Download X-ray spectrometer

The Next Generation of X-ray – Sensitive
Observatories and their Potential for Blazar
Variability Studies
Greg Madejski (SLAC/KIPAC)
including results from collaboration with:
Jeff Scargle, Rie Sato, Jun Kataoka, Tad Takahashi, Marek Sikora, others
Outline:
•Motivation: impending launch of GLAST as the “next big tool” for blazar
studies
•Why the X-ray band?
•Two aspects of X-ray variability: characterization of the time series, crossband variability studies – and successes in both
•New technique applied to Asca data for search of the most rapid variability
•Future X-ray satellites: mission parameters relevant to blazar studies
EGRET All Sky g-ray Map (>100 MeV)
3C279
Cygnus
Region
Vela
Geminga
Crab
Cosmic Ray
Interactions
With ISM
LMC
PSR B1706-44
PKS 0208-512
PKS
0528+134
Schematic principle of operation of the GLAST
Large Area Telescope
g
e
+
e–
* g-rays
interact with the hi-z material in the foils, pair-produce: e+/e- are tracked
with silicon strip detectors: GLAST is a transistor, vs. EGRET – a vacuum tube
* The instrument “looks” simultaneously into ~ 2 steradians of the sky with the peak
effective area of ~ 10,000 cm2
* Energy range is ~ 30 MeV – 300 GeV - allows an overlap with TeV observatories
GLAST LAT’s expected performance
GLAST sensitivity - time required to measure
the flux to 20% (solid), PL index to +/- 0.1 (dashed)
as a function of source flux (E>100 MeV)
Expected flux and spectral index
measurements by GLAST for 3C279
Why is the X-ray band important?
Broad-band spectra of two classes of blazars:
3C279 (data from Wehrle et al. 1998)
Compton component: X-rays probe the
total jet content (particles radiating at the low
end of the distribution are most numerous)
Mkn 421 (data from Macomb et al. 1995)
Synchrotron component: X-rays probe the
most energetic end of particle
distribution
Two facets of time variability
Two “directions” for variability studies:
(1) Sensitive measurements of the properties
of the time series (PDS, structure f’n, …) –
Kataoka’s, McHardy’s talks
(2) Cross-correlations with multiple energy
bands
Recent successes:
* Location of the “blazar dissipation zone” –
probably >pc from the central source:
* D. Harris’s/T. Cheung’s M87 results
* A. Marscher’s BL Lacertae
* Implications of the 3C454.3 monitoring
(Sikora, Moderski, GM 2008)
* Acceleration / cooling time scales 1218+304 Suzaku observations (Sato et
al. 2008)
Time series analysis – in search for the shortest variability
time scales: Results for Mkn 421(work in progress)
•A scalegram technique
(variation of a wavelet
method) can be fruitfully used
to search for variability power
at the shortest time scales
(work with Jeff Scargle)
•This particular
implementation requires for
photons to be time-tagged to a
precision much better than the
photon interarrival time, and
data must be free of
background (hence Asca GIS
data)
•Results of an application of
the wavelet scalegram to the
Asca GIS data for Mkn 421:
- there is some residual
significant power at about 500
sec time scale, the
extrapolation to the longer
time scales consistent with the
PDS / structure f’n calculated
by Kataoka et al. 2001
Asca light curve from
“long look” of Mkn 421
(Takahashi et al. 2001)
Recent results from Suzaku X-ray variability of TeV-emitting blazars
(see Rie Sato’s poster for details)
Asca data for Mkn 421
Photon Index
2.3
2.4
2.5
Flux
From Asca data: Mkn 421 showed that during flares
the spectrum gets “hard” very quickly, then if softens as
the source gets fainter: signature of energy-dependent
electron cooling time scale (Takahashi, GM, +, 1996)
Suzaku observed another TeV blazar, 1218+304,
reveals that hard X-rays lag soft X-rays:
20 ks delay of 6 keV vs. 0.6 keV X-rays clear energy-dependent acceleration time scale?
(Sato et al. 2008)
-> Implications on the structure of B-field
X-ray facilities for blazar monitoring
• Current
– Suzaku: v. sensitive, 0.3-50 keV bandpass (for blazars), but
constrained pointing (90+/-15 deg to the Sun)-> ~ 1 month max at a
time, low-Earth orbit
– XMM-Newton: also sensitive but limited bandpass (0.3-12 keV),
deep orbit
– RXTE: 3-30 keV bandpass, good all-sky coverage, but limited
sensitivity (~ 10-11 erg/cm2/s), nearing the end of its lifetime
– Swift: reasonable sensitivity, quick slew, all-sky pointing, but low
Earth orbit, GRBs a priority
– Chandra: v. good for structure studies (extended jets), but suffers
from photon pile-up for bright sources. Great for difficult IDs!
Near future for GLAST/X-ray monitoring: Suzaku
X-ray spectrometer
(XRS: 0.3-10 keV)
Hard X-ray detector
(HXD: 10-600 keV)
X-ray imaging spectrometer
(XIS:0.3-10 keV)
X-ray facilities for blazar monitoring
• Future:
– MAXI: to be launched soon, all-sky monitor
– NuSTAR: 2011-2012 launch, hard X-ray bandpass (6 - 80 keV):
blazars a priority
– NeXT: 2013 launch, but the calorimeter is the primary instrument > high resolution X-ray spectroscopy a priority (clusters, SNR
rather than blazars)
– Constellation-X: In principle might be excellent, but probably far
in the future (2018?); high-resolution spectroscopy a priority
– EXIST: great all-sky capability, hard X-ray band (~ 20 – 600 keV),
but probably will be approved / launched beyond GLAST (2018?)
– Simbol-X: Hard X-ray bandpass, but still in the study phase,
launch 2015?
– Astrosat? Spectrum X-Gamma? Xeus?
MAXI Payload
To be attached to the Space Station in March 2009
Radiator for X-ray CCD camera
Mass: 530 kg
80cm
185cm
ISS
JEM/EF
107cm
X-ray Gas Camera
Gas Slit Cameras (GSC)
Xe-filled proportional counter
2—30 keV; 5350 cm2
Optical Star Sensor
(for attitude
determination ）
Ｘ-ray CCD Camera
Solid-state Slit
Cameras (SSC)
32 CCD chips
0.5—15 keV; 200 cm2
MAXI sensitivity and targets
1 orbit
1 day
1 week
1 Month
2 Years
Hard X-ray imaging satellite NuSTAR
• NASA’s Small Explorer mission,
slated to fly in 2011-2012
• Two identical coaligned grazing
incidence hard X-ray telescopes:
– Multilayer coated segmented
glass optics
– Actively shielded solid state
CdZnTe pixel detectors
• Extendable mast provides 10-m focal
length
• Pegasus rocket / satellite in lowEarth orbit, inclination TBD
• Energy bandpass 6 – 80 keV
• Blazar observations joint w/GLAST
important part of the science drivers:
plan is for 3 months of observing time
for blazars alone
Star tracker
Mast
Adjustment
Mechanism
X-ray optics
Mast
Shielded
focal plane
detectors
NuSTAR performance and blazar observing strategy
Parameter
Performance
Mission launch
August 2011
Mission duration
Energy band
* The duration and cadence of monitoring will
become more clear once GLAST is in orbit
* Sensitivity: for the brightest GLAST blazars,
average 10-80 keV flux is ~ 10-11 erg cm-2 s-1
-> we should get about 0.1 NuSTAR count/s
-> Dflux ~ 7% , Da~0.1 in a NuSTAR orbit
* Probably will do “continuous looks”
2 years (prime
mission)
6 - 80 keV
Angular resolution
40” HPD
Spectral resolution
1 keV FWHM @70
keV
Field of View
Sensitivity (10 - 30
keV, 106 s)
13 arcmin
1 microCrab
Advertisement: a tool to announce MW campaigns
(Adler Planetarium: from Lucy Fortson)