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

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1. Introduction

V592 Her (Nova Herculis 1968, S 10376) was discovered by Richter (1968) on Sonneberg plates showing the object in outburst reaching 12.3 mag. Duerbeck (1987) tentatively classified V592 Her as a dwarf nova or, based on the similarity to V616 Mon (A0620-00), as an X-ray nova. Two more outbursts of V592 Her have been recorded: one in 1986 (Richter 1986a) and one very recently (Waagen 1998). Richter (1986b) reports that no outburst was recorded on 397 sky patrol plates taken between 1929 and 1966. A recurrence time of [FORMULA] yr and an outburst amplitude of [FORMULA] mag are not unusual for a recurrent nova, but the reported decay time of [FORMULA] days and the blue color at maximum are most consistent with a dwarf nova (Duerbeck 1987). Howell et al. (1995) list V592 Her as a member of the "tremendous outburst amplitude dwarf novae" (TOADs), a group of dwarf novae which show outburst amplitudes of 6-10 mag and interoutburst times of months to decades. The presence of superhumps with a period of [FORMULA] hr during the 1998 outburst (Duerbeck & Mennickent 1998) rules out the recurrent nova hypothesis, and makes V592 Her a TOAD with one of the largest outburst amplitudes.

Duerbeck (1987) proposed two candidate identifications for the postnova. Unfortunately, the labels on his finder chart are inconsistent with the given positions. Howell et al. (1991) obtained photometry of the field of V592 Her and claimed that only Duerbeck's candidate star #1 showed significant variability, with large-amplitude flickering of [FORMULA] mag over a 1.7 hr time interval. The position of V592 Her measured from a recent outburst image (Masi 1998) corresponds almost exactly to the coordinates of Duerbeck's star #1. In this Letter , we re-address the identification of the quiescent object and present R and I-band photometry of V592 Her obtained almost exactly one year before its 1998 outburst and serendipitous ROSAT X-ray observations obtained in 1992.

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© European Southern Observatory (ESO) 1999

Online publication: February 23, 1999