Peremennye Zvezdy

Peremennye Zvezdy (Variable Stars) 27, No. 8, 2008

Received 22 October; accepted 20 November.

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Photometric Investigation of Bright Type II-P Supernova 2004dj

D. Yu. Tsvetkov, V. P. Goranskij, N. N. Pavlyuk

Sternberg Astronomical Institute, University Ave. 13, 119992 Moscow, Russia


CCD photometry is presented for type II SN 2004dj for about 1200 days, starting on day 2 past discovery. The photometric behaviour is typical of SNe II-P, although some minor peculiarities are noticed. We compare the photometric data for the host cluster S96 before and after the SN 2004dj outburst and do not find any significant changes.


1. INTRODUCTION

The brightest supernova of the past decade, SN 2004dj, was discovered by K. Itagaki (Nakano et al., 2004) on 2004 July 31.76 UT in the nearby SBcd galaxy NGC 2403. The spectra taken immediately after discovery indicated it to be a type II-P event found long after the outburst (Patat et al., 2004). The object was also detected in radio (Stockdale et al., 2004), infrared (Sugerman and Van Dyk, 2005; Kotak et al., 2005) and X-ray bands (Pooley and Lewin, 2004). The optical photometry for SN 2004dj was published by Korcáková et al. (2005), Zhang et al. (2006), Vinkó et al. (2006). Spectroscopic observations were reported by Vinkó et al. (2006) and Korcáková et al. (2005). The results show that SN 2004dj is a typical SN II-P, regarding both photometric and spectral evolution. The ejected mass is estimated to be about 10 , and the mass of synthesized Ni was about 0.02 . light curves and spectra in the nebular phase were presented by Chugai et al. (2005) who pointed out strong asymmetry of the H emission line at the nebular epoch. The photometric observations by Chugai et al. (2005) were reprocessed by us, and the magnitudes presented here supersede the data reported in Chugai et al. (2005). Spectropolarimetry reported by Leonard et al. (2006) indicates strong departure from spherical symmetry for the inner ejecta. Asymmetry of Ni ejecta that results in the observed asymmetry of the H emission line and the possibility that this effect can also account for the polarization of SN radiation was discussed by Chugai (2006).

The association of SN 2004dj with the compact cluster Sandage 96 attracted particular attention, the data on this cluster were reported by Yamaoka et al. (2004), Maíz-Apellániz et al. (2004), Wang et al. (2005), Chugai et al. (2005), and Vinkó et al. (2006). The data suggests a cluster age of 14 - 20 Myr, which results in probable SN progenitor mass of 12 - 15 .

2. OBSERVATIONS AND REDUCTIONS

We started observations of SN 2004dj on 2004 August 2, two days after the discovery, but the field was also imaged at the 1-m reflector of the Special Astrophysical Observatory on 2001 January 19, long before the explosion.

The observations of supernova were carried out with the following telescopes and CCD cameras: the 1-m reflector of the Special Astrophysical Observatory equipped with an EEV42-40 CCD (S100) (only the images obtained before the discovery of the supernova were taken with an Electronika K-585 CCD); the 70-cm reflector of the Sternberg Institute in Moscow (M70) with Apogee AP-7p (a) or AP-47p (b) cameras; the 60-cm reflector of the Sternberg Institute's Crimean Laboratory (C60) with Princeton Instruments VersArrayB1300 (c), AP-47p , AP-7p, or SBIG ST-7 (d) CCD cameras; the 50-cm Maksutov telescope of the Sternberg Institute's Crimean Laboratory with a Meade Pictor 416XT CCD camera (C50).

During three years of observations, different filter sets were used at M70 and C60, they are identified by numbers after the code for the telescope and CCD camera. The color terms were derived solving equations from Tsvetkov et al. (2006), they are reported in Table 1. The observations at C50 were carried out only with a filter close to the standard system, and no correction was applied.

Table 1. Color terms for different telescope/camera/ filter combinations


Code
M70a1   -0.11 -0.032 -0.24  -0.38
M70a2   -0.14 -0.023 -0.12  -0.38
M70b -0.05 -0.21 -0.023 0.09  -0.39
C60a   -0.10 -0.002 -0.45  -0.37
C60b1 -0.03 -0.21 -0.017 0.09  -0.38
C60b2 -0.05 -0.16 -0.033 -0.03  -0.45
C60c -0.06 -0.10 -0.026 -0.025 -0.43
C60d   -0.34 -0.02  0.05   
S100   -0.10 0.09  0.036  

The standard image reductions and photometry were made using IRAF1.

Photometric measurements of the SN were made relative to local standard stars using PSF-fitting with IRAF DAOPHOT package. We did not try to subtract prediscovery images from the images with supernova.

The magnitudes of local standard stars were calibrated on photometric nights, when photometric standards were observed at different airmasses. They are presented in Table 2. The image of the SN with marked local standards is shown in Fig 1.

Fig. 1. SN 2004dj with local standard stars


Table 2. Magnitudes of local standard stars


Star
1 10.43 0.02 10.48 0.02 9.95 0.02 9.62 0.02 9.35 0.02
2 14.82 0.07 14.72 0.03 14.08 0.02 13.68 0.02 13.35 0.02
3 17.21 0.13 16.48 0.03 15.56 0.02 15.05 0.02 14.61 0.02
4 14.78 0.02 14.31 0.02 13.50 0.01 12.97 0.04 12.63 0.02
5 15.78 0.04 15.45 0.02 14.75 0.02 14.28 0.04 13.98 0.02

The magnitudes for our stars 1, 2, 3, 5 were derived by Vinkó et al. (2006), and for stars 2, 3, 4, 5, by Stetson2. The differences between our magnitudes and those from Vinkó et al. (2006) are quite significant, especially in the band, the mean differences are: . The magnitudes from Stetson are in a much better agreement with our data, the mean differences are: .

The good agreement of our data with the magnitudes from Stetson suggests that our calibration is more reliable than that by Vinkó et al. (2006).

The photometry for SN 2004dj is reported in Table 3.

3. THE LIGHT AND COLOR CURVES

The light curves are presented in Fig. 2. They are typical of SNe II-P, but only a small part of the plateau was covered by observations. After the fast decline from the plateau, prominent flattening, or a secondary plateau, is evident on the light curves in the and bands, which lasts about 160 days, and only after about JD 2453480 the linear decline begins. At about JD 2453800, the light curves in all bands flatten, as the cluster S96 becomes the dominant source of luminosity. We can subtract the luminosity of the cluster from magnitudes obtained for the sum of the cluster and supernova. For subtraction, we used the , , magnitudes of S96 derived from images obtained before the explosion, and we adopted from our last image in this band. The resulting light curves are shown in Fig. 3. The linear fits to the magnitudes in the JD 2453500-2453800 time interval give the following decline rates (in mag day): 0.0063 in , 0.0096 in , 0.010 in , and 0.011 in the band. In all bands except , the rate is very close to the decay slope of Co, which is 0.0098 mag day.

Table 3. Observations of SN 2004dj


JD 2450000+ Telescope
1929.48     18.61 0.04 18.22 0.03 17.82 0.03     S100
3220.31     12.49 0.02 11.89 0.02 11.51 0.02 11.36 0.02 M70a1
3222.32     12.49 0.02 11.89 0.02 11.51 0.02 11.33 0.02 M70a1
3238.27     12.92 0.03 11.96 0.02 11.54 0.02 11.34 0.02 M70a1
3242.52     12.90 0.02 11.97 0.02 11.58 0.02 11.31 0.02 M70a1
3244.57 13.80 0.03 12.91 0.02 11.97 0.02 11.53 0.02     C60c
3248.55 13.92 0.06 12.95 0.02 12.01 0.02 11.61 0.02     C60c
3249.47     12.97 0.02 12.05 0.02 11.59 0.02 11.44 0.02 M70a1
3250.48         12.03 0.02         C50
3251.51         12.06 0.02         C50
3253.47         12.05 0.02         C50
3254.52     13.02 0.02 12.07 0.02 11.65 0.02 11.36 0.02 M70a1
3255.50         12.07 0.02         C50
3255.56 14.11 0.05 13.09 0.03 12.07 0.02 11.69 0.02 11.40 0.02 C60c
3256.24         12.10 0.02         C50
3257.22         12.09 0.03         C50
3257.58 14.20 0.04 13.11 0.03 12.11 0.02 11.65 0.02 11.41 0.03 C60c
3259.60         12.12 0.02 11.71 0.03 11.46 0.03 C60c
3261.60 14.20 0.11 13.12 0.03 12.15 0.02 11.70 0.03 11.41 0.03 C60c
3263.54     13.20 0.02 12.22 0.02 11.79 0.02 11.56 0.02 M70a1
3269.51     13.32 0.03 12.32 0.02 11.89 0.02 11.60 0.02 M70a1
3294.49 16.16 0.09 14.75 0.03 13.79 0.03 13.36 0.02 13.01 0.03 M70b
3307.49     15.98 0.03 14.63 0.02 14.21 0.02 13.78 0.03 M70b
3309.63     15.95 0.03 14.67 0.02 14.16 0.05 13.74 0.02 C60c
3312.60     15.94 0.03 14.72 0.02 14.23 0.02 13.72 0.03 M70a1
3315.57 17.16 0.10 15.96 0.03 14.74 0.02 14.22 0.02 13.80 0.03 C60c
3317.51     15.98 0.03 14.81 0.02 14.29 0.02 13.86 0.03 C60a
3318.54 17.11 0.15 15.98 0.03 14.77