Life after eruption – IV. Spectroscopy of 13 old novae

Abstract

We present data on 13 post-nova systems. This includes the recovery via UBVR photometry of the five post-novae X Cir, V2104 Oph, V363 Sgr, V928 Sgr and V1274 Sgr and their spectroscopic confirmation. We provide accurate coordinates and finding charts for those objects. Additional first-time or improved spectroscopic data are presented for V356 Aql, V500 Aql, V604 Aql, V1370 Aql, MT Cen, V693 CrA, V697 Sco and MU Ser. Investigating the behaviour of a few easily accessible parameters yields (limited) information on the accretion state and the system inclination. We predict that X Cir and V697 Sco are likely to reveal their orbital period via time series photometry and that long-term photometric monitoring of V356 Aql, V500 Aql, V1370 Aql and X Cir has a good chance of discovering outburst-like behaviour in these systems.

SALT observations of southern post-novae

“…From the mean values and Fig. 2, it is obvious that most of the Ringwald et al (1996) power-law exponents are above the steady-state disk exponent, while the majority of the Schmidtobreick et al (2005c) and Tappert et al (2012Tappert et al ( , 2014 exponents are below this value. Our exponents are more or less symmetrically distributed around the steady disk exponent.…”

“…For all the objects, a single power law was fitted in the wavelength range 4000−6500 Å. The errors of the exponents represent only The double exponents for V630 Sgr, V842 Cen, V2109 Oph, V604 Aql and V2104 Oph (Schmidtobreick et al 2005c;Tappert et al 2012Tappert et al , 2014 are connected with dashed lines. Our exponent for V842 Cen is also connected by a dashed line to the line between its two exponents from Schmidtobreick et al (2005c).…”

“…For a sample of eight post-novae Tappert et al (2012) found "that α for most systems falls well below the value of 2.33 for a steady-state accretion disk (Lynden-Bell 1969)". Excluding the objects fitted with two power laws and V529 Ori, which shows an atypical SED, 13 post-novae published by Schmidtobreick et al (2005c) and Tappert et al (2012Tappert et al ( , 2014 remain for which an average α = 2.13 ± 0.67 can be estimated.…”

“…2 our power-law exponents, together with these from Ringwald et al (1996) 2 , Schmidtobreick et al (2005c), and Tappert et al (2012Tappert et al ( , 2014, are presented as a function of the time since outburst. From the mean values and Fig.…”

On the absence of nova shells

“…Schmidtobreick et al 2005;Tappert et al 2012Tappert et al , 2014 This is expected as the recurrence time, i.e. the time between two nova outbursts, is supposed to be smaller for high mass transfer systems and so they are more likely to be observed during a nova eruption.…”