Notiziario n. 0 - Giugno 1994 |
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Circolari I.A.U. |
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a cura di Christian Lavarian (Associazione Astrofili Trentini) |
Queste circolari dell'Unione Astronomica Internazionale (IAU) sono prelevate dalla rete telematica Fidonet raggiungibile con un modem senza difficoltà. Chi avesse a disposizione un computer e fosse interessato a riceverle direttamente a casa può contattare Andrea Gelpi o Christian Lavarian.
Recent visual magnitude estimates indicate that the nova is now fading rapidly: Feb. 1.13 UT, 8.0 (J. Pleszka, Cracow, Poland); 2.12, 8.3 (C. E. Spratt, Victoria, BC); 3.09, 8.4 (J. D. Shanklin, Cambridge, England); 4.72, 8.5 (A. Lauvstad, Levanger, Norway); 5.86, 8.3 (P. Rapavy, Rimavska Sobota, Slovakia); 6.76, 8.2 (M. Verdenet, Bourbon-Lancy, France); 8.02, 8.2 (G. W. Kronk, Troy, IL); 9.11, 8.1 (R. Royer, Lakewood, CA); 10.23, 8.3 (P. Schmeer, Bischmisheim, Germany); 12.03, 8.5 (R. Hays, Worth, IL); 12.80, 8.4 (B. H. Granslo, Fjellhamar, Norway); 13.10, 8.6 (Royer); 13.73, 9.0 (Granslo); 14.76, 9.0 (Schmeer); 15.06, 9.2 (W. G. Dillon, Missouri City, TX); 15.78, 9.6 (Granslo); 16.04, 9.9 (Hays); 16.78, 10.1 (Schmeer); 17.06, 10.1 (Dillon); 17.77, 10.5 (T. Vanmunster, Landen, Belgium). 1994 February 17 (5934) Brian G. Marsden
IAUC 5906 discusses orbits that utilize the first postconjunction observations of nine of the nuclei. MPC 22931 contains orbits for two more nuclei, 16 and 19, for which preconjunction data could be linked with postconjunction data on two or more nights. MPC 23105-23107 include orbits for six more nuclei--2, 4, 8, 18, 20 and 21. However, the pre- to postconjunction linkage for nucleus 8 was incorrect. The correct linkage is shown on MPEC 1994-D02, which contains new orbits for nuclei 8 and 9. Much of the recent analysis depends on measurements by H. Weaver from images obtained with the Hubble Space Telescope (HST) during Jan. 24-27. These images, as well as the HST image of 1993 July 1, indicate that nuclei 7 and 8 are in fact double, the bright nucleus 7a having a faint companion 7b currently 1".2 to the north and the moderately bright nucleus 8b a somewhat fainter companion 8a currently 2".2 to the west. For orbit-determination purposes the original nuclei 7 and 8 are linked with the current 7a and 8b. The original nuclei 10 and 13 have disappeared. Nucleus 3 still appears to exist, but there are no other postconjunction measurements. The list of collision times with Jupiter given on IAUC 5906 can therefore be supplemented as follows: nucleus 21, July 16.8 UT; 20, 17.1; 19, 17.2; 18, 17.4; 16, 18.0; 9, 20.4; 8, 20.6; 4, 21.6; 2, 22.1. 1994 February 18 (5936) Brian G. Marsden
R. J. Cumming, Royal Greenwich Observatory (RGO); W. P. S. Meikle, Imperial College; and T. R. Geballe, Joint Astronomy Center (JAC), report: "Near-infrared spectra (resolution 800-1200 km/s) of SN 1994D were obtained by J. V. Wall (RGO), C. R. Jenkins (RGO), Geballe, and D. M. Walther (JAC) with the U.K. Infrared Telescope (+ CGS4) on Mar. 12.52 (J, H, K bands) and 13.51 UT (K only). The J-band spectrum shows a wide absorption feature centered at 1.052 microns and extending blueward as far as 1.036 microns. If this is due to a P-Cyg profile of He I 1.083-microns, it implies ejecta velocities as high as 14 000 km/s. On Mar. 12.52, the K-band spec- trum showed absorption features centred at 2.30, 2.33, 2.36, and 2.39 microns, all having a depth of 8-9 percent of the continuum. We identify these features with first-overtone CO absorption at the redshift of NGC 4526. The 2-0 band head at 2.300 microns is unre- solved at a resolution of 850 km/s. The spectrum of Mar. 13.51 shows the 2-0 band at approximately the same strength and the band head still unresolved, but the other CO bands have weakened considerably. An optical spectrum taken using ISIS on the William Herschel Telescope on Mar. 10.14 by L. J. Smith (University College London), M. Pettini and D. L. King (RGO), and C. Martin (Isaac Newton Group) shows no evidence for narrow emission or absorption in H-alpha associated with the supernova. We judge that the origin of the CO features must be intrinsic to the supernova system. This is supported by the change in their visibility. The early appearance and narrowness of the features imply that the CO lay above the ejecta." T. Shanks and S. M. Croom, University of Durham; and N. R. Tanvir, Insititute of Astronomy, report: "We obtained provisional photometry (+/-0.01) of SN 1994D using the Jacobus Kapteyn 1.0-m telescope: Mar. 10.16 UT, U = 13.4, B = 13.7, V = 13.7, R = 13.6, I = 13.7; 11.17, 12.8, 13.3, 13.3, 13.2, 13.2. The B-V color is close to the mean for type-Ia supernovae at maximum. The supernova appears 3"-4" to the north of a dust lane in this early-type galaxy. These observations are consistent with a Virgo type-Ia supernova nearing maximum in the next few days." P. M. Kilmartin and A. C. Gilmore, Mount John, report the fol- lowing equinox 2000.0 position for SN 1994D: R.A. = 12h34m02s.37, Decl. = +7o42'04".7 (corresponding 1950.0 position is R.A. = 12h31m29s.99, Decl. = +7o58'36".5). 1994 March 14 (5951) Daniel W. E. Green
M. P. Womack, Northern Arizona University; and S. A. Stern, Southwest Research Institute, report: "We have obtained millimeter- wave observations resulting in upper limits on the CO column abundance in the coma of (2060) Chiron. These observations were made during Feb. 25-26 UT using the Caltech Submillimeter Observatory on Mauna Kea; we observed the CO J = 2-1 transition at a frequency of 230 GHz (1.3 mm). Data were obtained with resolutions of both 50 and 500 kHz in good observing conditions (i.e., tau about 0.08). We achieved 3-sigma upper limits for the 2-1 emission of 75 and 35 mK at the 50- and 500-kHz resolutions, respectively. Assuming (i) Chiron's coma fills the 30" CSO beam and (ii) the gas excitation, rotational, and kinetic temperatures are all between 10 and 50 K, then for both resolutions, the upper limit corresponds to an average CO column density in the beam of < (3 +/- 1) x 10E13 cmE-2. A Haser model calculation, assuming an isotropic coma expansion at velocities of 0.2-0.5 km sE-1 and a CO line-width twice the coma expansion velocity, implies production-rate upper limits of Q(CO) < 6.5-15 x 10E27 sE-1, respectively, if CO is a parent molecule, and < 9.0-36 x 10E27 sE-1 if CO is the daughter product of an H_2CO parent. If the coma is not expanding isotropically, and instead the CO J = 2-1 line widths are much narrower (e.g., about 1/3 the coma expansion velocity), then the derived column densities and CO production limits could be up to five times lower." 1994 March 25 (5957) Daniel W. E. Green
J. L. Elliot, Massachusetts Institute of Technology (MIT) and Lowell Observatory; E. W. Dunham, Ames Research Center, NASA; and C. B. Olkin, MIT, report on the prediction and successful Kuiper Airborne Observatory (KAO) observation of the Mar. 9 occultation of the 11.9-mag star Ch08 (Bus et al., A.J., in press) by (2060) Chiron: "CCD-strip-scan observations were made by C. Ford (SETI Institute) and R. P. S. Stone (Lick Observatory) using the Crossley telescope at Lick. These data were reduced by S. W. McDonald, R. M. Bandyopadhyay, and their colleagues at MIT. The KAO optical light curve shows one integration interval of 0.5 s (at 23h28m55s UT, when the KAO was near Recife) to have a drop of about 60 percent, with lesser drops in several neighboring intervals on either side. This is similar in character to the occultation light curve for Ch02 obtained from Palomar on 1993 Nov. 7 (IAUC 5898). Simultaneous K- band observations were made but have not been reduced yet. The occulting object was almost certainly some structure within the coma near the nucleus rather than the nucleus itself. Other members of the KAO observing team were D. K. Gilmore, D. M. Rank, and P. Temi (University of California at Santa Cruz and Lick Observatory); D. Lazzaro (Observatorio Nacional) participated as Brazil's primary scientific representative." W. B. Hubbard, University of Arizona, writes: "Ground-based observations of the Mar. 9 occultation by Chiron were attempted in Brazil at the Pico dos Dias Observatory, Itajuba, by H. Reitsema (Ball Aerospace), A. Barucci (Paris Observatory), and J. Barroso (Observatorio Nacional), and by three mobile teams from MIT, Lowell Observatory, and the University of Arizona, working in collaboration with the Observatorio Nacional and the Paris Observatory (S. J. Bus, D. F. Lopes, M. Buie, B. Sicardy, R. Marcialis, D. W. Foryta), but no data were gathered due to clouds. At the South African Astronomical Observatory, Sutherland, conditions were photometric, and D. Kurtz (University of Cape Town) observed the occultation in Johnson V with the 0.5-m telescope, recording a single brief and deep event at about 23h23m45s UTC. The event lasted <0.5 s, with a maximum stellar signal drop of about 75 percent; it resembles the unresolved dips detected during the 1993 Nov. 7 Chiron occultation (IAUC 5898) and may be associated with an opaque feature a few km wide but extending some hundreds of km from the nucleus." 1994 April 5 (5965) Daniel W. E. Green
Parabolic orbital elements from MPC 23322: T = 1994 May 27.3322 TT Peri. = 57.3602 Node = 166.5614 2000.0 q = 1.160114 AU Incl. = 131.2843 1994 TT R. A. (2000) Decl. Delta r Elong. Phase m1 Apr. 8 7 56.00 +31 50.2 0.862 1.395 96.7 45.5 14.1 13 7 33.40 +35 23.2 0.972 1.354 86.6 47.7 14.3 18 7 15.24 +37 58.7 1.086 1.316 77.9 48.3 14.4 23 7 00.61 +39 56.1 1.201 1.281 70.4 47.7 14.5 28 6 48.72 +41 27.9 1.314 1.250 63.6 46.2 14.6 May 3 6 38.93 +42 42.5 1.423 1.223 57.4 44.0 14.6 8 6 30.74 +43 45.1 1.526 1.200 51.8 41.3 14.7 13 6 23.77 +44 39.5 1.622 1.182 46.6 38.4 14.8 18 6 17.73 +45 28.1 1.710 1.170 41.8 35.2 14.8 23 6 12.38 +46 12.5 1.789 1.162 37.5 32.0 14.9 28 6 07.55 +46 54.0 1.858 1.160 33.7 29.0 15.0 1994 April 8 (5970) Daniel W. E. Green
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