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XMM-Newton CCF Release Note
XMM-CCF-REL-331 Up date of the RGS Gain and CTI (August 2007 - Decemb er 2009)
R. Gonzґlez-Riestra and C. de Vries a December 1, 2015

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CCF comp onents

Name RGS1 RGS2 RGS1

of CCF ADUCONV 0026 ADUCONV 0033 CTI 0014

VALDATE 2007-08-01T06:00:00 2007-08-17T02:00:00 2007-08-01T06:00:00

EVALDATE 2009-12-31T23:59:59 2009-12-31T23:59:59 2009-12-31T23:59:59

RGS2 CTI 0015

2007-08-17T02:00:00

2009-12-31T23:59:59

List of Blocks changed OFFSET GAIN OFFSET GAIN CTI CTI EXTENDED XCTI CTIY1-9 CTI CTI EXTENDED XCTI CTIY1-9

XSCS flag NO NO NO

NO

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Changes
lamps plane in the of the

It has been recently reported that in some RGS observations the signal from the calibration is systematically displaced with respect to the position of the masks in the Beta(Lambda)/PI (see an example in Fig. 1). Further investigation has shown that this happens in data taken period August 2007 - December 2009. This has led to the re-evaluation (done by C. de Vries) ADUCONV and CTI CCFs for this epoch.

The new files discussed in this Release Note replace RGS1[2] ADUCONV 0022[25] and RGS1[2] CTI 0010[11] described in [1].

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Figure 1: Example of the incorrect placement of the extraction masks for an observation processed with the current versions of CTI and ADUCONV.

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Scientific Impact of this Up date

An incorrect placement of the extraction masks can lead to a loss of source events. This effect can be seen in Fig. 1, where the 1st and 2nd spectra are partly below the extraction regions, in particular at high energies. Several datasets taken during this epoch have been processed with both sets of calibration files (current and new), and the results have been compared. The results of the comparison can be summarised as follows:

· Extraction masks The energy of the events processed with the new files show a noticeable difference in energy. With the new calibration the spectral data are now better placed within the spectral extraction masks (Fig. 2).


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Figure 2: Result of processing the observation of Mkn 421 shown in Fig. 1 with the new CCFs.

· Number of events As a consequence of the previous point, the spectra extracted from events file processed with the new files have more events. For the datasets considered, the number of events increases by 2-3% and by 8-10% in first and second order spectra, respectively. In first order, the largest differences are in CCDs 7, 8 and 9, and in second order, in CCDs 3 to 8 (see Table 3). · Position of the lamps Due to new energy calibration, the measured energy of the lamps increases, more for the Al-K lamp: up to 60 eV in RGS1, and between 50 and 80 eV in RGS2 (see Table 4).

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Test pro cedures & results
· The fits viewer fv has been used to inspect the new CCFs, their structure, validity dates and contents.


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Table 1: Ratio of number of events in extracted spectra (New/Current) Ob ject Obsid Rev RGS1 o1 RGS1 o2 RGS2 o1 RGS2 o2 PKS 2155-304 0411780301 1543 1.02 1.08 1.02 1.08 Mkn 421 0560980101 1640 1.02 1.08 1.02 1.08 Mkn 421 0560983301 1732 1.02 1.08 1.02 1.08 PKS 2155-304 0411780401 1734 1.03 1.09 1.02 1.08 Mkn 421 0411083201 1820 1.02 1.08 1.02 1.10

Table 2: Measured energy of the calibration lamps RGS 1 F K CCD8 653 (21) 656 (21) 625 (-5) 653 (21) 669 (31)

Ob je PK S Mkn Mkn PK S Mkn

ct 2155-304 421 421 2155-304 421

Rev 1543 1640 1732 1734 1820

Al CCD1 1445 (-1) 1443 (-1) 1440 (-1) 1445 (-1) 1434 (0)

K CCD2 1480 (61) 1487 (62) 1483 (62) 1481 (61) 1492 (65)

Ob je PK S Mkn Mkn PK S

ct 2155-304 421 421 2155-304

Rev 1543 1640 1732 1734

RGS 2 F K CCD7 CCD8 CCD1 651 (22) 680 (8) 1469 (73) 649 (18) 670 (-) 1468 (74) 652 (7) 647 (21) 656 (8) 1467 (73)

Al K CCD2 CCD6 1475 (-) 1471 (54) 1484 (84) 1484 (84) 1478 (82) 1466 (54)

CCD7

1480 (50)

Line energy is given in eV. Numbers in brackets are the differences with respect to the current calibration. · The SAS task cifbuild has been run to confirm that the right CCFs version is selected. · Several observations of bright BL Lac ob jects taken in this period of time have been processed with the new CCFs and the results have been examined. In all cases the spectra fall well within the extraction masks, and the lamps are in the correct position.

For completeness, we include three figures showing the temporal evolution of the Gain and the CTI, similar to those shown in [2] including the new values in the CCFs described in this RN.


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Figure 3: Example of extracted spectra of Mkn 421 and PKS 2155+305 obtained with current (black) and new (red) CCFs.


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Figure 4: Evolution of the Gain (left RGS1, right RGS2). The new values are shown as red lines.

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Exp ected Up dates

Both CCFs should be revised regularly to evaluate the degradation due to radiation. Observations of a bright continuum source off axis in the cross-dispersion direction must be performed every two years to monitor the parallel CTI.

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References

[1] "Recent evolution of RGS gain and CTI", A. Pollock, XMM-CCF-REL-289, July 2012 (http://xmm2.esac.esa.int/docs/documents/CAL-SRN-0289-1-0.ps.gz) [2] "Update of the RGS Gain and CTI", R. Gonzґlez-Riestra and C. de Vries, XMM-CCF-REL-319, a July 2014 (http://xmm2.esac.esa.int/docs/documents/CAL-SRN-0319-1-0.pdf)


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Figure 5: Evolution of the Serial CTI (left RGS1, right RGS2). RGS2 started to be read through a single node (C) in August 2007. Since then, the serial CTI for RGS2 (formerly) node D is simply the negative of the node C values. The new values are shown as red lines.


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Figure 6: Evolution of the Parallel CTI (left RGS1, right RGS2). The points represented are the CTI values at centre of the chip. The new values are shown as red lines.