Astron. Astrophys. 342, L45-L48 (1999)

3. Astrometry

In order to measure the position and proper motion of V592 Her, we obtained scanned images of three archival plates from the Sonneberg Plate Stacks taken during and after the 1968 eruption. The plates were taken with the GC-Astrograph (400 mm aperture, f/4) on 1968 June 30, 31 and July 29. The astrometric analysis was performed using both our own routines and the MIDAS ASTROMET package using 30 stars from the HST Guide Star Catalogue.

The image of V592 Her from 1968 June 30 was too saturated to provide an accurate position, but the other two plates both provided a position of and . This position corresponds almost exactly to that of Duerbeck's candidate #1 (though not to his finder chart) and is only away from a very faint star on our McDonald R-band images.

The position of our candidate star was obtained by adding 20 secondary standards measured from the Digital Sky Survey image to the 5 GSC stars in the field: and , in agreement with the position measured during the recent outburst by Masi (1998). Thus, this faint star is clearly V592 Her in quiescence. From our photometry we derive mean magnitudes for V592 Her of and . Given an outburst brightness of (Waagen 1998), the amplitude of the 1998 outburst was mag. We note that there is no evidence for a nova shell down to a magnitude of , which would be expected if the outbursts of V592 Her are the result of thermonuclear runaways.

Our mean R-band image is shown in Fig. 1, along with the mean Sonneberg position. The slight difference between the 1968 and 1998 positions corresponds to a proper motion of /century, or a velocity perpendicular to the line-of-sight of 70-280 km/s at a distance of 500 pc - a reasonable velocity for an old disk or halo cataclysmic variable (CV).

Fig. 1. Mean R image of V592 Her. Stars 1 and 2 correspond to Duerbeck's candidates 1 and 2. Star 3 is very red and may not have been visible on Duerbeck's CCD frame. The circle shows the position of Nova Herculis 1968 obtained from Sonneberg plates. The galaxies belong to the cluster 1629.1+2140 or the cluster 1626.2+2045. The streak in the upper left-hand corner is a diffraction spike of  Her

© European Southern Observatory (ESO) 1999

Online publication: February 23, 1999
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