Detection of Six Trans-Neptunian Binaries with NICMOS: A High Fraction of Binaries in the Cold Classical Disk

Abstract

We have analyzed a homogeneous set of observations of 81 trans-Neptunian objects obtained with NIC2 on the Hubble Space Telescope with the goal of identifying partially resolved binaries. Using PSF fitting we have identified six likely binaries in addition to the three new binaries already found in this data set. We find that 11 þ5 À2 % of transNeptunian objects are binaries at the separation and brightness limits of NIC2. The identification of these new binaries significantly increases the known lower limit to the binary fraction among trans-Neptunian objects. The origin of such a high fraction of binaries remains to be determined. Most interestingly, detectable binaries appear to be about 4 times more common among the cold classical disk than in the dynamically excited populations.

Discovery of a binary Centaur

“…The iterative PSF fitting is described in detail in Stephens and Noll (2006). We found a separation of 4.36±0.08 pixels, equal to an angular separation of 0.109±0.002 arcsec.…”

“TNOs are Cool”: A survey of the trans-Neptunian region

“…(79360) 1997 CS 29 is a dynamically cold object with at least one satellite (Stephens & Noll 2006) and with an orbit very close to the Neptunian 7:4 MMR. The NEATM analysis of the two PACS measurements was not conclusive, only an unrealistically high η-value above 5 could connect the two fluxes.…”

Evidence for two populations of classical transneptunian objects: The strong inclination dependence of classical binaries

“…The detection limit in these cases is determined, in part, by the brightness of the primary, as shown by Stephens and Noll (2006) in their Figure 2. It is interesting to note that given sufficient S/N, i.e.…”

“…Any such fraction must be qualified by the detection limits of the instrument configuration used to carry out the observations. As the number of detected binaries increases, it is becoming clear that the fraction of detectable TNBs is a function of factors beyond instrument sensitivity (Stephens and Noll 2006).…”