6P/d'Arrest

A'Hearn. M. F. et al.    Icarus 118, 223-270, 1995
"The Ensemble Properties of Comets: Results from Narrowband Photometry of 85 Comets, 1976-1992"
 

Data for a complete apparition

log Q(CN)/Q(OH)	=	-2.62
log Q(C2)/Q(OH)	=	-2.37
log Q(C3)/Q(OH)	=	-4.26
log Q(NH)/Q(OH)	=	-2.27

log Q(OH) max = 27.47 at 1.41au --> log Q(H₂O) = 27.9 max at perihelion based on derived active area

¤¤¤¤¤

Campins, H. and Schleicher, D. G.    27th DPS Abstracts, p. 59, 1995
"Comet d'Arrest: A Small and Rapidly Rotating Nucleus?"

• Observations obtained with IRTF on 2-5 August 1995
• Nucleus is non-spherical
• Mean radius = 3.5±0.15km (assuming an isothermal latitude model)
• Mean radius = 2.3±0.10km (assuming a standard thermal model)
• Lightcurve amplitude is 25%
• Period less than 5 hours [Note: D. Schleicher says ~3 hours with 1 day precession (personal comm. 1999)]

¤¤¤¤¤

Photometry of d'Arrest in 1976, 1982 with individual observations on many dates. Produced Q(OH) and Afrho normalized to 1.5au.

• Q(OH) = 9.8E27
• Afrho = 100

¤¤¤¤¤

Festou, M. et al.    ACM91 pp 177-182, 1992
"The Gas Production Rate of Periodic Comet d'Arrest"

Gives IUE OH measures and ground-based C₂ and CN from 1982 apparition.

• Lightcurve: brightness maxima occur 40 ± 20 days after perihelion and has not changed much since discovery
• Q(H₂O)= 1.2-3.0e28 mol/sec    (factor of 10 below above Copernicus data)
• Afrho = 190 cm (1/10 Halley) --> dust does not contribute much to the coma
• conclude that much of the surface may be active (half of nucleus?) but may have a strong seasonal effect

¤¤¤¤¤

• Argues a linkage of comet d'Arrest with comet La Hire in 1678.
• d'Arrest "does not exhibit any secular fading but has the most pronounced recurrent asymmetry of the light curve among all short-period comets."
• steep increase 3-4 weeks post-perihelion, followed by an almost constant brightness level persisting over one to two months.
• Almost no change in absolute magnitude over three centuries
• Argues that the main active area is situated near one of the rotation poles.

¤¤¤¤¤

1AU production rates: 14 Oct 1982 R=1.34

log Q(CN)	=	25.02
log Q(C3)	=	24.40
log Q(C2)	=	25.24

¤¤¤¤¤

Observations of d'Arrest were obtained on 19 Sep and 3 Oct 1976 when d'Arrest was at R=1.27 and 1.34au and delta=0.31 and 0.43au. The doppler shift was not sufficient to separate the cometary and geocoronal Ly alpha lines so they were modeled. Values for the cometary Ly alpha brightness of 1.2 and 3.4 kR were derived. Hydrogen production rates (scaled to 1au) of 0.8e29 and 3.3e29 were derived (within a factor of 2 or 3 of west).

[editorial comment: these results seem implausible with the production rate so high. Inconsistent with the CN production rate using normal ratios. Suspect the geocoronal was improperly modeled]

¤¤¤¤¤

A'Hearn, M. F. et al.    AJ 84, 570-579, 1979
"Gas and Dust in Some Recent Periodic Comets"

Production Rates (Perihelion on 12 Aug 1976) 

Date	R	delta	log Q(CN)	log Q(C2)	diaphram  (arcsec)
12 Aug 76	1.164	0.151	25.12	25.60	109/78
13 Aug 76	1.164	0.151	25.10	25.49	78
14 Aug 76	1.164	0.152	25.14	25.47	78
19 Aug 76	1.167	0.158	25.23	25.63	78
31 Aug 76	1.189	0.204	25.26	25.66	155
14 Sep 76	1.238	0.285	25.49	25.97	155
20 Oct 76	1.447	0.566	25.38	25.83	155

 

¤¤¤¤¤

Fay, T. D. and Wisniewski, W.   Icarus 34, 1-9, 1978
"The Light Curve of the Nucleus of Comet d'Arrest"

• Obtained photometry on 4,5, and 6 August 1976, just prior to perihelion.
• First two nights in a V filter and last night in a continuum only filter.
• Also obtained colors.
• Derive a period of 5.17±0.01 hr (sort of double peaked) which is the same on all 3 nights. Agreement good.
• Color never changes.
• Aperture = 16 arcsec = 1000km so includes some coma.
• Amplitude 0.15±0.02 mag.

¤¤¤¤¤

• The first detection of radio OH in a short-period comet.
• Found the 1665MHz feature in emission and the 1667MHz feature in absorption but argue they are real anyway.
• Derive Q=3.1e27 mol/sec

Last modified 25 June 1999

Additional references or comments: anita@barolo.as.utexas.edu