Circular No. 5497 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Postal Address: Central Bureau for Astronomical Telegrams Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Telephone 617-495-7244/7440/7444 (for emergency use only) TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505 MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU) NOVA CYGNI 1992 R. D. Gehrz, Department of Astronomy, University of Minnesota, reports near-simultaneous infrared measurements on Apr. 12.5 UT by T. J. Jones, G. Lawrence and himself, using a multifilter bolometer on the 0.75-m telescope at the O'Brien Observatory, and by T. Hayward, J. Hauck and J. Miles, of Cornell University, using a 7-13-micron array spectrometer (lambda/dlambda = 2000) on the Hale 5-m telescope at the Palomar Observatory. The O'Brien photometry gives J = 6.0, H = 6.3, K = 5.8, L = 4.7, N = 2.9. The slope of the continuum beyond H is constant, showing that the nova is still in an optically thin, free- free expansion phase. The high-resolution data show the presence of emission from Humphreys alpha at 12.37 microns and of [Ne II] at 12.8 microns. Additional measurements by the Cornell group on Apr. 13.5 show that the hydrogen line is a factor of four and the neon line a factor of 13.5 above the continuum. The full width of the infrared lines appears to be about 3000 km/s. Further visual magnitude estimates: Apr. 10.09 UT, 7.6 (M. Verdenet, Bourbon-Lancy, France); 12.02, 7.6 (P. Rapavy, Rimavska Sobota, Czechoslovakia). PERIODIC COMET MUELLER 4 (1992g) Further precise positions have been reported as follows: 1992 UT R.A. (2000) Decl. m1 Observer Apr. 12.66736 14 11 26.19 +28 23 04.6 17 McNaught 14.77882 14 10 19.52 +28 41 24.5 17 Seki 14.79063 14 10 19.15 +28 41 28.6 " R. H. McNaught (Siding Spring). Uppsala Southern Schmidt. Object slightly diffuse; definitely cometary. T. Seki (Geisei). 0.6-m reflector. Communicated by S. Nakano. Computations from the available observations, Apr. 9-14, show that the comet is of short period: T = 1992 Jan. 27.560 TT Peri. = 37.481 e = 0.40498 Node = 146.151 2000.0 q = 2.62296 AU Incl. = 30.082 a = 4.40815 AU n = 0.106492 P = 9.26 years 1992 April 15 (5497) Brian G. Marsden
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