Central Bureau for Astronomical Telegrams
IAUC 8862: C/2006 P1; N Vul 2007
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Circular No. 8862
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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COMET C/2006 P1 (McNAUGHT)
C. M. Lisse and N. Dello Russo, Applied Physics Laboratory,
Johns Hopkins University; Y. Fernandez, University of Central
Florida; G. H. Jones, Mullard Space Science Laboratory, University
College, London; and M. Sitko, Space Science Institute, report that
the Spitzer Space Telescope's IRS instrument observed comet C/2006
P1 on May 4-5 (at r = 2.4 AU, Delta = 2.2 AU). A very round,
featureless coma with no obvious extension in the anti-sun
direction appeared as the central source of emission in the peak-up
imager at 16 microns. The 5- to 35-micron spectrum of the
outflowing dust showed only a mild excess (about 10 percent) due to
silicate emission at 8-13 microns. The flux density at 10 microns
was about 0.1 Jy, and at 20 microns was 0.6 Jy. The effective
temperature of the dust was 190 +/- 10 K. The local equilibrium
temperature at 2.4 AU was 182 K. Lisse et al. estimate a
production rate of dust to be about 6 x 10**3 kg/s. The spectrum is
remarkably featureless and dominated by infrared emission from
large particles, and is similar to that derived from comet-surface
mantles. This is unexpected for a comet that, in Dec. 2006-Jan.
2007, had demonstrated large outflows of material, a highly
structured dust tail due to the presence of 0.1- to 10-micron dust
particles, and was still emitting dust at the time of Spitzer
observations at a rate comparable to the strongly-mid-infrared-
featured comets C/1996 B2 (Hyakutake) and 1P/1982 U1 (Halley) when
passing closest to the earth. Lisse et al. further surmise that
either the comet has a very thick surface mantle that was only
temporarily breached during the perihelion passage by a jet or the
material being emitted in May 2007 is from a surface mantle that
has regrown since the comet's perihelion passage four months
earlier.
NOVA VULPECULAE 2007
C. Buil, Castanet, France, writes that a spectrogram of the
possible nova reported on IAUC 8861, obtained on Aug. 9.91 UT with
a 0.28-m telescope (+ Lhires spectrograph; resolution 6800 at
H_alpha), shows evident H_alpha with a deep P-Cyg profile and a
FWHM of 1750 km/s (+/- 80 km/s); the intensity of the H_alpha peak
intensity is 2.4 times that of the local 670-nm continuum.
M. Fujii, Kurashiki, Okayama, Japan, reports that a low-dispersion
spectrogram (range 375-833 nm; resolution about 1 nm) of the apparent
nova was obtained on Aug. 9.48 UT with a 0.28-m reflector; the
spectrum shows H_alpha, H_beta, H_gamma, and He I 447.2-, 471.3-,
492.2-, 501.5-, 587.6-, 667.8-, and 706.5-nm emissions with P-Cyg
profiles (H_alpha FWHM = 1900 km/s). These emissions suggest that
the variable is indeed a classical nova.
(C) Copyright 2007 CBAT
2007 August 10 (8862) Daniel W. E. Green
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