Discovery Of Transient Iron Fluorescence In The Bare Seyfert Ark 120

2016

Publication Year

2020-05-27T08:41:07Z

Acceptance in OA@INAF

Discovery Of Transient Iron Fluorescence In The Bare Seyfert Ark 120

Title

NARDINI, EMANUELE; Porquet, D.; Reeves, J.; BRAITO, Valentina; Lobban, A.; et al. Authors 10.5281/zenodo.163789 DOI http://hdl.handle.net/20.500.12386/25207 Handle

Emanuele Nardini

Keele University

in collaboration with:

D. Porquet, J. Reeves, V. Braito, A. Lobban, G. Matt

Discovery of transient

iron fluorescence in the

1

10

100

Energy (keV)

0.3

1

3

Flux

(k

eV

s

cm

ke

V

)

AGN X-ray spectral energy distribution

Compton

hump

soft

excess

warm/cold

absorption

X-ray continuum

Fe-K line(s)

Ark

120: the ‘bare Seyfert’ prototype

Suzaku 2007 Nardini+11

Nearest and brightest

D = 144 Mpc

F

= 7

10

erg/s/cm

Bare line of sight

N

< a few

10

cm

BH mass known from

reverberation mapping

M

= 1.5

10

M

All X-ray spectral traits of a

radiatively efficient SMBH

2014 X-ray campaign (PI: D. Porquet)

Four consecutive XMM-Newton orbits (7.5 days, net exposure 330 ks)

Chandra HETG spectrum overlapping with XMM#2 + XMM#3 (120 ks)

NuSTAR observation simultaneous with XMM#3 (65 ks)

6.0

6.5

7.0

Rest-frame energy (keV)

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Data/Contin

uum

Chandra HETG spectrum

narrow

core

I

XXV

XXVI

red

XMM time-averaged spectrum

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

2 broad Gaussians

FWHM = 2x Hβ

wrong!

XMM time-averaged spectrum

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

2 broad Gaussians

FWHM = 2x Hβ

wrong!

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

2 narrow Gaussians

BLR-like FWHM

disk line

r

= 60 r

q = 3, i = 30º

XMM time-averaged spectrum

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

2 broad Gaussians

FWHM = 2x Hβ

wrong!

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

2 narrow Gaussians

BLR-like FWHM

disk line

r

= 60 r

q = 3, i = 30º

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

Data/Contin

uum

Chandra ΗΕΤG

Fe-K profile

noise and/or

variability?

XMM03 Suzaku07 XMM13 XMM14a XMM14b XMM14c XMM14d 0 1 2 3 4

In

te

nsi

ty

(⇥

10

photons

s

cm

)

Fe-K variability, long timescales

narrow Fe

I, 6.40 keV

disk line, 6.45—6.55 keV

narrow Fe

XXVI

(?)

, 6.98 keV

2.5σ

5σ

Fe-K variability, long timescales

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

0.9

1.0

1.1

1.2

1.3

N

or

m

al

iz

ed

di

ffe

re

nce

5.5

6.0

6.5

7.0

7.5

Rest-frame energy (keV)

0.9

1.0

1.1

1.2

1.3

N

or

m

al

iz

ed

di

ffe

re

nce

Fe-K difference spectrum

2014/high — 2013/low

disk line from

Elapsed time (ks)

O

bse

rv

ed

en

er

gy

(k

eV

)

Excess emission (10

_{counts s}

_cm

₎

Fe-K variability, short timescales

Excess map technique, used to reveal energy/intensity modulation of Fe-K lines

within long exposure observations, but at smaller BH mass

Energy vs. time resolution: 100 eV

x

5 ks (orbital time at Kerr ISCO)

Elapsed time (ks)

O

bse

rv

ed

en

er

gy

(k

eV

)

Excess emission (10

_{counts s}

_cm

₎

Fe-K variability, short timescales

quiescent red flare blue flare

Transient red/blue structures with no obvious periodicity nor correlation with

each other: short-lived, individual hotspots at several tens of gravitational radii?

Any alternative explanation that involves some kind of inhomogeneity is viable,

e.g. disk instability (photon bubbles on suborbital timescales) or hybrid corona

(no Fe-K feature from around the ISCO). Theoretical effort might be worthwhile.

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

red flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

red flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

red flare

blue flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

blue flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

red flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

red flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

red flare

blue flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

blue flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

red flare

The orbiting hotspots picture

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

red flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

red flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

red flare

blue flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

blue flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

red flare

6.0

6.5

7.0

Rest-frame energy (keV)

1.0

1.1

1.2

1.3

1.4

Data/Contin

uum

quiescence

red flare

blue flare

The orbiting hotspots picture

6.0

6.5

7.0

Rest-frame energy (keV)

0

0.5

1.0

Flux

(10

ke

V

s

cm

ke

V

)

r = 30–40 r

= 217–228 deg

r = 15–25 r

= 40–65 deg

Summary

Evidence for rapid (several tens of ks) variability of Fe-K

fluorescence in the bare Seyfert Ark

120, compatible with

flares/hotspots, inhomogeneity and/or instability

Are these physical conditions and the underlying processes

common among AGN? Should we expect any implications on

broad Fe-K features and SMBH spin measurements?

To reveal any fine structure in the Fe-K profile and perform

a proper time-resolved spectral analysis, large effective

area AND high energy resolution (read: Athena) are needed.

Ark

120 is possibly the most promising source to study the

properties of the accretion disk/X-ray corona system in a

nearby AGN, and of its flaring, transient component(s).