Post on 30-Dec-2015
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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.