M. Pilar Esquej, XMM-Newton European Space Astronomy Centre Page 1 Status of the XMM-Newton Slew Survey P. Esquej, R. Saxton, B. Altieri, A. Read, M. Freyberg,

M. Pilar Esquej, XMM-M. Pilar Esquej, XMM-NewtonNewtonEuropean Space Astronomy CentreEuropean Space Astronomy Centre

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Status of the XMM-Newton Slew Survey

P. Esquej, R. Saxton, B. Altieri, A. Read, M. Freyberg, D. Bermejo, V. Lazaro


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Outline

Overview Processing challenges

Attitude reconstruction and positional accuracySpurious sourcesExtended sources

Conclusions


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Overview- PN exposures in Medium filter in FF, eFF and LW modes- Open-slew speed = 90 degrees / hour, i.e. on-source time

~14 secs- Very low background of average ~0.1 c/arcmin2

- Area covered to date ~6300 deg2 (~15% of sky)

ecliptic coordinates


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Processing strategy

-Slew data processing using a small s/w change (available in SAS 6.5)

-Tangential projection not valid over whole slew. Divide slew into 1 deg2 images and recalculate sky positions.

-Source search using near-standard pipeline eboxdetect/emldetect combination tuned for ~zero background.

-Use sources with DET_ML>10 (equivalent to 3.9 )

-Search independently in three bands and produce three catalogues :

soft (0.2-2 keV) hard (2-12 keV) total (0.2-12 keV)


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Current Status

2005 2010 2015

Equivalent fraction of sky covered

15%

(20)*

45%

(55)

80%

(~100)

Number of sources

4000

(5500)

12000

(15000)

20000

(25000)

Completeness

* Including high background slews

- Initial processing of 424 slews (FF, eFF or LW) – 25% have high background

- Images & exposure maps created and source searched for 220 slews giving

4178 sources in total (0.2-12 keV) 4178 sources in total (0.2-12 keV) bandband2750 sources in soft (0.2-2.0 keV) 2750 sources in soft (0.2-2.0 keV) bandband844 sources in hard (2.0-12.0 keV) 844 sources in hard (2.0-12.0 keV) bandband

Source density: ~0.65 sources per Source density: ~0.65 sources per square degreesquare degree

~56% have RASS counterpart within 60 arcsec


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Attitude Reconstruction

- Crucial in determination of source coordinates

- Provided by the AOCS: a star-tracker operates in adition with the Sun-sensor provide the information for reconstructing the astrometry (1 arcsec for pointed observations)

- Two types of attitude data can be used during event file processing: Raw Attitude File (RAF) and Attitude History File (AHF)

- Different in slew observations than that used for pointed observations


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Astrometry: initial comparisonAstrometry: initial comparison

Comparison with ROSAT survey positions shows a wide distribution, with a tail up to 1 arcmin

Two types of positional error

(1) Real error of ~15″

(2) Error of 0-60″ (mean 30″)


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Attitude Problem: correctionAttitude Problem: correction

Two types of positional error

(1) Real error of ~10″

(2) Error of 0-60″ (mean 30″) but only in slew direction

Slew direction

AB Dor

‘Error ellipse’ around source (slew-oriented)

Good relative astrometry: ~15 arcsec, but poor absolute astrometry: ~30 arcsec

Systematic shift was evidenced, traced to :• quantisation of time to 1 second in AHF • timing error in the RAF, due to a delay of 0.75s of the star tracker CCDs leading to a systematic offset

Optimal attitude file: RAF subtracted by 0.75 s from every entry


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Achieved astrometric accuracyAchieved astrometric accuracy

RASS : 15” (1) SIMBAD : 8” (1)


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Spurious sources

- Detector flashes: due to low-energy events

- Within extended or within halo of bright source: look for images with high number of sources

- High background images: spurious detections due to localised background flares

- Position suspect: several cases

- False detection: background related?


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Extended vs point-like sources

FF mode point sources are fitted well by a PSF, e.g. source 4

Low background and tight PSF gives good sensitivity to extended sources

Enough counts to detect extension in brightest sources

Point-like source

Extended source


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Example of extended sources


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Comparison ROSAT / XMM-NewtonComparison ROSAT / XMM-Newton

Mean count rate ratio XMM/ROSAT ~ 10

We can study source variability


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XMM-Newton Slew 1(XMMSL1)

Aitoff projection


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ConclusionsConclusions 220 slews source-searched (using best strategies):

4013 sources (after removing spurious sources) Sky coverage: ~6300 deg2 (~15% of sky) ~0.65 sources per square degree

XMM-Slew positional accuracy ~8″

Soft X-ray band detection limit close to ROSAT BS catalogue Hard X-ray band detection limit deepest ever:

> 10 × deeper than EXOSAT, HEAO-1 ~ 2.5 × deeper than RXTE (only has 1° positional accuracy)

Topics under current investigation: optical correlation, refinement of spurious detection, source extension strategy, recovering science from high-background slews, source variability

Aim to issue first slew source catalogue (XMMSL1) before end of 2005

Provide an upper limit server in 2006

Documents

M. Pilar Esquej, XMM-Newton European Space Astronomy Centre Page 1 Status of the XMM-Newton Slew Survey P. Esquej, R. Saxton, B. Altieri, A. Read, M. Freyberg,