Newsletter No. 64 May 1994
IN THIS ISSUE:
- Notes from the Editor - Kevin Hurley
- News and Notes from Headquarters - Alan Bunner
- ROSAT Status - Rob Petre
- High Energy Astrophysics Science Archive Center -
Nick White
- SkyView: An All-Sky Data Service - Thomas A.
McGlynn, Nicholas E. White, and Keith Scollick
- Four Years of SIGMA Observations - Pierre Mandrou
- ASCA Status Report - Nick White
- EUVE Report - Yoji Kondo and Ron Oliversen
- INTEGRAL - Christoph Winkler
- . Meetings
issue marks the first use of electronic mail for the HEAD newsletter. As I explained in
my April letter, I hope to save the membership about $700/year and forestall another dues
increase by doing this. However, I do not want to disenfranchise HEAD members who have no
access to e-mail (about 31 members out of 395 appear to be in this situation). Thus for
the time being, both electronic and paper copies are being distributed. Even some members
with e-mail seem to prefer the paper version. Out of 27 replies to my letter, the
responses ranged from "I'm willing to pay an extra dollar for a paper version"
to "go electronic and forget the hard copy", but the majority voted for an
electronic version. There were some other interesting suggestions, such as making the
newsletter available on the World Wide Web, so as to be able to include figures. I will
investigate all the possibilities (including TeX and Postscript versions) and report back
to you in the next issue. However, for now, I would like to put this to a vote. Do you
support the idea of a plain ASCII (no figures) newsletter distributed by electronic mail?
Please take a moment to fill in the form at the end of this article and return it to me.
(Those who replied to my letter need not vote unless you've changed your mind - your
replies have been saved and will be tallied with the rest.)
Those of you who have e-mail addresses have probably received several communications by
now - my letter, one from NASA Headquarters announcing the Theory Program, and the
announcements of the 1994 HEAD meeting. I will use this mailing list to circulate
information which cannot wait for the bi-annual newsletter. Another use for this
electronic mailing list might be to re-establish HEADmail. Some of you may remember that
this system was once in use as an automatic mail forwarding service. If you didn't know my
e-mail address, for example, you could address it to khurley@head.stanford.edu (this is
just an example - don't do it, because it won't work any more) where it would be routed to
me. In the earlier days of e-mail, this was used somewhat, but the level of use decreased
to zero, and the routing service was not maintained. My feeling is that it is not
necessary any more, but you can vote on this issue also. One concern that has been voiced
is that HEADmail should not be used as an exploder, because of the large volume of e-mail
which most of us have to go through every day.
On the subject of mailing lists, the AAS sometimes receives requests from publishers,
for example, who want to distribute catalogs to HEAD members. The policy up to now has
been to grant these requests on an individual basis. However, if any members do not wish
to receive these mailings, we can remove them from our list.
Finally, an increase in the HEAD dues, currently $5/year, has unfortunately become
necessary. This has nothing to do with the newsletter, but was voted by the Executive
Committee to maintain the value of the Rossi Prize. As of next year, HEAD membership will
cost $6/year.
BALLOT FOR THE USE OF E-MAIL
Choose one:
I would like to see an e-mail only HEAD newsletter.
I would like to see a paper-only HEAD newsletter.
I would like to see both a paper and an e-mail HEAD newsletter.
Choose one:
I would use HEADmail for routing my e-mail if it were available (but NOT as an
exploder).
I would not use HEADmail.
Comments:
Please return to khurley@sunspot.ssl.berkeley.edu, or Kevin Hurley, University of
California, Space Sciences Laboratory, Berkeley, CA 94720-7450, (FAX: 510 643 8302). Thank
you.
by Alan Bunner, NASA HQ
Dan Weedman took over as Director of the Astrophysics Division at NASA Headquarters in
early November 1993. These are not easy times at NASA and we owe Dan our thanks for taking
on this responsibility.
At the root of all that has happened with the NASA budget recently is the national
deficit and the concern within the White House and Congress regarding the NASA budget.
This in turn has led to demands on the Administrator, Dan Goldin, to seek ways of living
with a flat NASA budget, while maintaining a balanced NASA program, i.e., a balance among
human space flight, science, and aeronautics and technology. Mr. Goldin has expressed a
strong interest in creating new missions in space science, with emphasis on the smaller,
cheaper, faster variety. He has suggested that the only way to create a wedge for new
missions is to seek out economies in our ongoing programs, curtail/cease operations/data
analysis on old missions, and shrink the scope of new missions to a cost-effective
minimum.
The growing budget needs for AXAF as it moves into its peak spending phase, combined
with a level overall budget for astrophysics, has resulted in flat or shrinking budgets in
other parts of our program. The first casualty was the cancellation by Congress, last
October, of the AXAF-S mission. Dramatic cuts to the data analysis programs for our active
missions followed. Some cuts have also been felt in our ATD and SR&T programs.
In light of this difficult situation, I'd like to offer a few goals that the High
Energy Astrophysics Branch at NASA Headquarters is pursuing as highest priorities for the
near future. (1) Retain AXAF-I. (2) Secure funding for U.S. participation in Japan's
Astro-E, including flight of the x-ray calorimeter instrument displaced from AXAF-S. (3)
Seek an extended mission for Compton Observatory (the current budget plan does not support
GRO operations beyond FY 1995). (4) Identify some modest funding for U.S. participation in
ESA's INTEGRAL program. (5) Provide some increased support for operations and data
analysis for ASCA and ROSAT, two of the Division's most productive collaborations, both
operating under stringent budgetary constraints. (6) Work to restore funding for the
appropriate baseline mission lifetime for XTE (e.g. 3 years rather than two years) and
devise a low-cost approach for extended operations (5 years or beyond).
All the above goals would have been readily achievable a year or two ago, but now all
represent a challenge. If Congress reduces the FY'95 NASA budget significantly below the
$14.3 B requested level, NASA's major missions now in development (AXAF and Cassini) could
be threatened. Active community support for full funding of NASA's FY 1995 budget request
is therefore of critical importance.
Future Mission Studies:
Notwithstanding the bleak prospects for the near-term budget, Dan Weedman has noted the
lack of established mission concepts for the next generation of astrophysics flight
programs beyond AXAF and SIRTF. We expect to have a robust complement of satellites flying
in 1996-2002, but there are virtually no missions currently under study for the post-2003
era. To remedy this situation, Weedman has proposed issuing, this year, a wide-ranging
solicitation for future mission concept studies. The solicitation (now being drafted) will
include everything from SmEx and Mid-Ex class concepts to major observatories, including
international collaborations, and possibly even lunar-based instruments. A modest number
of proposals for mission concept studies will be selected via peer review. My feeling is
that these modestly-funded studies will have a high importance in establishing a set of
future mission candidates.
X-Ray Program Working Group Report:
Now very close to going to the printer's, the long-awaited report of the X-Ray Program
Working Group (XRPWG) is finally complete. Our thanks go out to the cast of dozens who
contributed. A key recommendation of the report is for establishment of a series of
moderate missions ("Observers") to fill in some of the key scientific gaps in
x-ray astronomy. Anyone wishing to receive a copy may put in their request now. See the
NASA HQ e-mail addresses below.
Forging New International Collaborations:
One of the tenets of Dan Goldin's administration at NASA appears to be a strong support
for cost-effective international collaborations. Discussions have been encouraged by the
Administrator with a variety of possible international partners, in the interest of
accomplishing space science at a fraction of the cost of a U.S.-only mission. Of course,
all the usual caveats still apply (technically sweet, strong scientific return, clean
interfaces, reliable partners), but it is noteworthy that the NASA Administrator has
placed such an emphasis on international collaborations.
Astro-E Resolution:
At a meeting of the High Energy Astrophysics Management Operations Working Group
(HEAMOWG) on January 19, the committee offered a strong endorsement of U.S. participation
in Japan's Astro-E as an alternative means of addressing the canceled AXAF-S mission
science objectives. An excerpt from the HEAMOWG resolution follow:
"The HEAMOWG expresses grave concern over the cancellation of the AXAF-S mission,
scheduled to carry the X-ray Spectrometer (XRS) for a mission of high resolution,
broadband X-ray spectroscopy. The scientific rationale that made the XRS investigation
part of the original AXAF mission, and later the core of AXAF-S when the mission was split
into two, has not changed. Indeed, recent spectroscopic results from BBXRT and ASCA, not
available when AXAF was originally designed, strengthen even further the need for the
flight of XRS, as they stress that a rich X-ray emission and/or absorption line spectrum
is common to a large variety of astrophysical objects. ... Further, the XRS capabilities
are in excellent complementarity to those of the grating spectrometers on AXAF-I, and are
thus an essential companion to that investigation. ... A balanced program of deep X-ray
imaging, coupled with spectroscopy of the soft sources with the AXAF-I gratings and harder
and extended sources with the XRS, was a prime reason for the very strong and repeated
endorsements of the AXAF program by the Field and Bahcall NAS survey committees, and these
inextricably intertwined capabilities should not be sacrificed.
The HEAMOWG has considered how a flight of portions of the original XRS investigation
in collaboration with the Japanese aboard ASTRO-E might address the goals of the AXAF
program. Although there are obvious disadvantages to this approach over AXAF-S (e.g., a
reduction, possibly substantial, in the amount of observing time directly available to
American investigators), there are also great attractions to this concept. The ASTRO-E
implementation of the XRS would exceed the sensitivity of any past similar scientific
investigation such as the Einstein FPCS by orders of magnitude. ... The cost to the U.S.
is of course also far less than a dedicated AXAF-S. A flight of the XRS on ASTRO-E would
still provide the U.S. community with the rewards of a successful and particularly
difficult technology development program, which, apart from X-ray astronomy, has
strengthened the national infrastructure in multiple areas of cryogenics and solid state
detectors.
For all of these reasons the HEAMOWG provides its most enthusiastic endorsement of a
plan to fly the XRS aboard Astro-E."
Support for U.S. Participation in INTEGRAL:
The ESA INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) mission is planned
for launch in 2001. It represents the realization of hopes for an observatory having
(among other capabilities) high resolution gamma-ray spectroscopy capabilities similar to
the GRSE investigation (an instrument on Gamma Ray Observatory lost through descoping in
1983) and the Nuclear Astrophysics Explorer (NAE), proposed to NASA's Explorer program in
1989. The mission life will be 2 to 5 years and will include an internationally open guest
observer program. NASA's Gamma Ray Astronomy Program Working Group in 1988 asserted that
high resolution gamma-ray spectroscopy (of the type proposed for INTEGRAL) was the highest
priority need in gamma-ray astronomy in the post-GRO era. INTEGRAL represents a
cost-effective alternative to a U.S.-only intermediate class mission in the field of
gamma-ray spectroscopy. No other planned mission, in any country, will address this
general need in the foreseeable future. In recognition of the importance of this area,
NASA SR&T funds have been allocated for gamma-ray spectroscopy technology since the
demise of GRSE. We propose to allocate a portion of these existing funds for the INTEGRAL
program to support proposals for participation in the INTEGRAL program. Relevant U.S.
investigator roles include Mission Scientist, Co-investigators on European instruments,
and Data Center Scientists. Proposals will be selected via peer review by both NASA and
ESA.
Branch Theory Programs Merged:
Dan Weedman has instituted a change in the support of theory efforts within NASA's
Astrophysics Division. In the past, there have been two channels to receive support for
theoretical investigations relevant to NASA's High Energy Astrophysics program: under the
High Energy Astrophysics (HEA) Theory Program, or the broader Astrophysics Theory Program
(ATP). As many of you are aware, an announcement for the latter, issued in November 1993,
has been on hold for several months. The decision has been made to consolidate (including
the associated funding) all of the discipline-specific theory programs, including HEA,
under the ATP. As a result, to propose a new theoretical investigation or request
continuation of an existing theory grant, you must respond to the NRA for the ATP which
was recently reissued.
NASA Headquarters E-Mail Addresses:
Your NASA HQ friends may now be reached at the following INTERNET e-mail addresses:
Alan Bunner: abunner@gm.ossa.hq.nasa.gov
Lou Kaluzienski lkaluzienski@gm.ossa.hq.nasa.gov
by Rob Petre, petre@lheavx.gsfc.nasa.gov
The satellite has been returned to normal operations after being hindered for several
months by secondary problems associated with the failure of a gyro in November. The full
viewing zone, 75-105 degrees from the sun, has been restored, and the observing efficiency
is currently about 40 percent (compared with 50 percent before the failure). No other
vital systems show any evidence of degradation. Standard operations now incorporate the
HRI as the primary instrument. The PSPC is being placed into the focal plane for
approximately one week per month in order to complete AO1-4 observations and carry out
Target of Opportunity Observations. The amount of PSPC remaining PSPC gas is unknown, and
could be anywhere between a few weeks' and a few months' worth. Reprocessing of all
pointed data has now commenced. Data will be reprocessed using the current version of
SASS, that incorporates all the improvements made during the course of the mission, and
placed into the new "rationalized data format FITS files. As data are reprocessed,
they will be redistributed to PI's, who have proprietary rights for six months. It is
anticipated that reprocessing will take 16 months to complete. A total of 172 proposals
were received in in the U.S. in response to the AO5 solicitation for HRI observations. The
total time requested in these proposals was 22 million seconds, comparable with the
response of the U.S. community to previous AO's. Approximately 4 million seconds of U.S.
observations will be carried out during the AO5 period; approximately 6 million seconds of
U.S. time will be carried at priority A, B, or C in the AO5 observing program. The
proceedings of the ROSAT Science Symposium and Data Analysis Workshop has gone to press.
An August distribution date is anticipated.
by Nick White, LHEA/GSFC, white@lheavx.gsfc.nasa.gov
1. Overview.
The High Energy Astrophysics Science Archive Research Center, HEASARC, located at the
Goddard Space Flight Center, was created in 1990 as a site for X-ray and Gamma-ray
archival research. The HEASARC was created to provide a multimission archive for the
ROSAT, GRO, BBXRT, ASCA, and XTE missions that would be co-located with data from past
astrophysics missions such as Einstein, EXOSAT, Ginga, HEAO 1, HEAO 3, OSO 8, SAS 2 and 3,
Uhuru, and Vela5B. The total data volume will be of the order of 1 Tb by 1996. HEASARC is
a collaboration of Goddard's Laboratory for High Energy Astrophysics, LHEA, and the NSSDC.
The dilemma facing the HEASARC is that every mission produces a data set in a different
format, with a different set of analysis software. This makes the long term support and
distribution of a multimission archive problematic, since every mission is a special case.
In addition, combining datasets from different missions is non-trivial. The HEASARC
solution is to reformat all the data to the flexible image transport system, FITS. This is
an IAU and NASA standard for astronomical data. To enable both the HEASARC and future
missions to reformat to FITS, the HEASARC is providing a portable FORTRAN 77 and C
subroutine library to write and read FITS files. This package, called FITSIO, was released
two years ago and has proved extremely popular (it can be obtained from the anonymous ftp
account on legacy.gsfc.nasa.gov under software/fitsio). The HEASARC is also defining
mission independent FITS file structures for spectra, lightcurves, and photon lists. These
will allow data products to be distributed transparently between different analysis
packages. Other services provided by HEASARC include online access to data and catalogs,
multimission analysis software (e.g. XSPEC and FTOOLS), data restoration of the older
missions and expertise in the data holding.
The HEASARC publishes a journal twice a year called "legacy" that describes
the latest activities. To receive a copy of future issues and a complete set of back
issues send your name and address to request@legacy.gsfc.nasa.gov. Here some of the latest
HEASARC services and features are described.
2. World Wide Web Access
The HEASARC has released a next generation BROWSE interface using the World-Wide-Web,
WWW. Through the xmosaic interface (obtained from legacy.gsfc.nasa.gov in /software/www or
from ftp.ncsa.uiuc.edu) it is now possible to make coordinate and object name searches of
many astronomical catalogues, as well as access data from high energy astrophysics
missions. This new release includes an interface to the SIMBAD name-coordinate resolver so
that most astronomical names will be recognized, plus a new HEASARC name-coordinate
resolver. Files can be downloaded or, by following the setup information, directly
display: fits images, postscript and ASCII text files.
To access the WWW HEASARC home page please open
http://heasarc.gsfc.nasa.gov/
The new BROWSE interface can be accessed from this page by clicking on
"browse". The HEASARC WWW Browse provides a simple interface whereby typing the
name of the object (e.g. Cyg X-1) or its coordinates causes all the entries in the
specified catalog at that position to be retrieved. If there are any data files associated
with a particular entry, they can be retrieved by clicking on the underlined entry. All
the data files are stored either in FITS format or ASCII text files. FITS images can be
directly viewed by setting up your .mime.types and .mailcap files (these can be copied
from the legacy anonymous ftp area) to spawn the appropriate FITS image viewer (e.g.
saoimage).
The casual user might start with the master catalogs which summarize the contents of
the HEASARC database. These master catalogs are divided into observation logs, optical,
radio and X-ray catalogs. Once the mission (e.g. ROSAT) or catalog has been established
then a more detailed overview is obtained by going to that mission or catalog. To avoid
cluttering up the screen with too much information, by default only standard information
is displayed from the database. All the fields for any table can be displayed by selecting
all "Fields". The input and output equinox, as well as the input coordinate type
can be specified before a search is made. The current capabilities are limited compared to
the original browse (see below), but the ease of use of this point and click interface is
a tremendous advance. The HEASARC plans to continue to add additional capability to this
method of accessing its archival data.
The HEASARC has begun providing two other pages on the WWW called "StarTrax"
and "WebStars". StarTrax provides a central point to access many HEASARC WWW
service. WebStars provides access to astronomical information and facilities on the Web.
These pages can be accessed from the HEASARC home page.
3. New HEASARC online Service Features
While the WWW will be the future focus for the HEASARC remote access, the current
HEASARC remote login online service will continue to be supported and maintained. This
service has recently been moved from ndads to legacy. It is accessed in the same way as
before, i.e.
telnet legacy.gsfc.nasa.gov
username: xray [note in lowercase]
legacy is an ultrix workstation and while all the basic services remain the same, the
switch from a vms to unix platform should make the service more friendly to our unix users
(who form the vast majority). There are some new services in browse:
a) There is a new command called "simbad" which accesses a simbad name-
coordinate resolver. This allows you to enter any recognized astronomical object name. If
the object is in the simbad database, then the coordinates are returned, and browse will
automatically make a cone search around that position (using the default radius used by
the sc command). We thank the SIMBAD group for making this available.
b) With the online service on legacy, the data in the anonymous ftp can now be directly
accessed from browse. Thus all the ROSAT public archive data can now be extracted (using
the browse xp command).
c) For large lists of coordinates it can be a bit tedious to type in all the
coordinates. It is now possible to make searches by e-mail. A list of source positions and
coordinates can be submitted and the results will be e-mailed back. This is particularly
useful if, e.g. you have a list of objects and want to check if ROSAT observed them and if
they are in the archive. To use this service, send an empty e-mail message to
hdbreq@legacy.gsfc.nasa.gov. Instructions will be automatically sent back by e-mail.
4. ROSAT Archive News
All of the ROSAT archival data has now been copied to a dedicated jukebox system that
is permamently mounted to the HEASARC anonymous ftp on legacy.gsfc.nasa.gov. All the
currently public data can be directly accessed through this account, and as new data
becomes public it will also be added. The data can be found under the directory
rosat/data/INSTRUMENT/processed_data/XXXXXX/YYYYYYYY, where INSTRUMENT = either hri or
pspc XXXXXX = sequence id group (from 100000 to 900000) YYYYYYYY = sequence id
for example, data associated with the data set having sequence id rp300023 is located
in the directory
rosat/data/pspc/processed_data/300000/rp300023
A new list of public ROSAT data is now available via anonymous ftp from the legacy
machine in the directory rosat/doc/archive. The new list includes all the currently
available public rosat data (for both U.S. processed and MPE processed data sets) for both
the PSPC and HRI and should make identification of public data much easier for users. The
list is issued in sequence-ordered and position-ordered formats; these are named
rosarchive_yymm.pos (position ordered)
and
rosarchive_yymm.seq (ordered by sequence id)
where yymm is the year and month for which the archive list is current. Any questions
about the ROSAT archive and its access should be addressed to the ROSAT archive scientist:
Mike Corocoran (corcoran@barnegat.gsfc.nasa.gov)
All of the broad-band images from the mission will be distributed on cd rom. Volume 1,
consisting of the first six months of data released to the archive, is now available. It
was first distributed at the Washington AAS meeting in January. The CD-ROM can be browsed
from xmosaic by opening:
http://heasarc.gsfc.nasa.gov/0/docs/rosat/cdvol1/rosatcdvol1.html
The second volume will contain all the remaining archival images released up to
December 1993. It is currently in production and if all goes well will be distributed at
the June 1994 Minneapolis AAS meeting. If you would like to order a copy of either volume
please send an e-mail to ksmale@lheavx.gsfc.nasa.gov. Please include your name, address
and which volumes you would like. Supplies are limited and will be sent on a first come
first serve basis.
by Thomas A. McGlynn, Nicholas E. White, and Keith Scollick, LHEA/Goddard Space Flight
Center, mcglynn@grossc.gsfc.nasa.gov
In the past decade digital versions of several all-sky surveys have become available.
The explosion in the information processing capability of computer systems has meant that
the actual images from these surveys can be delivered to the community rather than simply
catalogs of interesting objects derived from the images. Some of these surveys have been
distributed to the astronomical community on CD-ROM's. However, in practice it can still
be very difficult to use these surveys. The coordinate system, scale, orientation, epoch,
... used to distribute the survey rarely matches the user's requirements. We have built a
network facility, SkyView, which addresses these issues.
SkyView lets users to pick a region of the sky and obtain images at a number of
wavelengths. The user chooses the projection, coordinate system, scale, orientation, and
size of the desired image. This can exactly match existing data from ground- or
space-based observations or meet other research needs. The data is transformed from
available all-sky and wide-area surveys and the users are given FITS files or can display
images of the results. SkyView can contour one image over another, do multi-color imagery,
get catalog overlays and perform other useful image manipulations.
SkyView is available through Mosaic using the URL
http://skview.gsfc.nasa.gov/skyview.html
(Note the missing `y' in the node name.) and through the HEASARC xray account. Logon as
`xray' on legacy.gsfc.nasa.gov. Then enter the command `skyview'. The Mosaic interface
does not currently support all of the functions in the full interface but its capabilities
are expanding rapidly.
Surveys currently in SkyView include:
CGRO EGRET All sky at .5 degree resolution.
HEAO 1 A2 Approximately 1 degree resolution
ROSAT PSPC All of the public ROSAT pointed data
(8% sky coverage)
EUVE The initial low resolution release
IRAS The entire sky including low ecliptic latitudes.
Radio 4850, 1420 and 408 Mhz surveys.
We anticipate getting the optical data from ST ScI plate scans of the southern and
northern skies, the ROSAT WFC survey data, high resolution products from EUVE and many
other surveys as we are able to incorporate them into the system.
The SkyView User's Guide is available on anonymous FTP on skview.gsfc.nasa.gov. Please
contact
Thomas McGlynn 301-286-7743 mcglynn@grossc.gsfc.nasa.gov or
Keith Scollick 301-286-8143 scollick@skview.gsfc.nasa.gov
for further information.
SkyView is funded by NASA's Astrophysics Data Program, grant NAS5-32068.
by P. Mandrou CESR-CNRS/UPS - 9 av. du Colonel Roche - 31029 Toulouse Cedex-France
mandrou%cnesta.SPAN@mx.nsi.nasa.gov
Introduction
The SIGMA telescope was first proposed to the French Space Agency (CNES) in June 1981
by two laboratories, the Centre d'Etude Spatiale des Rayonnements (CESR- CNRS/UPS) in
Toulouse and the Service d'Astrophysique of the CEA at Saclay; it was constructed by these
two laboratories under CNES management and support. SIGMA was launched on board the Soviet
space observatory GRANAT on December 1st, 1989. After a period of performance
verification, the first scientific observations started in early March 1990. This hard
X-ray, soft gamma-ray instrument, (weighing 1.1 tons, 3.5 m high by 1.2 m diameter) is the
first coded aperture telescope sensitive to radiation in the 35 keV - 1.3 MeV energy range
operating in space. The coded aperture mask, with a basic 29 x 31 pattern, is a uniformly
redundant array (URA), known to have ideal properties. It is located 2.5 m from a position
sensitive detector based on the principle of the Anger Camera, providing an angular
resolution of about 13 arc minutes and a source positioning accuracy up to 0.75 arc
minutes for the strongest objects. A heavy CsI active shield surrounds the detector and
limits the field of view to about 1 steradian. Since 1990, the telescope has been
providing sky images with unprecedented angular resolution.
Observations and results
As of mid-1994, about 12,000 hours of observation time have been accumulated on about
65 different astrophysical targets. More than 40 high-energy emission sources have been
observed and analyzed, and many new and exciting results have been obtained on various
objects: the galactic center region, new transients exhibiting unexpected hard tails such
as Nova Muscae or Nova Persei , active galactic nuclei, and hard X-ray binaries such as
GX339-4, 4U1700-377. We present here some of the most important results.
The Galactic Center Region
During the last 25 years, the galactic center region has been observed many times both
by balloon-borne telescopes and spacecraft experiments, in the hard X-ray and low-energy
gamma- ray domains. The most prominent result obtained in the seventies was the discovery
of e+-e- annihilation line emission associated with this region. Further observations with
high energy resolution telescopes clearly demonstrated that this line was narrow (less
than 3.2 keV) and centered at 511 keV. It was found, with several observations using the
same detectors, that this emission could be considered to be variable, suggesting that it
originates from a variable compact object situated close to the galactic center.
From 1990 to 1994, two series of observations per year have been carried out in two
periods (Feb/March/April and September/October), with the SIGMA telescope. More than 1,800
hours of useful observing time were accumulated on this region. Six different sources
(1E1740.7-2942, GRS1758-258, GX1+4, X1724- 308/Terzan 2, KS1731-260 and GX354-0) have been
detected above 40 keV, in a 12 x 12 degree area centered on the radio source SgrA* and
monitored continuously by SIGMA. This constant monitoring highlighted the high variability
of the objects in this region. Among them, three have successively dominated the hard
X-ray emission coming from this region : 1E1740.7- 2942, GRS1758-258 and GX354-0. These
objects have undergone long duration outbursts as well as long duration quiet states.
In early 1990, during the first SIGMA observation, two sources were discovered,
dominating the emission above 40 keV, in a 6 x 6 degree area centered on the radio source
SgrA*. The most luminous was the Einstein object 1E1740.7-2942. The other, GRS1758-258,
was discovered 45 arc minutes away from GX5-1, thanks to the high angular resolution of
the telescopes ART-P and SIGMA on board GRANAT. This source is probably the origin of the
variable hard X-ray tail attributed by mistake to the soft X-ray source GX5-1 as a result
of the poor angular resolution of the detectors used in the past, which could not separate
these objects.
1E1740.7-2942
Our observations of this object (located 48 arc minutes from Sgr A*) during the spring
of 1990, led us to believe that it had a persistent constant emission. Its energy spectrum
(obtained in the spring) was well fitted by a comptonized disk model with an electron
temperature kTe=32 keV . However, observations performed in September/October 1990
revealed its true, variable nature. During the October 13-14th observation, a
"spectacular" event was recorded. The spectrum was found to exhibit an
unexpected feature from 200 to 700 keV . This bump, detected during the entire observing
session (4.5 10**4 sec), is unambiguously apparent at the source position in the image
made in the 330-540 keV energy band, showing that this effect is not an artifact, but is
really coming from the object.
This feature is well represented by a Gaussian line centered at 480 keV with a FWHM of
240 keV. It should be stressed that it is well resolved and cannot result simply from a
narrow line convolved with the detector spectral resolution, which is 8% at 511 keV. This
shape suggests that it could be attributed to a redshifted electron-positron annihilation
process, coming from a massive production (in the vicinity of a compact object) of a hot
pair plasma with a characteristic temperature of about 5 x 10**8 K. It contains about 60%
of the total energy radiated by the source. Such an overall complex structure was also
noticed in the Cyg X-1 high state (gamma 1), but centered at higher energies (1 MeV).
During the spring of 1991 the source intensity decreased by a factor of approximately
4, and by the end of the summer the source was totally absent from the SIGMA images. It
reappeared in 1992 in the images of the galactic center region and continuously increased
during 1992, recovering its "nominal" state at the end of the year.
GRS1758-258
GRS1758-258 was found to have an emission spectrum variable in intensity, well fitted
by the Sunyaev- Titarchuk Comptonized disk model with a characteristic electron
temperature of kTe=33 keV. It decreased in intensity to below the detection threshold of
SIGMA in the autumn of 1991. During 1992, it was judged to be very weak from the SIGMA
observations . Its variable nature is now well established.
GX1+4
Four other objects were monitored in the SIGMA galactic center field of view. The X-
ray pulsar GX1+4, well known to be variable in intensity, revealed, in addition, a
surprising change in the spin down rate during the autumn of 1990 and the spring of 1991.
It has now recovered a linear spin down rate, but slightly higher than that observed
before 1990.
KS1731-260, GX354-0, Terzan 2
One of the most surprising results obtained from the processing of such large images
was the discovery of hard X-ray emission up to about 150 keV from soft X-ray transients or
X-ray bursters. The duration of such hard tails is typically a few days. SIGMA found hard
X-ray emission from the type I X-ray burster KS1731- 260 and the transient X-ray burster
GX354-0. It also detected emission from the globular cluster Terzan 2 which could be
associated with the X-ray burster X1724- 308. From spectral correlative analysis the hard
tails observed by SIGMA from these objects strongly suggest that some X-ray burst sources
become hard X-ray emitters when reaching a low soft X-ray luminosity state.
Active galactic nuclei
During the first year of operation, SIGMA was pointed at many extragalactic objects
considered interesting candidates for emission in the gamma-ray domain (on the basis of
previous balloon observations or extrapolation of their X-ray spectra). Up to now, SIGMA
has definitely detected only three extragalactic objects with good statistical
significance: NGC4151, 3C273 and CEN-A. With less significance, NGC4051 and NGC4388 in the
Virgo cluster have been detected.
A few hundred hours have been spent on NGC4151 from 1990 to 1993. The source was
detected up to 200 keV and has been well identified with the Seyfert Galaxy, thanks to
SIGMA's angular resolution. The photon spectrum was found to be unusually soft (alpha=3)
when compared with results obtained by previous instruments up to few MeV. This difference
can be attributed to a variation in the spectral shape. Nevertheless the SIGMA detection
is in agreement with the previous HEAO-1 A-4 observation in June 1978 and the
extrapolation of the spectrum to tens of MeV falls below the SAS-2 and COS-B upper limits.
An interesting result must be pointed out when comparing the SIGMA spectrum with that
obtained by the ART-P telescope operating on GRANAT at lower energies at the same time. A
break in the spectrum around 50 - 60 keV is needed to fit the SIGMA and ART-P results.
This break is predicted by recent models including Compton reprocessing by cold optically
thick material very close to the central engine, and could be taken as evidence of the
contribution of Seyfert galaxies to the cosmic diffuse background which also presents a
break around 60 keV. During the NGC4151 observation sessions, distributed over these 4
years, its flux has been found to be variable by a factor of 2 over half- year periods.
The quasar 3C273 is also one of the main SIGMA extragalactic objectives. It too was
found to be highly variable over the 1990 - 1994 observing sessions. It was easily
detected during 3 sessions in 1990 and 3 others in 1991 with flux variations of a factor
of 2. During the remaining 2 sessions, only upper limits could be determined. Variations
are observed on timescales as short as 40 days. The data are well fitted by a power law of
photon index alpha= 1.5 up to 500 keV. Comparison with previous results in the X- ray
domain indicates that the spectrum is probably characterized by a simple power law shape
from 2 keV to a few hundred keV. Recent measurements by GRO/COMPTEL and GRO/EGRET have
shown that a spectral break is found around 1 MeV.
Another interesting result of the 3C273 observations was obtained during November 1990
. SIGMA images revealed a 5.5 sigma excess in a location RA(1950) = 12h27mn21s, DEC(1950)
= 02d29m12s with an associated error circle of radius 5 arcmintues. This source, named
GRS1227+025, located only 15 arc min. away from 3C273, could help explain some strange
results observed from this quasar (e.g. the detection of a half-day flare by Ariel V). The
spectrum of GRS1227+025 has been detected up to 120 keV. The presence of a transient
source close to the quasar clearly demonstrates the need for high resolution imaging in
the hard X- ray, low energy gamma- ray domain.
The radio galaxy NGC5128 (Cen A) has been observed by SIGMA on three occasions during a
one year period. A comparison between the observations indicates a flux increase of a
factor of three over the year, but even more interesting is a similar decrease which was
observed in just four days. Such a short timescale variation has never been seen before at
this energy. Despite the intensity variation of a factor of 2 or 3, the observed spectral
shape is well fitted by a power law of index alpha = 1.9 +/- 0.4 up to 200 keV over all
the observations . If extrapolated to higher energies, in order to agree with the SAS-2
and COS-B upper limits, the broad band spectra require a break or steepening above 200
keV, in both the high and low intensity states.
X-ray Binaries and X-ray Novae
SIGMA has spent a large fraction of its time on the exploration of the galactic disk.
Thanks to the wide field of view of the telescope (12 x 12 degrees), large parts of the
sky have been monitored with good sensitivity. This led to the observation and discovery
of random outbursts from binaries such as 4U1700- 377, GX339-4 , X-ray pulsars such as
GRS0834-430 and spindown, e.g. in OAO1657-415.
Impressive results have also been obtained on targets of opportunity, such as Nova
Muscae and Nova Persei. A day after its discovery by the all-sky instrument WATCH on board
GRANAT, the X-ray nova GRS1124-684 (in Musca) was detected by SIGMA at the edge of its
field of view. In the 6-15 keV band, the source intensity increased from 0.7 Crab (on
January 8th) to 2 Crab on January 13th. The X-ray peak at low energies (below 15 keV) was
observed from the source between January 12 and 16 and was followed by a smooth
exponential decay with a characteristic time around 30 days. The source was observed by
SIGMA in the 40-150 keV band with 55 sigma significance and located at RA(1950) =
11h24mn08s, DEC(1950) = -68d23m06s with a square 3.3 x 3.3 arcminute error box, fully
compatible with the identification at other wavelengths. The 40-150 keV flux decreased
from 1 Crab to 0.4 Crab within six days. Later, the flux decreased continuously, with
irregularities on timescales of several days.
In all the observations, this nova was detected up to 300 keV with a spectrum well
fitted by a power law model with a spectral index 2.3 Recent photometry and spectroscopy
work on Nova Muscae shows that the binary system is an association of a secondary star of
spectral type in the range K0 V to K4 V and a compact object with a conservative lower
limit mass function 3.1 +/- 0.4 solar masses. This result leads the authors to conclude
that a black hole is present in this binary system.
Discovered by GRO/BATSE in August 1992, Nova Persei (GROJ0422+32 = GRS0418+328) was
observed by SIGMA between August 15 and September 25, 1992, and positioned to RA(1950) =
04h18mn28.6s, Dec(1950) = 32d47m20s. It was found to be extremely bright (3 Crab in the
35-200 keV energy band), with a hard spectrum extending to 600 keV. On the basis of its
light curve and spectral properties, Nova Persei joins A0620-00, GS2023+33, GS2000+25 and
Nova Muscae in the subclass of X-ray transients exhibiting a hard tail. These objects are
believed to be low mass X-ray binaries in which the compact objects are the more secure
black hole candidates. Further, timing analysis revealed quasi- periodic like oscillations
at 0.36 Hz while the BATSE instrument reported "QPO like" behavior at 0.04 Hz
and 0.2 Hz. These "QPO-like" lower frequencies are thought to be related to the
accretion disk. It should be stressed that after the SIGMA discovery of QPO-like behavior
in Cyg X-1 (0.6 Hz) the presence of QPOs is not in contradiction with a black hole
hypothesis. Moreover, the two frequencies are comparable.
Conclusion
SIGMA has obtained unprecedented and exciting results in the gamma-ray domain. Thanks
to its high angular resolution, it has provided major contributions to the understanding
of complex regions of the sky. The fundamental result coming from these years of
successful operation is the high variability of the sky in the hard X-ray/soft gamma-ray
range, showing that spectacular phenomena can be observed on timescales of a few hours,
characteristic of compact objects.
The Future Of The Mission
In July 1994, GRANAT will be close to the end of its pointing phase. The gas will
theoretically be exhausted at this time. It is impossible to know exactly when the last
day will occur because of uncertainties in the calculations. Russian and French mission
specialists are studying the possibility of maintaining the experiments after this period
to work in an unpointed, degraded mode. The spacecraft has an in-orbit free- flight
natural equilibrium (due to radiation pressure and the solar wind) with the solar panels
oriented towards the Sun. Thus in this mode, all the systems will be electrically powered
. The spacecraft will slowly rotate around the solar axis, and SIGMA will scan the sky
about this axis. An all- sky scan would be performed in six months. The gamma-ray burst
detectors would operate normally. Nevertheless, all the SIGMA onboard software would have
to be modified to adapt to this new operating mode. The biggest problem would be to change
the star tracker operation to get the absolute position of the telescope axis with the
required accuracy as a function of time. Technically, this can be achieved, but the French
Space Agency has to estimate the time and costs required for these modifications.
Following this, a final decision will be made, around September 1994.
by N.E. White, LHEA/GSFC, white@lheavx.gsfc.nasa.gov
The results of the 2nd round of ASCA observing time (covering 1994, May 15 to November
15) are now available and can be obtained from the anonymous ftp account on
legacy.gsfc.nasa.gov, under the directory asca/timelines. The NASA Research Announcement
for the next year will be released around 1994, May 15 with proposals due 1994, August 15.
This 3rd round will cover 1 calendar year of observing time. To receive further
information about how to submit proposals please contact the ASCA Guest Observer Facility
via the e-mail address ascanra@athena.gsfc.nasa.gov. The 1st issue of the ASCA newsletter
is now available and can be obtained by sending email to humphrey@lheavx.gsfc.nasa.gov.
The mission continues well with many exciting new results. A special ASCA issue of the
Publications of the Astronomical Society of Japan, PASJ, is due out in June 1994 with
seventeen science result papers as follows:
The X-ray Satellite ASCA - Y. Tanaka et al.
Discovery of an Obscured Low Luminosity Active Nucleus in the Spiral Galaxy NGC4258
- K. Makishima et al.
X-ray Spectroscopy of SNR E0102-72 with the ASCA Satellite - I. Hayashi et al.
An ASCA Observation of One Orbital Cycle of AR Lac - N.E. White et al.
The Broad Band X-ray Spectrum of SN1978k and Two Other Luminous X-ray Sources in the
Spiral Galaxy NGC1313 - R. Petre et al.
ASCA Observations of NGC1068 - S. Ueno et al.
ASCA Observations of Three Bright Early-type Galaxies, NGC4472, NGC4406, and NGC4636
- H. Awaki et al.
A Non-Thermal X-Ray Spectrum from the Supernova Remnant W50 - S. Yamauchi et al.
Resolving the Cygnus X-3 Iron K Line - S. Kitamoto et al.
The X-ray Emission of 3C273 Observed with ASCA - T. Yaqoob et al.
ASCA Observations of Two High Redshift Quasars: Evidence for Complex Continuum
Emission - P. Serlemitsos et al.
Metal Concentration and X-Ray Cool Spectral Component in the Central Region of the
Centaurus Cluster of Galaxies - Y. Fukazawa et al.
ASCA Observations of the warm absorber in MCG 6-30-15; the Discovery of a Change in
Column Density - A.C. Fabian et al.
ASCA Observations of Hard X-ray Emission from the Rho Ophiuchi Dark Cloud - K.
Koyama et al.
ASCA Observations of the Wolf-Rayet Binary HD 193793 - K. Koyama et al.
Plasma Structure of the North-East Rim of the Cygnus Loop Observed with ASCA - E.
Miyata et al.
The ASCA PV Phase Observation of FO Aquarii - K. Mukai et al.
Observations of EX Hydrae with ASCA - M. Ishida et al.
More papers that were too late for this issue will appear in the August PASJ. A special
issue of the Astrophysical Journal Letters is planned for November this year, where a
further 15-20 papers will appear.
by Yoji Kondo and Ron Oliversen, kondo@stars.gsfc.nasa.gov
(I) Second Guest Observer Year: For the second guest observer year that covers the
epoch from 1994 January to 1995 January, 50 observing programs have been selected from 108
proposals submitted.
(II) Highlights of Scientific Results: Among the highlights of the observational
results, based primarily on reports by J. Holberg, F. Bruhweiler, H. Shipman, H. Marshall,
D. Hall, A. Dupree, A. Brown, G. Doschek, P. Judge, J. Cassinelli, S. Howell, J. Liebert
and others, are:
(A) Active Galactic Nuclei: The interstellar matter within our galaxy is sufficiently
transparent through the galactic disk in some directions to permit observations of
extragalactic sources. The observed 'UV bump', which is attributed to the accretion disk,
shows that the 'bump' is due to a continuum rather than a small number of strong emission
lines. EUV flux comprises a dominant fraction of the total energy output. The EUVE flux
varied by as much as a factor of 10 in one object, indicating that the source is most
likely a compact region.
(B) Coronae in Cool Stars: Dense emitting plasmas in the coronae were discovered in
several stars. Such high density regions have not been detected in the Sun. The first
abundance studies have been conducted for the coronae of a star other than the Sun; the
results for Procyon do not show the abundance anomalies found in the Sun. The corona of
Capella shows a temperature minimum at 10E6 K in contrast to the 10E5 K observed in the
Sun.
(C) Cataclysmic Variables: A clear evidence for the accretion column occurring at the
magnetic poles of the white dwarf component has been observed in the EUV. Early analysis
indicates that there are 'blobs' in the accretion column. EUVE observations also show a
hot area -- several hundred kilometers wide -- near the surface of the white dwarf; it
varies in some cataclysmics. Outbursts have been observed in SS Cyg and U Gem, yielding
rich, variable EUV spectra.
(D) B Stars: The star epsilon CMa is the brightest extrasolar source, being some 10 to
30 times brighter than the predictions of LTE and non-LTE models. It dominates the local
radiation field at 500 A.
(E) White Dwarfs: A number of EUV bright white dwarfs are being observed. New dithered
observations of brightest sources promise to yield spectral features, which will
significantly improve theoretical models.
(F) The Local Interstellar Medium: EUVE is a unique and powerful tool in studying the
LISM as it can measure directly the ionization fraction of helium as well as infer that of
hydrogen.
Our knowledge of the LISM is expected to improve substantially when EUVE observations
are fully analyzed.
(G) Solar System Objects: (a) Helium has been observed for the first time in the
Martian and Jovian atmospheres. (b) In the Io plasma torus, the emission lines due to
doubly ionized sulfur at 680 A and the singly ionized oxygen at 539 A have been detected.
(H) Serendipitous observations of the scanners, pointed 90 degrees from where the EUVE
spectrometer is pointed to observe guest observer targets, have thus far lead to the
discovery of 99 new sources not previously reported -- the discovery rate has been about 1
for every 10 square degrees.
(III) The Third -- and Forthcoming -- Guest Observer Year: The EUVE guest observer
opportunity (NRA) for the third year, covering the period 1995 January through 1996
January, will be announced in 1994 June. Proposals are due on 1994 September 16. The guest
observer opportunities will be primarily for the EUVE Spectrometer but proposals for the
Deep-Survey and Scanner instruments will also be considered in the peer review. In support
of this NRA, all calibration data sets will be made available to the public by August 1.
In addition, the second EUVE All-Sky catalog will also be released by the EUVE Science
Principal Investigator Stuart Bowyer. The public release of the first guest observer year
data, whose proprietary rights have expired or are expiring, has started on May 1 and will
continue on a monthly basis.
by Christoph Winkler, ESA-ESTEC, cwinkler@estsa2.estec.esa.nl
INTEGRAL (International Gamma-Ray Astrophysics Laboratory), -- the second medium-size
mission (M2) of ESA's long term scientific programme Horizon 2000 -- was selected by ESA's
Science Programme Committee on 3 June 1993. The approved budget covers all design &
development phases including two years of mission operations.
INTEGRAL addresses the fine spectroscopy and accurate positioning of celestial
gamma-ray sources (15 keV - 10 MeV). Key design features of the model payload include a
spectral resolution of 2 keV at 1 MeV utilising cooled Germanium detectors and coded
aperture mask imaging in combination with a multilayer detector pixel array resulting in
17 arcmin FWHM angular resolution (within few deg fully coded FOV). Instrument design
sensitivities are: 3x10^-8 ph/cm2/s/keV @ 1 MeV (continuum) and 1.5x10^-6 ph/cm2/s @ 1 MeV
(narrow line) (both 3 sigma in 3x10^6 s). Complementary observations in the X-ray and
optical band will be performed by two monitor instruments.
INTEGRAL's science covers a wide variety of high energetic astrophysical processes
taking place in or close to neutron stars, black holes, supernovae and active galactic
nuclei. The following (incomplete) list of scientific objectives can be highlighted:
The diffuse gamma-ray emission from the Galactic plane will be mapped on a wide range
of angular scales from arc minutes to degrees in both discrete nucleosynthesis lines, e.g.
1.809 MeV from Al^26 and 511 keV, and the wideband continuum. At the same time, source
positioning at the arc minute level within a wide field of view of both continuum and
discrete line emissions will be performed.
The Centre of our Galaxy houses some of the most energetic gamma-ray objects in the
Galaxy and is host to sources of transient emission, including variable line emission from
the annihilation of positrons. INTEGRAL will provide the tools for using gamma-rays as a
sensitive probe of the astrophysical processes going on within a few hundred parsec of the
nucleus of our Galaxy.
One of the most important scientific objectives of INTEGRAL is to study compact
objects, e.g. neutron stars and black holes. INTEGRAL will image these sources in
unprecedented detail at high energies and the spectroscopic capabilities of the mission
will provide the first detailed physical diagnostics of these systems at gamma-ray
energies.
Observations of gamma-ray lines from nuclear transitions in the decay of radionuclei
and the annihilation of positrons produced in various explosive nucleosynthetic processes
(supernovae and novae, including historic events) provide the most direct method of
studying current sites, rates and models of nucleosynthesis. Measurements with INTEGRAL of
the shapes of the gamma-ray line profiles from supernovae will provide information about
the expansion velocity and density distribution inside the envelope, whilst the relative
intensities of the lines provide direct insight into the physical environment at the time
of the production.
INTEGRAL will monitor the Galactic plane regularly in order to detect transient
sources, determine their duty cycle and their luminosity function.
The study of AGN in both fine and broadband spectroscopy will yield new insight into
particle interactions taking place in the central region. Sub-degree resolution imaging is
essential to avoid source confusion from the large population of AGN and to associate
gamma-ray sources unambiguously with their optical, infrared and radio counterparts.
INTEGRAL will be launched in 2001 into either a 72 h (52 deg inclination) or a 24 h (65
deg) high elliptical orbit providing long uninterrupted observations. Launchers under
study include a Russian PROTON (baseline) and an Ariane 5 (backup). The nominal mission
duration will be 2 years and most of the observing time will be made available to the wide
scientific community (General Observers). Real time science data rate is 40 kbps.
INTEGRAL will utilize the same service module (carrier, or bus) which is under
development for the ESA cornerstone X-ray mission XMM.
ESA is responsible for the overall mission and spacecraft design, system integration,
testing and spacecraft operations. The launcher would be provided by Russia or by ESA.
NASA would contribute to the science instruments, to the data centre and would provide one
or possibly two ground stations. The science instruments and the INTEGRAL science data
centre will be provided by the science community (based on national funding for ESA member
states) as selected by ESA following the AO.
INTEGRAL will be operated as an observatory with most of the observing time available
for the astronomical community. Observing time will be granted following standard peer
review procedures. Scientific data will be accessible via the INTEGRAL science data centre
or through science support centres in USA and Russia.
ESA will publish an Announcement of Opportunity (AO) soliciting proposals for
instrument Principal Investigators (PI's), for the PI of the INTEGRAL Science Data Centre
(to be located at a scientific institute in an ESA member state) and for Mission
Scientists. The AO will be open for ESA member states, USA and Russia. The scheduled
release of the AO is 01 July 1994. Proposals would be due early December 1994 (to be
confirmed). Final selection of the payload, the data centre and appointment of Mission
Scientists will be announced in June 1995 (TBC).
Details on the INTEGRAL Phase A study, completed in 1993, are contained in ESA report
ESA SCI(93)1, available free of charge from the author.
30th COSPAR, Hamburg, Germany, July 11-21, 1994. Contact: COSPAR Secretariat, Paris,
29531::COSPAR, Fax 33-1-40509827
SPIE International Symposium on Optics, Imaging, and Instrumentation, San Diego, CA,
24-29 July, 1994. Contact: SPIE, Fax (206) 647 1445, Phone (206) 676 3290
22nd General Assembly of the IAU, The Hague, The Netherlands, 15 - 19 August, 1994.
Aspen Workshop on Gamma-Ray Bursters, Aspen, CO, 22 August - 11 September, 1994.
Contact: Aspen Center for Physics, Fax (303) 920 1167, Phone (303) 925 2582
14th European Cosmic Ray Symposium, Balatonfured, Hungary, 28 August - 3 September,
1994. Contact: A. Varga, fax 36 1 169 6567, 14ecrs@rmki.kfki.hu
Imaging in High Energy Astronomy, 26-30 September, 1994, Anacapri, Italy. Contact: L.
Bassani, fax 39 51 6398723, 38045::CAPRI, capri@botes1.tesre.bo.cnr.it
TeV Gamma Ray Astrophysics, Heidelberg, Germany, 3-7 October, 1994. Contact: F.
Aharonian, aharon@peter.mpi-hd.mpg.de
The Multi-Mission Perspective, Incorporating ROSAT and ASCA Workshops (High Energy
Astrophysics Division of the AAS 1994 Meeting), Napa Valley, CA, 2-5 November, 1994.
Contact: Eureka Scientific, Inc., fax 510 530 2416, eureka@netcom.com
Flares and Flashes, A Multi-Wavelength Approach to Short-Term Phenomena, IAU Colloquium
151, 5-9 December, 1994, Sonneberg, Germany. Contact: W. Duerbeck, fax 49 251 833669,
hilmar@cygnus.uni-muenster.de
17th Texas Symposium on Relativistic Astrophysics, Munich, Germany 12-17 December,
1994. Contact: G. Morfill, MPE Garching, fax 89 3299 3235
185th AAS, Tucson, AZ, January 1995
Towards the Source of Gamma-Ray Bursts, ESTEC, Noordwijk, The Netherlands, 25-27 April,
1995
3rd Compton Symposium, Munich, Germany, 12-14 June 1995.
HEADNEWS, the electronic newsletter of the High Energy Astrophysics Division of the
American Astronomical Society, is issued by the Secretary-Treasurer, at the University of
California Space Sciences Laboratory, Berkeley, CA 94720-7450. The HEAD Executive
Committee Members are:
Martin Elvis, Chair (elvis@cfa.harvard.edu)
Neil Gehrels, Vice-Chair (gehrels@lheavx.gsfc.nasa.gov)
Kevin Hurley, Secretary-Treasurer (khurley@sunspot.ssl.berkeley.edu)
Rob Petre, Member (petre@lheavx.gsfc.nasa.gov)
Belinda Wilkes, Member (belinda@cfa.harvard.edu)
Hakki Ogelman, Member (ogelman@astrog.physics.wisc.edu)
Rick Rothschild, Member (rrothschild@ucsd.edu)
Mel Ulmer, Member (ulmer@ossenu.astro.nwu.edu)
Diana Worrall, Member (dmw@cfa.harvard.edu)
Virginia Trimble, Member and Past Chair (vtrimble@astro.umd.edu)
Please send newsletter correspondence to khurley@sunspot.ssl.berkeley.edu
