Multiwaveband Variability of
Seyferts and LINERS
Relationship to X-rays
Ian McHardy
University of Southampton 1 Southampton Outline
X-ray / UV / Optical variability
X-ray / Radio variability
2 Southampton
X-ray / UV/ Optical Variability
What causes UV/optical variability in Seyferts?
• Reprocessing of X-rays? - X-rays lead uv/optical by short (hour-days) light travel time. Expect Lag ∝Wavelength1.33
• Intrinsic disc variability – X-rays lag: two possibilities
– Long lag (months), viscous propagation timescale for perturbations to reach X-ray region from optical in disc
– Short lag (hour-day), light travel time of UV seed photons to corona 3 Southampton NGC 4051: optical – X-ray
4 Southampton NGC 4051
5 Southampton NGC4051
Optical lags by 1.5+/- 0.5 d (above 99% confidence) Breedt et al 2010 6 Southampton MKN 79
(Breedt et al, 2009, MNRAS)
Long timescales (years) – uncorrelated behaviour. Intrinsic disc variations in optical?
Short timescales (days-weeks) - well correlated. Hint that optical lags, but lag not well defined
7 Southampton Swift UV / optical interband lags
Line is Lag ∝Wavelength1.33
NGC2617 – Shappee et al 2014 Between 20 – 50 data points per band
Fit to UV-optical with fixed power law slope of 4/3 does not go through X-ray point
8 Southampton Swift Monitoring of NGC5548: (> 500 observations)
Good correlation, but not perfect, eg large W2 rise after day 6480 McHardy et al, 2014, MNRAS, 444, 1469
9 Southampton Lag of X-rays by UVW2
Mean-subtracted lightcurves Lag distribution Intensively sampled period (Javelin – Zu et al 2011)
10 Southampton
NGC 5548 All Swift Bands
11 Southampton Lags as function of wavelength
Expect 4/3 power for 1.23 Shakura-Sunyaev disc. Lag ∝Wavelength So good agreement.
Fit goes through X-ray point BUT … observed lags are longer than expected for the Mass and m Model lags Red line is time for HALF of (McHardy et al, 2014) reprocessed light to arrive.
Microlensing obs (eg Morgan et al 2010) also require larger disc than SS model Hotter than expected disc (eg higher m , higher Lx)? Same result in extensive Inhomogeneous disc (Dexter and Agol 2011)? follow up observations (Edelson et al 2015, Time associated with the reprocessing mechanism? Fausnaugh et al 2015) 12 Southampton XMM and ground based lags for NGC4395
Mass 3.6x105, x100 lower than NGC5548, and x10 lower m
Does it also have longer lags than predicted?
UVW1 with OM
Ground based g-band monitoring around globe (Peterson, Elvis, Uemura Chand, Netzer, Kaspi and others)
(Connolly et al. in prep)
13 Southampton NGC4395: Swift X-ray / UVW2
Looking within individual Swift visits (TOO – 12 ks)
uvw2 lags X-rays by ~400s 14 Southampton XMM and ground based monitoring of NGC4395
X-ray XMM
UVW1- XMM OM
g-band ground
30-31 December 2014 15 Southampton NGC4395 - DCFs
X-rays vs UVW1 X-rays vs g-band
(Using Emmanouloupolos et al 2013 improved lightcurve simulation method for simulations)
16 Southampton NGC4395 – Javelin lags
UVW1 lags X-rays by g-band lags X-rays by 473 (+47, -98) s 788 (+44, -54) s
17 Southampton NGC4395 – Lags vs Wavelength
Lags very short. Intrinsic reprocessing time must be very short.
Simple linear fit (red) is best fit (forced through zero). However powerlaw of index 4/3 (blue) is also acceptable
So reprocessing dominates here also, but agreement with Shakura-Sunyaev models is closer than for NGC5548 – does disc structure depend on M, mdot, Temp?
18 Southampton NGC4395 - Models
observations
model emission profiles
Solid lines – total disc energy release in band, including X-ray contribution Dashed lines – gravitational energy release
Observed lags correspond to peak emission radii (models from P. Lira) 19 Southampton Dependence of reprocessing on disc temperature: X-ray / UV Variability of NLS1s
DCF
Swift UVW2
X-rays
Cameron et al, in prep Poor correlation
20 Southampton X-ray / optical correlation strength depends inversely on disc temperature
From Cameron PhD thesis; also Breedt Phd thesis 21
LINERS M81
Southampton M81 NuSTAR
NuSTAR 1000s bins 4d observation
With Andy Young, Bristol
23 Southampton LINER M81 – NuSTAR Spectrum
Disc reflection very weak or absent So optical is NOT reprocessed X-rays Cut-off PL is good fit
Γ=1.85 E_cut=230 keV
Hot iron line 6.62 keV
-ADAF?
(Young, McHardy et al, in prep) 24 Southampton
X-ray / UV Variability of M81
IF there is a UV/X-ray correlation, then
- X-rays lagging UV: UV could be seed photons for X-rays, eg cyclo/synchrotron from corona
- UV lagging X-rays: UV from synchrotron jet, downstream from X-ray corona
25 Southampton
X-ray / UV Variability of M81
Swift UV
Cameron 2014 Phd Thesis X-rays Southampton
26 Southampton
X-ray / W1 Variability of M81
Some short timescale correspondence 27 Southampton
X-ray / UV Variability of M81
W2 W1
-4 -2 0 2 4 Lag of X-ray by UVW2 (days) Javelin result from Harvey-Taylor Southampton UG Weak correlations, close to zero lag, possibly small UV lag
Suggests UV are not seed photons for X-rays but are from downstream jet
28 Could just be part of same emission component
Southampton
X-ray / UV Variability of LINERS
UVW1 UVW2
X-RAYS
29 Southampton X-Ray / mm / Radio Relationship in LINERS – NGC7213, M81
(More luminous radio sources than Seyferts)
Do the perturbations which drive the X-rays carry on into the jet?
Are liners the equivalent of `hard state’ X-ray binaries?
Southampton
NGC7213 – X-RAY/RADIO
3800 4400 5000 MJD-50000
S ~ ν + α (Bell et al, 2011)
31 Southampton
NGC7213 – X-RAY/RADIO
8 GHz lags X-rays by ~24 days 5 GHz lags X-rays by ~40 days 32 Southampton M81 sub-mas structure
Sub-mas bending jet similar to blazars
Here from Ros, McH et al; See also Marti-Vidal et al 2011
33 Southampton M81 radio-mm variability: strong correlation
Radio lags by approx 3d - consistent with standard synchrotron jet
34 Southampton SMA 1.3mm vs AMI 15GHz radio
Radio lags mm by a few days ie definite synchrotron jet 35 Southampton M81 Swift X-ray and AMI 15 GHz Radio
Guy Pooley
36 Southampton M81 X-ray vs Radio
AMI 15GHz from Pooley; OVRO from Richards, Readhead and Pearson 37 Southampton M81 X-ray / Radio ICCF / DCF
Good overall correlation. ICCF DCF Perturbations (from disc?) which drive X-rays may propagate down the jet to drive radio variations.
Lag of X-ray by Radio (days) Centroid of lag, using Peterson lagerror8 prog simulations 21 +/- 3d (Thanks to Peak of lag 44 +/- 3d Brad Peterson)
Scaling to binaries is unclear: X-ray / optical binary lag of 0.1s (Gandhi et al ‘10) is consistent (assuming also linear lag scaling with wavelength) But X-ray/radio lag of 7 minutes (Wilms et al 2007) is too long. 38 Southampton
M81 X-ray and Radio
When scaled for mass, M81 data fits on Fundamental Plane scaled for jet dominated sources very well
Merloni et al 2003, observed Falcke et al 2004, Koerding et al 2006
39 Southampton
LINER M81 Lags
Radio lags X-ray by approx ~ 21d - a messy correlation, OK on long timescales
Radio lags mm by ~ 3d - well defined correlation
UV lags X-rays by ~ 0.5d - weak correlation but lag, well defined.
Long X-ray / radio lag with shorter mm / radio lag could mean synchrotron emitting part of jet starting some way from BH and X-ray emitting corona. Then UV has to be part of the X-ray emission component.
Or maybe X-ray / radio lag is actually shorter, then jet could start near BH
40 Southampton Another Coronal / Jet Connection : QSO 3C273
RXTE X-ray
Gamma-ray
Only occasional simultaneous flares, but perhaps the Gamma-ray emission, overall, is greatest when the average X-ray level is highest? Southampton X-ray / Gamma-ray correlation : 3C273
So there may be a small amount of co-spatial X- and Gamma-ray emission, but most comes from separate emission regions. X-ray / Radio Variability of
‘Radio Quiet’ Seyferts
43 Southampton X-ray bright Seyfert: NGC4151
Mundell et al 2003
Radio jets commonly seen in nearby Seyferts but rarely (never?) luminous or compact enough to expect significant Synchrotron Self-Compton X-rays.
So is there a radio / X-ray relationship? If so, why? Southampton Radio variability from Seyferts, ie high accretion rate, Soft State, AGN
NGC5548 – Wrobel 2000 - radio variability over months but no parallel X-ray observations See also Mundel et al 2009
Seyferts are thought to be the equivalent of soft state X-ray binaries.
No detectable radio emission from soft state binaries – Russel et al 2010 45 Southampton NGC4051 - Seyfert
• Looks just like a classical radio galaxy – except much smaller and of much lower luminosity.
(Jones et al, in prep)
• Component separation is ~50 light years
(Girolleti and Panessa 2009) Southampton NGC4051 VLA A array observations
Default beam Radio Fixed beam
Smoothed X-ray
X-ray
Jones et al 2011 At best, only a very weak hint of X-ray/radio correlation 47 Southampton
NGC4051 Radio vs. X-ray - all arrays
No strong evidence for large amplitude radio variability (Jones et al, 2011)
48 Southampton NGC4051 on radio `fundamental plane’ for jet-dominated sources
(Merloni et al 2003, Falcke et al 2004, Koerding et al 2006
Here plotting just hard state objects from Koerding etal
NGC4051 is ~1 decade radio quiet
Jet orientation?
49 Southampton NGC4051 as a coronal radio source?
-5 If so, X-ray is integral of LR/Lx~10 radio emission
(Neupert effect – seen in stellar coronae)
Too faint to search for that effect here.
From Laor and Behar 2008
50 Southampton
NGC5548 AMI 15GHz
Compact core (Guy Pooley)
Other source is unrelated
51 Southampton
NGC5548 X-ray / Radio Variability
AMI 15GHz - Guy Pooley
Swift
RXTE
52 Southampton
NGC5548: X-ray / Radio Lag
Radio lags X-ray by 42 +/- 17d
Too long for radio to be seed photons in corona
Accretion rate fluctuations from disc, perturbing X-ray corona, could propagate down jet to radio emission
53 Southampton CONCLUSIONS
SEYFERTS: Short timescale UV/optical variability is X-ray reprocessing but implied disc size in NGC5548 is ~3x too big for Shakura Sunyaev model.
Are all AGN discs bigger than theoretically expected? If so, why?
LINERS: Short timescale UV variability in M81 correlates weakly with the X-rays with very short lag. No disc, so j et emission?
M81 radio lags X-rays by ~20d. Radio lags mm by ~3d. Possibly perturbations which drive X-rays also go down the jet.
Seyferts: weak correlation of X-ray and radio with radio lagging by about 40d. Some similarities to liner M81.
Southampton Southampton
Material I won’t show is below Southampton
Infrared – Optical Lags: NGC3783
Green is V-band, for comparison.
J-band similar lightcurve to V-band, but K-band lags.
V and J mostly reprocesing from disc, K includes some torus contribution
Lira et al, submitted also Saganuma et al 2006
57 Southampton XMM and ground based monitoring of NGC4395
100s bins
28-29 December 2014 58 Southampton X-ray / UV Variability of NLS1s
DCF
Swift UVW2
X-rays
Cameron et al, in prep 59 Southampton
NGC4051 X-ray Spectra and radio
60 Southampton X-ray / Gamma-ray variability : 3C273
Gamma-ray
X-ray
Much more high-frequency Gamma-ray variability in Gamma-rays Southampton
X-ray / Gamma-ray correlation : 3C273