Central Bureau for Astronomical Telegrams
IAUC 4111: 4U 1705-44; N Vul 1984 No. 2
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Circular No. 4111
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-495-7244/7440/7444
4U 1705-44
M. Sztajno, A. Langmeier, J. Frank, J. Trumper, G. Hasinger
and W. Pietsch, Max-Planck-Institut fur Extraterrestrische Physik
and Max-Planck-Institut fur Astrophysik; and J. van Paradijs,
University of Amsterdam, telex: "We have discovered x-ray bursts from
4U 1705-44 during observations with EXOSAT during Sept. 11.40-
12.54 UT. A total of 14 type-I bursts were observed. The waiting
time was between 111 and 151 min for 12 bursts with a duration of
~ 90 s. Much weaker bursts were observed 6 and 18 min after the
seventh and tenth bursts, respectively; their duration was only 30
s and their peak flux a factor of two smaller than the preceding
bursts. The persistent flux was near 1.1 x 10**-12 J m**-2 s**-1 (1-20
keV) and did not change noticeably during the observation. The
ratio of the gravitational energy released between two main bursts
to burst energy is ~ 40, and the ratio of the persistent flux to
the peak flux is ~ 0.1. In our earlier EXOSAT observation (1983
July 30), when the persistent flux was ~ 12 times higher, no
bursts occurred. However, six absorption dips with a periodicity
of 4700 s and 400 s duration were then observed. The absence of
these dips in our recent observation suggests that the accretion
disk is thinner at lower luminosity."
NOVA VULPECULAE 1984 No. 2
R. D. Gehrz, Department of Astronomy, University of Minnesota;
and G. L. Grasdalen and J. A. Hackwell, Wyoming Infrared
Observatory, report infrared photometry and spectrophotometry of
Nova Vul 1984 No. 2 on Aug. 13.4 and 23.4 UT that suggest that
silicate grains have formed in the ejecta. These observations
were made ~ 230 and 240 days after day zero (1984 Dec. 25.0) with
the 2.34-m Wyoming Infrared Telescope. N and Q photometry indicates
that both the 10- and 20-micron silicate emission features are
present. Spectrophotometry at lamba/Delta-lambda ~ 67 in the 10-micron
atmospheric window is consistent with emission from a 10-micron silicate
feature and shows that 12.8-micron [Ne II] emission is still strong with a
peak intensity of ~ 16 Jy. Preliminary reduction of the photometry
for Aug. 23.4 gives infrared magnitudes of [2.3 microns] = 8.1,
[3.6 microns] = 6.9, [4.9 microns] = 6.3, [8.7 microns] = 4.7, [10.0 microns]
(narrow band) = 3.0, N = 3.1, [11.4 microns] = 2.8, [12.6 microns] = 2.3,
Q = 2.0.
1985 September 23 (4111) Brian G. Marsden
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