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From: naze@astro.ulg.ac.be
Subject: TIME definition
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Date: Tue, 24 Nov 2009 15:23:16 GMT
From: naze@astro.ulg.ac.be
To: xmmhelp@sciops.esa.int
Cc: naze@astro.ulg.ac.be
Subject: TIME definition
Full_Name: Yael Naze
Submission from: (NULL) (139.165.20.204)


Hello,

The first column of the event files is "TIME" in second, since a beginning which
is not specified. Can we have the HJD corresponding to a specific TIME, either
that of the TIME=0 or that of one of our photon detection ? 

Regards,
Yael Naze


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From: Jan-Uwe Ness <xmmhelp@sciops.esa.int>
To: naze@astro.ulg.ac.be
Subject: Re: TIME definition (PR#42570)
Date: Tue Nov 24 16:13:45 2009
Dear Yael Naze,

 the beginning of the time is defined by the header keyword MJDREF that, for
XMM-Newton, is always 5.08140000000000E+04, corresponding to 1998-01-01T00:00:00
(terrestrial time).

 You may find the HEASARC tool xtime useful that you find under:
http://heasarc.gsfc.nasa.gov/cgi-bin/Tools/xTime/xTime.pl
You can use that to convert mission time units to Julian date etc. The
heliocentric correction depends on the coordinates and has not been applied.
Since different sources are in the field, no unique HJD can be given that would
apply to all sources in the field. There are several ways how you can get HJD,
for example from Julian date using the IDL tool helio_jd.

 Hope this helps. Let me know if you need further help.

Best wishes,
Jan-Uwe

> Full_Name: Yael Naze
> Submission from: (NULL) (139.165.20.204)
> 
> 
> Hello,
> 
> The first column of the event files is "TIME" in second, since a beginning
which
> is not specified. Can we have the HJD corresponding to a specific TIME,
either
> that of the TIME=0 or that of one of our photon detection ? 
> 
> Regards,
> Yael Naze


Followup 1

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Date: Tue, 24 Nov 2009 17:19:52 +0100
From: "naze@astro.ulg.ac.be" <naze@astro.ulg.ac.be>
To: Jan-Uwe Ness <xmmhelp@sciops.esa.int>
Subject: Re: TIME definition (PR#42570)
>  Hope this helps. Let me know if you need further help.
thanks !

yael naze


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