On 9 January 2013, Duende was observed again by Las Campanas Observatory and the observation arc immediately increased from 79 days to 321 days.
On 15 February 2013 at 19:25 UT, Duende passed 0.0002276 AU (34,050 km; 21,160 mi) from the center of Earth, with an uncertainty region of about 0.0000001 AU (15 km; 9.3 mi).

It passed 27,743 kilometers (17,239 mi) above Earth's surface, closer than satellites in geosynchronous orbit.
It briefly peaked at an apparent magnitude of roughly 7.2, a factor of a few fainter than would have been visible to the naked eye.
The best observation location for the closest approach was Indonesia.
Eastern Europe, Asia, and Australia also were well situated to observe Duende during its closest approach.

Duende was not expected to pass any closer than 1950 km to any satellites.
Goldstone Observatory observed Duende with radar from February 16 to February 20.
Radar observations showed that it is an elongated asteroid with dimensions of 20 by 40 meters (66 by 131 feet).
This gives Duende a geometric mean (spherical) diameter equivalent to 28 meters (92 ft).

During the close approach, an observational campaign involving 5 different telescopes in 4 different observatories was carried on in order to get information on the physical properties of this NEO.

Visible and near-Infrared photometry and visible spectroscopy were obtained at Gran Telescopio Canarias, Telescopio Nazionale Galileo and Calar Alto Observatory and put together.
The classification using the M4AST online tool says this is an L-type asteroid.
Those peculiar asteroids are characterized by a strongly reddish spectrum shortward of 0.8 μm, and a featureless flat spectrum longward of this, with little or no concave-up curvature related to a 1 μm silicon absorption band.

Time-series photometry was also obtained in the Observatorio de La Hita (I95) and Observatorio de Sierra Nevada during two consecutive nights (15–16 February 2013).
All of this data were co-phased to build a lightcurve of the object.
This lightcurve is double-peak and presents large variations in magnitude, implying a very elongated object, which is compatible with radar observations.
The amplitude of the lightcurve yields an axial ratio that, together with the long axis of 40 m inferred from the radar images by Goldstone, results in an equivalent diameter of 18 m, much smaller than the estimations before the close-approach.

The rotational period was precisely determined from the lightcurve obtaining a value of 8.95±0.08 h. This value is confirmed with an analysis of all the photometry of this objects reported to the Minor Planet Center.
Using data pre and post close approach the authors find that the object suffered a spin-up during the event that decreased the rotational period from 9.8±0.1 down to 8.8±0.1 hours, which is compatible with the more accurate value estimated from the light-curve.
On 9 January 2013, Duende was observed again by Las Campanas Observatory and the observation arc immediately increased from 79 days to 321 days. On 15 February 2013 at 19:25 UT, Duende passed 0.0002276 AU (34,050 km; 21,160 mi) from the center of Earth, with an uncertainty region of about 0.0000001 AU (15 km; 9.3 mi).
It passed 27,743 kilometers (17,239 mi) above Earth's surface, closer than satellites in geosynchronous orbit. It briefly peaked at an apparent magnitude of roughly 7.2, a factor of a few fainter than would have been visible to the naked eye. The best observation location for the closest approach was Indonesia. Eastern Europe, Asia, and Australia also were well situated to observe Duende during its closest approach.
Duende was not expected to pass any closer than 1950 km to any satellites. Goldstone Observatory observed Duende with radar from February 16 to February 20. Radar observations showed that it is an elongated asteroid with dimensions of 20 by 40 meters (66 by 131 feet). This gives Duende a geometric mean (spherical) diameter equivalent to 28 meters (92 ft).
During the close approach, an observational campaign involving 5 different telescopes in 4 different observatories was carried on in order to get information on the physical properties of this NEO.
Visible and near-Infrared photometry and visible spectroscopy were obtained at Gran Telescopio Canarias, Telescopio Nazionale Galileo and Calar Alto Observatory and put together. The classification using the M4AST online tool says this is an L-type asteroid. Those peculiar asteroids are characterized by a strongly reddish spectrum shortward of 0.8 μm, and a featureless flat spectrum longward of this, with little or no concave-up curvature related to a 1 μm silicon absorption band.
Time-series photometry was also obtained in the Observatorio de La Hita (I95) and Observatorio de Sierra Nevada during two consecutive nights (15–16 February 2013). All of this data were co-phased to build a lightcurve of the object. This lightcurve is double-peak and presents large variations in magnitude, implying a very elongated object, which is compatible with radar observations. The amplitude of the lightcurve yields an axial ratio that, together with the long axis of 40 m inferred from the radar images by Goldstone, results in an equivalent diameter of 18 m, much smaller than the estimations before the close-approach.
The rotational period was precisely determined from the lightcurve obtaining a value of 8.95±0.08 h. This value is confirmed with an analysis of all the photometry of this objects reported to the Minor Planet Center. Using data pre and post close approach the authors find that the object suffered a spin-up during the event that decreased the rotational period from 9.8±0.1 down to 8.8±0.1 hours, which is compatible with the more accurate value estimated from the light-curve.
367943 Duende