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Suzaku Guest Observer Facility

Suzaku Analysis - Frequently Asked Questions

Compiled by Suzaku Help Desk at RIKEN and GOF at NASA/GSFC

2007 Jan 1 Version


Processing

  1. How long does it take from the time of the observation to the data processing?
  2. How long after the observation should I expect to receive the data?
  3. How long is the processing itself?
  4. Our target moves at the beginning of the observation. What is this?

The XRT

  1. What is the pointing accuracy of Suzaku?
  2. What is the latest news on the attitude solution?
  3. How large is the point-spread function of XRT?
  4. How large is the effective area of one XRT?
  5. How big is the effect of straylight from nearby bright sources?
  6. How large is the difference in the pointing direction between XIS and HXD?

The XIS

  1. How good is the spectral resolution of the XIS?
  2. How large is the XIS field of view?
  3. What is the relation between the PI channel and photon energy?
  4. What is the difference between the 5x5 and the 3x3 data modes?
  5. What is the difference among the 4 XISs? Can I combine them in the analysis?
  6. Can you summarize the contamination problem?
  7. How are the data in the xis/event_cl/ directory cleaned?

The HXD

  1. Help! I don't know where to start with my HXD data!
  2. How large is the HXD PIN & GSO fields of view (FOV)?
  3. What is the recommended energy range to use in the PIN analysis?
  4. What is the recommended energy range to use in the GSO analysis?
  5. How do I get the background files or spectra required for HXD data analysis?
  6. How well do the instrument team know the background of the PIN?
  7. How well do the instrument team know the background of the GSO?
  8. The background spectra seem to have huge count rates. Is there something wrong?
  9. Could you explain the deadtime correction procedure? Do we do it also on the distributed background data?
  10. How are the data in the hxd/event_cl/ directory cleaned?
  11. What is the nature of the sharp cut-off in rev1.2 PIN spectra?

The Software and Analysis

  1. Where can we get the latest software for Suzaku data analysis?
  2. Are there any analysis manuals, i.e., "threads" "step-by-step" or "ABC guide" available?


Answers


Processing

  1. How long does it take from the time of the observation to the data processing?

    It typically takes about 1 to 2 weeks.

  2. How long after the observation should I expect to receive the data?

    It typically takes about 3 to 4 weeks.

  3. How long is the processing itself?

    It typically takes one week to process one month of data.

  4. Our target moves at the beginning of the observation. What is this?

    Before guide stars are available for the first time (the first 90 minutes or less), both attitude control and ground attitude determination may be less accurate. Users should check images and light curves carefully.

The XRT

  1. What is the pointing accuracy of Suzaku?

    The pointing accuracy currently is about 1 arcmin or less.

  2. What is the latest news on the attitude solution?

    In the data of processing v.1.2.2.3, the pointing error with a time scale longer than one satellite orbit is corrected and is reflected on the sky coordinate of each photon. However, there still remains 20"-50" fluctuation of the pointing direction originating from thermal distortion of the spacecraft body. This latter point will further be investigated using v.1.2.2.3 data.

  3. How large is the point-spread function of XRT?

    The Half Power Diameter (HPD) for XRT-I0, I1, I2 and I3 are 1.8 arcmin, 2.0 arcmin, 2.0 arcmin, and 2.3 arcmin, respectively. For more details, see Section 5.2.5 of the technical description.

  4. How large is the effective area of one XRT?

    The effective area (including the detector efficiency) at launch was about 330 and 370 cm2 on the FI and BI at 1.5 keV.

    The detector efficiency has been decreasing due to the contamination accumulating on the optical blocking filters. The user is referred to Section 2.1 of the technical description for further details.

  5. How big is the effect of straylight from nearby bright sources?

    Stray light is equal to or less than three orders of magnitude of the effective area at on-axis, depending on the off-axis angle and the energy of the stray source. For more details, please eee Section 5.2.6 of the technical description.

  6. How large is the difference in the pointing direction between XIS and HXD?

    Although the average optical axis of XIS and that of HXD-PIN differ by about 5 arcmin, the XIS field of view is entirely covered by the HXD-PIN field of view. Users therefore always obtain both XIS and HXD data simultaneously. Taking into account this difference, we prepared the two default pointing positions, XIS nominal and HXD nominal positions, which prioritizes the observation efficiency of XIS over that of HXD, and vice versa.

The XIS

  1. How good is the spectral resolution of the XIS?

    The spectral resolution depends on the observation modes and the observation date. The user should check it using the calibration source (55Fe) that is attached to the CCD.

  2. How large is the XIS field of view?

    The XIS field of view is about 17.8 arcmin x 17.8 arcmin.

  3. What is the relation between the PI channel and photon energy?

    PI = [E(eV)/3.65]
    You can also find this relation in the RMFs that are part of the Suzaku calibration database.

  4. What is the difference between the 5x5 and the 3x3 data modes?

    Basically the difference lies in the number of pixels read out around the center of each event; in the 5x5 or 3x3 mode, the data from 25 or 9 pixels are read. Please note that there is no difference in the basic analysis (we use only the 3x3 pixels around the central pixel) and users are free to sum up spectra of both modes. Users should note that, since the FITS structure of event files are different between the 5x5 and the 3x3 modes, 5x5 and 3x3 event files cannot be combined into a single event file without loss of information.

  5. What is the difference among the 4 XISs? Can I combine them in the analysis?

    We do not recommend combining data from the different XISs for analysis purposes, because XIS1 uses a Back-Illuminated CCD while the other three contain Front-Illuminated CCDs, with different properties. Moreover, the amount of contaminant is unique to each instrument. For more information on the CCD chips and their characteristics, the user is referred to Chapter 6 of the technical description.

  6. Can you summarize the contamination problem?

    The problem was first noticed in late 2005. The XIS instrument team has been studying the effects to determine the origin and the exact composition of the contaminant. They have provided a tool called xiscontamicalc as part of the newest distribution of HEASOFT. Please check the Suzaku website regularly for updates.

  7. How are the data in the xis/event_cl/ directory cleaned?

    Screening criteria are as follows:

    SAA_HXD==0 && T_SAA_HXD>500 && ELV>5 && DYE_ELV>20
    

The HXD

  1. Help! I don't know where to start with my HXD data!

    Please refer to the ABC Guide to Suzaku analysis. Also please visit the Suzaku Help Desk at RIKEN or ask your own question at the Suzaku GOF site at NASA/GSFC.

    An overview of HXD can be found in two articles ( Takahashi et al. & Kokubun et al.) to be published in the PASJ special issue.

  2. How large is the HXD PIN & GSO fields of view (FOV)?

    The field of view of the PIN diode is collimated by the passive fine collimator (FC) into 34'x34' squares. The situation is the same for GSO in below 100 keV. The FCs become transparent in above 100 keV, where the FOV becomes 4.5 degrees x 4.5 degrees.

  3. What is the recommended energy range to use in the PIN analysis?

    During the AO-1 period, the recommended range is 12 to 70 keV. Thermal noises sometimes appear in the 10-12 keV band, because of problems in the cooling system of the HXD from the initial phase.

  4. What is the recommended energy range to use in the GSO analysis?

    During the AO-1 period, the recommended range is 40 to 600 keV. Note, however, that the background above 300 keV is so high that even the Crab data are not used in the analysis at >300 keV.

  5. How do I get the background files or spectra required for HXD data analysis?

    During the AO-1/2 phases, the background files are available from the HXD background page at ISAS.

    In the longer term, the background files will be produced via an FTOOL named hxdnxbgen in the HEADAS package, and provided from the data archive centers.

  6. How well do the instrument team know the background of the PIN?

    It depends on the observation, but we have background systematic errors within roughly 5% in the 15-40 keV band if the data have a few x 10 ks exposure.

  7. How well do the instrument team know the background of the GSO?

    It depends on the observation, but again we have background systematic errors within roughly 3% in 50-100 keV band if the data have a few x 10 ks exposure.

  8. The background spectra seem to have huge count rates. Is there something wrong?

    No. The normalizations of the background spectra were multiplied by 10 for the PIN in order to reduce statistical uncertainties. Note that the GSO background data have been created with the same count rate as the real data.

  9. Could you explain the deadtime correction procedure? Do we do it also on the distributed background data?

    Deadtime correction of a (spectral) PI file can be performed using the hxddtcor tool in the HEADAS package. The details are available in the newest version of the ABC guide.

    If users want to correct the deadtime in their HXD light curves, they will need to perform the correction time bin by time bin. They should perform the deadtime correction for GSO background data, but need not do so for the PIN background data, which are generated with the correction built-in.

  10. How are the data in the hxd/event_cl/ directory cleaned?

    Screening criteria are as follows:

    ELV>5 && SAA_HXD==0 && T_SAA_HXD>500 && COR>8.
    

    The intervals with the high voltage set below 700 V are also screened out.

  11. What is the nature of the sharp cut-off in rev1.2 PIN spectra?

    Above 77 keV, gain parameters of the PIN are not defined in rev1.2 data, which is the cause of the cut-off. Please check this page at ISAS for the details.

The Software and Analysis

  1. Where can we get the latest software for Suzaku data analysis?

    Users should get the latest HEASOFT package from the HEAsoft main page.

    Currently, the latest version is 6.1.1.

  2. Are there any analysis manuals, i.e., "threads" "step-by-step" or "ABC guide" available?

    Please refer to the ABC Guide to Suzaku analysis. Also please visit the Suzaku Help Desk at RIKEN or ask your own question at the Suzaku GOF site at NASA/GSFC.


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This file was last modified on Tuesday, 26-Dec-2006 16:03:02 EST

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