Photometry of the Kuiper-Belt object 1999 TD10 at different phase angles

We present photometric observations of the Kuiper-Belt object 1999TD10 at different phase angles and for three different broadband filters (B, V and R). This object was observed with the Danish1.54-m telescope of ESO in Chile during six different observing nights corresponding to a phase angle of 0.30, 0.37, 0.92, 3.43, 3.48 and 3.66 degr. Extra observations were obtained in September 2002 with the VLTUT1/FORS1 combination to confirm that 1999 TD10 does not exhibit any cometary activity, and in October 2001 with the Sierra Nevada Observatory 1.50-m telescope in order to add relative magnitudes to improve the determination of the rotation period.The observations are compatible with a single-peaked rotational lightcurve with a 7h41.5min+/-0.1 min period or a double-peaked lightcurve with a 15h22.9min+/-0.1 min period. If a single-peaked rotational lightcurve is assumed the amplitude is 0.51+/- 0.03, 0.49+/-0.05 and 0.60+/- 0.09 mag for the R, V and B bands, respectively. We present the phase curve obtained when assuming that the lightcurve is single-peaked. This phase curve reveals clearly an increase of about 0.3mag and of similar importance for the three bands when phase angle decreases from 3.7 degr to 0.3 degr. The phase curve reveals a linear increase of the brightness with the decreasing phase angle and,consequently, does not permit a modeling of the opposition surge. Nevertheless the poor repartition of the observational data does not permit a firm conclusion concerning the presence or absence of an opposition surge on the phase angle range covered by our data. Complementary observations are needed. Tables 3, 4 and 5 are also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130 . 79 . 128 . 5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/407/1139 Based on observations obtained at the La Silla and the Very Large Telescope VLT observatories of the European Southern Observatory ESO in Chile.