A flattening in the optical light curve of SN 2002ap

We present the UBV RcIc broad band optical photometry of the Type Ic supernova SN 2002ap obtained during 2002 February 06 – March 23 in the early decline phases and also later on 2002 15 August. Combining these data with the published ones, the general light curve development is studied. The time and luminosity of the peak brightness and the peak width are estimated. There is a flattening in the optical light curve about 30 days after the B maximum. The flux decline rates before flattening are 0.127±0.005, 0.082±0.001, 0.074±0.001, 0.062±0.001 and 0.040±0.001 mag day −1 in U, B, V , Rc and Ic passbands respectively, while the corresponding values after flattening are about 0.02 mag day −1 in all the passbands. The maximum brightness of SN 2002ap MV = 17.2 mag, is comparable to that of the type Ic 1997ef, but fainter than that of the type Ic hypernova SN 1998bw. The peak luminosity indicates an ejection of � 0.06 M⊙ 56 Ni mass. We also present low-resolution optical spectra obtained during the early phases. The SiII absorption minimum indicates that the photospheric velocity decreased from � 21,360 km s −1 to � 10,740 km s −1 during a period of � 6 days.

[1]  Bradley E. Schaefer,et al.  The Late‐Time Light Curve of SN 1998bw Associated with GRB 980425 , 1999, astro-ph/9904397.

[2]  Alexei V. Filippenko,et al.  Optical spectra of supernovae , 1997 .

[3]  M. Bessell,et al.  JHKLM PHOTOMETRY: STANDARD SYSTEMS, PASSBANDS, AND INTRINSIC COLORS , 1988 .

[4]  Chien Y. Peng,et al.  UBVRI Photometry of the Type IC SN 1994I in M51 , 1996 .

[5]  D. Schlegel,et al.  Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds , 1997, astro-ph/9710327.

[6]  J. Thorstensen,et al.  The Peculiar Type Ic Supernova 1997ef: Another Hypernova , 2000 .

[7]  Mamoru Doi,et al.  THE TYPE IC HYPERNOVA SN 2002AP , 2002 .

[8]  S. Smartt,et al.  On the progenitor of the Type Ic supernova 2002ap , 2002, astro-ph/0205241.

[9]  Takashi Ichikawa,et al.  GALAXY COLORS IN VARIOUS PHOTOMETRIC BAND SYSTEMS , 1995 .

[10]  P. Mazzali,et al.  Early-Phase Spectra of “Hypernova” SN 2002ap , 2002, astro-ph/0208470.

[11]  J. Mathis,et al.  The relationship between infrared, optical, and ultraviolet extinction , 1989 .

[12]  S. Colgate,et al.  EARLY SUPERNOVA LUMINOSITY. , 1969 .

[13]  I. Karachentsev,et al.  Photometric distances to NGC 628 and its four companions. , 1996 .

[14]  W. Arnett,et al.  The Nature of Supernovae as Determined from Their Light Curves , 1982 .

[15]  Filippo Frontera,et al.  Accepted for publication in the Astrophysical Journal 2001, v. 555 Preprint typeset using L ATEX style emulateapj v. 14/09/00 THE METAMORPHOSIS OF SN 1998BW ‡ , 1999 .

[16]  Eran O. Ofek,et al.  Supernova 2002ap: the first month , 2002 .

[17]  J. Wheeler.  Supernovae and Gamma-Ray Bursts , 2000 .

[18]  P. Vreeswijk,et al.  A hypernova model for the supernova associated with the γ-ray burst of 25 April 1998 , 1998, Nature.

[19]  Optical Spectropolarimetry of SN 2002ap: A High Velocity Asymmetric Explosion , 2002, astro-ph/0205414.

[20]  Felix Ryde,et al.  SN 1998bw at late phases , 2000 .

[21]  D. Schlegel,et al.  Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds , 1998 .