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Proposal Identification No.: A2324 Date Received: 2007­Apr­03 14:17:15
Technical Page
Proposal Type: Urgent
General Category: Astronomy
Sub­Category: Spectroscopy
Observation Category: Solar System
Total Time Requested: 12 Hours
Minimum Useful Time: 1 hour
Proposal Title: Arecibo OH Observations of C/2007 E2 Lovejoy
ABSTRACT:
We propose to observe recently discovered C/2007 E2 Lovejoy in April 2007. This comet is already quite bright
(M v =11) and is at perihelion on 27 March 2007. It becomes visible to the Arecibo telescope on 21 April, with
predicted OH line strength between 3­8 mJy. However, comets frequently have outbursts, and brighten on short
timescales, so the line could be stronger than predicted. We plan to map the 18­cm OH lines in the cometary coma
in a hexagonal pattern around the nucleus position. The line flux gives a measure of the OH production rate, and
thus the production of water from the nucleus. The ratio of the nucleus­centered line strength to the o#­center
coma positions is sensitive to the amount of collisional quenching. The line width is a direct measure of the
outflow velocity, which we have measured in 16 comets to date. The velocity depends on the heliocentric distance,
overall gas production rate, and varys widely among di#erent comets. The outflow velocity frequently changes at
heliocentric distance of 1 AU, so we will be observing this comet at the transition distance.
Name Institution E­mail Phone Student
Ellen Howell NAIC ehowell@naic.edu
Remote Observing Request
X Observer will travel to AO
Remote Observing
In Absentia (instructions to oper­
ator)
Instrument Setup
L­wide
Atmospheric Observation Instruments:
Special Equipment or setup: none
1

RFI Considerations
Frequency Ranges Planned
1612­1667 MHz
2