Wednesday 5 August 2009

2009 July notes: (216523) 2001 HY7, 2001 AA50, 2009 NL and 2009 OF

With the short UK nights combined with the summer monsoon starting in the South-West of the US hampering the survey operations, there were only a handful of new Near-Earth objects to observe in July, but several objects were followed on a number of nights in an attempt to construct lightcurves for them.

Aten (216523) 2001 HY7 was observed on three nights in early July, but poor weather prevented getting enough coverage to find an unambiguous rotation period before it had faded out of range by mid-month.

Better luck was had with 2001 AA50, observed on 6 nights between July 20 and Aug 2, which showed an amplitude of 2 magnitudes. A rotation period of just under 26 hours is looking most likely, though a few more nights are still needed to be certain.

Apollo 2009 NL was a LINEAR discovery made on July 13th and was predicted to be magnitude 17 through the rest of the month. Photometry was obtained on 11 nights from July 14-Aug 2 and at magnitude 17-18 the scatter of measurements on individual nights was up to +/- 0.5 magnitudes but even so a likely rotation period of 25.2 hours and an amplitude of about 1 magnitude was able to be derived (see preliminary lightcurve).

2009 OF was another Apollo discovered by LINEAR, this time on July 17th and was initially listed by JPL and NEODys as a virtual impactor. It was observed on four nights from July 19-25, finally being taken off the risk registers on July 26th.