Central Bureau for Astronomical Telegrams
IAUC 4578: PKS 0537-441; 1987A
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Circular No. 4578
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
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
PKS 0537-441
R. Falomo, University of Padua; P. Bouchet, European Southern
Observatory; and L. Maraschi, E. G. Tanzi and A. Treves, Istituto di
Fisica, Milan, communicate: "Simultaneous optical spectrophotometry
(with the ESO 1.52-m telescope + BC + CCD) and infrared photometry
(ESO-MPI 2.2-m + InSb photometer) of the BL Lac object PKS 0537-441
were obtained on Jan. 7.5 and 9.5 at visual brightness close to the
faintest yet recorded: B = 17.6. An emission feature (FWHM 10 nm,
equivalent width 3.5 nm) was clearly present at 531.0 nm. This
feature, first reported by Petersen et al. (1976, Ap.J. 207, L5), was
absent in a number of spectra obtained subsequently by us at higher
intensity level. The infrared to optical spectral slope (alpha nu =
1.2) is close to that pertaining to higher intensity states (Tanzi et
al. 1986, Ap.J. 311, L13).
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
M. R. Haas, S. W. J. Colgan, E. F. Erickson, S. D. Lord and
M. G. Burton, NASA/Ames Research Center, communicate: "Singly ionized
iron lines at 26.0 and 17.9 micrometers were measured with 380 km/s
resolution from NASA's Kuiper Airborne Observatory on Apr. 5 and 7
during a deployment to Christchurch, New Zealand. The line profiles
are roughly gaussian and have similar FWHMs of about 3000 km/s; their
centroids are somewhat redshifted relative to the LMC. The similarity
of the two profiles suggests that the lines originate in the same
volume of gas. Since the 17.9-micrometer line is produced in a
transition that lies roughly 3000 K above the 26.0-micrometer
ground-state transition, the similarity in the line shapes also
implies that the temperature is fairly uniform throughout the ejecta.
The relatively large FWHM of the lines suggests that the iron is well
mixed with the material originally further from the center of the
star. If the line centers are optically thick, they imply a minimum
temperature of 3000 K. The signal-to-noise ratio of these
measurements is substantially better than we obtained for the
26-micrometer line in 1987 Nov. (Ap.J. Lett., in press). The line
flux appears to have increased somewhat since our previous
measurement, implying that this line was partially optically thick
last November, as inferred in the above reference."
Visual magnitude estimate by A. C. Beresford, Adelaide, South
Australia: Apr. 11.54 UT, 7.3.
1988 April 11 (4578) Brian G. Marsden
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