Coronal geometry at low mass- accretion rates from XMM and NuSTAR spectra Felix Fürst for the NuSTAR AGN physics and binaries teams
Accreting black holes Supermassive black hole: Cen A Central engine of AGN M BH ~ 10 7 M sun, d ~ 3.8Mpc Stellar mass black hole: GRS 1739-278 X-ray binary M BH ~ 10 M sun, d ~ 8.5kpc NASA/CXC/CfA/R.Kraft et al ESA, NASA, and F. Mirabel (CEA)
Accreting black holes Supermassive black hole: Cen A Central engine of AGN M BH ~ 10 7 M sun, d ~ 3.8Mpc Stellar mass black hole: GRS 1739-278 X-ray binary M BH ~ 10 M sun, d ~ 8.5kpc Accretion from circumnuclear material/torus Complex environment Visible across EMspectrum Accretion from lowmass companion Weak intrinsic absorption High extinction along line of sight Low temperatures, long time-scales High temperatures, Short time-scales NASA/CXC/CfA/R.Kraft et al ESA, NASA, and F. Mirabel (CEA)
Accreting black holes Supermassive black hole: Cen A Central engine of AGN M BH ~ 10 7 M sun, d ~ 3.8Mpc Stellar mass black hole: GRS 1739-278 X-ray binary M BH ~ 10 M sun, d ~ 8.5kpc Accretion from circumnuclear material/torus Complex environment Visible across EMspectrum Low temperatures, long time-scales Accretion from lowmass companion Weak intrinsic absorption High extinction along line of sight Physics deteremined by Eddington luminosity L Edd = 4 π G M m p c/σ T And gravitational radius R g = G M / c 2 High temperatures, Short time-scales NASA/CXC/CfA/R.Kraft et al ESA, NASA, and F. Mirabel (CEA)
Broad band spectra Supermassive black hole: Cen A Stellar mass black hole: GRS 1739-278 10-9 XMM EPIC-pn NuSTAR FPMA νfν (erg cm 2 s 1 ) 10-10 3 5 Powerlaw! Γ = 1.815±0.005 E fold > 1 MeV L edd < 0.2% 8 10 20 Energy [kev] 40 70 νfν (erg cm 2 s 1 ) 10-11 10-12 10-13 10-14 Powerlaw (w/ cutoff)! Γ = 1.39±0.04 E fold = 55±12 kev L edd = 0.02% 0.5 1 2 5 10 Energy [kev] 20 50 Absorption is 17 10 22 cm -2 Low/hard state at the very end of a the outburst
Centaurus A νfν (erg cm 2 s 1 ) Ratio 10-9 10-10 1.1 1 0.9 3 5 8 Fürst et al., 2016 kt e = 216±20 kev Ad-hoc Iron line at 6.40±0.01 kev 10 20 40 70 Energy [kev] Iron line cannot be modeled with reflection model (pexrav): R < 0.011! Comptonization model gives realistic temperature (for compact corona, see Fabian et al., 2015) Cutoffpl is not the correct model to describe the shape, measured folding energies are unreliable
Centaurus A: iron line A torus model can explain iron line strength selfconsistently. Torus material not Compton-thick, therefore no Compton hump at high energies seen. Inclination >63 deg, Opening angle ~60 deg NASA/JPL-
GRS 1739-278 νfν (erg cm 2 s 1 ) Ratio 10-11 10-12 10-13 10-14 2 1.5 1 0.5 0.5 1 2 5 10 Energy [kev] Fürst et al., in prep. 20 50 Can be self-consistently fitted with reflection model (xillver): R = 0.047 +0.039-0.024 Relativistic effects are difficult to constrain, as reflection is very weak.
GRS 1739-278: multi-epoch Ratio νfν (erg cm 2 s 1 ) 10-9 10-10 10-11 10-12 10-13 10-14 1.5 1 Using previous observations during bright hard state (Miller et al., 2015) to fix coronal geometry, assuming lamppost geometry à Inner radius in low state is 54 +70-25 r g 0.5 Fürst et al., in prep. 1 2 5 10 20 50 Energy (kev)
Results Supermassive black hole: Cen A Stellar mass black hole: GRS 1739-278 No reflection visible: inner accretion disk must be truncated strongly Continuum described by hot Comptonizing corona, additional features through torus Weak reflection: inner accretion disk truncated around 50 r g Continuum described by hot Comptonizing corona, additional features reflection Low Eddington accretion rates are consistent with the picture of a truncated accretion disk;; replaced, e.g., with ADAF (Narayan & Yi 1995)
Summary Hard spectra at low fluxes with weak reflection features are connected to radio activity X-ray radio correlation important tool to understand physics Corona could be the base of the jet (Markoff et al., 2005) and outflowing (Beloborodov et al., 1999) XMM+NuSTAR is unique to study low-luminosity black holes Will continue to be unique for the next decade But proper (cross-)calibration is very important
Backup slides
Centaurus A Chandra X-ray jet NuSTAR >3 kev XMM MOS 1 < 5keV X-ray jet not visible at hard X-rays! Fürst et al., 2016
Cen A: calibration cts s 1 kev 1 χ (a) 1 0.1 0.01 10-3 (b) 5 0-5 (c) 5 Known issues with gain in NuSTAR Pile-up in EPIC-pn Dust scattering in the prominent dust band changes spectrum as function of extraction region size and PSF χ 0-5 2 5 Energy [kev] 8 10 15
GRS 1739-273: light curve Rate (mcrab) 500 450 400 350 300 250 200 150 100 50 BAT 15 50 kev MAXI 2 20 kev XRT 3 9 kev NuSTAR 3 78 kev XMM-Newton 1 10 kev 10 1 0.1 600 620 640 10 1 0.1 200 180 160 140 120 100 80 60 40 20 NuSTAR rate (3 79 kev) (cts s 1 ) 0 100 200 300 400 500 600 Time (d) since MJD 56658.0 (2014-01-01) 700
Accreting black holes Supermassive black holes Cen A Stellar mass black holes: GRS 1739-278