Central Bureau for Astronomical Telegrams
IAUC 6086: X-RAY N IN Sco; 1994m
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Circular No. 6086
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
Phone 617-495-7244/7440/7444 TWX 710-320-6842 ASTROGRAM CAM
MARSDEN@CFA.HARVARD.EDU or GREEN@CFA.HARVARD.EDU (science)
X-RAY NOVA IN SCORPIUS
R. M. Hjellming and M. P. Rupen, National Radio Astronomy Observatory,
report: "We have obtained 13 epochs of VLA 22.5-GHz images (Aug. 18-Sept.
29) of the resolved radio source identified with GRO J1655-40. The
earliest maps show a double source evolving to a triple; this, together
with VLBA images at much higher resolution taken on Aug. 18, 22 and 25 at
1.7 GHz, supports the conclusion that we are seeing twin-jet ejection of
relativistic plasma from the central component. The originally-reported
(IAUC 6073) total separation rate of 0".056 per day can now be separated
into the oppositely-directed linear motions of the two outer components,
the one to the northeast moving at 0".040 +/- 0".005 per day, the one to
the southwest at 0".020 +/- 0".005 per day. An additional (fourth)
component appeared northeast of the core in our maps on Sept. 11, our
first observation following the radio outburst on Sept. 6 (IAUC 6077);
this component also appears to be moving at 0".040 per day, along the same
trajectory as the original northeast blob. Assuming a distance of 3.5 kpc
(IAUC 6062), these expansion rates indicate apparent transverse speeds
with respect to the central component of 0.8c for the northeast components
and 0.4c for the one to the southwest. This relativistic motion is
supported by the relative brightnesses of the components, with the blobs
to the northeast being more prominent than those to the southwest. Taking
the apparent difference in speeds as a relativistic effect, we find an
intrinsic speed for the ejecta of (0.33 +/- 0.12)c/cos theta, where theta
is the inclination of the trajectory to the line-of-sight. This implies
that the angle to the line-of-sight is 70 deg or less, suggesting there
should be a significant radial-velocity component in any spectral lines
associated with the jet. The preliminary VLBA images show that all
three of the components seen at early times had complex structure
elongated along the apparent directions of motion. The central component
continues to show variations in flux density (based on multifrequency
VLA monitoring) that are most prominent at frequencies above 8 GHz.
Given the high apparent velocities, frequent optical spectroscopy is
urgently needed."
COMET NAKAMURA-NISHIMURA-MACHHOLZ (1994m)
Total magnitude estimates: Sept. 3.04 UT, 9.0 (J. D. Shanklin,
Cambridge, England, 0.20-m refractor); 6.22, 8.2 (C. E. Spratt,
Victoria, BC, 0.20-m reflector); 9.20, 8.3 (Spratt); 12.20, 8.8
(Spratt); 25.47, 12.8 (A. Nakamura, Kuma, Shikoku, Japan, 0.60-m
reflector + unfiltered CCD); 27.46, 10: (P. Camilleri, Cobram,
Victoria, Australia, 20 x 80 binoculars).
1994 October 1 (6086) Brian G. Marsden
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