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[vsnet-campaign-news 6] News from VSNET No. 6
*** News from VSNET ***
VSNET (Variable Star Network) is an international variable star observing
network, covering various areas of novae, supernovae, cataclysmic variables
(CVs), X-ray transients, and other classical eruptive, pulsating, and
eclipsing variables. VSNET is one of invited contributing organizations
to the SkyPub AstroAlert system.
The "News from VSNET", mainly focusing on recent remarkable activities of
CVs and related systems, is issued on a weekly basis, except on occasions
of extremely urgent or transient events.
Please refer to the VSNET Home Page for more details of events and
objects listed.
VSNET Home Page: http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/
VSNET provides a number of mailing lists, on which various news and topics
are discussed. Subscriptions to the VSNET mailing lists are free of charge;
please refer to the instruction on the above page if a reader needs more
information of the list structure.
Regards,
Taichi Kato
On behalf of the VSNET administrator team
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The following was issued on Jun. 12, 2000, as VSNET campaign circulation 202.
XTE J1118+480 is the unusual X-ray nova in Ursa Major (IAUC 7389),
whose optical counterpart was discovered by the VSNET team and announced
as vsnet-alert 4503 and IAUC 7390. The reported slow fading seem to have
become apparently stopped. Hump features with a changing profile has been
continuously observed. Recent studies have clarified that X-ray and optical
correlations of QPOs (what were observed by the ASCA-VSNET collaborations)
provide an unprecedented opportunity in unveiling the mystery of accretion
disk where the matter becomes swilled by the black hole! The vast amount
of data collected on this "once-in-decades" black hole X-ray nova have been
being intensively analyzed. The VSNET Collaboration on XTE J1118+480 page:
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Xray/xtej1118-camp.html
Several other interesting dwarf novae are reported in outburst, and
followed by a number of observers. Particularly interesting is the helium
dwarf nova V803 Cen, which has undergone an extremely bright superoutburst,
showing prominent superhumps (the binary is believed to have a ultrashort
period of 27 min!). The present outburst is one of the best-studied
outbursts of helium dwarf novae. Visual observations can also greatly
contribute to the V803 Cen campaign, by intensively following large-amplitude
fluctuations or outbursts (up to 1-1.5 mag) with a time-scale less than
a day. Very frequent observations and multilongitude coverage are of key
importance. The sample light curves by Jennie McCormick, Fred Velthuis
and Stan Walker can be seen at:
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-campaign/mag00201.html
CCD observations of such targets are a relatively easy task for a 20-40cm
telescope; simply take as many CCD frames (with exposure times 10-30 sec)
as possible, spanning several hours per night. The only requirements are
the weather and your patience! If you need more help on the observing
technique, please feel free to ask on the vsnet-campaign list.
CI Aql = the recurrent nova Aql 1917,2000 has entered the rapid decline
stage. R. J. Bouma has provided a detailed chart using Henden's V-magnitude
sequence down to mag 15 (see the URL below). The chart will be very useful
especially for visual observers. Time-series CCD observations at all binary
phases would clarify the evolution of emerging eclipse profile, necessary
for modelling the binary parameter.
We would sincerely appreciate volunteers who would join the VSNET
Collaboration team to study the wonders of these exotic variable stars.
To join the VSNET campaign collaborative list, send an e-mail to
vsnet-adm@kusastro.kyoto-u.ac.jp (VSNET administrator)
with a line "SUBSCRIBE vsnet-campaign."
(VSNET campaign members are strongly recommended to subscribe to vsnet-alert
at the same time).
Other current topics in other VSNET mailing lists include discussion on
eta Carinae, recent supernovae, new cataclysmic variable candidates,
"world-record run" of visual observations etc.
The on-line light curves at the VSNET Website have been also greatly
updated by courtesy of the AFOEV (Association Francaise des Observateurs
d'Etoiles Variables) and the VSOLJ (Variable Star Observers' League in Japan).
Light curves drawn from more than 2 million and 1.4 million observations,
respectively, can be now easily browsed.
AFOEV light curve entry page:
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/AFOEV/LCs/index/index.html
VSOLJ light curve entry page:
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/VSOLJ/LCs/index/index.html
VSNET light curve entry page:
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/LCs/index/index.html
Select the constellation name from these pages, and select the variable
star name. By clicking "years" button, such as [1995], under each light
curve, you can reach the desired enlarged segment of the light curve.
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VSNET Weekly Campaign Summary
*** Last week news ***
(new targets)
V493 Lyr (RA = 19h01m31.9s, Dec = +42d54m46.5s)
G. Poyner reported the outburst of V493 Lyr at 14.2mag on June 6
(vsnet-alert 4949). The last recorded outburst occurred during August
1999. G. Hanson confirmed the outburst (vsnet-alert 4950).
T. Vanmunster observed on June 07/08 and the resulting light curve
is extremely flat, showing no variability and definitely no superhump
structure. He also noticed that it did not exclude of course the
development of superhumps over the next days (vsnet-campaign 193).
The outburst is now ongoing. Time-series observations are encouraged
to study the short time modulation.
(continuous targets)
V803 Cen (RA = 13h23m44.5s, Dec = -41d44m30.1s)
William S G Walker successfully detected the superhumps during this
superoutburst (vsnet-campaign 176). In vsnet-campaign 201, he posted
light curves from Farm Cove (Jennie McCormick and Fred Velthuis) and
Wharemaru (Stan Walker) which illustrate the strongly periodic 27 minute
signal. It has suddenly faded from 13.0mag on June 7 to 14.1mag
on June 8 (vsnet-campaign 192), and then, as reported by R. Stubbings
and A. Pearce, it has rebrightened up to 13.4mag on June 11
(vsnet-campaign 198). According to the Walker's report, it seems
that the star may now have recovered to the bright level where it
cycles between 13.4 and 14.8 over a period of 22 to 24 hours.
In 1999 and 2000 there were indications that this cycling period may
have become even shorter (vsnet-campaign 201).
Superhump phasing observations are very important at this stage
of outburst. Observations are strongly requested.
CI Aql (RA = 18h52m03.6s, Dec = -01d28m38.9s)
From the data on June 5 by Kyoto team, the object rose by 0.25 mag
in 1.5 hour and the time of eclipse-like minimum corresponds to the
predicted primary eclipse. This observation may indicate the growing
eclipse feature as the system fades (vsnet-campaign 178). The rapid
fading trend has apparently stopped on June 6. Smooth variation was
present on the June 6 light curve, whose light maximum closely
corresponds to the binary phase 0.75 (vsnet-campaign 184).
The fading trend is again apparent on June 7 (vsnet-campaign 187).
In this phase, clear eclipses are expected. Time-series photometry
is strongly encouraged.
V660 Her (RA = 17h42m07.3s, Dec = +23d47m37.3s)
The superoutburst continues. It keeps gradual fading but still bright
on June 10 (15.1mag) (vsnet-campaign 200). The superhump (or possibly
late superhump) should be observed.
XTE J1118+480 (RA = 11h18m10.9s, Dec = +48d02m12.9s)
The object again show the slight fading trend from short plateau
(vsnet-campaign 183). This fading trend has apparently become slower
again (vsnet-campaign 197).
The object is still bright and the humps are prominent. To study
the period change, more observations are encouraged.
BD Pav (RA = 18h43m12.0s, Dec = -57d30m45.1s)
The eclipsing dwarf nova BD Pav has finally entered the decline stage
from the current rare outburst since June 10 (vsnet-campaign 196).
On June 11, it kept fading to quiescence (vsnet-campaign 199).
We should keep attention to detect the possible rebrightenings.
*** General information ***
CI Aql
As the system is fading beyond many of conventional charts, R. J. Bouma
has provided a detailed chart using Henden's V-magnitude sequence down
to mag 15. The chart is available either from the CI Aql top page
(http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Novae/ciaql.html) or directly at
http://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/Novae/nova_aql00/ci-f-bouma.gif
BD Pav
eclipse ephemeris, see [vsnet-campaign 180] and [vsnet-campaign 196]
V803 Cen
the light curve sent from William S G Walker, see [vsnet-campaign 201]
(This summary is reproduction free.)
Regards,
Makoto Uemura
vsnet-adm@kusastro.kyoto-u.ac.jp
Return to Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
VSNET Home Page