We report observations of the Type Iax supernova (SN Iax) 2012Z at optical and near-infrared wavelengths from immediately after the explosion until ∼ 260 days after the maximum luminosity using the Optical and Infrared Synergetic Telescopes for Education and Research (OISTER) Targetof-Opportunity (ToO) program and the Subaru telescope. We found that the near-infrared (NIR) light curve evolutions and color evolutions are similar to those of SNe Iax 2005hk and 2008ha. The NIR absolute magnitudes (M J ∼ −18.1 mag and M H ∼ −18.3 mag) and the rate of decline of the light curve (∆ m 15 (B)= 1.6 ± 0.1 mag) are very similar to those of SN 2005hk (M J ∼ −17.7 mag, M H ∼−18.0 mag, and ∆ m 15 (B)∼ 1.6 mag), yet differ significantly from SNe 2008ha and 2010ae (M J ∼ −14 − −15 mag and ∆ m 15 (B)∼ 2.4 − 2.7 mag). The estimated rise time is 12.0 ± 3.0 days,which is significantly shorter than that of SN 2005hk or any other Ia SNe. The rapid rise indicates that the 56 Ni distribution may extend into the outer layer or that the effective opacity may be lower than that in normal SNe Ia. The late-phase spectrum exhibits broader emission lines than those of SN 2005hk by a factor of 6-8. Such high velocities of the emission lines indicate that the density profile of the inner ejecta extends more than that of SN 2005hk. We argue that the most favored explosion scenario is a 'failed deflagration' model, although the pulsational delayed detonations is not excluded. Subject headings: supernovae: general -supernovae: individual (SN 2012Z) -supernovae: individual (SNe 2005hk)

Multi-wavelength observations of the black-widow binary system 2FGL J2339.6−0532 are reported. The Fermi gamma-ray source 2FGL J2339.6-0532 was recently categorized as a black widow in which a recycled millisecond pulsar (MSP) is evaporating up the companion star with its powerful pulsar wind. Our optical observations show clear sinusoidal light curves due to the asymmetric temperature distribution of the companion star. Assuming a simple geometry, we constrained the range of the inclination angle of the binary system to 52 • < i < 59 • , which enables us to discuss the interaction between the pulsar wind and the companion in detail. The X-ray spectrum consists of two components: a soft, steady component that seems to originate from the surface of the MSP, and a hard variable component from the wind-termination shock near the companion star. The measured X-ray luminosity is comparable to the bolometric luminosity of the companion, meaning that the heating efficiency is less than 0.5. In the companion orbit, 10 11 cm from the pulsar, the pulsar wind is already in particle dominant-stage, with a magnetization parameter of σ < 0.1. In addition, we precisely investigated the time variations of the X-ray periodograms and detected a weakening of orbital modulation. The observed phenomenon may be related to an unstable pulsar-wind activity or a weak mass accretion, both of which can result in the temporal extinction of radio-pulse.

No abstract

No abstract

No abstract