## 6. Distance to the nova and absolute magnitude at maximumUsing the doublet-ratio method (Münch 1968) for the Na I D1 and D2 lines (Fig. 5 of Münch), we have a column density of Na I atoms to the nova: from the equivalent widths of the interstellar components of Na I
D1 and D2 lines, where N(Na I) is the space density of Na I atoms and
`d' is the distance. If we assume the space density of Na I atoms as
2 cm A well studied open cluster NGC 457 locates within an angular distance of from the present nova. Pesch (1959) estimated the distance to the cluster as 2.880.58 kpc and the interstellar reddening as . Some members of the cluster have had higher reddenings such as (Pesch 1959), but the higher ones may have been due to the interstellar matter in the own cluster. An approximate formula for the distribution of interstellar extinction in our galaxy was proposed by Parenago (1948) : where `a' is an amount of extinction in magnitude per kpc, `b' is
the galactic latitude, c kpc is a scale height,
and `d' is distance in kpc. Since the galactic latitude of NGC 457 is
, the amount of the extinction in this direction
may be about 0.94 mag kpc The UBV photometric data supplied by V. Goranskij (Fig. 1), show that the light maximum in the B band occurred on 1995 December 17 by . The absolute B magnitude at the maximum may have been about . Using the Eq. (6) of Livio (1992), we have a mass of the white dwarf as 0.58. This value is close to the lower limit of the mass of a white dwarf which performs nova's explosion (Kovetz & Prialnik 1985). © European Southern Observatory (ESO) 1998 Online publication: September 17, 1998 |