Bibcode
Campins, Humberto; Licandro, J.; Fernandez, Y.; Hergenrother, C.; Ziffer, J.; Emery, J.; Cruikshank, D.; Pinilla-Alonso, N.
Bibliographical reference
American Astronomical Society, DPS meeting #38, #20.04; Bulletin of the American Astronomical Society, Vol. 38, p.516
Advertised on:
9
2006
Citations
0
Refereed citations
0
Description
Dynamical arguments indicate that 944 Hidalgo is most likely an extinct
or dormant comet. Hidalgo's Tisserand invariant (T = 2.07) suggests
strongly that this object came either from the Kuiper belt or the Oort
cloud (e.g., Weissman et al. 2002). We obtained low-resolution
near-infrared spectra in the 0.8-2.4 micron region on UT Oct 22, 23, Nov
19 and Dec 11, 2004, using the SpeX instrument on NASA's Infrared
Telescope Facility (IRTF) on Mauna Kea, Hawaii (Oct. and Nov.) and the
NICS instrument on the Telescopio Nazionale Galileo (TNG) on La Palma,
Spain (Dec.). Our reflectance spectra show a range of slopes. To
characterize these slope differences, we normalized each spectrum to 1.0
reflectance at 1.25 microns and measured the reflectance at 2.2 microns.
These values are listed in the table for the seven spectra obtained on
the two dates when we have temporal coverage, Oct 22 and 23. The
uncertainty in each reflectance value is ± 3%. Hidalgo's
rotational light curve has a period of 10.06 hours and amplitudes
ranging from 0.31 to 0.6 magnitudes in the visible (Harris and Warner
2006, Minor Planet Center). We define the time of our first observation
on Oct. 22 as zero rotational phase and give the other six phases in the
table. The table shows a systematic temporal variation of the spectral
slope consistent with the rotational period. Based on an unpublished
visible light curve obtained 10 days earlier (C. Hergenrother personal
communication) we determine that one of the small ends of Hidalgo
corresponds to our "reddest” spectrum (phase 0.36) while one of
the broad sides has the flattest spectrum (phase 0.77).
Reflectance at 2.2 μm | 1.26 | 1.31 | 1.39 | 1.36 | 1.27 | 1.24 | 1.23 |
Rotational Phase | 0.0 | 0.14 | 0.36 | 0.59 | 0.62 | 0.72 | 0.77 |