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ELECTRONIC NEWSLETTER OF THE EUVE OBSERVATORY
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Vol. 7, No. 11 26 November 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 NSSDC To Take Over EUVE Archival Data Delivery
1.2 Public GO/RAP Data Release for 1 December 1997
1.3 Abstracts of Recently *Accepted* EUVE-Related Publications
2. EUVE Satellite Mission Operations News
2.1 EUVE Conducts Reaction Wheel Assembly Tests
2.2 On-Line Access to EUVE
3. EUVE Outsourced Extended Mission Status Report
3.1 PACOR Replacement Nears Completion
3.2 IP Transition Proceeding
To comment on or make suggestions for the EUVE electronic newsletter,
please send e-mail to ceanews@cea.berkeley.edu (Internet).
*****************************************************
******* H A P P Y T H A N K S G I V I N G *******
*** F R O M T H E E U V E P R O J E C T !! ***
*****************************************************
The EUVE observatory performed well throughout the month of October
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(*)
=======================================================================
2MASPJ0345*+25* M9 271:19:00 (28 Sep) Stringfellow 2 EGO
M 15 LMXB 271:19:00 (28 Sep) Callanan 2 RAP
TT Ari DwNova 274:05:20 (01 Oct) Howell 1 EGO,COO
RX J0719*+655* CV:AM 275:19:36 (02 Oct) Howell 1 EGO,COO,TOO
PC 0025+0447 M 275:19:36 (02 Oct) Mathioudakis 3 RAP
EUVE J2115-58.6 CV:AM 277:09:05 (04 Oct) Christian 2 EGO,COO
QS Tel CV:AM 279:02:05 (06 Oct) Rosen 1 EGO
0006+18 NeutSt 279:02:05 (06 Oct) Edelstein 3 RAP
2EUVE J0632-05.0 WD:DA 279:16:12 (06 Oct) Wolff 1 EGO,CAL,MU1
MS 0037.7-0156 AGN 279:16:12 (06 Oct) Fruscione 3 RAP
US 0039-0158 AGN 279:16:12 (06 Oct) Fruscione 3 RAP
FK Aqr M0Vpe 282:12:11 (09 Oct) Drake 1 EGO,SPI
Moon Moon 288:16:20 (15 Oct) Vallerga 1 DDT,CFG,MOV,MU2,TCO
RX J0757.0+6306 CV:AM 288:16:20 (15 Oct) Howell 1 RAP
FK Aqr M0Vpe 288:17:50 (15 Oct) Drake 1 EGO,SPI
Survey ---- 297:19:47 (24 Oct) ------ - ENG
Saturn Planet 298:02:00 (25 Oct) Gladstone 1 EGO,MOV,MU3,TCO
=======================================================================
(*) Key to Notes:
CAL = Science calibration observation
CFG = Special payload configuration: detectors 1-6 off, low
thresholds opened up, rate shutdown parameters widened
COO = Observation coordinated with ground-based telescopes
DDT = Director's Discretionary Time
EGO = EUVE Guest Observer observation
ENG = Engineering observation to calibrate star trackers
MOV = Moving target
MU1 = Multiple pointings: one at the nominal location and two
others at +/0.25 deg off-axis
MU2 = Multiple pointings (7)
MU3 = Multiple pointings (18) required for this observation
RAP = Right-angle program observation
SPI = Spiral-dithered observation
TCO = Time-critical observation
TOO = Target of Opportunity
1. EUVE Science News
====================
1.1 NSSDC To Take Over EUVE Archival Data Delivery
--------------------------------------------------
by Dr. Roger Malina, EUVE Observatory Director
This message is directed to all potential users of the EUVE archive
data. As you know the EUVE Project has delivered non-proprietary data
products to users for the past five years. In that time, we have
delivered thousands of sets of data to hundreds of users.
The EUVE Project has just completed the reprocessing and delivery
of permanent archive quality data sets to NASA's National Space
Science Data Center (NSSDC). These data consist of all EUVE
observations that are publicly available. The NSSDC has a long
history as the archive for all space science data and has the
facilities and charter to supply all your requests for EUVE data.
As of Saturday, 22 November 1997, the EUVE Project will no longer
supply tape or CD-ROM copies of non-proprietary EUVE data sets; each
archive researcher must directly contact the NSSDC
(request@nssdca.gsfc.nasa.gov; http://nssdc.gsfc.nasa.gov/) who will
fulfill your request. We will work with the NSSDC to ensure that you,
the researcher, are provided with the same level of service that you
have come to expect from the EUVE Project. We encourage you to make
us immediately aware of any difficulties that you encounter. Please
feel free to send any questions or comments to the EUVE Guest Observer
Center (egoinfo@cea.berkeley.edu) or the EUVE Project Manager (Michael
Gunter; gunterm@cea.berkeley.edu).
1.2 Public GO/RAP Data Release for 1 December 1997
--------------------------------------------------
by Dr. Nahide Craig, EUVE Scientist
The table below lists the GO/RAP observations that become public on
1 December 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). As of 22 November 1997 all
public data sets can be ordered from the NSSDC via e-mail
(request@nssdca.gsfc.nasa.gov) or WWW (http://nssdc.gsfc.nasa.gov/).
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 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 DECEMBER 1997:
***** CYCLE 4 Targets *****
T Leo 56 21 Feb - 23 Feb 1997 CV go0619
T Leo 53 23 Feb - 24 Feb 1997 CV go0620
beta CMa 23 24 Feb - 24 Feb 1997 B1II/III go0621
beta CMa 248 27 Feb - 07 Mar 1997 B1II/III go0622
DK UMa 229 14 Mar - 22 Mar 1997 G4III-IV go0623
2EUVE J1618-17.9 26 22 Mar - 23 Mar 1997 NOID go0624
2EUVE J1627+10.1 26 23 Mar - 24 Mar 1997 NOID go0625
Canopus 133 30 Mar - 03 Apr 1997 F0II go0626
Canopus 93 04 Apr - 08 Apr 1997 F0II go0627
GRB 970402 25 03 Apr - 04 Apr 1997 NOID go0628
HD 74389 B 167 08 Apr - 14 Apr 1997 WD:DA go0629
***** CYCLE 5 Targets *****
2EUVE J1034+39.6 163 14 Apr - 20 Apr 1997 AGN:Sy1 go0630
----------------------------------------------------------------
RAP DATA SETS AVAILABLE 1 DECEMBER 1997:
***** NONE *****
================================================================
1.3 Abstracts of Recently *Accepted* EUVE-Related 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.
--------------------------------------------------------------
SIRIUS B: A NEW MORE ACCURATE VIEW
J.B. Holberg, M.A. Barstow, F.C. Bruhweiler, A.M. Cruise, and A.J. Penny
To Appear in Astrophysical Journal.
Long standing questions regarding the temperature, gravity, mass
and radius of the well-known white dwarf Sirius B are considered in
light of new data. Recently obtained Extreme Ultraviolet Explorer
(EUVE) observations and reprocessed IUE NEWSIPS data have produced a
new, well-defined effective temperature of 24,790 +/- 100 K and a
surface gravity of log g = 8.57 +/- 0.06 for Sirius B. A new
Hipparcos parallax for the Sirius system of pi = 0.37921 +/- 0.00158
arcsec is used in conjunction with the above spectroscopic results and
the previously published gravitational redshift to yield a mass of
0.984 +/- 0.074 M_Sun and a radius of R = 0.0084 +/- 0.00025 R_Sun for
the white dwarf. Combining these results with the existing
astrometric mass for Sirius B gives a refined mass estimate of M =
1.034 +/- 0.026 M_Sun. The mass and radius for Sirius B are found to
be consistent with the theoretical mass-radius relation for a
carbon-core white dwarf. The EUVE spectrum is also used to determine
a firm upper limit of He/H = 1.8E-05 for the helium mixing ratio in
the photosphere of Sirius B. IUE echelle spectra of Sirius B provide
an estimate of log N_HI = 17.72 +/- 0.1 for the interstellar HI column
to this star.
--------------------------------------------------------------
DISSECTING CAPELLA'S CORONA -- GHRS SPECTRA OF THE FeXXI 1354 A AND
HeII 1640 A LINES FROM EACH OF THE CAPELLA STARS
J.L. Linsky, B.E. Wood, A. Brown, and R.A. Osten
To appear in Astrophysical Journal.
We report on moderate (lambda/dlambda = 20,000) and high
(lambda/dlambda = 90,000) resolution spectra of the 104 day period
Capella binary system (HD 34029) obtained with HST's Goddard High
Resolution Spectrometer (GHRS) on 1995 September 9 and 1996 April 9.
The observations include a long-duration moderate resolution spectrum
of the coronal FeXXI 1354 A line and both moderate and high resolution
spectra of the HeII 1640 A multiplet.
Our objective in observing the FeXXI line formed at T = 1E+07 K is
to determine for the first time the line shape parameters and
contribution of each star's corona. This is feasible because the GHRS
can resolve the 53 km/sec radial velocity separation of the stars.
Our analysis led to four surprising results: (1) The contribution of
the slowly-rotating G8III star to the total FeXXI 1354 A flux is
similar to that of the more active rapidly-rotating G1III star, in
contrast to other UV lines formed at lower temperatures. (2) The
centroid velocities of the FeXXI lines from both stars are near their
respective photospheric radial velocities. Thus, there is no evidence
for downflows or winds, and the hot coronal plasma must be confined,
presumably by strong, closed magnetic fields. This is the first
direct kinematic evidence for magnetic confinement in the corona of a
giant star. (3) The line widths are thermal, indicating very low
turbulence (xi < 23 km/sec) compared to the 54 km/sec thermal speed.
(4) Our analysis of EUVE spectra that include four FeXXI lines shows
that the volume emission measures of these lines are about a factor of
3 smaller than for the 1354 A line, which was observed several months
after the closest EUVE observation. We consider possible explanations
for this discrepancy and conclude that variability of the high
temperature coronal emission is the most likely explanation.
We observed the HeII 1640 A line twice with a time separation of 7
months, corresponding to about 2 orbital periods. The profiles are
nearly identical, except for a large difference in flux near the
expected radial velocity of the G8III star. We believe that the broad
HeII emission produced by the G1 star is formed mostly by collisional
excitation in its transition region, while the emission from the G8
star is produced predominantly by a photoionization/recombination
process driven by EUV radiation from the G8 star's corona. The HeII
1640 A flux that we measure from the G8 star is consistent with
predictions based on EUVE flux measurements. The decrease in the 1640
A emission from the G8 star between the phase 0.73 and 0.78
measurements indicates that its EUV radiation is variable as is
observed by EUVE.
--------------------------------------------------------------
THE CORONAE OF MODERATE MASS GIANTS IN THE HERTZSPRUNG GAP AND THE
CLUMP
T.R Ayres, T. Simon, R.A. Stern, S.A. Drake, B.E. Wood, and A. Brown
To appear in Astrophysical Journal.
We have used ROSAT, EUVE, and HST to measure X-ray and ultraviolet
emissions of moderate mass (~2-3 M_Sun) giants in the Hertzsprung gap
(spectral types earlyF-midG) and the post-helium-flash "clump"
(~G8-K0). Our motivation was to document the evolution of hot coronae
(T > 1E+06 K) along the post-main-sequence trajectories traveled by
such stars; to gain insight concerning the "X-ray deficiency" of the
F-G0 giants, and the strong braking of stellar rotation at the red
edge of the Hertzsprung gap.
With few exceptions, Hertzsprung gap and clump giants observed by
ROSAT PSPC show hot (T ~ 1E+07 K) coronal energy distributions,
regardless of any X-ray deficiency. EUVE spectra of gap star 31 Com
(G0III) indicate a broad coronal emission measure hump at ~1E+07.2 K,
while the active clump giant beta Ceti (K0III) displays a sharp peak
at ~1E+06.8 K, as seen previously in the mixed clump/gap binary
Capella (alpha Aur; G8III + G0III). The gap giants upsilon Peg
(F8III) and 24 UMa (G4III) have EUV emissions of intermediate
temperature (~1E+07.0 K).
31 Com, psi^3 Psc (G0III), and beta Cet exhibit redshifted
transition zone (TZ; ~1E+05 K) lines in HST GHRS spectra, as reported
earlier in Procyon (alpha CMi; F5IV-V) and Capella G0. Such redshifts
on the Sun are thought to signify flows in magnetic loops. beta Cas
(F2III) -- a rare soft coronal source among the gap stars -- displays
blueshifts of CIV and OIV], although emissions at cooler and hotter
temperatures are near the photospheric velocity. The remarkably broad
line profiles of the fastest rotating gap giants suggest that the
1E+05 K "subcoronal" emission zones extend to h ~ R_star, about fifty
scale heights.
In contrast to the TZ line redshifts, the upper chromospheric
emissions (e.g., MgII and SiIII) of 31 Com and psi^3 Psc have
blueshifted cores. Blue-asymmetric peaks in the solar MgII lines are
thought to indicate dynamical heating in the chromosphere.
Observations of the HI Ly-alpha feature of 31 Com taken nine months
apart reveal striking profile changes, reminiscent of those noted
previously in the Ly-alpha blue peak of the Capella G0 star.
We used the far-ultraviolet diagnostics, in combination with ROSAT
X-ray photometry and EUVE high-excitation line strengths, to constrain
physical models of the stellar outer atmospheres. Quasistatic
magnetic loops can simulate the empirical coronal emission measures of
the giant stars, but the inferred pressures for sensible loop lengths
conflict with direct measurements of subcoronal densities.
Furthermore, the high rate of emission at ~1E+05 K cannot be explained
by thermal conduction down the legs of hot quasistatic loops.
On the other hand, the possible existence of elongated (l ~ R_star)
emission structures on the gap giants leads to a speculative scenario
to explain the X-ray deficiency. It is based on the increased
importance of the dynamical filling phase ("explosive evaporation") of
the loop lifecycle; conductive cooling, yielding TZ emissions at the
footpoints, when the heating is interrupted; and the possibility for
transitions between "hot" and "cool" energy balance solutions owing to
dynamical suspension and centrifugal trapping of the cooling gas. The
long loops might represent a vestigial global "magnetosphere"
inherited from the MS phase, which ultimately is disrupted near ~G0 by
the deepening convective envelope and growth of a more solar-like
dynamo. Coronal emissions might be boosted temporarily as the X-ray
deficiency is removed, but soon would be quenched by wind braking
previously inhibited by the magnetospheric "dead zone."
--------------------------------------------------------------
2. EUVE Satellite Mission Operations News
=========================================
by Brett A. Stroozas, EUVE Mission/Flight Director
The month of October was a busy one for EUVE mission operations.
During the month the EUVE Observatory conducted 17 total observations
of 16 separate targets: nine for Guest Observers, six for the
Right-Angle Program, one as Director's Discretionary Time, and one
engineering (star tracker) calibration. Of these observations one
(2EUVE J0632-05.0) was also a science calibration, one (RXS
J071913.4+655734) was a target of opportunity, two (Moon and Saturn)
were moving targets, three were coordinated with ground-based
observatories, three required multiple pointings, and two were
time-critical. In addition, on the early morning hours on 31 October
EUVE reached another milestone when it completed its 30,000th orbit!
The following subsections discuss a few of the month's highlights.
2.1 EUVE Conducts Reaction Wheel Assembly Tests
-----------------------------------------------
On 16-20 October 1997 the EUVE Flight Operations Team (FOT)
conducted a series of tests with the spacecraft's Reaction Wheel
Assembly (RWA), which is part of its attitude control system. The
spacecraft's RWA consists of four "reaction wheels": one wheel
co-aligned with each of the primary spacecraft axes (the so-called X,
Y, and Z wheels), and a fourth wheel (the so-called SKEW wheel)
aligned at equal angles to those axes. Spinning a wheel up or down
torques the spacecraft, allowing it to maneuver in the frictionless
space environment. Three wheels (e.g., the X, Y, and Z wheels) are
required for stable attitude control; the SKEW wheel provides
redundancy and momentum bias.
The recent "flight testbed" RWA tests, conducted for Mr. Bob Bauer
(of Bauer Engineering), were similar to tests conducted for him back
in December 1994 and January 1995. The purposes for these tests were
as follows:
o To characterize in-flight reaction wheel performance by examining
the RWA parameters: drag torque, torque offset and scale factor
used in the drive electronics, and torque noise.
o To improve existing attitude dynamics models by grounding them to
their in-flight characterizations.
o To refine spacecraft performance predictions.
For each wheel the FOT conducted two types of tests: (1) manually
spinning the wheel up or down, allowing the other wheels to compensate
in order to maintain spacecraft stability, all the while watching the
various wheels accelerate and decelerate; and (2) disabling
("failing") a wheel and watching it coast down under its own
mechanical friction. A specialized subroutine in the on-board
computer was used throughout these tests in order to maximize the
amount of RWA data acquired.
The tests were conducted smoothly, with no major problems, and with
no negative impact on the concurrent science observations. The
resulting data is excellent and engineers have already begun
processing the data for analysis. A paper on the results will be
published for, and presented at, the 1998 GSFC Flight Mechanics
Symposium.
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")
o GS 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? Do you
lack sufficient disk space and/or CPU power in your EUVE data
analysis? If you answer "yes" to any of the above, the Guest
Scientist (GS) 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 few 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 October 1997.
3.1 PACOR Replacement Nears Completion
--------------------------------------
Since the launch of EUVE GSFC's Packet Processor (PACOR) facility
has routinely routed EUVE realtime and tape recorder dump telemetry
data to UCB. With the outsourcing of spacecraft operations from GSFC
to UCB in March of this year, there was no longer any compelling need
for continued PACOR support for EUVE. At that time UCB began
developing new software systems to replace the three PACOR functions:
processing of realtime and tape recorder dump data, and the weekly
delivery of spacecraft attitude data to the GSFC Flight Dynamics
Facility (FDF).
Early in October 1997 UCB began operationally using its new
recorder tape dump data processing software system. By mid-month we
had completed testing of the realtime data processing software system
and began using it operationally. We were also able to successfully
begin handling the weekly delivery of attitude data to FDF. With all
of the pieces in place and working well, effective 25 October UCB
approved of PACOR not staffing or supporting EUVE on a routine basis;
PACOR personnel continue, however, to be available on-call for
emergency support only. UCB has targeted 14 November as the official
termination date for PACOR's support of EUVE.
3.2 IP Transition Proceeding
----------------------------
As part of its ongoing efforts to transition from its proprietary
4800-bit-block communications protocol to Internet protocol (IP), NASA
Communications (NASCOM) personnel installed the Programmable Telemetry
Processor (PTP) units at UCB on 15 October. This installation, which
required that the operations network be brought down for a short
period of time, was completed quickly and with no negative impacts on
operations. The PTPs are configured to communicate via NASCOM over
the new T1 line that was installed some months back. Now that all of
the major pieces are in place, UCB is awaiting NASCOM's readiness to
begin overall system testing. Once fully tested out, EUVE operations
will be switched over to use the new IP communications lines.
--------------------------------------------------------------------------
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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