The variable X-ray spectrum of PDS456

and High-Velocity OutflowsShai Kaspi

Technion – Haifa; Tel-Aviv University Israel&

Ehud Behar, James Reeves

“The X-ray Universe 2008” – Granada, Spain – 29 May 2008

O’Brien P.T, Ward M., Braito V., Fabian A., Miller L., Mushotzky R. , Turner T.J.

Outline

- High-velocity mass outflows in AGNs

- New data and first results of the varying

spectrum of PDS 456

- Varying spectrum of PG 1211+143

- Summary

Mass Outflow From AGNs

• Collimated jets and/or lobs in “Radio loud” quasars – 5%-10% of quasars are “Radio loud”.

• Broad absorption lines (BALs) – Blueshifted up to 0.1c - UV lines of ~10% “radio quiet” quasars.

Does mass outflow from AGNs?

Is mass loss an important component in most AGNs?

Past decade UV (HST) and X-ray (XMM & Chandra) observations detected outflowing mass (velocities of several hundreds km/s) in the majority of moderate luminosity Seyfert galaxies (~70%), indicating the importance of mass outflow.

Mass outflow

• How much mass is carried out of the AGN by the outflow?

• How does it compared to the amount of matter being accreted?

• Does the ionized outflow carry a significant fraction of the energy output of the AGN?

Answers are currently model dependent

Mass outflow in low-luminosity AGNsOutflows can provide key results about AGNs’ central regions, e.g.:

• Dynamics: outflows velocities of several 100 km/s in

multiple components.

• Range of ionization parameters UOxygen ~ 0.01 to 1

(degeneracy of location and density).

• Column density ~ 1021-23 cm-2.

• Normal outflows are not very significant in terms

of energy as the outflow is of ~ 0.1-5 M yr-1 .

High-velocity mass outflows are potentially energetically significant.

High-Velocity OutflowsSourceVout [c]NH

[1023 cm-2] UV BAL

(km/s)L / LEdd

APM 08279+5255

Chartas et al. (2002)

0.2 , 0.41 ± 0.5Y (12.4k)

~ 0.04c

high

PG 1211+143Pounds et al. (2003, 2006)

0.08 - 0.15N1.1

PG 1115+080Chartas et al. (2003, 2007)

0.1 ,

0.34

0.1 ± 0.05 ,6.9

Y )?(0.7

PG 0844+349Pounds et al. (2003)

0.2 -0.264N0.3

PDS 456Reeves et al. (2003)

0.165Y(?~12k)1.0

IC 4329 AMarkowitz et al. (2006)

0.10.14N>0.5

Mass outflow of several M yr-1

PDS456The most luminous radio-quiet type I quasar in the nearby Universe

Discovered a decade ago (Torres 1997)

Z=0.184 LBol ~ 1047 erg/sec NH(Galactic)=2X1021 cm-2

RXTE light curve

Two main flux states: high and low

XMM observation 2001 Feb 26 - 40KsReeves, O'Brien, Ward (2003)

EPIC spectra show soft excess and a deep absorption trough around 7 keV which if interpreted as Fe K-Shell absorption edges is an outflow at ~50000 km/sec.

RGS spectra show deep absorption around 1 keV which if interpreted as a blend Fe L-shell absorption is an outflow at ~50000 km/sec.

Chandra/HETGS observation two years after the XMM one.PDS456 is in a low state and hardly any features can be detected.

40 ks

145 ks

Chandra Observation 2003 May 7 – 145 ks

Two more XMM Observations

Spectral variability over 1-2 daysBehar et al. in prep.

EPIC-pn image - 2007

Problem with background in 2007

.

Background

Source - Background

Source + Background

Background is showing strong narrow fluorescence emission lines due to K of Al, Ni, Cu, and Zn from the CCD structure.

Source+Background does not show these lines as the center of the CCD is free of these lines.

Source-Background will indicate a false absorption line at ~8 keV.

.

.

No Problem with background of 2001The background of the 2001 observation does not show the narrow emission lines.

The deficit in flux around 8 keV is not caused by the background lines

XMM 2001 and 2007 comparison

Strong variability over 6 years. Also spectral variability over 2 days.

Behar et al. in prep.

RGS spectra

Variability over 1-2 days – however features are not identified

Behar et al. in prep.

L-shell absorption region

2007 observations do not show same absorption feature from 2001

Behar et al. in prep.

Suzaku – 2007-2-24 - 370 ks

Fe absorption line

Reeves et al. in prep.

Black – Suzaku 2007 ; Red – XMM-Newton 2001

Fe XXVI1s-2p6.97 keV

If the detected absorption is the Fe XXVI line then the outflows are at 0.26c and 0.31c

Spectra comparison from 2001 to 2007

Ratio of spectra to a =2 power law illustrating the drastic long term spectral variability

XMM 2001

Chandra 2003=1.3

Suzaku 2007=2.3

PG1211+143

Pounds, Reeves et al. (2003) claim to detect an outflow of at ~ 0.1c.NH ~ 1024 cm-2

RGS

O V

III

O V

III O

VII

Fe XXVI

S XVI

EPIC-pn

Kaspi & Behar (2006) gave alternative interpretation of an outflow at 3000 km/sec. NH ~ 1021.5 cm-2

Two interpretations – differ by two orders of magnitude in the outflowing mass

PG1211+143 Two RGS observations2001-06-15

2004-06-21

Spectra are generally consistent,

but a bit different slope and some different details.

Object varied in time or a result of the poor S/N

Simultaneous XMM-Newton and Chandra

Xmm-Newton/RGS and Chandra/LETGS spectra are consistent overall, but differ in many details –

probably a consequence of the poor S/N.

Three Chandra/LETGS observations

PG 1211+143 doubled its luminosity in two days. Narrow line features does not reproduce in the different spectra.

• High-velocity outflows are not found in low-luminosity AGNs.

• Several High-luminosity AGNs have high-velocity outflows,

indicating mass outflow that can affect the surrounding host galaxy.

• High-Velocity outflow are varying on time scales of days to years.

• The causes of the variability is yet to be determine:

- Changes in the covering factor of the absorber.

- Changes in the column density of the absorber.

- The absorber is moving fast in and out of the line of sight.

• High-velocity mass outflow are potentially energetically significant but their

variations and model dependent parameters cannot yet give a coherent picture.

Summary – What can we learn …

• If High-velocity outflows are a transit phenomenon this needs to be

taken into account when calculating the effect of the mass outflow on the

surrounding.