Eike W. Guenther and Sylvio Klose (Thüringer Landessternwarte Tautenburg)

report:

High-resolution spectra of SN 2004dj (Fig. 1) were aquired with the Tautenburg 2-m telescope equipped with the Echelle-spectrograph on August 4, 2:00 UT and August 5, 1:20 UT. The exposure time was 2400 sec and 2 x 2700 sec, respectively. The spectrograph uses a 2k x 2k CCD chip with 15 micron pixels. The spectral resolution is R = 25 000 (dispersion 0.05 Angstrom per pixel) for a 3 arcsec slit. The spectra were reduced in a standard fashion. Wavelength calibration was performed by means of ThAr lamps. The signal-to-noise ratio per pixel is about 20 for the data gained at the first night and 30 for the combined spectrum obtained during the second night. At the time of the observations SN 2004dj had an apparent magnitude of about V=11.7 [1]. We detect redshifted NaI D1 and D2 at a heliocentric velocity of (164.8 +/- 0.1) km/s (Figs. 2, 3), in agreement with the radial velocity of the host galaxy [2]. For the D1 and the D2 component we measure an equivalent width of (92 +/- 5) milli-Angstrom. Following previous work [3], we assume that the empirical relation between the equivalent width of Na I D1 and interstellar reddening in our Galaxy [4] is also representative for the interstellar medium in NGC 2403. In doing so, we arrive at a reddening in the supernova host of E(B-V) = (0.026 +/- 0.002) mag. Thus, assuming a ratio of total-to-selective extinction of 3, our data imply an extinction in the host galaxy of A_V (host) = (0.08 +/- 0.01) mag.


References:

[1] Schmeer, P., Hornoch, K.,Lehky, M. 2004, IAUC 8379
[2] Simbad data base
[3] Klose, S., Guenther, E., Woitas, J. 2002, GCN Circ. 1248
[4] Munari, F. & Zwitter, T.: Astron. Astrophys. 318 (1997) 269

Fig. 1: H-alpha image of NGC 2403 obtained with the Tautenburg Schmidt focus CCD camera in 2003. It shows the potential SN progenitor as a bright stellar object (indicated). Naturally, based on these data one cannot exclude that this is indeed a compact stellar cluster.

Fig. 2: High-resolution spectra of SN 2004dj aquired with the Tautenburg Echelle-spectrograph on August 4. Shown is a zoom-in around the Na I D1 line (lower panel) and the Na I D2 line (upper panel). The redshifted Na I D components from the SN host galaxy are indicated. In velocity space the data are normalized to the Galactic Na I D components, which themselfs are blended with a bright emission line presumably coming from the geocorona.

Fig. 3: The same as Figure 2 but for the data from August 5.

Fig. 4: H-alpha image of NGC 2403 obtained with the Tautenburg Schmidt focus CCD camera on August 10, 2004 by B. Stecklum. The SN is indicated.

These data are made public prior to publication in a referee journal.

S. Klose & E. Guenther, Thüringer Landessternwarte Tautenburg.

Last modified: August 10, 2004