High energy emissions from supernovae (SNe), originated from newly formed radioactive species, provide direct evidence of nucleosynthesis at SN explosions. However, observational difficulties in the MeV range have so far allowed the signal detected o
nly from the extremely nearby core-collapse SN 1987A. No solid detection has been reported for thermonuclear SNe Ia, despite the importance of the direct confirmation of the formation of 56Ni, which is believed to be a key ingredient in their nature as distance indicators. In this paper, we show that the new generation hard X-ray and soft gamma-ray instruments, on board Astro-H and NuStar, are capable of detecting the signal, at least at a pace of once in a few years, opening up this new window for studying SN explosion and nucleosynthesis.
This is the summary of the parallel session entitled White Dwarf Pulsars and Rotating White Dwarf Theory, chaired by Yukikatsu Terada in Thirteenth Marcel Grossmann Meeting. The origin of cosmic rays remains a mystery, even over 100 years since their
discovery. Neutron stars (NSs) are considered textbook cases of particle acceleration sites in our Galaxy, but many unresolved numerical problems remain. Searches for new acceleration sites are crucial for astrophysics. The magnetized white dwarfs (MWDs) have the same kind of rotating magnetosphere as NSs, and may be the source of up to 10% of galactic cosmic ray electrons. In the parallel session of the white dwarf pulsars and rotating white dwarf theory, we focus on the current observational results on white dwarf pulsars, related theories of the radiation process both in white dwarfs and neutron stars, and the origin and rule of white dwarf pulsars, as well as surveying on the current theories of the internal structure and the equation of state of white dwarfs.
The bow shocks of runaway stars with strong stellar winds of over 2000 km s$^{-1}$ can serve as particle acceleration sites. The conversion from stellar wind luminosity into particle acceleration power has an efficiency of the same order of magnitude
as those in supernova remnants, based on the radio emission from the bow shock region of runaway star BD+43$^circ$3654 citep{Benaglia10}.If this object exhibits typical characteristics, then runaway star systems can contribute a non-negligible fraction of Galactic cosmic-ray electrons. To constrain the maximum energy of accelerated particles from measurements of possible non-thermal emissions in the X-ray band, Suzaku observed BD+43$^circ$3654 in April 2011 with an exposure of 99 ks. Because the onboard instruments have a stable and low background level, Suzaku detected a possible enhancement over the background of $7.6pm 3.4$ cnt arcmin$^{-2}$ at the bow shock region, where the error represents the 3 sigma statistics only. However, the excess is not significant within the systematic errors of non-X-ray and cosmic-ray backgrounds of the X-ray Imaging Spectrometer, which are $pm 6.0$ and $pm 34$ cnt arcmin$^{-2}$, respectively, and the 3-sigma upper limit in the X-ray luminosity from the shock region, which is $1.1 times 10^{32}$ erg s$^{-1}$ per 41.2 arcmin$^2$ in the 0.5 to 10 keV band. This result leads to three conclusions: (1) a shock-heating process is inefficient on this system; (2) the maximum energy of electrons does not exceed $sim$ 10 TeV, corresponding to a Lorentz factor of less than $10^7$; and (3) the magnetic field in the shock acceleration site might not be as turbulent as those in pulsar wind nebulae and supernova remnants.
Pulsar systems are very good experimental laboratories for the fundamental physics in extreme environments which cannot be achieved on ground. For example, the systems are under conditions of high magnetic field strength, large gravitational potentia
l, and fast rotation, containing highly-ionized hot plasmas with particle acceleration etc. We can test phenomena related to these extreme condition in the X-ray to sub-MeV bands. In future, we will get fantastic capabilities of higher sensitivities, larger effective area, higher energy resolutions, and X-ray imaging capabilities with wider energy band than current missions, in addition to opening new eyes of polarization measurements, and deep all sky monitoring capabilities, with future X-ray missions including ASTRO-H, eRossita, NuSTAR, GEMS, International X-ray Observatory (IXO) and so on. In this paper, we summarize current hot topics on pulsars and discuss expected developments by these future missions, especially by ASTRO-H and IXO, based on their current design parameters.
The fast rotating magnetized white dwarf, AE Aquarii, was observed with Suzaku, in October 2005 and October 2006 with exposures of 53.1 and 42.4 ks, respectively. In addition to clear spin modulation in the 0.5--10 keV band of the XIS data at the bar
ycentric period of 33.0769 pm 0.0001 s, the 10--30 keV HXD data in the second half of the 2005 observation also showed statistically significant periodic signals at a consistent period. On that occasion, the spin-folded HXD light curve exhibited two sharp spikes separated by about 0.2 cycles in phase, in contrast to approximately sinusoidal profiles observed in energies below about 4 keV. The folded 4--10 keV XIS light curves are understood as a superposition of those two types of pulse profiles. The phase averaged 1.5--10 keV spectra can be reproduced by two thermal components with temperatures of $2.90_{-0.16}^{+0.20}$ keV and $0.53_{-0.13}^{+0.14}$ keV, but the 12-25 keV HXD data show a significant excess above the extrapolated model. This excess can be explained by either a power-law model with photon index of $1.12_{-0.62}^{+0.63}$ or a third thermal component with a temperature of $54_{-47}^{+26}$ keV. At a distance of 102 pc, the 4--30 keV luminosities of the thermal and the additional components become $1.7_{-0.6}^{+1.3}$ and $5.3_{-0.3}^{+15.3} times 10^{29}$ erg s$^{-1}$, respectively. The latter corresponds to 0.09% of the spin down energy of the object. Possible emission mechanisms of the hard pulsations are discussed, including in particular non-thermal ones.
The hard X-ray detector (HXD) on board the X-ray satellite Suzaku is designed to have a good timing capability with a 61 $mu$s time resolution. In addition to detailed descriptions of the HXD timing system, results of in-orbit timing calibration and
performance of the HXD are summarized. The relative accuracy of time measurements of the HXD event was confirmed to have an accuracy of $1.9times 10^{-9}$ s s$^{-1}$ per day, and the absolute timing was confirmed to be accurate to 360 $mu$s or better. The results were achieved mainly through observations of the Crab pulsar, including simultaneous ones with RXTE, INTEGRAL, and Swift.
