Swift-XRT Calibration Experience Applicable to SXT · E0102 SNR E0102 has been observed regularly (˘6 months) by XRT Has a good phenomenological model (IACHEC) and been used to Initially

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.


Outline

1 Swift Status


3 E0102

4 RXJ1856

5 SXT (Preliminary)


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


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


Gain / CTI

Gain and CTI are temperature dependent and evolve with time

Included in gain file and used by XRTCALCPI


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


Outline

1 Swift Status


3 E0102

4 RXJ1856

5 SXT (Preliminary)


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


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


Outline

1 Swift Status


3 E0102

4 RXJ1856

5 SXT (Preliminary)


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


Outline

1 Swift Status


3 E0102

4 RXJ1856

5 SXT (Preliminary)


SXT Corner Source data

Gain/CTI derived from corner source PHA (grade 0) data


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−


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 ?


E0102

Processed with new (linear) gain/CTI


Documents

Swift-XRT Calibration Experience Applicable to SXT · E0102 SNR E0102 has been observed regularly (˘6 months) by XRT Has a good phenomenological model (IACHEC) and been used to Initially