Photometric and spectroscopic data of the energetic Type Ic supernova (SN) 2002ap are presented, and the properties of the SN are investigated through models of its spectral evolution and its light curve. The SN is spectroscopically similar to the "hypernova" SN 1997ef. However, its kinetic energy [∼ ergs] and 51 (4-10) # 10 the mass ejected (2.5-5) are smaller, resulting in a faster evolving light curve. The SN synthesized M , ∼0.07 of 56 Ni, and its peak luminosity was similar to that of normal SNe. Brightness alone should not be M , used to define a hypernova, whose defining character, namely very broad spectral features, is the result of high kinetic energy. The likely main-sequence mass of the progenitor star was [20][21][22][23][24][25] , which is also lower than M , that of both hypernovae SN 1997ef and SN 1998bw. SN 2002ap appears to lie at the low-energy and low-mass end of the hypernova sequence as it is known so far. Observations of the nebular spectrum, which is expected to dominate by the summer of 2002, are necessary to confirm these values.
Intermediate resolution phase-resolved spectra of WZ Sge were obtained on five consecutive nights (July 23 -27) covering the initial stage of the 2001 superoutburst. Double-peaked emission lines of HeII at 4686 A, which were absent on July 23, emerged on July 24 together with emission lines of CIII / NIII Bowen blend. Analyses of the HeII emission lines using the Doppler tomography revealed an asymmetric spiral structure on the accretion disk. This finding demonstrates that spiral shocks with a very short orbital period can arise during the initial stage of an outburst and may be present in all SU UMa stars.
We report on the spectral evolution of 6 classical novae (V1186 Sco, V2540 Oph, V4745 Sgr, V5113 Sgr, V458 Vul, and V378 Ser), based on low-resolution spectra obtained at the Fujii-Bisei Observatory and the Bisei Astronomical Observatory, Japan. In the light curves, these 6 novae show several rebrightenings during the early phase lasting $\sim\ $10 d after the first maximum in fast novae, and $\sim\ $100 d in slow novae. The early spectra of all of these novae had emission lines with a P-Cygni profile at the maximum brightness. The absorption component of the P-Cygni profiles then disappeared after the maximum, and reappeared when the novae brightened to the next maximum. We suggest that the re-appearance of the absorption component at the rebrightening can be attributable to a re-expansion of the photosphere after it once shifts sufficiently inside. From the light curves, we found that the time intervals of the rebrightenings of these 6 novae show a similar systematic trend, which is applicable to all types of novae; fast and slow, and Fe II type and hybrid type. Moreover, we note the difference between the spectra at the rebrightenings during the early phase and at the rebrightening in V2362 Cyg, and at the oscillation during the transition phase in V1494 Aql, which means a difference in the physical mechanism of the rebrightening during the early phase and the later oscillations.
Abstract. The 2000 outburst of the recurrent nova CI Aql was followed by optical photometry and spectroscopy. Our time-resolved photometry revealed its intraday variations during the outburst. The orbital modulation of the light curve appeared after entering the plateau stage. We found that primary eclipses were ∼0.6 mag in depth, but the profile of the eclipse was significantly different from that in the quiescent phase. The folded orbital light curve was represented by a wide wing of a primary eclipse and it suggests the existence of the accretion disk at the plateau stage. In this outburst, we obtained accurate determination of several minima of primary eclipses, and found that the timings of minima showed a substantial delay compared to the previously reported ephemeris. However, no significant evidence of a change in the orbital period was observed since the discovery of the eclipsing nature of this object. We examined the evolution of optical spectra through the outburst, which reconfirmed the nova nature of this object. A spectrum taken on 2000 October 10 showed the Hα in emission and indicated that the object had not yet reached quiescence. The overall light curve and late-stage spectroscopy have revealed that the plateau is the longest one among recurrent novae.
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