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ELECTRONIC NEWSLETTER OF THE EUVE OBSERVATORY
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Vol 4, No. 12 22 Dec 1994 ISSN 1065-3597
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Notes from the Editor
=====================
by Brett A. Stroozas, Data Archive and Science Support (DASS) Manager
Welcome to the electronic newsletter for NASA's Extreme Ultraviolet Explorer
(EUVE) satellite, which is compiled and published monthly by the EUVE Science
Archive group at the Center for EUV Astrophysics (CEA) in Berkeley, CA. The
contents of this issue of the EUVE electronic newsletter are as follows:
1. NASA Announces EUVE Extended Mission
2. Recent EUVE Science Highlights
3. EUVE Science at 185th AAS Meeting
4. CEA WWW Developers Workshop
5. Notes from the EUVE Guest Observer Center
5.1 Cycle 3 Peer Review
5.2 EGO Center Software Release 1.5
6. Notes from the EUVE Science Operations Center
6.1 UCB Distinguished Service Awards
6.2 Innovations in Operations Procedures
7. Notes from the EUVE Science Archive
7.1 GO Data Release List for 1 Jan 1995
7.2 GI Science Program
7.3 Mailserver Disabled
7.4 Accessing the Archive
8. Abstracts of Recently *Accepted* EUVE Papers
To comment on or make suggestions for the EUVE electronic newsletter, please
send e-mail to ceanews@cea.berkeley.edu (Internet). CEA would like to wish
everyone a Happy Holiday Season -- Merry Christmas and a Happy New Year!
The EUVE observatory performed well throughout the month of November,
completing observations of the following Guest Observer (GO) targets (alternate
name and spectral type information taken from the SIMBAD or internal CEA
databases):
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Target Alternate Spectral Observation
Name Name Type GMT Date(s) Notes
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PSR 0437-4713 ------ Pulsar 23 Oct - 12 Nov 1994 --
Moon ------ SolSys 12 Nov - 12 Nov 1994 --
AB DOR HD 36705 K1IIIp 12 Nov - 17 Nov 1994 --
RE0506-213 ------ M2 17 Nov - 20 Nov 1994 --
Nova Cyg 1992 V1974 Cyg Nova 20 Nov - 20 Nov 1994 --
Borrelly ------ Comet 20 Nov - 22 Nov 1994 --
Nova Cyg 1992 V1974 Cyg Nova 22 Nov - 25 Nov 1994 --
Vela RE0838-430 SupNova 25 Nov - 28 Nov 1994 --
V471 Tau RE0350+171 K0 28 Nov - 02 Dec 1994 --
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1. NASA Announces EUVE Extended Mission
=======================================
by Dr. Roger Malina, EUVE Instrument PI and CEA Acting Director
As a result of the recent Senior Review at NASA Headquarters, NASA has
notified the EUVE Project at CEA that EUVE operations will be extended from
January 1996 (the original end-of-operations) through October 1997. We would
like to thank both the EUVE Users Committee and the astronomical community for
their support of the mission, and for the rapid publication of EUVE results
that demonstrates the value and interest of EUVE observations to a wide variety
of astrophysical problems.
NASA commended the Project on the aggressive efforts to find new lower cost
means of operating EUVE and for transferring this methodology to other missions.
With the support of Codes "O" (communications division) and "X" (technology
division), NASA has approved the establishment of the EUVE Operations Test-bed
to develop and implement new approaches.
NASA also noted the effective educational outreach program being carried out
by the Project and indicated that this program was to continue as an integral
part of EUVE operations during the extended mission.
2. Recent EUVE Science Highlights
=================================
by Dr. Antonella Fruscione, CEA Scientist
The following are recent science highlights from the EUVE mission:
* Schmitt, Drake, Stern and Haisch have determined the coronal density of the
nearby star alpha Canis Minoris (CMi), using ratios from detected iron
spectral lines of different ionization stages (ranging from FeIX to FeXIV).
All the studied line ratios yield densities consistent with those found in
solar active regions. This implies that the corona of alpha CMi is,
presumably, structured in a similar manner as to that of the Sun and,
furthermore, the coronal filling factor is estimated to be about 20%.
* Drake, Laming and Widing have analyzed spectral lines due to the elements
Ne, S, Ar, Fe, and Si in the EUVE spectrum of the alpha Centaurus AB system.
The results indicate a significant enhancement of the species with low first
ionization potentials (FIPs) -- Fe and Si -- in the corona with respect to
their photospheric abundances. A similar situation exists in the solar
corona (the "FIP Effect"). This result is the first detection of the FIP
effect in a stellar corona.
* Monsignori-Fossi, Landini, Fruscione, and Dupuis have studied the EUVE
spectra of the star EQ Pegasi which was detected at all EUVE wavelengths and
was successfully monitored by the Deep Survey photometer. They identified
the main features observed in the spectra and concluded that a number of
lines are produced by high ionization stages of iron. Evidence of activity
modulation during the observation is present in both photometric and
spectroscopic data.
3. EUVE Science at 185th AAS Meeting
====================================
The 185th meeting of the American Astronomical Society (AAS) will be held
8-12 January 1995 in Tucson, AZ. As usual, EUVE science will be represented.
The following is a *tentative* list of the EUVE-related abstracts:
* "The Hydrogen Ionization in the Local Interstellar Medium: Effects of New
EUV Sources," K.P. Cheng, Fred Bruhweiler, and Yoji Kondo
* "On the Extragalactic Content of the Extreme Ultraviolet Explorer All-Sky
Survey," A. Fruscione
* "Analysis of EUVE Lightcurves of AM Her Systems," S.B. Howell and M.M. Sirk
* "Preliminary Results from the Second EUVE Source Catalog," J. Lewis,
S. Bowyer, M. Lampton, X. Wu, P. Jelinsky, V. Saba, R. Lieu, and R.F. Malina
* "In Pursuit of the FIP Effect and Element Abundance Anomalies in Late-Type
Stellar Coronae with EUVE," J.J. Drake, J.M. Laming, and K.G. Widing
* "HST/GHRS and EUVE Spectra of the Active Clump Giant beta Ceti (K0 III),"
T.R. Ayres, A. Brown, S. Drake, T. Simon, R.A. Stern, and B.E. Wood
* "Insights into the ISM and the Spectral Evolution of White Dwarfs from EUVE
Observations of GD 659 and EUVE J2009-604," S. Vennes, J. Dupuis,
and S. Bowyer
* "Neutron Stars as Physics Laboratories," F.K. Lamb
* "X-Ray-Induced Ionization in the Winds of Early-B Stars: Constraints Imposed
by EUVE," J.J. MacFarlane, D.H. Cohen, and J.P. Cassinelli
* "Optical Identification and Spectroscopy of EUV Sources," N. Craig,
A. Fruscione, M. Abbott, C.A. Christian, J.J. Drake, J. Dupuis,
and M. Mathioudakis
* "EUVE Observations of Algol," R.A. Stern, J.R. Lemen, J.H.M.M. Schmitt,
and J.P. Pye
* "Simultaneous/Contemporaneous EUVE, ASCA, IUE, VLA & AT Observations of the
RS CVn binary HR1099 in August 1994," A. Brown, S. Skinner, R. Stewart,
S. Drake, and B. Deeney
* "Rapid Multiwavelength Flaring of the BL Lac Object PKS 2155-304,"
C.M. Urry, J.E. Pesce, R. Sambruna, A. Treves, E. Pian, L. Maraschi,
T. Kii, K. Sasaki, F. Makino, R. Fujimoto, C. Otani, F. Makino, M. Tashiro,
T. Takahashi, H. Marshall, G. Madejski, S. Penton, and J.M. Shull
For those researchers attending the upcoming AAS meeting, we invite you to
stop by the EUVE booth where you will find the latest information regarding the
EUVE Project. As an additional service, CEA will distribute pre-prints of those
journal papers reporting EUVE data analysis results. If you have a such a
pre-print that you wish to have distributed, please bring copies to the CEA
booth and leave them with Jennifer Hinchman. As always, CEA wishes to see
that EUVE science -- both recent accomplishments and new results -- is
well-represented at the meeting.
4. CEA WWW Developers Workshop
==============================
by Behram Antia, DASS Research Associate
CEA hosted its first World Wide Web (WWW) developers workshop on 5 Dec 1994.
The first invited speaker, Dr. Carol Christian of CEA, discussed the National
Information Infrastructure Testbed (NIIT) as well as the CEA WWW endeavors.
The meeting brought together people from the academic and business communities
to discuss advanced techniques and issues related to WWW development. Topics
such as dynamic page generation, database interfaces and 3-D Webs were discussed
with the aid of available workstations. This initial workshop was specifically
targeted towards programmers and developers who were already quite familiar
with the WWW and its use in presenting material; future workshops will be more
widely advertised and will be broader in scope. Through these workshops, CEA
aims to increase the usefulness of its own WWW site and resources, and to
continue to improve our data delivery and presentation using new and innovative
technologies and techniques.
5. Notes from the EUVE Guest Observer Center
============================================
The EUVE mission is now into the second year (Cycle 2) of the Guest Observer
(GO) Program in which the satellite conducts pointed spectrometer observations.
Through a yearly process, GOs propose to NASA to use the EUVE instruments to
observe their target(s) of interest. Approved GOs are supported by the EUVE GO
(EGO) Center at CEA which is responsible for providing them with software, data
processing, and scientific and technical support for the analysis of their
observational data (to which they typically have one year proprietary data
rights). The following sections describe some of the recent highlights from
the EGO Center.
5.1 Cycle 3 Peer Review
-----------------------
by Dr. Ron Oliversen, EUVE Associate Project Scientist at GSFC
The EUVE peer review for the Cycle 3 Guest Observer proposals was held 8-9
December at Goddard Space Flight Center (GSFC). Results from the peer review
are expected to be released in January. Any questions about the review results
should be directed to Ron Oliversen at GSFC by telephone (301-286-6290) or via
e-mail on the Internet (oliversen@stars.gsfc.nasa.gov).
5.2 EGO Center Software Release 1.5
-----------------------------------
by Anne Miller, EGO Center Technical Writer
The EGO Center recently announced the release of version 1.5 of its IRAF/EUV
layered software package for the processing and analysis of GO data. A new
release of the reference data set (EGODATA 1.9) is also available. These
releases introduce a number of changes; those which most affect GOs are
summarized briefly below.
A variety of changes and improvements have been made to the nominal data
reduction procedure, resulting in changes to data product format and/or content.
Among the major changes are the inclusion of times of earth blockage, the
reduction in the size of spectral images, and the inclusion of data from the
Deep Survey photometer.
A number of the tasks in the IRAF/EUV software layered package have been
changed to produce the data product changes noted above. The major changes
are that certain tasks (e.g., "specmod" and "euvextract") have been rewritten
to improve performance, other tasks (e.g., "euvecombine") have been replaced
by new improved ones (e.g., "suborder" and "divea"), and the ability to handle
Deep Survey photometric data has been added to the event processing task
("cep").
The new version of the EGODATA reference data set contains additional look-up
tables of calibration data to support reduction of Deep Survey photometric data.
The EGO Center documentation, which describes many details of the software
and data products distributed to GOs, is still in the process of being updated
to reflect the latest changes. The documentation is also being reorganized to
make it more complete and easier to use. The EGO Center Software User's Guide
will be augmented by a Data Products Guide, which documents the new data
product formats. A third document, which provides a more detailed description
of the reference data set than has been previously available, is scheduled for
release next year.
In addition to the major changes summarized above, numerous minor ones have
also been implemented. For additional information and details, as well as for
the release products themselves, see "What's New" on the EGO Center HomePage
section of the CEA WWW site (http://www.cea.berkeley.edu/) or refer to the CEA
anonymous ftp site (ftp.cea.berkeley.edu).
6. Notes from the EUVE Science Operations Center
================================================
The EUVE Science Operations Center (ESOC) is responsible for the day-to-day
operations of the EUVE science payload. In particular, this includes payload
commanding, instrument health and safety monitoring, and the planning of science
observations. The following sections describe some of the recent ESOC
highlights.
6.1 UCB Distinguished Service Awards
------------------------------------
by Jennifer Hinchman, CEA Public Affairs
In November, University of California, Berkeley (UCB), Vice Chancellor of
Research, Joseph Cerny, awarded the following members of the CEA "Eworks" team
with the 1993-1994 "Distinguished Service Award": Martha Eckert, Forrest
Girouard, Allen Hopkins, Linda John, Frank Kronberg, Pat Ringrose, Larry Wong,
Paul Wang, Paul Eastham, and Dave Korsmeyer. [Note: "Eworks" is the augmented
intelligence software package which is being phased into ESOC operations to
autonomously monitor the EUVE science payload.]
The team, which includes staff members from CEA, NASA Ames Research Center
(ARC), and undergraduate UCB students, was awarded for their efforts to
implement and develop new satellite operations technology and techniques which
will substantially reduce the cost of operating the EUVE satellite.
This project required innovative thinking and the willingness to find new
ways of doing tasks. It required new software and convincing management that
the plan was credible. In addition, the accomplishment of this project required
close collaboration with NASA ARC which had experts willing to work with UCB
to find ways to cut operating costs.
6.2 Innovations in Operations Procedures
----------------------------------------
by Frank Kronberg, ESOC Payload Controller
The ESOC Procedures, a set of approximately 50 descriptions of what, how,
why, and when to perform specific functions and tasks in the ESOC have been
re-formatted in a consistent manner (using the capabilities of the FrameMaker
text processing software) so that they may be easily and automatically updated.
Because there are a total of about 300 pages of text, updating these procedures
has always been a daunting job. Now with the start of simulated single-shift
operations [Note: part of the "3-to-1" transition; see V4, No. 10 -- "3.
Mission Operations Innovation at CEA"], it is very important that the updating
process be as easy as possible.
Part of this process includes user-generated input with suggestions,
criticisms, revisions, and additions to each procedure. A manual system, which
includes a "USER INPUT" page for each procedure has been created. For now,
users write down their comments on each procedure's "USER INPUT" page and this
input is the basis for timely revisions of the procedures. This process has
been repeated a number of times since the start of simulated single-shift
operations in November.
During a recent visit to check on the progress of the single-shift operation
simulation, CEA Acting Director, Dr. Roger Malina, remarked "With this quick
response time, in the revision of the procedures, users can see their
suggestions implemented quickly, rather than waiting a number of months before
the revisions appear."
This manual system of user input will be replaced by an automated system
which will allow for the real-time user updating of ESOC documentation using
a software-based revision control system. Each change in automating the flow
of information will be tested manually before it is automated in order to
prevent (as much as possible) problems and errors in the implementation. The
automated information flow aspect of the EUVE 3-to-1 transition is an attempt
to reach NASA Administrator Dan Goldin's goal of "faster, cheaper, better".
7. Notes from the EUVE Science Archive
======================================
by Brett Stroozas, DASS Manager
The EUVE Science Archive at CEA has been established in order to archive and
distribute EUVE data, software, and documentation in an innovative and efficient
manner. The Archive officially became operational on 17 July 1992 as an
anonymous FTP site; it has since expanded significantly (e.g., on the WWW) to
deal with the expiration of proprietary data rights which began in early 1994.
The following sections describe some of the recent Archive highlights.
7.1 GO Data Release List for 1 Jan 1995
--------------------------------------------
The table below lists the GO observations which become public on 1 January
1995; all have been reprocessed with the most recent versions of the EGO Center
software and reference data. For each entry is given the target name, the
approximate exposure time in kiloseconds, the GMT start and end date(s) for
the observation, the spectral type of the target, and the data identification
code. All public data sets may be ordered from the archive via WWW and
electronic or postal mail (see addresses below). Please be sure to include
in your order the DataID(s) of interest.
The data rights policy for GO observations states that GOs have proprietary
rights to the data for one year 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
one-year proprietary period begins after the GO receives the final piece of
the complete observation.
===============================================================
Target ~Exp Observation Date(s) SpT DataID
Name (ksec) Start End
===============================================================
Data Sets Available 1 Jan 1995:
HD220140 83 Nov 11 1993 - Nov 14 1993 G9V go0131
HD66811 58 Nov 16 1993 - Nov 18 1993 O5Ia go0132
IX_VEL 78 Nov 26 1993 - Nov 29 1993 CV go0133
IX_VEL 21 Nov 29 1993 - Nov 30 1993 CV go0134
IX_VEL 93 Dec 2 1993 - Dec 5 1993 CV go0135
MOON 2 Nov 24 1993 - Nov 25 1993 SolSys go0136
MOON 2 Dec 3 1993 - Dec 3 1993 SolSys go0137
NGC1360 94 Nov 18 1993 - Nov 22 1993 CSPN go0138
P/ENCKE 55 Nov 30 1993 - Dec 2 1993 SolSys go0139
PKS2155-304 137 Jun 16 1993 - Jun 20 1993 BLLac go0140
PKS2155-304 169 Jul 5 1993 - Jul 11 1993 BLLac go0141
PKS2155-304 14 Jul 27 1993 - Jul 28 1993 BLLac go0142
RE0431+833 45 Dec 8 1993 - Dec 10 1993 NOID go0143
RE0623-374 36 Nov 23 1993 - Nov 24 1993 WD go0144
RE0847+594 17 Nov 25 1993 - Nov 25 1993 NOID go0145
===============================================================
7.2 GI Science Program
----------------------
In order to promote research using EUVE data, CEA has implemented the EUVE
Guest Investigator (GI) Science Program. The purpose of the Program is as an
educational service which provides to researchers education and training in
the use of public EUVE data. The basic EUVE data sets are skymaps and
"pigeonholes" (photon event lists) from the the all-sky and deep surveys and
multi-channel spectra from the GO Program.
As GIs, researchers will receive from CEA a standard package of support to
assist them with their data reduction and analysis. This standard package
offers to researchers one week (five working days) of free access -- either as
a local visitor or remotely -- to a variety of CEA resources including
administrative (e.g., workspace for local visitors) and computer (e.g., cpu
power and disk space storage) resources as well as a scientific/technical
assistant who will assist the researcher in understanding and using the EUVE
data. At the end of the five days, it is anticipated that GIs will be fully
able to analyze EUVE data on their own and at their home institutions. In
effect, the GI Program offers CEA's technical experience and intricate knowledge
of the EUVE instrumentation and data to the external research community.
The timing of the implementation of the GI Program coincides well with the
recent NASA Research Announcement (NRA 94-OSS-17) from the Astrophysics Data
Program (ADP) which includes EUVE data in its call for proposals. (More
information on the ADP and the proposal process is available via anonymous ftp
at ftp.astrophysics.hq.nasa.gov in the directory /pub/NRAs/ADP/94-OSS-17.) If
considering submitting an ADP proposal for EUVE research, you are encouraged to
make use of the GI Program first to familiarize yourself with the data. GI
slots are available between now and the proposal deadline (25 January 1995).
Please contact the Archive (addresses below) for more information on the GI
Program.
7.3 Mailserver Disabled
-----------------------
In order to better serve the archival user community, the Archive mailserver
program was disabled on 22 November; all requests will now be handled manually.
This higher level of service will increase the levels of communication and
personal interaction between the Archive and the user community, ensuring that
the needs of users are met more completely and efficiently.
7.4 Accessing the Archive
-------------------------
Listed below are the various methods for accessing EUVE archival material:
o CEA World Wide Web URL:
http://www.cea.berkeley.edu/ (Mosaic/lynx remotely)
telnet www.cea.berkeley.edu 200 (lynx locally at CEA)
o NASA's Astrophysics Data System:
http://adswww.colorado.edu/adswww/adshomepg.html (Mosaic/lynx)
o e-mail: archive@cea.berkeley.edu
o anonymous FTP (or gopher): ftp.cea.berkeley.edu
o CD-ROM Series: Volumes 1.1, 2.1, and 2.2 (seven separate CDs) available
o EUVE Electronic Newsletters:
To subscribe: mail majordomo@cea.berkeley.edu ("subscribe euvenews")
To unsubscribe: mail majordomo@cea.berkeley.edu ("unsubscribe euvenews")
Post message to all subscribers: mail euvenews@cea.berkeley.edu
o Postal Mail:
The EUVE Public Science Archive
Center for EUV Astrophysics
2150 Kittredge St.
Berkeley, CA 94720
510-642-3032 (voice) or 510-643-5660 (fax)
archive@cea.berkeley.edu
8. Abstracts of Recently *Accepted* EUVE Papers
===============================================
Included below are abstracts of EUVE-related papers recently *accepted*
for publication. For those papers authored by CEA scientists, the EUVE
publication numbers are indicated. Unless otherwise noted, researchers may
obtain pre-prints of 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; abstracts or full papers
will also be posted under the CEA WWW Home Page. Please send all abstracts
or papers to archive@cea.berkeley.edu.
--------------------------------------------------------------
ORFEUS AND EUVE OBSERVATIONS OF THE COOL DO HD149499B
R. Napiwotzki, S. Jordan, D. Koester, V. Weidemann, S. Bowyer, and M. Hurwitz
To appear in "White Dwarfs", eds. D. Koester & K. Werner (Springer Verlag,
Berlin), Proceedings of the 9th European Workshop on white dwarfs.
We present an analysis of FUV and EUV observations of the cool DO white
dwarf HD149499B. It is by far the brightest star (V = 11.7) of this class.
However, it is a secondary in a binary system, separated from a K0V primary 3
mag brighter in V by only 1.5". This makes optical observations of the white
dwarf nearly impossible. However, in the FUV/EUV region the flux of the hot
white dwarf is virtually undisturbed by the cool companion. HD149499B was
observed with the Berkeley EUV/FUV spectrometer of the ORFEUS (Orbiting
Retrievable Far and Extreme Ultraviolet Spectrograph) experiment during the
September 1993 mission of the Space Shuttle Discovery. The spectrometer covers
the wavelength range from 390 A to 1170 A with a spectral resolution of 3000.
Since the interstellar hydrogen column density is relatively high (see below)
only the FUV range (lambda > 912 A is usable). This data is supplemented by an
EUV spectrogram of HD149499B taken with the EUVE satellite (resolution 300).
Detectable flux is observed in the 240-380 A region.
The first lines of the HeII resonance series are clearly visible. We carried
out NLTE and LTE analyses of the FUV and EUV spectrograms with atmospheres
containing helium and hydrogen. NLTE models were calculated with the ALI code
developed by Werner (1986; A&A 161, 177), for details see Napiwotzki & Rauch
(1994; A&A 285, 603). LTE calculations were performed with the program of
Koester. We determined T_eff and g simultaneous by a fit of the HeII (2->n)/HI
Lyman series observed by ORFEUS. If He/H is kept fixed at He/H = 100 the best
solution with the NLTE program can be achieved at T_eff = 50000+/-2000 K and
log g = 7.8+/-0.4. The best fit with LTE models was obtained for log(g) = 8.0,
T_eff = 50300 K, log H/He = -1.07+/-0.2, meaning that the Lyman line profiles
are much better reproduced if photospheric and not only interstellar hydrogen
is present. Assuming log g = 8 and He/H = 10 the best fit to the EUVE
spectrogram with a LTE model can be achieved at an effective temperature of
50000+4000/-1000 K and an interstellar column density of 7+/-0.4E+18 cm. The
best fits with the NLTE models tend to yield T_eff higher by 1000-2000K. An
independent check of the interstellar hydrogen column density can be performed
with the Lyman lines in the ORFEUS spectrogram. Our preliminary analysis
yielded NH = 1E+19.
--------------------------------------------------------------
HIGH TEMPERATURE LINE AND CONTINUUM EMISSION IN ALGOL
R.A. Stern, J.R. Lemen, J.P. Pye, and J.H.M.M. Schmitt
Meeting of the AAS High Energy Astrophysics Division, Nov. 2-5, 1994.
The prototype eclipsing binary Algol was observed in the 30-150 eV range
over nearly 1.5 orbital periods with the spectrometers on EUVE. High
temperature (up to 20 MK or kT ~ 1.7 keV) Fe XVI-XXIV emission lines are
clearly detected in the overall spectrum. The emission measure distribution
requires a multi-temperature plasma and rises steeply towards higher
temperatures. In addition, a quiescent continuum is present which increases
towards shorter wavelengths. Using synthesized spectra of the combined line
and continuum emission folded through the instrumental response, we will
examine constraints on the the [Fe/H] coronal abundance in Algol. Lightcurves
of the high temperature lines compared to line emission at He II 304 A show
considerable differences, with much stronger eclipses present in the He II line
during both primary and secondary eclipse. Toward the end of the observation
a moderate flare lasting ~6 hours was detected in the high temperature Fe
emission lines. We will discuss these results in the context of past IUE,
EXOSAT, GINGA, ROSAT, and, we expect, current ASCA observations of the
Algol system.
--------------------------------------------------------------
THE FIRST SEARCH FOR A GAMMA RAY BURST QUIESCENT COUNTERPART IN THE EXTREME
ULTRAVIOLET WITH EUVE
K. Hurley, P. Li, J. Laros, G. Fishman, C. Kouveliotou, and C. Meegan
To appear in the Astrophysical Journal.
The opening of the extreme ultraviolet window by the EUVE satellite has
provided the unique opportunity to perform the first search for a quiescent
gamma ray burst counterpart at these wavelengths. Such emission might be
expected if some bursts are related to nearby hot neutron stars or neutron
stars with accretion disks, among other objects. We report here on a 40 ksec
observation of the 1992 March 25 gamma-ray burst error box, determined by
triangulation with the Third Interplanetary Network. No quiescent 40-190 A
EUV source was identified using the Deep Survey instrument, and a 3s upper
limit of 2.9E-14 ergs cm^(-2) s^(-1) was obtained. Similarly, upper limits
to the 140-380 and 280-760 A fluxes were obtained with the medium- and
long-wavelength spectrometers; they are 1.1E-12 and 5.0E-13 erg cm^(-2) s^(-1),
respectively. We discuss the constraints which these limits impose on
thermally radiating quiescent counterparts.
--------------------------------------------------------------
EPSILON CANIS MAJORIS AND THE IONIZATION OF THE LOCAL CLOUD
J. V. Vallerga and B. Y. Welsh
To appear in Astrophysical Journal.
The Lyman continuum radiation from the brightest extreme ultraviolet (EUV)
source, the B2 II star epsilon CMa (Adara), is so intense that it dominates the
local stellar EUV radiation field at wavelengths longer than 450 A and therefore
sets a lower limit to the ionization of hydrogen in the Local Cloud. Using
the EUV (70-730 A) spectrum of epsilon CMa taken with the Extreme Ultraviolet
Explorer Satellite (EUVE) and simple models that extrapolate this spectrum to
the Lyman edge at 912 A, we have determined the local interstellar hydrogen
photoionization parameter, gamma, solely from epsilon CMa to be 1.1E-15 s^(-1).
This figure is a factor of 7 greater than previous estimates of gamma calculated
for all nearby stars combined (Bruhweiler & Cheng 1988). Using measured values
of the density and temperature of neutral interstellar hydrogen gas in the Local
Cloud, we derive a particle density of ionized hydrogen, n(H^+), and electrons,
n_e, of 0.015-0.019 cm^(-3) assuming ionization equilibrium and a helium
ionization fraction of less than 20%. These values correspond to a hydrogen
ionization fraction, X_H from 19% to 15%, respectively. The range of these
derived quantities is due to the uncertainties in the local values of the
neutral hydrogen and helium interstellar densities derived from both (a) solar
backscatter measurements of Lyman alpha lines of hydrogen and helium (1216 A
and 584 A), and (b) the average neutral densities along the line-of-sight to
nearby stars. The local proton density produced by epsilon CMa is enough to
allow the ionization mechanism of Ripken & Fahr (1983) to work at the
heliopause and explain the discrepancy between the neutral hydrogen density
derived from solar backscatter measurements and line-of-sight averages to
nearby stars. A large value of electron density in the Local Cloud of n_e ~
0.3-0.7 cm^(-3) (T ~= 7000 K) has recently been reported by Lallement et al.
(A&A, 168, 225, 1994) using observations of Mg II and Mg I toward Sirius A. We
show that if such a high value exists, it cannot result from the EUV stellar
radiation field and, therefore, must be due to a strong diffuse source of EUV
radiation.
--------------------------------------------------------------
THE WORLD WIDE WEB: THE CORNERSTONE FOR THE EUVE SCIENCE ARCHIVE
K. McDonald, B. Stroozas, B. Antia, B. Roberts, K. Chen, N. Craig,
and C. Christian
To appear in proceedings of ADASS '94 Conference, Astronomical Society of the
Pacific Conference Series, 1995. [CEA publication #628]
The Science Archive for the Extreme Ultraviolet Explorer (EUVE) satellite is
using the World Wide Web (WWW) client/server software model as the cornerstone
for the dissemination of EUVE archival material. A number of on-line services
are available for accessing the large amounts of EUVE data that have been
released publicly in the past year; additional services provide access to
EUVE-related software and information. This paper outlines the current Archive
WWW services and discusses plans for the future.
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INTERACTIVE FITTING OF EUVE EMISSION LINE SPECTRA
M. Abbott
To appear in proceedings of ADASS '94 Conference, Astronomical Society of the
Pacific Conference Series, 1995. [CEA publication #627]
An interactive IRAF task for the analysis of Extreme Ultraviolet Explorer
(EUVE) emission line spectra is presented. The line flux in extracted spectra
may be measured by multiple techniques, including fitting individual lines.
Blended lines may be fit simultaneously with the EUVE spectral PSF. To aid in
identifying lines, the positions of known lines may be marked on the spectrum
during the fitting process. Also, model EUVE spectra may be constructed and
overlaid using plasma emissivities and source emission measures supplied by the
user. The task is fully compatible with the calibration data set distributed
by the EUVE Guest Observer (GO) Center and retrieves all needed instrumental
parameters from that data set. It also makes use of the newly available IRAF
support for windowing graphical user interfaces.
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EXTREME ULTRAVIOLET SPECTROSCOPY AND PHOTOMETRY OF VV PUPPIS DURING A HIGH
ACCRETION STATE
S. Vennes, P. Szkody, E.M. Sion, and K. Long
To appear in Astrophysical Journal. [CEA publication #625]
We determine the physical properties of the accretion region of the AM
Her-type binary VV Puppis using extreme ultraviolet (EUV) medium-resolution
spectroscopy and photometry obtained with the Extreme Ultraviolet Explorer
(EUVE) observatory. The EUV continuum from VV Pup was detected in the
wavelength range from 75 to 135 A and was simultaneously recorded with the
Deep Survey/Spectrometer (DS/S) imaging telescope, allowing for the extraction
of an accurate light curve. VV Pup appeared to have entered a high-accretion
state just prior to the pointed EUVE observations. We use the EUV light curve
to infer the diameter of the accretion region (d = 220 km) assuming a
hemispherical geometry and a radius of 9,000 km for the white dwarf. We
perform a model atmosphere analysis and, based on the light curve properties
and assuming a distance of 145 pc, we derive an effective temperature of the
accretion region in the range 270,000 < T_eff < 360,000 K and a neutral
hydrogen column density in the local interstellar medium of n_H = 1.9-3.7E19
cm^(-2). The total EUV/soft X-ray energy radiated by the accretion region is
~3.5E32 erg/s. Our results provide a first verification of past suggestions
that deep heating of the white dwarf surface produces the soft X-ray flux from
polars. We present a possible detection of OVI} absorption features, and we
suggest that extensive EUVE observations targeting high-accretion events may
result in oxygen and heavier element abundance determinations in the accretion
region.
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ACTIVITY VERSUS ROTATION IN THE EXTREME ULTRAVIOLET
M. Mathioudakis, A. Fruscione, J.J. Drake, K. McDonald, S. Bowyer,
and R.F. Malina
To appear in Astronomy & Astrophysics. [CEA publication #624]
This paper presents extreme ultraviolet (EUV) fluxes for 74 main-sequence
stars observed with the Extreme Ultraviolet Explorer (EUVE). The sample of
stars was chosen on the basis of rotational period and includes 23 new EUV
detections. These detections are in addition to the ROSAT WFC and EUVE
catalogs and have increased the number of main-sequence stars detected in the
extreme ultraviolet by ~12%. We present an activity-rotation relation in the
EUV and show that in a sample of stars with different effective temperatures
the Rossby number is a better parameter for describing the levels of EUV
emission as compared to the rotational period. This is also known to be the
case for the chromospheric emission. A comparison with the emission in the
MgII h and k lines shows that saturation in the EUV occurs in lower Rossby
numbers than does chromospheric saturation, where saturation in X-rays occurs
in the same Rossby numbers as in the EUV. The radiative losses in the EUV are
comparable to the radiative losses in X-ray. The EUVE observations indicate
that the low activity dM star Gl 685 has a cool corona with a characteristic
temperature of < 2.5E6 K. A large amount of the coronal radiative losses in
low activity dwarfs is expected to emerge in EUV wavelengths.
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EUV Emission from a Sample of Active Galactic Nuclei
R. Lieu, J. Mittaz, S. Bowyer, J. Lewis, and C.Y. Hwang
To appear in COSPAR: Advances in Space Research. [CEA publication #622]
Active Galactic Nuclei (AGN) emit a substantial fraction of their total
radiated power in the EUV passband, because spectroscopically this band is
situated at or near the peak of the "big blue bump", which is bounded on either
side by the UV and soft X-ray excesses. Owing to the lack of observational
data, the shape of AGN spectra in the EUV is not well known. This Letter
presents broad band (65-190 eV) count rates of 11 AGN detected by the Extreme
Ultraviolet Explorer (EUVE). Assuming a power law spectral shape for the EUV
and soft X-ray energies, we demonstrate that the photon indices of the sources
are considerably steeper than typical AGN indices. For 6 sources where ROSAT
data are available to provide a more precise determination of their spectral
parameters in the 0.1-2.5 keV range, we have used these parameters to compute
predicted EUVE count rates and compared them with the observed values. The two
sets of quantities agree to within experimental error. We conclude that there
is no evidence of spectral steepening or turn-over of the soft X-ray excess at
EUV wavelengths, for a sample of AGN which covers a wide range of brightness.
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Stellar Coronal Abundances III: The Solar FIP Effect Determined from Full
Disk Observation
J.M. Laming, J.J. Drake, and K.G. Widing
To appear in Astrophysical Journal. [CEA publication #618]
In this paper we reanalyze the full disk quiet sun spectrum of Malinovksy &
Heroux (1973) with modern atomic data. The purposes of this are to check our
atomic data and methods in other investigations using data from nearby stars
obtained with the NASA Extreme Ultraviolet Explorer (EUVE) satellite, and to
confirm that the solar FIP effect investigated by previous authors studying
discrete solar regions is the same as that found in full disk spectra. We
recover the usual solar FIP effect of a coronal abundance enhancement of
elements with a low first ionization potential (FIP) of a factor ~3-4 for lines
formed at temperatures greater than ~1E6 K. For lower temperatures the FIP
effect seems to be substantially smaller, in qualitative agreement with other
data. Comparing our full disk result with those from discrete solar structures
suggests that the FIP effect is a function of altitude, with the lower
temperature full disk emission being dominated by the supergranulation network.
We also compare the recent Fe ionization balance of Arnaud & Raymond (1992)
with that of Arnaud & Rothenflug (1985).
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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. R.F. Malina and Professor
C.S. Bowyer. EGO and Archive Science Manger: C.A. Christian. Archive
Manager and Newsletter Editor: B.A. Stroozas. Funded by NASA contracts
NAS5-30180 and NAS5-29298. Send newsletter correspondence to:
ceanews@cea.berkeley.edu. The EUVE project is managed by NASA's GSFC.
The GSFC Project Manager: Paul Pashby, Project Scientist: Dr. Yoji
Kondo, Deputy Project Scientist: Dr. Ronald Oliversen. NASA HQ Program
Scientist: Dr. Robert Stachnik, Program Manager: Dr. G. Riegler. GSFC
Project Operations Director: Mr. Kevin Hartnett. Information on the
EUVE Guest Observer Program is available from: Dr. Y. Kondo, Mail Code
684, GSFC, Greenbelt, MD 20771 at (301) 286-6247 or e-mail to
euve@stars.span.nasa.gov.
END-----------EUVE------------ELECTRONIC---------------NEWS-------------END
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