The peculiar ejecta of the nova V1425 Aquilae

Many important details of the mechanisms underlying the ejection of material during a (classical) nova eruption are still not understood. Here we present optical spectroscopy and narrow-band images of the nova V1425 Aql, 23 years after the nova eruption. We find that the ejecta consist of two significantly different components. The first resembles what is commonly seen in novae, that is, a symmetric distribution centred on the position of the underlying cataclysmic binary and presenting both allowed (hydrogen and helium) and forbidden ([OIII] and [NII]) transitions. The second one, on the other hand, consists of material travelling at an approximately three times higher velocity that is not visible in the allowed transitions, presents a significantly different [NII] - [OIII] ratio, and is located at approximately 2.3 arcsec to the southwest of the position of the binary. Comparing the velocities and spatial extensions of the two ejecta, we find that both originated in the same nova eruption. We explore possible extrinsic and intrinsic mechanisms for the asymmetry of the high-velocity material in the form of asymmetrically distributed interstellar material and magnetic accretion, respectively, but find the available data to be inconclusive. From the expansion parallax, we derive a distance for the nova of 3.3(3) kpc.Comment: 13 pages, 9 figures. Version updated for language editin

The emission distribution of RR Pictoris

We present time-resolved optical spectroscopy of the old nova RR Pic. Two emission lines (Halpha and He I) are present in the observed part of the spectrum and both show strong variability. Halpha has been used for Doppler tomography in order to map the emission distribution in this system for the first time. The resulting map shows the emission from the disc as well as two additional emission sources on the leading and trailing side of the disc. Furthermore we find evidence for the presence of either a disc-overflow or an asymmetric outflow from the binary with velocities up to +- 1200km/s. The origin of the outflow would be the emission source on the leading side of the accretion disc.Comment: Latex, 7 pages, 10 figure

Life After Eruption: Best of 2009–2013

From our ongoing survey to study the post-nova population we present details on the four objects V728 Sco, AR Cir, V972 Oph and X Cir

Blind prediction of broadband coherence time at basin scales

A blind comparison with data is made with a model for the coherence time of broadband sound (133 Hz, 17-Hz bandwidth) at 3709 km. Coherence time is limited by changes in the ocean because the acoustic instruments are fixed to the Earth on the bottom of the sea with time bases maintained by atomic clocks. Although the modeled coherence time depends a bit on the difficult problem of correctly modeling relative signal-to-noise ratios, normalized correlation coefficients of the broadband signals for the data (model) are 0.90 (0.83), 0.72 (0.59), and 0.51 (0.36) at lags of 2, 4.1, and 6.2 min, respectively. In all these cases, observed coherence times are a bit longer than modeled. The temporal evolution of the model is based on the linear dispersion relation for internal waves. Acoustic propagation is modeled with the parabolic approximation and the sound-speed insensitive operator