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Supernova 1998bv in HS1035+4758

This supernova was discovered on April 6, 1998 on spectra obtained with 6m telescope of Special Astrophysical Observatory RAS (Kniazev et al. 1998). The supernova is located 3.1'' west and 3.7'' south of the center of the emission-line galaxy HS 1035+4758.

BVRI and H$_{\alpha}$ images were taken with the 1.52m EOCA telescope at Calar Alto on April 24, 1998. At that epoch a blue magnitude of 17.39 and colors U-B = 0.79, B-V = 0.85, V-R = 0.32 and R-I = 0.19 were determined. The available spectra for the SN, from April 6 and 19 taken with the 6m SAO Russian telescope and from May 26 with the NOT are shown in Figure 2.

  

Figure 2:

10cm7cm-90 sn.ps

The spectra are typical of a type II supernova. The comparison between the three epochs leads us to the conclusion that the first spectrum was taken no later than 20 days after the outburst. It seems remarkable that the common feature of helium lines in type II SN is not clearly present in our data. Meanwhile the remaining features characteristics of these SN type (FeII, broad H$_{\alpha}$ and H$_{\beta}$ and the P-Cygni profile of the absorption feature in Balmer series) are well defined. The calculated Balmer velocity difference between the absorption and broad emission appears to be of 5500 km/s for the April 19 spectra and 4400 km/s for the May epoch. From the blueshift of the FeII[37] and FeII[42] absorption feature, visible in all the spectra, we can estimate an analogous decrement in the velocity of the expelled gas: 4200 km/s in the April 6 spectra, 3200 km/s in the April 19 spectra and 2400 in the last spectra.

It has to be noticed that this is the second supernova detected in an HII galaxy (see Popescu et al., 1995). The SN1998bv shows a M_B = -14.77 at about one month from the outburst. Taken into account our age estimation, this supernova seems to be a ``REGULAR'' PLATEAU type II supernova, following the classification of Patat et al. (1994) or can be a prototype of ``FAINT'' PLATEAU type II supernova, more closely similar to the well studied SN1987A (see Mazzali et al. 1992 for references).

Acknowledgments
The data presented here have been taken using ALFOSC, which is owned by the Instituto de Astrofísica de Andalucía (IAA) and operated at the Nordic Optical Telescope under agreement between IAA and the NBIfA of the Astronomical Observatory of Copenhagen. HSS project is supported by INTAS grant Nr. 96-0500. SAO authors appreciate partial support from Russian RFBR grant 97-02-16755. This work was partly suported by a grant from the Plan Andaluz de Investigación de la Junta de Andalucía.