THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS
25 Birch Street, Cambridge, MA 02138 USA
Tel. 617-354-0484 FAX 617-354-0665
AAVSO ALERT NOTICE 218 (February 16, 1996)
MONITORING OF 1813+49 AM HERCULIS FOR INTERNATIONAL OBSERVING CAMPAIGN
1996 marks the 20th birthday of the discovery of AM Her, a magnetic cataclysmic
variable. In celebration of this birthday an international campaign has been
organized to obtain multiwavelength observations of AM Her using space-borne
telescopes, such as the International Ultraviolet Observer (IUE), Hubble Space
Telescope (HST), ROentgen SATellite (ROSAT), and Infrared Space Observatory
(ISO), and possibly the x-ray satellite SAX, as well as ground-based
photometric and spectroscopic observations.
Dr. Boris Gaensicke, Universitaetssternwarte Goettingen, Germany, writes, "It
would be very helpful, especially for the planning of satellite-based
observations, to keep track of the optical magnitudes of AM Her. I would
therefore like to ask if it would be possible to communicate [to] us on a
weekly basis the brightness of AM Her."
He continues, "AM Her shows an erratic variability, ranging from fluctuations
in a few days to prolonged low and high states (up to years). This may seem in
contrast to many of the dwarf novae displaying a more (or less) regular outburst
"However, the variability in dwarf novae is thought to be mainly due to the
dynamics of the accretion disk, while the variability in AM Her stars should
reflect directly changes in the mass-transfer rate from the secondary. Alas,
the behavior of AM Her is known in detail only at optical wavelengths, thanks
to the effort of many amateur astronomers around the world.
"When the last call for proposals for the IUE arrived, we thought that the
last episode of this space veteran offers a unique chance for an extended UV
monitoring of AM Her. Once this monitoring was decided, it became clear that
any observation at other wavelengths would highly profit from the detailed
knowledge of the accretion history in the system.
"Up to now, we [have] obtained for this project weekly IUE observations from
mid-February to mid-October, nine ROSAT pointings from up to the beginning of
May, two sets of HST observations planned to cover low and high states, and
infrared observations with ISO. We hope for additional coverage with the new
Italian-Dutch x-ray satellite SAX, and for optical spectroscopy and photometry
from several sites.
"Some of our scientific aims are 1) to determine changes in the mass transfer
rate over the nine months of IUE coverage; 2) to probe the thermal response of
the white dwarf to changes in the accretion rate; 3) to search for contamination
of the white dwarf by the metal-rich accreted material; 4) to derive the mass
of the white dwarf and the secondary from radial velocity measurements; and 5)
to determine the field structure and the accretion geometry..."
In order to monitor AM Her effectively, Dr. Gaensicke and his colleagues have
asked us to keep a close eye on this star and keep him informed regularly
throughout the year, particularly as they are estimating the frequent IUE
exposures. The first HST observations will take place this summer, and then
they will wait until the brightness state of AM Her changes. Below is the
preliminary schedule of IUE, ROSAT, and HST observations.
IUE: Feb. 18, 25
Mar. 01, 06, 11, 16, 21, 26, 31
Apr. 05, 15
then UV monitoring continues at ~ weekly intervals up to mid-October
ROSAT: Feb. 25
Mar. 06, 16, 26
Apr. 05, 15
plus some additional slots to be scheduled
HST: July 1996
ISO: still to be determined
SAX: still to be determined
Please monitor AM Her closely, and communicate your observations regularly to
AAVSO Headquarters. Presently, AM Her is in its high state, where it has been
for several years. If its state changes, i.e., if it goes into its down state,
please call in your observations immediately so that we may alert the
astronomers involved in this international campaign. Accompanying are AAVSO
preliminary 'd' and 'f' scale charts of AM Her.
MONITORING OF THE CATACLYSMIC VARIABLE 0523-03 V1159 ORIONIS
Dr. Paula Szkody, University of Washington, has asked our assistance in
monitoring the interesting dwarf-nova type cataclysmic variable V1159 Ori
during her coordinated campaign, which will involve three satellites, X-ray
Timing Explorer (XTE), ROSAT, and IUE, and possibly the Extreme Ultraviolet
V1159 Ori is a very interesting dwarf nova. From the superhumps that were
observed in 1992 during a long outburst, and from the orbital period measured
in 1992, it is classified as an SU UMa-type dwarf nova. However, it is a
peculiar SU UMa star in that it has very frequent narrow outbursts (every
two to three days) and also very frequent superoutbursts (about every 44.5
days). J. Bortle described the strange behavior of this star in the section
titled "Bizarre Stars" in the Observer's Forum of AAVSO Newsletter No. 16,
page 16, 1995.
Accompanying is an AAVSO 'e' scale preliminary chart of V1159 Ori. Please
monitor this star closely and telephone, fax, or email your observations to
AAVSO Headquarters so we may assist Dr. Szkody. In addition, those who have
email may send a copy of their observations to Dr. Szkody at
FLUCTUATIONS OF 0059+53 NOVA CASSIOPEIAE 1995
N Cas 95 (see AAVSO Alert Notices 213, 214, and 217) has been very closely
monitored by our observers. This interesting nova showed a slow rise in
brightness starting JD 2450022, from mean visual magnitude 8.7 to 8.5, then
a much faster rise starting JD 2450059 from 8.5 to 7.2 on 2450068. This rise
was followed by a rapid decline over 2450071 and 2450072 from 7.1 to 8.0. The
slow decline continued to about magnitude 9.5 until JD 2450114. Since then
the star has been brightening slightly and showing oscillations, as indicated
by the following observations reported to AAVSO Headquarters by observers
around the world:
Feb 1.0118 UT, 9.5, J. Bortle, Stormville, NY; 3.0236, 9.2, R. Hays, Worth,
IL); 3.81, 9.5, M. Zanotta, Milano, Italy; 3.9979, 9.4 (M.A. Komorous, London,
Ontario, Canada; 4.0535, 9.4, W. Dillon, Missouri City, TX; 4.0646, 9.3, Hays;
4.883, 9.1, G. Poyner, Birmingham, England; 4.9340, 9.0, G. Gliba, Chagrin
Falls, OH; 5.0264, 9.1, Hays; 5.0757, 9.0, Dillon; 5.1118, 8.9, P. Collins,
Scottsdale, AZ; 5.9764, 9.2, Gliba; 6.0896, 9.3, Hays; 6.9806, 9.4, P.
Dombrowski, Glastonbury, CT; 6.9917, 9.5, Bortle; 7.0424, 9.4, J. McKenna,
Upper Montclair, NJ; 7.1486, 9.4, R. Royer, Lakewood, CA; 7.9833, 9.3, Gliba;
8.1028, 8.9, Collins; 9.1049, 9.0, Collins; 11.0924, 9.3, Gliba; 11.1326, 9.4,
T. Burrows, Novato, CA; 12.0049, 9.0, Gliba; 12.0785, 9.2, A. Dill, Wichita, KS;
12.1215, 9.3, Burrows; 12.9896, 9.3, Dombrowski; 13.0132, 9.3, Bortle; 13.1201,
9.2, Burrows; 13.1618, 9.3:, Dillon; 13.9799, 8.8, Gliba; 13.9861, 8.6,
Dombrowski; 14.0222, 9.0, Bortle; 14.0431, 8.9, McKenna; 14.2014, 8.8, Dillon;
14.87, 8.5, Zanotta; 15.09, 8.5, Zanotta; 15.1361, 9.2, Dillon.
Accompanying are revised AAVSO 'b' and 'd' scale preliminary charts for
N Cas 95. Please continue to monitor this star closely, and phone, fax, or
email your observations to AAVSO Headquarters.
It is interesting to note that the overall optical behavior of this nova has
been and continues to be quite similar to that of HR Del, whose light curve we
published in AAVSO Alert Notice 213.
REQUEST TO MONITOR 2138+43 SS CYGNI
The brightest northern hemisphere dwarf nova, SS Cyg, continues to be of
interest to astronomers observing with various spacecraft. Throughout 1996,
several satellites will be monitoring SS Cyg, namely IUE (during an anomalous,
symmetrical outburst), XTE, and HST. We have been asked by astronomers at
Space Telescope Science Institute, Lawrence Livermore National Laboratory,
Goddard Space Flight Center, and the IUE stations in Vilspa, Spain, and in
Germany to continue to monitor SS Cyg closely and to inform them of the start
of outbursts from now until the end of the year.
Please monitor SS Cyg and phone, fax, or email your observations to AAVSO
Headquarters, particularly when you see the star brightening, i.e., growing
brighter than magnitude 11.5, so we may inform the astronomers interested.
REQUEST TO MONITOR 0207-63 WX HYDRI
Astronomers at the Space Telescope Science Institute will be observing WX Hyi
with HST in the second half of 1996. They have asked us to monitor WX Hyi
closely all year long in order to have good coverage of its behavior.
We ask our southern hemisphere observers please to monitor WX Hyi closely
throughout the year, and report their observations to AAVSO Headquarters.
REQUEST TO MONITOR 0324+43 GK PERSEI
We have been asked to monitor GK Per closely (see AAVSO Alert Notice 211)
and to inform astronomers in England as soon as it starts to brighten.
GK Per, which shows minor outbursts every 2-1/2 to 3 years, is now overdue for
a minor outburst. Thanks to all of you, it is being very closely monitored.
The following recent observations indicate that it has been showing some
activity, which may be a prelude to a minor outburst:
Jan 15.1438 UT, 13.1, J. McKenna, Upper Montclair, NJ; 16.1618, 13.1, McKenna;
19.1417, 13.0, W. Dillon, Missouri City, TX; 21.0528, 13.2, J. Bortle,
Stormville, NY; 26.0257, 13.1, Bortle; 29.1347, 13.2, McKenna; Feb 1.0278, 13.1,
Bortle; 04.912, 13.0, G. Poyner, Birmingham, England; 7.0042, 13.1, Bortle;
11.1861, 12.9, T. Burrows, Novato, CA; 13.0188, 13.0, Bortle; 13.1097, 13.1,
McKenna; 13.899, 13.1, Poyner; 14.0278, 13.0, Bortle; 15.1493, 12.9, Dillon.
We once again remind observers to keep a close eye on GK Per and to call in
your observations, particularly if you see it brighter than magnitude 12.7.
The last outburst of this nova occurred in July 1992.
FOLLOW-UP ON INTERNET SERVICE
Following up on our warning of possible Internet service interruption (see
AAVSO Alert Notice 217) due to the US federal budget impasse, we are happy to
inform you that our network connection was NOT affected, and we continue to
have very satisfactory connection to the Internet, and we thank NASA
Astrophysics and NASA Science Internet for this. We invite our observers who
have access to the Internet to visit our home page, where we have recently
posted new light curves, including those of AM Her and N Cas 95, and some
charts. We will continue to do this periodically. We welcome suggestions and
recommendations from our observers and readers.
CHARTS AVAILABLE ON AAVSO FTP SITE AND AAVSO HOME PAGE
Chart links are obsolete; 11/2013 create charts using VSP at http://www.aavso.org/vsp
We have prepared electronic copies of the AAVSO charts of AM Her, V1159 Ori,
and N Cas 95 mentioned in this Alert Notice. They are available from our FTP
ftp.aavso.org (18.104.22.168), in /pub/alert218
They have also been placed on our home page:
The answering machine at AAVSO Headquarters is on nights and weekends for your
convenience. Please call our charge-free number (800-642-3883) to report your
observations. We also encourage observers to send observations by fax to
617-354-0665 or by e-mail through the Internet to email@example.com.
Many thanks for your valuable astronomical contributions and your efforts.
Janet A. Mattei
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