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Notiziario n. 0 - Giugno 1994

Circolari I.A.U.

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

(2060) CHIRON

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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