
the magnetic
field changes?
FUTURE
MISSIONS!
• More data and more models are needed to explain the observations
Thanks for listening
Gamma-ray polarisation detected in Cyg X-1
Polarised γ-ray emission from Cygnus X-1 might be from the jet (Laurent
et al. 2011, Science)
Polarisation strength is very high: 67 +- 30 % !! (0.4-2 MeV)
Derived from 58 days of exposure time with INTEGRAL
This would imply a very highly ordered, constant B field at the base of
the jet of Cyg X-1
 Jourdain et al. 2012 confirmed the
result using a different instrument on
INTEGRAL
BUT THERE IS
IN
 76A
+- SPANNER
15 % at 230-850 keV
 <20%
at 130-230
keV
THE
WORKS….
 (Jet) synchrotron is the only
plausible origin
Broadband polarisation measurements of Cyg X-1
We observed Cyg X-1 in near-IR with WHT + LIRIS and mid-IR with GTC + CanariCam
No previous IR polarisation measurements published
Its bright: achieved polarisation accuracy of 0.07 % in NIR
The 10.4 m Gran Telescopio Canarias (GTC) on La Palma
Broadband polarisation measurements of Cyg X-1
A simple model can reproduce the broadband
fractional linear polarisation (FLP) given the input
SED (Russell & Shahbaz 2014)
Components:
• Self-absorbed synchrotron (radio to IR)
• Optically thin synchrotron (IR to gamma-ray)
with cut-off in gamma-ray
Max FLP = 82%
• Comptonized corona, assumed here to be
unpolarised (chaotic corona geometry, no net
aligned field?)
• We find f ~ 0.9
• This implies a stable, highly ordered
magnetic field on long timescales
• Magnetic field is perpendicular to the jet
axis in inner regions of the jet
• Needs confirmation from mid-IR or radio!
Polarisation of optically thin synchrotron emission
Gliozzi et al. 1998
Some radio
data exist:
Some optical
data exist:
A few %
polarised
A few %
polarised due
to scattering
(James
Miller-Jones’
talk)
Very little opt/NIR data exist, but growing
field (Shahbaz, Russell, Baglio, Chaty)
Shahbaz et al. 2008
(e.g. Dolan,
Gliozzi, Baglio)
• In NIR, the observed emission of X-ray binaries can be highly polarised
• Depends on magnetic field configuration
• Ordered field  up to ~80% polarised
• Tangled field  ~ no net polarisation (low f)