Low-frequency radio observations of jets from X-ray binaries

James Miller-Jones
LOFAR and the Transient Radio Sky, Amsterdam, December 2008

Transcript

1. James Miller-Jones Jansky Fellow, NRAO jmiller@nrao.edu Anna Kapinska, Katherine Blundell, and The LOFAR Transients Key Project collaboration (Fender, Stappers, Wijers et al.)
2. ¨  Compact objects in binary systems with less evolved stars ¨  X-rays emitted from the central regions ¨  Radio emission from jets ¨  Accretion and ejection fundamentally linked
3. ¨  All X-ray binaries thought to produce jets ¨  Compact, flat-spectrum jets exist in quiescence ¨  Bright, relativistic jets observed during outburst Mirabel & Rodriguez (1994) Fuchs et al. (2003)
4. Fender, Belloni & Gallo (2004)
5. ¨  Census of transient sources ¨  Duty cycles ¨  Impact on the environment ¨  Energetics via calorimetry ¨  Shape of the low-energy electron distribution ¨  Absorption properties of the surrounding gas
6. ¨  Delayed rise, lower peak at low frequencies ¨  Smoothed-out lightcurves
7. ¨  X-ray binaries exhibit different ‘states’ ¨  Jet properties related to X-ray state ¨  Compact hard state jet ¨  Lorentz factor increases as intensity rises ¨  Internal shocks cause outbursts ¨  Constrain duty cycles using a proper census Fender, Belloni & Gallo (2004) Migliari & Fender (2006)
8. ¨  Constant input of energy and momentum into ISM ¨  Jets can inflate bubbles in their surroundings ¨  Few known examples; most jets in dynamically underpressured, underdense environments Gallo et al. (2005) Tudose et al. (2006)
9. ¨  Synchrotron energy spectra are power laws ¨  Measure low frequency spectrum to determine power-law shape ¨  Determines if a low- energy cutoff exists ¨  Implications for electron acceleration mechanisms ¨  Low-frequency turnover can constrain surrounding gas density van der Horst (2007)
10. ¨  High-energy processes lead to radio and X-ray emission ¨  RXTE ASM shows variable X-ray sky ¨  Large fields of view at low frequencies make radio sky monitoring possible
11. ¨  Take X-ray luminosity function, use Fundamental Plane ¨  Convolve with Galactic distribution ¨  Expect several XRBs detectable at all times, plus transients Heinz & Grimm (2005)
12. Instrument Frequency range (MHz) Primary beam (deg) Resolution (arcsec) Sensitivity (mJy/bm) VLA 74 700 24-850 15 (12h) 330 150 6-200 0.2 (12h) GMRT 151 186 20/420 1.5 235 114 13/270 0.6 325 81 9/200 0.3 WSRT 117-175 300-480 104-160 3-5 310-390 160 55 0.25
13. ¨  Fixed dipoles, rather than steerable dishes ¨  Split into compact core and extended array ¨  Full polarization imaging ¨  Point source sensitivity: ¡  0.4 mJy (1h, high band, full array) ¡  11-20 mJy (1h, low band, full array) ¨  Synthesised beam 3-20” (full array), 1-14’ (core only)
14. ¨  5 quiescent black hole systems ¨  Not detected by GMRT at 1280, 610 or 235 MHz Source Epochs 235-MHz upper limit (mJy) log10(LX ) (erg/s) Predicted LR (mJy) XTE J1118+480 7 <4.8 30.5 9x10-3 GRO J1655-40 4 <5.7 31.2 8x10-3 XTE J1748-288 4 <3.8 - GRS 1758-258 8 <3.7 - 1E 1740.7-2942 8 <4.2 - Pandey et al. (2007)
15. ¨  Persistent sources detected below 1 GHz ¨  All unresolved Pandey et al. (2007) Pandey et al. (2006) Sco X-1 0.61 GHz Cyg X-1 0.61 GHz Cyg X-3 0.61 GHz
16. ¨  Persistent sources detected below 1 GHz ¨  All unresolved LS 5039 330 MHz
17. ¨  Cyg X-1, Cyg X-3, Sco X-1, LSI +61 303: α>0 ¨  SS 433, LS 5039: α<0 Cyg X-1 SS433 Pandey et al. (2007) α=-0.25, -0.1, 0.26 α=-0.69 to -1.05
18. ¨  Soft X-ray transient ¨  2002 May flare ¨  GMRT/VLA monitoring ¨  Gradually becomes optically thin Ishwara-Chandra et al. (2006)
19. ¨  Highly variable at 610 MHz
20. ¨  Classical self- absorbed spectrum 13 . 0 G) mas)/(B/1 /1 ( 1/4 ≈ θ ¨  Within 2d, turnover had decreased to <610 MHz
21. ¨  Flare in 1998 April ¨  VLBI monitoring ¨  Smothered jet Mioduszewski & Rupen (2004)
22. ¨  Delayed rise of the low frequency emission
23. ¨  Most massive known stellar-mass black hole (14±4 MO ) ¨  Archetypal microquasar: compact jet and occasional relativistic outbursts ¨  Two IRAS sources equidistant and aligned with the jet axis ¨  Proposed as the interactions of the jet with the ISM Rodriguez & Mirabel (1998) Kaiser et al. (2004)
24. ¨  rms 5.5 and 60 mJy/bm ¨  GRS 1915+105 detected at ~4σ at 330 MHz (21.4 mJy)
25. ¨  Steep spectrum from 244 to 610 MHz ¨  S ν α ν-1.57 ¨  Optically-thin synchrotron emission Ishwara-Chandra et al. (2005)
27. ¨  Extrapolate steep spectrum to 15GHz ¨  Implies flux density of 1- 2 mJy ¨  Spectrum must flatten Dhawan et al. (2000) Mirabel & Rodriguez (1994), Fender et al. (1999)
28. Image courtesy G. Pooley
29. ¨  High-mass X-ray binary with Wolf-Rayet companion ¨  Occasional very strong radio flares (to ~20 Jy) ¨  VLBA observations indicate a relativistic jet ¨  No evidence for proposed hotspot candidates Miller-Jones et al. (2004)
30. ¨  Source not detected ¨  Constrains spectral index α>0.5 (Sν α να)
31. ¨  Rose out of pre-flare quench state on 2006 May 4 ¨  Peaked at ~14 Jy at 15 GHz on May 9 ¨  e-VLBI imaging detects jet-like structures ¨  GMRT 610-MHz monitoring shows flux density rising from May 10-12 Tudose et al. (2007)
32. ¨  27 July 2005 ¨  rms 42 mJy bm-1 ¨  Non-detection ¨  20 May 2006 ¨  rms 15 mJy bm-1 ¨  Detection at 1.02 Jy bm-1
33. ¨  May 17,20: spectrum from 140MHz – 30GHz ¨  Still not optically thin at lowest frequencies ¨  Rise time > 16d
34. ¨  Super-Eddington X-ray binary ¨  Precessing jets trace out corkscrew pattern ¨  Jets inflate W50 nebula Dubner et al. (1998) Blundell & Bowler (2004)
35. ¨  Simultaneous dual- frequency observations ¨  Ionospheric imaging algorithm ¨  11.9o primary beam ¨  B-D configuration ¨  rms 190 mJy/bm ¨  W50 nebula detected ¨  SS433 detected ¨  SNRs in Galactic Plane
36. ¨  SS433 detected and variable at 74 MHz ¨  W50 has unbroken integrated spectrum down to 74 MHz ¨  Eastern wing shows spectral turnover
37. ¨  A-configuration observations just after a flare ¨  Spectrum turned over at 1 GHz ¨  B, C configurations show an unbroken steep spectrum
38. ¨  Quasi-simultaneous observations at 310-380 and 115-170 MHz ¨  8 simultaneous spectral windows ¨  SS433 also detected in both bands ¨  Inverted spectrum suggests new component ejected
39. ¨  Plenty of XRBs will be bright enough to monitor in the hard state ¨  Several transient outbursts per year will be detected ¨  Primarily explosive synchrotron events ¨  Slow evolution and long timescales at low frequencies ¨  Bright for many weeks to months after outburst ¨  Good census of transient sources
40. ¨  Persistent X-ray binaries are also radio loud at low frequencies ¨  X-ray binaries show low-frequency variability ¨  Wide fields of view available enable radio sky monitoring for the first time ¨  Delayed rise in synchrotron events ¨  Low surface brightness sensitivity key to probing environments ¨  Good prospects for LOFAR!