Visible spectroscopy in the neighborhood of 2003EL₆₁

¹ Fundación Galileo Galilei & Telescopio Nazionale Galileo, PO Box 565, 38700 S/C de La Palma, Tenerife, Spain e-mail: npinilla@tng.iac.es
² Instituto de Astrofísica de Canarias, c/Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain

Received: 20 May 2008
Accepted: 15 July 2008

Abstract

Context. The recent discovery of a group of trans-neptunian objects (TNOs) in a narrow region of the orbital parameter space and with surfaces composed of almost pure water ice, being 2003 EL₆₁ its largest member, promises new and interesting results about the formation and evolution of the TNb and the outer Solar System.

Aims. The aim of this paper is to obtain information of the surface properties of two members of this group ((24835) 1995 SM₅₅, (120178) 2003 OP₃₂) and three potential members (2003 UZ₁₁₇, (120347) 2004 SB₆₀ and 2005 UQ₅₁₃) and to use that in order to confirm or reject their association.

Methods. We obtained visible spectra of five TNOs using the 3.58 m Telescopio Nazionale Galileo at the “Roque de los Muchachos Observatory” (La Palma, Spain).

Results. The spectra of the five TNOs are featureless within the uncertainties and with colors from slightly blue to red (%/0.1 μm). No signatures of any absorption are found.

Conclusions. We confirm the association of 1995 SM₅₅ and 2003 OP₃₂ with the group of 2003 EL₆₁ as their spectra are almost identical to that of 2003 EL₆₁. Only one of the three candidates, 2003 UZ₁₁₇, can be considered as a possible member of the EL₆₁-group, as its visible spectrum is compatible with a spectrum of a surface composed of almost pure water ice and no complex organics. The other two, 2004 SB₆₀ and 2005 UQ₅₁₃ are red and must be considered as interlopers.