SN 1998A: explosion of a blue supergiant

We present spectroscopic and photometric observations of the peculiar Type II supernova (SN) 1998A. The light curves and spectra closely resemble those of SN 1987A, suggesting that the SN 1998A progenitor exploded when it was a compact blue supergiant. However, the comparison with SN 1987A also highlights some important differences: SN 1998A is more luminous and the spectra show bluer continua and larger expansion velocities at all epochs. These observational properties indicate that the explosion of SN 1998A is more energetic than SN 1987A and more typical of Type II supemovae. Comparing the observational data with simulations, we deduce that the progenitor of SN 1998A was a massive star (∼25 M ○. ) with a small pre-supernova radius (?6 x 10 12 cm). The Ban lines, unusually strong in SN 1987A and some faint II-P events, are almost normal in the case of SN 1998A, indicating that the temperature plays a key role in determining their strength.

[1]  M. Turatto,et al.  Low‐luminosity Type II supernovae: spectroscopic and photometric evolution , 2003, astro-ph/0309264.

[2]  Nial R. Tanvir,et al.  The Cepheid Distance to NGC 1637: A Direct Test of the Expanding Photosphere Method Distance to SN 1999em , 2003, astro-ph/0305259.

[3]  M. Turatto,et al.  Photometry and Spectroscopy of the Type IIP SN 1999em from Outburst to Dust Formation , 2003 .

[4]  M. Turatto,et al.  Peculiar, low-luminosity Type II supernovae: low-energy explosions in massive progenitors? , 2002, astro-ph/0210171.

[5]  C. Stubbs,et al.  Optical Photometry of the Type I[CLC]a[/CLC] Supernova 1999[CLC]ee[/CLC] and the Type I[CLC]b[/CLC]/[CLC]c[/CLC] Supernova 1999[CLC]ex[/CLC] in IC 5179 , 2002 .

[6]  M. Hamuy.  Observed and Physical Properties of Core-Collapse Supernovae , 2002, astro-ph/0209174.

[7]  Peter Nugent,et al.  Detailed Spectroscopic Analysis of SN 1987A: The Distance to the Large Magellanic Cloud Using the Spectral-fitting Expanding Atmosphere Method , 2002 .

[8]  J. Sollerman,et al.  Supernova 1998bw - the final phases , 2002, astro-ph/0204498.

[9]  R. Chornock,et al.  The Distance to SN 1999em in NGC 1637 from the Expanding Photosphere Method , 2001, astro-ph/0109535.

[10]  A. Filippenko,et al.  Spectropolarimetry of the Type II Supernovae 1997ds, 1998A, and 1999gi , 2001, astro-ph/0105295.

[11]  S. E. Persson,et al.  The Distance to SN 1999em from the Expanding Photosphere Method , 2001, astro-ph/0105006.

[12]  D. Branch,et al.  56Ni Mixing in the Outer Layers of SN 1987A , 2001, astro-ph/0104148.

[13]  S. Shapiro,et al.  The fading of supernova 1997D , 2000, astro-ph/0010332.

[14]  L. Ho,et al.  Detailed Analysis of Early to Late-Time Spectra of Supernova 1993J , 2000, astro-ph/0006264.

[15]  K. Nomoto,et al.  Radiation Hydrodynamics of SN 1987A. I. Global Analysis of the Light Curve for the First 4 Months , 1999, astro-ph/9911205.

[16]  D. Blair,et al.  LIGHT CURVES OF SN 1998A AND COMPARISON WITH SIMILAR UNUSUAL SNE , 1998 .

[17]  D. Branch,et al.  Ion Signatures in Supernova Spectra , 1998, astro-ph/9809236.

[18]  E. Baron,et al.  Numerical solution of the expanding stellar atmosphere problem , 1998, astro-ph/9808182.

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

[20]  J. Sollerman,et al.  The Peculiar Type II Supernova 1997D: A Case for a Very Low 56Ni Mass , 1998, astro-ph/9803216.

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

[22]  Brian Paul Schmidt,et al.  The atmospheres of type II supernovae and the expanding photosphere method , 1996 .

[23]  B. Schaefer.  Volume-limited Samples of Supernovae , 1996 .

[24]  M. Turatto,et al.  Observations of type II plateau supernova: SNe 1988A, 1988H and 1989C , 1993 .

[25]  D. V. Popov.  An analytical model for the plateau stage of type II supernovae , 1993 .

[26]  Robert P. Kirshner,et al.  The unusual supernova SN1993J in the galaxy M81 , 1993, Nature.

[27]  R. McCray,et al.  The He I emission lines of SN 1987A , 1993 .

[28]  Arlo U. Landolt,et al.  UBVRI Photometric Standard Stars in the Magnitude Range 11 , 1992 .

[29]  Nicholas B. Suntzeff,et al.  SOUTHERN SPECTROPHOTOMETRIC STANDARDS. I. , 1992 .

[30]  M. Dopita,et al.  Optical spectroscopy of supernova 1987 A at the AAT – I. The FORS data , 1991 .

[31]  N. Suntzeff,et al.  An optical spectrophotometric atlas of supernova 1987A in the LMC. II - CCD observations from day 198 to 805 , 1990 .

[32]  G. Neugebauer,et al.  Continuum energy distribution of quasars: Shapes and origins , 1989 .

[33]  S. Bergh,et al.  The intrinsic frequency of faint supernovae resembling SN 1987A , 1989 .

[34]  D. Branch,et al.  Absolute Light Curves of Type II Supernovae , 1989 .

[35]  C. J. Butler,et al.  Spectroscopic and photometric observations of SN1987A. V - Days 386-616 , 1989 .

[36]  J. Wheeler,et al.  Late-time optical spectra of SN1987A , 1988, Nature.

[37]  A. S. Monk,et al.  Spectroscopic and photometric observations of SN 1987A–IV. Days 260–385 , 1988 .

[38]  N. Chugai.  MEETINGS AND CONFERENCES: Supernova in the Large Magellanic Cloud: first year of observations , 1988 .

[39]  M. Hamuy,et al.  An Optical Spectrophotometric Atlas of Supernova 1987A in the LMC. I. The First 130 Days , 1988 .

[40]  A. S. Monk,et al.  The radio and optical axes of radio elliptical galaxies , 1987 .

[41]  A. S. Monk,et al.  Spectroscopic and photometric observations of SN 1987A – III. Days 135 to 260 , 1987 .

[42]  J. Tyson,et al.  EARLY OPTICAL SPECTROSCOPY OF SUPERNOVA 1987A. , 1987 .

[43]  C. D. Laney,et al.  Spectroscopic and photometric observations of SN 1987a: the first 50 days , 1987 .

[44]  Park,et al.  Observation of a neutrino burst in coincidence with supernova 1987A in the Large Magellanic Cloud. , 1987, Physical review letters.

[45]  Hirata,et al.  Observation of a neutrino burst from the supernova SN1987A. , 1987, Physical review letters.

[46]  W. Goss,et al.  Radio observations of the SNR Puppis A , 1983 .

[47]  J. Baldwin,et al.  Southern spectrophotometric standards for large telescopes , 1983 .

[48]  A. Sandage,et al.  Steps toward the Hubble constant. III. The distance and stellar content of the M101 group of galaxies , 1974 .

[49]  T. Piran,et al.  JERUSALEM WINTER SCHOOL FOR THEORETICAL PHYSICS QUANTUM COSMOLOGY AND BABY UNIVERSES , 2007 .

[50]  Thomas Rauscher,et al.  Nuclear astrophysics , 2001 .

[51]  R. Wainscoat,et al.  A Filter for Deep Near-Infrared Imaging , 1992 .

[52]  N. Suntzeff,et al.  SN 1987A in the LMC - UBVRI photometry at Cerro Tololo , 1988 .

[53]  J. Baldwin,et al.  Southern spectrophotometry standards for large telescopes – II , 1984 .