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blanksky_g#_#cor#.evt
caldb/data/asca/gis/bcf/bgd/94apr
Current - But Warning (see below)
These files contain GIS background datasets. Each
file is a superposition of 13 blank sky fields observed during the
ASCA PV phase (1993 May - Nov). Since the GIS internal
background increases as the magnetic cut-off rigidity (COR)
decreases, the files are sorted by COR values (in units of MeV/c). Like
the AO data, these background data were taken after the Spread
Discriminator was turned on (1993 May 27).
The naming scheme used is:
where
- is the GIS sensor
(=
2
or 3
)
- is the lower value of the magnetic cut-off rigidity (COR)
used to construct the dataset
( =
4
, 6
, 8
, 10
, 12
,
14
, or can be missing)
- is the upper value of the magnetic cut-off rigidity (COR)
used to construct the dataset
( =
4
, 6
, 8
, 10
, 12
,
14
, or can be missing)
Further information regarding the construction and use of these
dataset can be obtained from the
README file
in the above directory.
Ken Ebisawa (NASA/GSFC ASCA GOF) 1994 Mar 30.
(No OGIP multi-mission standard)
See above, and the
README file
in the above directory.
- Ken Ebisawa (ASCA GOF NASA/GSFC) 1994 Mar 30:
- In order to prevent the extraction of astrophysical information, all
the
X
& Y
values (sky pixel) are set to 1, and the
TIME
values are made constant.
Furthermore, events are sorted in ascending order of DETX
.
- These event files do not have the RTI (rise time invariance) values
so the PH dependent Rise Time discriminator cannot be applied.
ASCA GOF will soon supply the background event files with the RTI
column filled. Additionally, the ASCA GOF is planning to supply event
lists of night Earth data. Such data may be used for the study of X-
ray background.
- Ken Ebisawa (ASCA GOF NASA/GSFC) 1994 Dec 14:
- There are a number of moderately bright sources in these
'blank sky' fields which are not completely averaged out
by the summation of many fields. The
DETX,DETY
coords of the 3 most significant sources are:
- (113,118) in SIS2, and (120,118) in SIS3
- (122,142) in SIS2, and (128,141) in SIS3
- (98,142) in SIS2, and (104,143) in SIS3
The GOF advises that GOs take extra care when using background
data near these positions. In particular, sources (1) and (2)
are NGC6552, which is known to have a very strong iron
emission line (Fukazawa et al. 1994, PASJ, 46, L141;
Reynolds et al. 1994, MNRAS, 268, L55.).
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Mike Corcoran
2001-08-30