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Spectroscopic observation of comet C/2009 P1 (Garradd)

ATel #3784; M. M.M. Santangelo
on 28 Nov 2011; 15:07 UT
Credential Certification: Filippo Mannucci (filippo@arcetri.astro.it)

Subjects: Comet

M.M.M. Santangelo, Astronomical Observatory of Capannori (OAC) Italy, on 17.73 UT and 26.71 UT October 2011, obtained low dispersion CCD long-slit spectra from 350 to 950 nm of comet C/2009 P1 Garradd, at r = 1.8 AU. These spectra were obtained with OAC's 0.30-m telescope and Sbig DSS7 spectrometer + Sbig ST9-XE CCD camera, through three different 50, 100 and 200 microns wide slits at the dispersion of 1.2 nm/pixel. OAC's spectra of comet Garradd are dominated by Swan's emission bands of C2(0,0) at 516.5 nm , C2 (+1,0) at 473.7 nm, C2(-1,0) at 563.5 nm ; other emission bands are those of [OI] + NH2 at 630.0 nm and CN (0,0) at 388.3 nm. Weak emission bands of C2at 556.6 nm, C3at 404.3 nm and NH2at 609.8 nm can be detected. The comet spectrum can be classified as C1E2s(1.8) or C2E3s(1.8) in Bouska's classification scheme (Bouska 1974, NASA SP-393, part2, page 840). OAC's spectra of the comet Garradd have some resemblance with those of comets Kobayashi-Berger-Milon 1975h (at r = 0.78 AU) and P/Encke 1980, but with a weaker CN at 388.3 nm; our spectra are quite different from those of the same comet C/2009 P1 Garradd taken by C.Buil on July 2nd 2011 available on the Internet.