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ELECTRONIC NEWSLETTER OF THE EUVE OBSERVATORY Vol 2, No. 7 9/19/92
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EUVE SKY SURVEY PROCEDING SMOOTHLY
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The 100th day of the EUVE mission was just celebrated. The EUVE
all sky survey continues to be carried out smoothly. Initial
processing of the first 16 days of the sky survey has been carried out
and initial lists of possible EUVE sources have been released internally
to the EUVE Science Team. The large number of new EUV sources are being
screened for spurious sources, and optical counterpart identification
work has begun.

ALPHA CEN AND PROX CEN
----------------------
Initial results on EUVE observations of ALpha Centaurus and Prox
Cen were presented to the EUVE Science Team. Both sources are
strongly detected, and includes detections in all four EUVE filters.
The detection in all four EUVE filters is very encouraging and indicate
that spectroscopy will be possible to very long wavelengths.
For further information contact Dr Peter Vedder: pvedder@cea.berkeley.edu

REPROCESSED CALIBRATION SPECTRA OF WHITE DWARFS
-----------------------------------------------
The data from calibration white dwarfs WD 2309+105 and WD 1845 +019 
have been reprocessed revealing that a number of unexpected spectral
features will be useful for wavelength calibration, in addition to
the use of these sources as photometric standards. The detection of these
new spectral features is generating much excitement.The raw calibration
spectra will be released shortly through the public archive.

GEOMAGNETIC STORMS LEAD TO ENHANCED BACKGROUNDS
-----------------------------------------------
Dr Randy Gladstone reported that during the recent major solar
storms and associated geomagnetic storms, the Scanner A and B 
detectors experienced  very enhanced detector backgrounds of
above 1000 c/s. The data from these periods will lead to data
gaps that will have to be filled in during the second six month
phase of the mission. Further information from rgladstone@ssl.berkeley.edu

BLIND TASTE TESTING OF SOURCE DETECTION ALGORITHMS UNDER WAY
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EUVE BUDGET CUTS TO REDUCE PLANS FOR EUVE DATA ANALYSIS
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We are currently comparing the results of four different 
source detection algorithms which are being run on the same data
set from the first 16 days of the sky survey. The results will
be reviewed next week to see which algorithms detect the largest
number of EUV point sources in the data and which ones have the
lowest spurious source detection rates. The winning code from
this competition will be used for subsequent reprocessing
of the all sky survey data.  Due to the large cuts in the EUVE post launch
budgets, release of the monthly EUVE bright source lists
and catalogues will not be carried out and development of the EUVE diffuse
sky maps has been put on hold. The total impact of the budget cuts are
still being assessed.

Summary of cross-comparisons of EUVE, EXOSAT, and ROSAT WFC calibrations
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The EUVE in-flight calibration verification program includes folding
white dwarf models through the EUVE instrument effective areas, and choosing
parameters which give predicted count rates which match the observed count
rates. We will also be intercomparing observations taken with the EUVE
scanners, deep survey and spectrometer on the same objects. The same models
which fit the EUVE observations are then used to compare predicted and
measured count rates for the ROSAT WFC and for EXOSAT in the cases in which
EXOSAT and ROSAT WFC data are available. The EUVE all sky survey is also
being interrupted once a month to carry out calibrations to monitor any
change in EUVE instrument performance.

	In the case of CD -38 10980 (WD 1620-391), a ~24,000 K DA white
dwarf observed with the EUVE Deep Survey instrument, the same pure hydrogen
model fits both the EUVE Deep Survey Lexan and the WFC S1 and S2 count rates
to within a few percent.  

	In the case of WD 1845+019, which is somewhat hotter, the flux
peak is at 150 Angstroms, and significant flux is present up to 300
Angstroms.  For this object, the agreement between EUVE and the WFC is not
as good as for WD 1620-391.  The model which best fits EUVE Deep Survey
Lexan/B count rate overpredicts the WFC S1 and S2 countrates by about 20%.
A model can be selected which underpredicts EUVE by 10% and overpredicts
ROSAT WFC count rates by 10%. However, we are now investigating why the
EUVE vs WFC comparisons differ for objects with different flux distributions.

Initial discrepancies with the ROSAT WFC observations have been reduced
through the use of the recent amended ROSAT WFC instrument calibration
curves which we have now received and also  taking into account the
degradation curves provided for the drop of sensitivity during the ROSAT
WFC survey. We are still finding discrepancies with the EXOSAT Al/P
observations as models which fit the EUVE data overpredict the count rates
reported by EXOSAT by at least 50%. This is still being investigated.
Observed countrates by EUVE are a factor of ~3 higher than ROSAT WFC S1
for the same objects due to the larger grasp of the EUVE filters.

For further information on the EUVE calibration analysis contact
Dr David Finely and Dr Pat Jelinksy at david@cea.berkeley.edu

EUVE ARCHIVE ADDITIONS AND UPDATES
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New files have been added to the EUVE Public Archive. To access
the EUVE Public Archive for the first time send email to
archive@cea.berkeley.edu with the word 'help' on the first line
Now Available in Hardcopy form only:
-----------------------------------
1)Scanner A deep exposure showing calibration target WD 1254+223
2)Scanner B calibration pointing showing WD1254+223,
Also:
Updated Datarights document: clarification of all sky survey data rights
Updated  EUVE_bibs document: new available publications
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The EUVE Electronic Newsletter is issued by the  Center  for  Ex-
treme  Ultraviolet Astrophysics, University of California, Berke-
ley. The opinions expressed are those of the  authors.   Publish-
ers:  Roger F. Malina, C. Stuart Bowyer, Managing Editor: Camille
Trentacoste.  Funded by NASA Contracts NAS5-30180 and  NAS5-29298
Send newsletter correspondence to: pub@cea.berkeley.edu (Internet)
EUVE Public Archive via FTP: ftp.cea.berkeley.edu, pub/archive
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The EUVE Project is managed by NASA's GSFC.  The Project  Manager
at  GSFC  is  Mr.  Paul Pashby, the Project Scientist is Dr. Yoji
Kondo, the Deputy Project Scientist is Dr. Ronald Oliversen.  The
NASA  Headquarters  EUVE Program Scientist is Dr. Robert Stachnik
the Deputy Program Scientist is Dr.  Derek  Buzasi,  the  Program
Manager is  Dr. Guenter Riegler.  The Project Operations Director
is Mr. Kevin Hartnett.  Information  on  the EUVE  Guest Observer
Program is available from:  Dr. Yoji Kondo,  Mail Code 684  GSFC,
Greenbelt, MD 20771 (301)286-6247; euve@stars.SPAN.NASA.GOV