Bibcode
Campins, H.; Licandro, J.; Ziffer, J.; Fernandez, Y. R.; Hora, J.; Kassis, M.; Pinilla-Alonso, N.
Referencia bibliográfica
American Astronomical Society, DPS meeting #37, #16.02; Bulletin of the American Astronomical Society, Vol. 37, p.645
Fecha de publicación:
8
2005
Número de citas
0
Número de citas referidas
0
Descripción
We present initial results from infrared and visible observations of two
comet-asteroid transition objects. 944 Hidalgo is one of the asteroids
most likely to be an extinct or dormant comet. Comet 162P/Siding Spring
(henceforth 162P), displayed intermittent cometary activity shortly
after discovery in late 2004. This comet is the third inner solar system
object observed to have intermittent cometary activity even when
relatively close to the Sun (the others are 107P/Wilson-Harrington and
133P/Elst-Pizarro). Thermal infrared observations (at 8.7, 9.8, 11.7 and
24.5 microns) of 162P were obtained with MIRSI on NASA's infrared
telescope facility (IRTF) on Mauna Kea, Hawaii on UT Dec. 27, 2004.
These represent one the most complete samples of a comet nucleus'
spectral energy distribution and yield an effective radius of 6.0
± 1.0 km. Using an absolute visible magnitude of H=13.7, the
V-band albedo is 0.045 ± 0.015. Near-infrared spectra in the
0.8-2.4 micron region were obtained on UT Oct. 23 (Hidalgo) and Dec. 11
(Hidalgo and 162P), 2004 using SpeX on IRTF (Oct.) and NICS on the
Telescopio Nazionale Galileo (TNG) on La Palma, Spain (Dec.). Visible
spectra of both objects from 0.3 to 0.9 microns were obtained on UT Dec.
12, 2004 with ALFOSC at the Nordic Optical Telescope (NOT) on La Palma,
Spain. The visible and infrared reflectance spectra of both objects are
nearly identical, with a mean slope typical of D-type asteroids, and
they display no strong absorption features. The spectral similarity with
162P is consistent with, but does not prove, the cometary nature of
Hidalgo. A search for spectral variability with rotational phase in
Hidalgo yielded no obvious spectral changes. We also obtained spectra of
Hidalgo in the 2 to 4 micron region with SpeX at the IRTF and detected
no strong spectral features in this region due to ices, hydrated
minerals or organics.