STScI Preprint #1370

First Direct Measurement of Acceleration in the Outflow of a Nova: U Scorpii (1999)

Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA Contract NAS5-26555.

We report the first direct measurement of acceleration in the outflow of a nova: U Sco, observed 5 days after the start of an outburst. Spectroscopic time-series of the intense H emission-line, obtained with the STIS camera on board HST, shows a bright emission component moving across the spectrum at a rate of +0.16 ± 0.02 Å  in 30 minutes. This is consistent with a clump of emitting material having a line-of-sight acceleration a_r= +4.1 ± 0.5 m s^-2. The data suggest that this clump resides within a moderately collimated bipolar outflow. Due to projection effects, this implies an actual acceleration of the clump relative to the star of a +25 m s^-2.

Status:

Appeared in: The Astrophysical Journal (Letters)

Affiliations:

¹⁾Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
²⁾Present address: American Museum of Natural History and Hayden Planetarium, CPW at 79th Street, New York, NY 10036