2060 Chiron back to a minimum of brightness

Properties of the nuclei of Centaurs Chiron and Chariklo

“…But later in 1996, when Chiron was at a comparable level of activity, Lazzaro et al (1997) determined a very different value, G = 0.42. We do concur with Lazzaro et al (1996) that the correction for the phase effect poses a problem because of the activity of Chiron resulting in a variable coma and that the (H, G) formalism may not be appropriate in this case. In view of this situation, we decided to adopt the simple linear phase function with a coefficient β = 0.05±0.01 mag deg −1 , typical of cometary nuclei and also consistent with the data of Bus et al (1989).…”

New Activity of Chiron: Results from 5 Years of Photometric Monitoring

“…The observations, however, readily demonstrated that Chiron is indeed a very peculiar Centaur: as it approached perihelion, the brightness of Chiron was continuously diminishing (Bergeron andVanouplines 1995, Lazzaro et al 1996). Photometric and spectroscopic observations of Chiron, performed all along its passage through perihelion (Lazzaro et al 1997), indicated that it was still in a minimum of activity, very close to that of 1983-1985 and 1994-1995. Therefore, the large increase in brightness occurred in the period 1988-1991 and was preceded and followed by periods of minimum activity, which tend to indicate quasi-periodic behavior (Lazzaro et al 1996). The analysis of prediscovery photometric plates of Chiron indicated (Bus et al 2001, hereafter B01) that another outburst of activity probably occurred around aphelion, in 1972-1973, which reinforces the idea of some kind of sporadic activity.…”

“…However, the absolute magnitude is still used here in order to compare our results with those published by other authors (Bus et al 1989, Lebofsky et al 1984, Hartmann et al 1981 al. 1982, Marcialis and Buratti 1993, Hartmann et al 1990, Luu and Jewitt 1990, Bus et al 1988, Meech and Belton 1990, Buratti and Dunbar 1991, West 1991, Luu and Jewitt 1993, Lazzaro et al 1996, Lazzaro et al 1997, Davies et al 1998 and is recompiled in B01. The usual value of G = 0.70 ± 0.15 for the slope parameter (Bus et al 1989) was used.…”

(2060) Chiron: Evidence for Activity near Aphelion

“…Observations by Lazzaro et al (1996) taken in 1995 showed that Chiron had again returned to a minimum brightness level, even though perihelion passage occurred in early 1996, when cometary activity might be expected to peak. Ultraviolet spectra obtained with the HST Faint Object Spectrograph (Parker et al 1997) did reveal a 60% increase in Chiron's continuum flux over a 3-month interval in early 1996, though no molecular emission bands were detected in association with the flux increase.…”