swift-xrt calibration experience applicable to sxt · e0102 snr e0102 has been observed regularly...
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Swift-XRTCalibration Experience
Applicable to SXT
Andy Beardmore
University of Leicester
TIFR, Mumbai, 2016-April-11
Outline
1 Swift Status
2 XRT CalibrationGain / CTITrap Mapping
3 E0102
4 RXJ1856
5 SXT (Preliminary)
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 2 / 16
Swift Status
Swift has now been operating for 11+ yearsMakes ∼ 35000 slews per year (> 99% with 3 arcmin accuracy;∼ 40 targets per day)Over 1030 Swift detected GRBs (to 2016-Mar-25)Observing time: < 20% GRBs, 35% GI/fill-ins, 30% TOOs (> 850per year), 2% Calibration
XRT Calibration : ∼ 300 ks every 6 months; 150 ks on Tycho/Cas Afor charge trap mapping purposes
Swift data are available publicly within a few hours of theobservation→ publish quickly or get scooped!XRT CCD temperature range: −70C to −52C
97% of time below −54C, median of −60C.
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 3 / 16
Outline
1 Swift Status
2 XRT CalibrationGain / CTITrap Mapping
3 E0102
4 RXJ1856
5 SXT (Preliminary)
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 4 / 16
Gain / CTI
Gain/CTI:
Measured from Fe-55 cornersource data (-60C).
NOM – all columns in CSNO_TRAP – the best 5, trapfree, columns
Electronic noise :
Measured from ‘raw’ framestaken daily (-60C)Used as input to CCDsimulation model→ energyresolution
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 5 / 16
Gain / CTI
Gain/CTI:
Measured from Fe-55 cornersource data (-60C).
NOM – all columns in CSNO_TRAP – the best 5, trapfree, columns
Electronic noise :
Measured from ‘raw’ framestaken daily (-60C)Used as input to CCDsimulation model→ energyresolution
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 5 / 16
Gain / CTI
Gain and CTI are temperature dependent and evolve with time
Included in gain file and used by XRTCALCPI
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 6 / 16
Charge Traps
After ∼ 3 years, CTI becamemore and more dominated bythe formation of deep chargetraps in individual pixelsTraps mapped using Si-Kα linein Tycho and Cas A SNRs.
Trap depths/locations stored ingain file and corrected usingXRTCALCPI. Give goodrecovery of the line FWHM.
WT : FWHM 270→ 170 eVPC : FWHM 210→ 150 eV
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 7 / 16
Outline
1 Swift Status
2 XRT CalibrationGain / CTITrap Mapping
3 E0102
4 RXJ1856
5 SXT (Preliminary)
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 8 / 16
E0102
SNR E0102 has been observed regularly (∼ 6 months) by XRTHas a good phenomenological model (IACHEC) and been used to
Initially modify CCD electrode thickness→ deeper Oxygen edgeRMF resolutionLow E gain calibration→ energy dependent trap depths
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 9 / 16
E0102
SNR E0102 has been observed regularly (∼ 6 months) by XRTHas a good phenomenological model (IACHEC) and been used to
Initially modify CCD electrode thickness→ deeper Oxygen edgeRMF resolutionLow E gain calibration→ energy dependent trap depths
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 10 / 16
Outline
1 Swift Status
2 XRT CalibrationGain / CTITrap Mapping
3 E0102
4 RXJ1856
5 SXT (Preliminary)
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 11 / 16
NS RXJ1856 with XRT
Soft spectrum (63 eV blackbody) constant source
PC Mode :
0.01
0.1
1
norm
aliz
ed c
ount
s s−
1 ke
V−
1
RXJ1856.5−3754
10.5
12
ratio
Energy (keV)
WT Mode :
0.01
0.1
1
norm
aliz
ed c
ount
s s−
1 ke
V−
1
RXJ1856.5−3754
10.5
12
ratio
Energy (keV)
2005 2008 2013Low-E losses more apparent in WT spectra.
Traps are deeper in WT→ effective event threshold has increasedSuggests origin of this effect might be trap/threshold related
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 12 / 16
Outline
1 Swift Status
2 XRT CalibrationGain / CTITrap Mapping
3 E0102
4 RXJ1856
5 SXT (Preliminary)
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 13 / 16
SXT Corner Source data
Gain/CTI derived from corner source PHA (grade 0) data
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 14 / 16
Corner source data (cont’d)
All 4 corners combined using new (linear) gain/CTIRevised redistribution model calculated by Monte-Carlosimulation: thr = 150 eV; CTIp,s = 7,2× 10−6; en = 6.75e−
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 15 / 16
Corner source data (cont’d)
Grade 0–12 CS data from different epochs : black: 2015-Nov, red:2016-FebSlight differences in the redistribution seen.
Could be caused by inaccurate bias subtraction ?
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 16 / 16
E0102
Processed with new (linear) gain/CTI
apb (UoL) XRT Experience TIFR, Mumbai, 2016-April-11 17 / 16
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