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ELECTRONIC NEWSLETTER OF THE EUVE OBSERVATORY
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Vol. 7, No. 10 31 October 1997 ISSN 1065-3597
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(C) 1997, Regents of the University of California
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Notes from the Editor
=====================
by Brett A. Stroozas, EUVE Mission/Flight Director
Welcome to the electronic newsletter for NASA's Extreme Ultraviolet
Explorer (EUVE) satellite, compiled and published monthly by the
Center for EUV Astrophysics (CEA) at the University of California,
Berkeley (UCB). The contents of this issue of the EUVE electronic
newsletter are as follows:
1. EUVE Science News
1.1 Science Highlights
1.2 Cycle 6 AO Announced
1.3 Cycle 6 Proposal Review Process
1.4 Public GO/RAP Data Release for 1 November 1997
1.5 Abstracts of Recently *Accepted* EUVE Publications
2. EUVE Satellite Mission Operations News
2.1 FDF Sees Unexpected Decrease in EUVE's Velocity
2.2 On-Line Access to EUVE
3. EUVE Outsourced Extended Mission Status Report
3.1 Progress Continues on PACOR Replacement
To comment on or make suggestions for the EUVE electronic newsletter,
please send e-mail to ceanews@cea.berkeley.edu (Internet).
The EUVE observatory performed well throughout the month of
September 1997, completing and/or beginning observations of the
following Guest Observer (GO) and Right-Angle Program (RAP) targets.
For each target is listed its name, its spectral type (generally from
the SIMBAD database), the observation start day/time
(day-of-year:hours:minutes), name of Principal Investigator (PI),
observation type/priority, and any relevant notes:
=======================================================================
Target SpT GMT Start PI T Notes(*)
=======================================================================
AR Psc G5 238:14:14 (26 Aug) Dupree 1 EGO,CON
WX Cet DwNova 249:02:49 (06 Sep) Howell 1 EGO,CON,COO,TOO
1954+2923 NeutSt 249:02:49 (06 Sep) Edelstein 3 RAP
AR Psc G5 251:19:30 (08 Sep) Dupree 1 EGO,CON
PSR J1932+1059 Pulsar 257:00:00 (14 Sep) Bowyer 2 EGO
0111-151 AGN 257:00:00 (14 Sep) Lieu 3 RAP
PSR J0152-1637 Pulsar 257:23:40 (14 Sep) Bowyer 2 EGO
Survey ------ 258:17:39 (15 Sep) ------ - ENG,CF1
QS Tel CV:AM 258:23:20 (15 Sep) Rosen 1 EGO
RXJ1802.1+1804 CV:AM 260:00:30 (17 Sep) Szkody 1 EGO,CON,COO,TCO
rxradJ2358-0801 AGN 260:00:30 (17 Sep) Fruscione 3 RAP
BY Dra K6Ve 265:02:00 (22 Sep) Brown 2 EGO,CON,COO,CF2
LHS 2 MV: 265:02:00 (22 Sep) Mathioudakis 3 RAP
rxradJ2358-0801 AGN 265:02:00 (22 Sep) Fruscione 3 RAP
2MASPJ0345*+25* M9 271:19:00 (28 Sep) Stringfellow 2 EGO
M 15 LMXB 271:19:00 (28 Sep) Callanan 2 RAP
=======================================================================
(*) Key to Notes:
CF1 = Special payload configuration (XY telemetry mode,
Scanner C Sn filter unblanked)
CF2 = Special payload configuration (Scanner C off)
CON = Contiguous observation
COO = Observation coordinated with ground-based instruments
EGO = EUVE Guest Observer observation
ENG = Engineering test to calibrate star trackers
RAP = Right-Angle Program observation
TCO = Time-critical observation
TOO = Target of Opportunity
1. EUVE Science News
====================
1.1 Science Highlights
----------------------
by Dr. Jean Dupuis, EUVE Scientist
***********************************************
*** Discovery of White Dwarf Star Companion ***
******* to the B5 V Star HR 2875 (y Pup) ******
***********************************************
Dr. Stephane Vennes (Space Sciences Laboratory, UCB and
Astrophysical Theory Centre, Australian National University), Dr.
Thomas Berghoefer (Space Sciences Laboratory at UCB) and Dr. Damian
Christian (CEA at UCB) announce the discovery of the presence of a hot
white dwarf companion to the B star HR 2875. This constitutes the
first confirmed B star plus white dwarf (WD) system. An EUVE pointed
observation (5-14 April 1996, 113 ksec) reveals a weak continuum
spectrum in the short wavelength (SW) spectrometer characteristic of a
hot WD. An analysis of the EUVE spectrum based on a pure hydrogen
model spectra confines the WD effective temperature between
34500-52000 K and the HI column density between (1.8-5.0)E+19 cm^(-2).
Vennes et al. discuss the likeliness that this WD is more massive than
average field white dwarfs (~0.6 solar mass), which is a consequence
of the fact that the progenitor of this WD would have been a main
sequence star earlier than B5 (mass greater of equal to 6 solar mass).
Further study of this system is crucial to constrain the theoretical
final-to-initial mass relation between WD and main sequence stars.
More details about this discovery will soon be published in the
Astrophysical Journal Letters.
1.2 Cycle 6 AO Announced
------------------------
by Drs. Damian Christian and Jean Dupuis, EUVE Scientists
CEA has released the Announcement of Opportunity (AO) for the Sixth
Cycle ("Cycle 6") of EUVE Guest Observations. Information on this
Call for Proposals is available on the CEA WWW site
(http://www.cea.berkeley.edu/~science/html/EUVE_call97.html) or via
its anonymous ftp site (ftp.cea.berkeley.edu; directory /pub/nra97).
There is a new electronic format for proposal submission. If you
plan on submitting a Cycle 6 proposal please send an e-mail letter of
intent to euveprop@cea.berkeley.edu by 1 Nov 1997. Please include in
your letter the name of the PI and the appropriate research category
for your proposal as taken from the following list:
o Solar System Objects
o Interstellar Medium
o Compact Objects and Hot Stars
o Cool Stars and Related Binaries
o Cataclysmic Variables and Related Binaries
o Extragalactic Objects
o Other
This letter of intent is non-binding, but will help us plan for the
proposal review process, the schedule for which is as follows:
06 Oct 1997 -- Release of the Cycle 6 AO Call for Proposals
01 Nov 1997 -- E-mail letters of intent due at CEA
21 Nov 1997 -- Proposals due at CEA
Jan 1998 -- Proposal review period ends
Mar 1998 -- Beginning of Cycle 6 EUVE Guest Observations
So, the EUVE Project encourages researchers to get to work now on that
proposal, and thanks you in advance for your interest, time, and
consideration!
1.3 Proposal Review Process for Cycle 6
---------------------------------------
by Dr. Jean Dupuis, EUVE Scientist
As a result of the recent outsourcing of EUVE science management
responsibilities from GSFC to CEA, the EUVE Cycle 6 proposal review
process will differ from previous Cycles. For Cycle 6, proposals will
be reviewed by a Time Allocation Committee (TAC) appointed by the EUVE
Science Advisory Board (ESAB); the TAC Chairman will be Professor Jim
Liebert from the University of Arizona. Depending on the number of
proposals submitted, the TAC will be divided into 4-6 committees, each
having 3-4 members. Special attention will be given in the selection
of reviewers to avoid conflict-of-interest situations and to assure a
balance of experts within each sub-discipline. The TAC review process
will be very low-cost; it will be carried out "on-line" via
teleconference and e-mail, saving the significant traditional travel
and lodging costs; the only face-to-face TAC meeting will be held at
the January 1998 meeting of the American Astronomical Society (AAS) in
Washington, DC (see below). By minimizing costs in the proposal
review process more money will be available for GO grants.
The reviewers will be asked to rank the proposals and comment on
their strengths and weaknesses. Each committee will debate their
proposal rankings during the month of December, with technical support
provided by CEA (i.e., electronic distribution of proposals,
teleconference organization, technical reviews by CEA scientists).
The Chairs of each committee and of the TAC will convene during the
January 1998 AAS meeting, and will finalize the ranking of the
proposals and decide upon an equitable distribution of telescope time
among the highest-ranked proposals. It is anticipated that a final
list of targets will be ready by mid-January 1998 for approval by the
EUVE Observatory Director, Dr. Roger Malina.
1.4 Public GO/RAP Data Release for 1 November 1997
--------------------------------------------------
by Dr. Nahide Craig, EUVE User Support Scientist
The table below lists the GO/RAP observations that become public on
1 November 1997. For each observation is given the target name, the
approximate exposure time in ksec, the GMT start/end dates, the
target's spectral type, and the assigned data identification code (GO
and RAP data are marked accordingly). All public data sets can be
ordered from the EUVE Science Archive via WWW and electronic or postal
mail (see addresses below). Please be sure to include in your order
the DataID(s) of interest. Processed data sets are shipped via postal
mail on 8mm tape or, if requested, on CD-ROM.
The data rights policies for observations state that PIs have
proprietary rights to their data for a given period of time from the
date (s)he receives it. It is often the case that long observations
are broken up over many months; e.g., an observation approved for 60
ksec may actually be observed for 10 ksec one month, 20 ksec the next,
and 30 ksec three months later. In such cases the proprietary period
begins after the PI is sent the final piece of the completed
observation; note that, per the new ESAB policy, RAP targets observed
as of 15 Mar 1997 do *not* have associated proprietary periods. See
the UCB/CEA WWW site (address below) for a complete list of publicly
available EUVE data products.
===============================================================
Target ~Exp GMT Observation Dates SpT DataID
Name (ksec) Start End
===============================================================
GO DATA SETS AVAILABLE 1 NOVEMBER 1997:
CYCLE 3 Targets
ST LMi 29 30 Jan - 01 Feb 1996 CV go0616 *
xi UMa 184 01 Feb - 07 Feb 1996 F8.5V go0617 *
DH Leo 7 18 Nov - 19 Nov 1995 K0V go0618 *
* ==> Scanning telescope imaging observation
----------------------------------------------------------------
RAP DATA SETS AVAILABLE 1 NOVEMBER 1997:
***** none *****
================================================================
1.5 Abstracts of Recently *Accepted* EUVE Publications
------------------------------------------------------
by Brett A. Stroozas, EUVE Mission/Flight Director
Included below are abstracts of EUVE-related papers recently
*accepted* for publication. For those papers authored by UCB/CEA
personnel, the UCB/CEA publication numbers are indicated. Unless
otherwise noted, researchers may obtain preprints of the UCB/CEA
papers by sending an e-mail request containing the publication
number(s) of interest to pub@cea.berkeley.edu.
Researchers are encouraged to contribute *accepted* EUVE-related
abstracts for inclusion in future editions of this newsletter and for
posting under the UCB/CEA/EUVE WWW site. Please send all abstracts to
archive@cea.berkeley.edu.
--------------------------------------------------------------
PHOTOSPHERIC METALS IN HOT DA WHITE DWARFS
B. Wolff, D. Koester, S. Dreizler, and S. Haas
To appear in Astronomy and Astrophysics.
Previous observations of the soft X-ray and EUV region with the
Einstein, EXOSAT, and ROSAT satellites have indicated the presence of
photospheric absorbers in most DA white dwarfs with effective
temperatures greater than 40000 K. Several of these objects have now
been observed with the Extreme Ultraviolet Explorer (EUVE). Since the
detection of individual metal lines is rather difficult with EUVE
spectra we chose the well studied DA G 191-B2B as reference object for
the analysis of other white dwarfs. In spectra obtained with the GHRS
of the Hubble Space Telescope photospheric lines of nitrogen, silicon,
iron, and nickel could be detected. With the abundances determined
from these observations we were able to reproduce the EUVE spectrum of
G 191-B2B. The main source of EUV opacity turned out to be iron,
followed by nickel. The analysis of both the EUV continuum and the
hydrogen Balmer lines led to an effective temperature of 56000 +- 2000
K. For the analysis of other DA white dwarfs we used the same
relative abundances as for G 191-B2B but introduced a free scaling
factor (metallicity) for the total amount of metals. From EUVE
spectra we determined relative metallicities for 20 objects with
temperatures greater than 40000 K. The main result is that all DAs
above 50000 K contain additional photospheric absorbers, whereas at
lower temperatures all observations, with the exception of GD 394, are
compatible with pure hydrogen atmospheres. As in the case of G
191-B2B, iron determines also the EUV opacity in the objects at >50000
K. This is in agreement with radiative levitation theory which
predicts the support of iron above this temperature.
--------------------------------------------------------------
THE STELLAR EUV RADIATION FIELD
J. Vallerga
To appear in Astrophysical Journal.
The local extreme ultraviolet (EUV) radiation field from stellar
sources has been determined by combining the EUV spectra of 54 stars,
taken with the spectrometers aboard the Extreme Ultraviolet Explorer
satellite. The resultant spectrum over the range 70-730 A is
estimated to be 95% complete above 400 A and 90% complete above 200 A.
The flux contributed by two B stars and three hot white dwarfs
dominate the spectrum except at the shortest wavelengths where an
assortment of EUV source type contribute. The high electron densities
measured toward nearby stars can be accounted for by photoionization
from this radiation field, but the spectrum is too soft to explain the
over-ionization of helium with respect to hydrogen recently measured
in the Local Cloud.
--------------------------------------------------------------
2. EUVE Satellite Mission Operations News
=========================================
by Brett A. Stroozas, EUVE Mission/Flight Director
The month of September was a relatively smooth one for EUVE mission
operations. During the month the EUVE Observatory conducted
observations of 16 separate targets -- 9 GO, 6 RAP, and one
engineering calibration test. Three of these observations were
coordinated with ground telescopes, two required special payload
configurations, and two were time-critical or targets of opportunity.
The following subsections discuss a few of the month's highlights.
2.1 FDF Sees Unexpected Decrease in EUVE's Velocity
---------------------------------------------------
On 22 Sep the Flight Dynamics Facility (FDF) at GSFC detected an
unexpected decrease in the velocity of the EUVE satellite. FDF
detected an instantaneous velocity decrease of 2 cm/sec that, when
compounded by atmospheric drag and propagated over time, amounted to a
total "delta-V" of ~2 m/sec by the time it was detected some three
days after the fact. FDF analysis indicates that the delta-V event
occurred at ~06:00 GMT on 19 Sep, and has been independently confirmed
in tracking data from both FDF and NORAD. CEA engineers have reviewed
the available EUVE telemetry and confirmed that there is no sign of
any disturbance on-board the satellite. This type of delta-V event is
of the same scale as one caused by a large solar flare, although FDF
doesn't believe that this was the cause of this particular event since
it was only seen to occur on EUVE (a solar flare would presumably
affect multiple orbiting satellites). FDF's best guess is that this
delta-V event was the result of a collision between EUVE and a
micrometeroid. Once again, this event has had no significant impacts
on the EUVE orbital parameters or the on-board satellite systems.
2.2 On-Line Access to EUVE
--------------------------
Listed below are the various methods for on-line access to EUVE:
o UCB/CEA WWW URL: http://www.cea.berkeley.edu/
o anonymous FTP: ftp.cea.berkeley.edu
o EUVE Electronic Newsletters
Past issues -- available via the UCB/CEA WWW site
Subscriptions -- mail majordomo@cea.berkeley.edu ("subscribe
euvenews")
Post message (moderated) to all subscribers:
mail euvenews@cea.berkeley.edu
o GI Program
Are you interested in finding out about or using EUVE data? Do
you need help in understanding EUVE data sets? Do you need help
in using the available EUVE data analysis software tools? If you
answer "yes" to any of the above, the Guest Investigator (GI)
Program at UCB/CEA can help YOU! For more information see the
UCB/CEA WWW site or contact the EUVE Science Archive
(archive@cea.berkeley.edu).
o Public RAP
The Public RAP is a simple and easy method for researchers to
propose for long-exposure EUVE imaging data. For more
information on the Public RAP and the simple proposal process see
the UCB/CEA WWW site (address below) or contact the EGO Center
(egoinfo@cea.berkeley.edu). Mail all proposals to
euverap@cea.berkeley.edu.
o Contact information for the EUVE Science Archive or EGO Center:
Center for EUV Astrophysics
2150 Kittredge St.
Berkeley, CA 94720-5030
510-642-3032 (voice)
510-643-5660 (fax)
archive@cea.berkeley.edu
egoinfo@cea.berkeley.edu
3. EUVE Outsourced Extended Mission Status Report
=================================================
by Brett Stroozas, EUVE Mission/Flight Director
Work continues to clean up the remaining open issues from the
outsourcing of EUVE Explorer Platform (EP) spacecraft operations from
GSFC to UCB/CEA. The following subsections describe some of the
outsourcing highlights from September 1997.
3.1 Progress Continues on PACOR Replacement
-------------------------------------------
Since launch, GSFC's PACOR (Packet Processor) facility has been
responsible for packaging and routing to UCB all science telemetry.
As the final part of the successful outsourcing of EUVE spacecraft
operations from GSFC, UCB programming and Flight Operations Team
personnel have been working to outsource the PACOR functions as well:
the pre-processing of EUVE tape recorder (TR) and realtime telemetry
data, and the weekly delivery of large blocks of EUVE attitude data to
FDF.
During September UCB made significant progress on this task. UCB
has completed development of the software and operational procedures
for handling TR data. Successful tests of the overall system were
conducted and it was subsequently put into operational use. On 29
September PACOR has ceased routing all TR data to UCB; we are now on
our own for this function and the new system is working very well.
With the successful implementation of the TR data handling system,
work has shifted to the realtime data processing. UCB has completed
development on the relevant software, installed it with some
associated development tools on the operational computer network, and
successfully completed preliminary unit testing. Full system testing
will occur in early October and we expect to being using it in
operations soon thereafter.
Finally, some preliminary work has been done on the means of
delivering large blocks of EUVE attitude data to FDF. UCB is working
with FDF to determine not only what FDF currently receives from PACOR,
but exactly what FDF desires; the hope is that UCB can provide FDF
with data products more tailored with FDF's needs and wants.
Although UCB's progress on the PACOR replacement project has been
good, we will not meet our 1 October target completion date. However,
UCB expects to have the full-up PACOR replacement systems in
operational use by late-October. We will then run in this mode for a
few extra weeks, with PACOR available as a backup, before finally
completing the project by mid-November; at that time we expect to
terminate all PACOR support for EUVE.
--------------------------------------------------------------------------
The EUVE Electronic Newsletter is issued by the Center for Extreme
Ultraviolet Astrophysics, University of California, Berkeley, CA
94720, USA. The opinions expressed are those of the authors. EUVE
Principal Investigators and Newsletter Publishers: Dr. Roger F.
Malina and Professor Stuart Bowyer. EUVE Newsletter Editor: Brett
Stroozas. Funded by NASA/UCB Cooperative Agreement NCC5-138. Send
newsletter correspondence to ceanews@cea.berkeley.edu.
The EUVE project is managed for NASA by UCB: Dr. Roger F. Malina,
EUVE Observatory Director; Dr. John Vallerga, EUVE Observatory
Deputy Director; Dr. Mike Gunter, EUVE Project Manager; Mr. Brett
Stroozas, EUVE Mission/Flight Director; Mr. Rob Nevitt, EUVE
Operations Manager. NASA HQ: Dr. Guenter Riegler, Program Manager.
EUVE Science Advisory Board: Dr. Steve Howell (Chair).
END-----------EUVE------------ELECTRONIC---------------NEWS-------------END
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