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.

No abstract

No abstract

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.

We report a sporadic sodium layer (SSL), in particular its fine structure, observed at 92–98 km between 20:00 and 23:30 UT (21:00–24:30 LT) on 11 January 2011 using a sodium lidar, which was installed in the European incoherent scatter (EISCAT) radar site at Tromsø, Norway (69.6°N, 19.2°E) in early 2010. The sodium lidar measurement with 5‐sec time‐resolution reveals the details of dramatic sodium‐density increase as well as short‐period wavelike structure in the SSL. The rate of increase of height‐integrated sodium density at the beginning of the SSL event was 6.4–9.6 × 1010 m−2 s−1. Dominant oscillation periods in the wavelike structures were 7–11 min at 95–98 km and 3 min at 92–95 km. The calculated power spectral densities are well represented by power laws, implying the presence of the short‐period waves and turbulence in the frequency range of 10−4–10−1 Hz.

Observations were made of the optical afterglow of GRB020813 (Fox, Blake & Price, 2002) with the KISO observatory 1.05 m Schmidt telescope and the Bisei astronomical observatory 1.01 m telescope. Four-band (B, V, R, and I) photometric data points were obtained from 2002, August 13 10:52 to 16:46 UT, or 0.346−0.516 days after the burst. In order to investigate the early-time (<1 day) evolution of the afterglow, four-band light curves were produced by analyzing the data taken at these two astronomical observatories, as well as publicly released data taken by the Magellan Baade telescope (Gladders and Hall, 2002c). The light curves can be approximated by a broken power law, of which the indices are approximately 0.46 and 1.33 before and after a break at ∼0.2 days, respectively. The optical spectral index stayed approximately constant at ∼0.9 over 0.17 ∼ 4.07 days after the burst. Since the temporal decay index after the break and the spectral index measured at that time are both consistent with those predicted by a spherical expansion model, the early break is unlikely to be a jet break, but likely to represent the end of an early bump in the light curve as was observed in the optical afterglow of GRB021004.

[1] Using a simultaneous and common-volume observation by a European incoherent scatter (EISCAT) VHF radar and a sodium lidar at Tromsø, Norway (69.6 ı N, 19.2 ı E), we have determined, for the first time, the effect of pure particle precipitation, excluding that of the electric field, on sodium density variations. Our observation on 24-25 January 2012 showed that sodium atom density decreased when there was no ion temperature enhancement (indicating a weak electric field) and the electron density increased (indicating strong particle precipitation). From the results, we have concluded that auroral particle precipitation induced sodium atom density decrease in this event. Furthermore, a discussion is provided regarding the time response of the decrease in sodium density. Citation: Tsuda, T. T., et al. (2013), Decrease in sodium density observed during auroral particle precipitation over Tromsø, Norway, Geophys. Res. Lett., 40,[4486][4487][4488][4489][4490]

We report on the evolution of superhumps and late superhumps in an ultrashort period dwarf nova, 1RXS J232953.9$+$062814, during the superoutburst in 2001 November. Ordinary superhumps were observed throughout a plateau phase, a rapid fading phase, and a rebrightening phase. During the plateau phase, the superhump period increased with time at a large rate of $P_\mathrm{dot} = 1.19 \pm 0.24 \times 10^{-4}$. In conjunction with the rebrightening phenomenon, these characteristics indicate that an accretion disk expanded further outward from the $3:1$ resonance radius, which caused a large amount of left over matter at the outer disk, even after the superoutburst. In the post-outburst phase, we detected late superhumps superimposed on dominant double-peak modulations. Late superhumps were observed at least for 10 d without a significant period change. We detected the first normal outburst of this object on 2001 December 26. The interval between the superoutburst and this normal one is 53 d. This short recurrence time supports a high mass-transfer rate in this system. Concerning the evolutionary status of 1RXS J232953.9$+$062814, we propose that it is a progenitor of AM CVn stars on the evolutionary course of the cataclysmic variable channel in which systems have a secondary star with a hydrogen-exhausted core.