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We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution of superhump period are found to be composed of three distinct stages: early evolutionary stage with a longer superhump period, middle stage with systematically varying periods, final stage with a shorter, stable superhump period. During the middle stage, many systems with superhump periods less than 0.08 d show positive period derivatives. Contrary to the earlier claim, we found no clear evidence for variation of period derivatives between superoutburst of the same object. We present an interpretation that the lengthening of the superhump period is a result of outward propagation of the eccentricity wave and is limited by the radius near the tidal truncation. We interpret that late stage superhumps are rejuvenized excitation of 3:1 resonance when the superhumps in the outer disk is effectively quenched. Many of WZ Sge-type dwarf novae showed long-enduring superhumps during the post-superoutburst stage having periods longer than those during the main superoutburst. The period derivatives in WZ Sge-type dwarf novae are found to be strongly correlated with the fractional superhump excess, or consequently, mass ratio. WZ Sge-type dwarf novae with a long-lasting rebrightening or with multiple rebrightenings tend to have smaller period derivatives and are excellent candidate for the systems around or after the period minimum of evolution of cataclysmic variables (abridged)., Comment: 239 pages, 225 figures, PASJ accepted

We investigated the superhump evolution, analysing optical photometric observations of the 2000 February-March, the 2002 October-November, and the 2006 September superoutbursts of SW UMa. The superhumps evolved in the same way after their appearance during the 2000 and the 2002 superoutbursts, and probably during the 2006 one. This indicates that the superhump evolution may be governed by the invariable binary parameters. We detected a periodicity in light curve after the end of the 2000 superoutburst without phase shift, which seems to be the remains of the superhumps. We found QPOs at the end stage of the 2000 and the 2002 superoutbursts, but failed to find extraordinarily large-amplitude QPOs called `super-QPOs' which previously have been observed in SW UMa., 17 pages, 19 figures

The X-ray imaging of materials with low atomic number elements is difficult through a conventional photoabsorption contrast method whereas much higher contrast can be achieved by phase-contrast imaging. We have constructed a compact size imaging system using a microfocus X-ray generator with a few µm spot size. We present here the evaluation of basic characteristics and sample results, as well as future prospects.

We present here the analysis of the early and late multiwavelength afterglow emission, as observed by Swift a small robotic telescope and very large telescope (VLT). We compare early observations with late afterglow observations obtained with Swift and the VLT and we observe an intense rebrightening in the optical band at about 1 day after the burst, which is not present in the X-ray band. The lack of detection in X-ray of such a strong rebrightening at lower energies may be described with a variable external density profile. In such a scenario, the combined X-ray and optical observations allow us to derive that the matter density located at ∼10 17 cm from the burst is approximately a factor of 10 higher than in the inner region. This is the first time in which a rebrightening has been observed in the optical afterglow of a gamma-ray burst that is clearly absent in the X-ray afterglow.

Kiyoshi Hayashida,1,∗) Ken’ichi Torii,1 Masaaki Namiki,1 Naohisa Anabuki,1 Satoru Katsuda,1 Noriaki Tawa,1 Tomofumi Miyauchi,1 Kazuto Hasuike,1 Masaaki Nagai,1 Hiroshi Tsunemi,1 Hironori Matsumoto,2 Takeshi G. Tsuru,2 Hideyuki Mori,2 Hiroshi Nakajima,2 Hiroya Yamaguchi,2 Yoshiaki Hyodo,2 Tatsuya Inui,2 Hideki Uchiyama,2 Midori Ozawa,2 Katsuji Koyama,2 Eric D. Miller,3 Mark W. Bautz,3 Beverly LaMarr,3 Steve E. Kissel,3 Tadayasu Dotani,4 Hiroshi Murakami,4 Masanobu Ozaki,4 Takayasu Anada,4 Aya Bamba,5 Junko Hiraga,5 Atsushi Senda,5 Dai Takei,6 Shunji Kitamoto,6 Koji Mori,7 Shouta Maeno7 and the Suzaku XIS Team

Giovanni Miniutti,1,∗) Andrew C. Fabian,1 Jamie Crummy,1,2 Josefin Larsson,1 Naohisa Anabuki,3 Yasushi Fukazawa,4 Luigi C. Gallo,5 Yoshito Haba,6 Kiyoshi Hayashida,3 Steve Holt7, Hideyo Kunieda,8 Alex Markowitz,9 Chiho Matsumoto,8 Masanori Ohno,4 James N. Reeves,9,10 Tadayuki Takahashi,11 Yasuo Tanaka,12 Yuichi Terashima,11,13 Ken’ichi Torii,3 Yoshihiro Ueda,14 Masayoshi Ushio,11 Shin Watanabe,11 Makoto Yamauchi15 and Tahir Yaqoob9,10

A bright, long gamma-ray burst (GRB) was detected and localized by the instruments on board the High Energy Transient Explorer 2 satellite (HETE-2) at 02:44:19.17 UTC (9859.17s UT) on 2002 August 13. The location was reported to the GRB Coordinates Network (GCN) about 4min after the burst. In the prompt emission, the burst had a duration of approximately 125s, and more than four peaks. We analyzed the time-resolved 2-400keV energy spectra of the prompt emission of GRB 020813 using the Wide Field X-Ray Monitor (WXM) and the French Gamma Telescope (FREGATE) in detail. We found that the early part of the burst (17-52s after the burst trigger) shows a depletion of low-energy photons below about 50keV. It is difficult to explain the depletion by either synchrotron self-absorption or Comptonization. One possibility is that the low-energy depletion may be understood as a mixture of ``jitter'' radiation with the usual synchrotron radiation component.

We describe and discuss the global properties of 45 gamma-ray bursts (GRBs) observed by HETE-2 during the first 3 years of its mission, focusing on the properties of X-ray flashes (XRFs) and X-ray-rich GRBs (XRRs). We find that the numbers of XRFs, XRRs, and GRBs are comparable, and that the durations and the sky distributions of XRFs and XRRs are similar to those of GRBs. We also find that the spectral properties of XRFs and XRRs are similar to those of GRBs, except that the values of the peak energy Eobspeak of the burst spectrum in νFν, the peak energy flux Fpeak, and the energy fluence SE of XRFs are much smaller (and those of XRRs are smaller) than those of GRBs. Finally, we find that the distributions of all three kinds of bursts form a continuum in the [SE(2-30 keV), SE(30-400) keV] plane, the [SE(2-400 keV), Epeak] plane, and the [Fpeak(50-300 keV), Epeak] plane. These results provide strong evidence that all three kinds of bursts arise from the same phenomenon.

GRB 020124 and GRB 030323 constitute half the sample of gamma-ray bursts with a measured redshift greater than 3. This paper presents the temporal and spectral properties of these two gamma-ray bursts detected and localized with HETE-2. While they have nearly identical redshifts (z=3.20 for GRB 020124, and z=3.37 for GRB 030323), these two GRBs span about an order of magnitude in fluence, thus sampling distinct regions of the GRB luminosity function. The properties of these two bursts are compared with those of the bulk of the GRB population detected by HETE-2. We also discuss the energetics of GRB 020124 and GRB 030323 and show that they are compatible with the Epeak - Eiso relation discovered by Amati et al. (2002). Finally, we compute the maximum redshifts at which these bursts could have been detected by HETE-2 and we address various issues connected with the detection and localization of high-z GRBs., Comment: 19 pages, 4 figures, submitted to ApJ

We report High Energy Transient Explorer 2 (HETE-2) Wide Field X-ray Monitor/French Gamma Telescope observations of XRF030723 along with observations of the XRF afterglow made using the 6.5m Magellan Clay telescope and the Chandra X-ray Observatory. The observed peak energy E_pk_obs of the nu F_nu burst spectrum is found to lie within (or below) the WXM 2-25 keV passband at 98.5% confidence, and no counts are detected above 30 keV. Our best fit value is E_pk_obs=8.4+3.5/-3.4 keV. The ratio of X-ray to Gamma-ray flux for the burst follows a correlation found for GRBs observed with HETE-2, and the duration of the burst is similar to that typical of long-duration GRBs. If we require that the burst isotropic equivalent energy E_iso and E_pk_rest satisfy the relation discovered by Amati et al. (2002), a redshift of z=0.38+0.36/-0.18 can be determined, in agreement with constraints determined from optical observations. We are able to fit the X-ray afterglow spectrum and to measure its temporal fade. Although the best-fit fade is shallower than the concurrent fade in the optical, the spectral similarity between the two bands indicates that the X-ray fade may actually trace the optical fade. If this is the case, the late time rebrightening observed in the optical cannot be due to a supernova bump. We interpret the prompt and afterglow X-ray emission as arising from a jetted GRB observed off-axis and possibly viewed through a complex circumburst medium due to a progenitor wind., Comment: 14 pages, 9 figures, to appear in ApJ

Wediscoveredsuperhumpsin an eclipsingdwarf nova, XZEridani, during an outburst in 2003 January–February. We determined the orbital and average superhump periods to be 0.061159602 ± 0.000000044d and 0.062808 ± 0.000017d, respectively. Our observations thus established that XZ Eri belongs to a rare class of deeply eclipsing SU UMa-type dwarf novae. The object has the shortest orbital period among seven known objects in this class. The superhump period decreased with time during a mid-plateau phase of the superoutburst, as observed in a number of ordinary, long-period SU UMa stars. During an early phase of the superoutburst, however, the superhump period increased, as observed in several short-period systems. XZ Eri is a unique object with which we can study the evolution of accretion-disk structures through eclipses during the phase of the superhump period increase.

GRB 030329 is the first Gamma-ray burst event for which a connection with a supernova (SN 2003dh) has been confirmed spectroscopically in its early phase. We present optical spectroscopy of this object 40 and 85 days after the burst (35 and 73 rest-frame days, respectively) obtained with the Subaru 8.2-m telescope. After subtracting the host galaxy template spectrum, the second-epoch spectrum shows nebular-phase emission lines emerging from the dominated photospheric-phase spectrum. The transition from the photospheric phase to the nebular phase has just started, or was slowly progressing at the time of our second-epoch observations. Our spectral analysis of the nebular-phase emission lines suggests that the explosion of the progenitor of the GRB 030329 was aspherical, and that the axis of an asphericity is well aligned to both the GRB relativistic jet and our line of sight. Although the decay index and the color evolution in the rest frame during our two epochs are very consistent with those of the Type Ic supernovae SN 1998bw and SN 1997ef, the nebular-phase lines emerged slightly earlier than in the case of these supernovae. These results infer that the most important factor that distinguishes SNe with GRB from SNe without GRB is the scale of the jet activity, or a viewing-angle effect, or both of them.

We report High Energy Transient Explorer 2 (HETE-2) Wide Field X-Ray Monitor/French Gamma Telescope observations of the X-ray flash XRF 020903. This event was extremely soft: the ratio log(SX/Sγ)=0.7, where SX and Sγ are the fluences in the 2-30 and 30-400 keV energy bands, is the most extreme value observed so far by HETE-2. In addition, the spectrum has an observed peak energy of Eobspeakobspeak is due to the cosmological redshift, and show that this is very unlikely. We find that the properties of XRF 020903 are consistent with the relation between the fluences S(7-30 keV) and S(30-400 keV), found by Barraud et al. for GRBs and X-ray-rich GRBs, and are consistent with the extension by a decade of the hardness-intensity correlation found by the same authors. Assuming that XRF 020903 lies at a redshift z=0.25, as implied by the host galaxy of the candidate optical and radio afterglows of this burst, we find that the properties of XRF 020903 are consistent with an extension by a factor ~300 of the relation between the isotropic-equivalent energy Eiso and the peak Epeak of the νFν spectrum (in the source frame of the burst) found by Amati et al. for GRBs. The results presented in this paper therefore provide evidence that X-ray flashes (XRFs), X-ray-rich GRBs, and GRBs form a continuum and are a single phenomenon. The results also impose strong constraints on models of XRFs and X-ray-rich GRBs.

We employed a new line-detection method and tried to separate two radiant points corresponding to the dust trails of Comet 55P/Tempel–Tuttle’s perihelion passages in 1699 and 1866. This method integrates the pixel values of a CCD image along a line direction, which enables us to detect 30-times fainter meteors than when using the usual detection methods. It can also precisely determine the angle of the line direction. Two telescopic optics equipped with cooled CCD cameras were pointed to regions that make a right angle with the radiant points in order to precisely determine their positions. Radiant points of the 2001 Leonids derived by this method were found to be consistent with those predicted by McNaught and Asher.

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 Pdot =1 .19 ±0.24 ×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 10d 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 53d. 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

Shore protection works should be designed in harmony with natural environment of coastal areas. This paper shows impacts of shore protection works on loggerhead turtles as a representative animal on sandy beach. Based on the impacts, this paper also shows knowledge necessary for basic plan of shore protection works, design of coastal structures, construction of coastal structures, and administration of coastal area.

We present the study of the aperiodic time variation of the binary X-ray pulsar Centaurus X-3 observed with the Rossi X-Ray Timing Explorer (RXTE). We extracted light curves from six energy bands and calculated cross-spectral functions between the energy band containing the iron K lines (iron band) and the remaining bands. We discovered, for the first time, that the temporal variation of iron band emission is delayed as compared with that of the other energy X-rays by 0.39 ± 0.10 ms (1 σ error). We also discovered that the time difference shows a general trend such that the higher energy X-rays are advanced in comparison with the lower energy X-rays with the exception of the iron band. Assuming that the iron emission lines are fluorescent lines in origin and are emitted by circumstellar matter, we derived 5.6 ± 1.5 ms for the time delay of the temporal variation of the iron line from the average temporal variation in the energy band above the iron absorption edge, taking into account the energy spectral shape and the photoelectric absorption cross section. This result leads to a determination of (1.7 ± 0.5) × 108 cm for the distance between the original X-ray source and the reprocessor, which emits the iron lines. The general trend of the hard X-ray advance is considered to be related to the X-ray emission mechanism on the neutron star.

著者人数：11名, Accepted: 2001-02-05, 資料番号: SA1001905000

This paper has been withdrawn because the class file must not be uploaded., Comment: Appeared in PASJ. Also available at http://www-cr.scphys.kyoto-u.ac.jp/member/jun/job/

ASCA's long look at the 288 millisecond radio pulsar, PSR J0631+1036, reveals coherent X-ray pulsation from this source for the first time. The source was first detected in the serendipitous Einstein observation and later identified as a radio pulsar. Possible pulsation in the gamma-ray band has been detected from the CGRO EGRET data (Zepka, et al. 1996). The X-ray spectrum in the ASCA band is characterized by a hard power-law type emission with a photon index of about 2.3, when fitted with a single power-law function modified with absorption. An additional blackbody component of about 0.14 keV increases the quality of the spectral fit. The observed X-ray flux is 2.1e-13 ergs/s/cm2 in the 1-10 keV band. We find that many characteristics of PSR J0631+1036 are similar to those of middle-aged gamma-ray pulsars such as PSR B1055-52, PSR B0633+17 (Geminga), and PSR B0656+14.

AX J2049.6+2939 is a compact X-ray source in the vicinity of the southern blow-up region of the Cygnus Loop supernova remnant (Miyata et al. 1998a). This source was the brightest X-ray source inside the Cygnus Loop observed during the ASCA survey project. The X-ray spectrum was well fitted by a power-law function with a photon index of $-2.1 \pm 0.1$. Short-term timing analysis was performed and no coherent pulsation was found. Follow-up observations with ASCA have revealed a large variation in X-ray intensity by a factor of $\simeq$ 50, whereas the spectral shape did not change within the statistical uncertainties. In the second ASCA observation, we found another X-ray source, AX J2050.0+2941, at the north east of AX J2049.6+2939. During the three ASCA observations, the X-ray intensity of AX J2050.0+2941 varied by a factor of $\simeq$4. No coherent pulsations could be found for AX J2050.0+2941. We have performed optical photometric and spectroscopic observations in the vicinity of AX J2049.6+2939 at the Kitt Peak National Observatory (KPNO). As a result, all objects brighter than $B$-band magnitude of 22 in the error box can be identified with normal stars. Combined with the X-ray results and the fact that there are no radio counterparts, AX J2049.6+2939 is not likely to be either an ordinary rotation-powered pulsar or an AGN. The nature of AX J2049.6+2939 is still unclear and further observations over a wide energy band are strongly required. As to AX J2050.0+2941, the long-term X-ray variability and the radio counterpart suggests that it is an AGN., Comment: 23 pages, 4 figures, Accepted for publication by Astrophysical Journal

We report the discovery of an X-ray pulsar AX J1740.1-2847 from the Galactic center region. This source was found as a faint hard X-ray object on 7--8 September 1998 with the ASCA Galactic center survey observation. Then, coherent pulsations of P=729 +/- 14 sec period were detected. The X-ray spectrum is described by a flat power-law of ~= 0.7 photon index. The large absorption column of log NH ~= 22.4 (cm^-2) indicates that AX J1740.1-2847 is a distant source, larger than 2.4 kpc, and possibly near at the Galactic center region. The luminosity in the 2--10 keV band is larger than 2.5 x 10^33 erg/s, or likely to be 3.2 x 10^34 erg/s at the Galactic center distance. Although the slow pulse period does not discriminate whether AX J1740.1-2847 is a white dwarf or neutron star binary, the flat power-law and moderate luminosity strongly favor a neutron star binary., Comment: To appear in PASJ Dec. 25, 2000 issue, Vol.52 No.6; 5 pages LaTeX files, uses PASJ95.sty, PASJadd.sty, psfig.sty; also available at http://www-maxi.tksc.nasda.go.jp/%7Esakano/work/paper/index-e.html

We present follow-up observations of the serendipitously discovered 7-s X-ray pulsar AX J1845-0258, which displays characteristics similar to those observed in the anomalous X-ray pulsars (AXPs). We find a dramatic reduction in its 3-10 keV flux in both new ASCA and RXTE datasets. Within the pulsar's position-error locus, we detect a faint point source, AX J184453-025640, surrounded by an arc of diffuse X-ray emission. This arc is coincident with the South-East quadrant of the radio shell of the newly discovered supernova remnant G29.6+0.1, reported in our companion paper (Gaensler et al. 1999). Lack of sufficient flux from the source prevents us from confirming the 7-s pulsed emission observed in the bright state; hence, at present we cannot definitively resolve whether AX J1845-0258 and AX J184453-025640 are one and the same. If they are the same, then the peak-to-peak luminosity changes recorded for AX J1845-0258 may be larger than seen in other AXPs; closer monitoring of this pulsar might lead to a resolution on the mechanism that drives AXPs., Comment: 5 pages with 2 figures, LaTex, emulateapj.sty. To appear in the Astrophysical Journal Letters

MAXI has been approved as one of the first payloads on JEM-EF (Japanese Experiment Module - Exposed Facility) on the International Space Station. It will be developed in collaboration with NASDA (NAtional Space Development Agency of Japan) to be launched in 2003. The objective of MAXI is to monitor X-ray sources over the whole sky with unprecedented sensitivity (less than 3 mCrab in 1 day). Two instruments are planned. The GSC (Gas Slit Cameras) are 1-dim position sensitive proportional counters. The SSC (Solid-state Slit Cameras) contain X-ray CCDs. The GSC covers 2–30 keV with a large window size (more than 5000cm 2 ) and a low background rate. The SSC has a smaller window (∼ 200cm 2 ), but has a higher energy resolution ( E Δ E ∼ 50) and a sensitivity in the lower energies (0.5–10 keV). MAXI will be the first spectroscopic all-sky monitor. Objects to be observed are X-ray transients, AGNs, γ-ray burst afterglows, CXB and so on.

During the course of our X-ray studies of composite supernova remnants, we have discovered two young pulsars. The 65 ms pulsar, AX J1811.5-1926, is found to be associated with the central X-ray emission from the candidate of the historical SNR G11.2-0.3; and the 69 ms pulsar near the SNR RCW 103 is identified with a previously reported GINGA pulsator. Here, we present an observational summary of these two pulsars.

Accepted: 1999-07-19, 資料番号: SA1001387000

We report here the discovery of a new X-ray pulsator, AX J170006-4157, in the Galactic plane. The source was observed three times between 1994 and 1997 by the Advanced Satellite for Cosmology and Astrophysics. Significant pulsations with P = 714.5 ? 0.3 s were discovered from the third observation made between MJD 50,707.8926 and MJD 50,710.2199. The X-ray spectrum is described by a flat power-law function with a photon index of 0.7. Although the spectrum could also be fitted by thermal models, the temperature obtained was unphysically high. The hard spectrum suggests that the source is a neutron star binary pulsar similar to X Persei (4U 0352+309), but we cannot completely exclude the possibility that it is a white dwarf binary.

We have performed an experiment on the signal rise time of a Xe gas proportional counter using a polarized X-ray beam of synchrotron orbital radiation with energies from 10 to 40 keV. When the counter anode is perpendicular to the electric vector of the incident X-ray photons, the average rise time becomes significantly longer than that for the parallel case. This indicates that the conventional gas proportional counters are useful for X-ray polarimetry. The moderate modulation contrast of this rise-time polarimeter (M"0.1 for 10 keV X-rays and M"0.35 for 40 keV X-rays), with capability of the simultaneous measuring X-ray energies and the timing, would be useful for applications in X-ray astronomy and in other fields. ( 1999 Elsevier Science B.V. All rights reserved.

We report here the discovery of a faint 220 s X-ray pulsar, AX J1749.2-2725, with ASCA. In the analysis, we used a method that can detect a pulsating source in a field of view contaminated by stray light. The source was observed on four occasions between 1995 March and 1997 September. The observed source flux was ~3.0 × 10-11 ergs s-1 cm-2 (2-10 keV) in 1995 March and became an order of magnitude fainter during the 2.5 yr interval. We cannot rule out the possibility that AX J1749.2-2725 is a nearby (d 1.3 kpc) DQ Her-type white dwarf binary, while the hard X-ray spectrum and the transient behavior suggest that it is a distant (d ~ 8.5 kpc) binary system containing a neutron star.

We report here a serendipitous discovery of a faint X-ray pulsar, AX J1845.0-0300, with ASCA. Its period of ~7 s, together with its low luminosity and the soft spectrum, suggest that it may be the eighth candidate member of braking X-ray pulsars. Two observations, 3.5 yr apart, showed a significant flux decrease of more than 1 order of magnitude. The source is in the Scutum arm region (l ~ 30°), which was claimed as a colony of X-ray pulsars by Koyama et al. This discovery strengthens the hypothesis by Koyama et al. that there may be a number of low-luminosity pulsars on the Galactic plane, particularly in the Scutum arm region.

Accepted: 1998-03-01, 資料番号: SA1001942000

著者人数：14名, Accepted: 1997-10-10, 資料番号: SA1001912000

Accepted: 1997-12-16, 資料番号: SA1001378000

Microfocus X-ray generators have been extensively used for magnification radiography. In these applications, the sharpness of an image depends on the X-ray source size. Therefore, it is important to evaluate and optimize the X-ray spot quantitatively. Although several methods have been devised to date, some require complicated systems whereas others are not fully quantitative. Here, we introduce a simple, practical, and quantitative method that makes use of the penumbra of a knife edge. Because the method is very simple, it can be readily integrated as an auto focusing system of a focal spot.

CTA 1 is a center-filled supernova remnant (SNR) whose morphology and spectrum indicate the presence of a central pulsar, a synchrotron nebula, and a thermal component associated with the expansion of the blast wave into the interstellar medium. The centrally bright emission surrounds the position of a faint point source of X-rays observed with the ROSAT PSPC. Here we report on ASCA observations that confirm the nonthermal nature of the diffuse emission from the central regions of the remnant. We also present evidence for weak thermal emission that appears to increase in strength toward the outer boundary of the SNR. Thus, CTA 1 appears to be an X-ray composite remnant. Both the aftermath of the explosive supernova event and the energetic compact core are observable.

We report ASCA results of a featureless X-ray spectrum from RX J1713.7-3946, a new shell-like SNR discovered with the ROSAT all sky survey. The northwest part of RX J1713.7-3946 was in the field of the ASCA Galactic Plane Survey Project and was found to exhibit a shell-like structure. The spectrum, however shows neither line emission nor any signature of a thermal origin. Instead, a power-law model with a photon index of 2.4-2.5 gives reasonable fit to the spectrum, suggesting a non-thermal origin. Together with the similarity to SN1006, we propose that RX J1713.7-3946 is the second example, after SN1006, of a synchrotron X-ray radiation from a shell of SNRs. Since the synchrotron X-rays suggest existence of extremely high energy charged particles in the SNR shell, our discovery should have strong impact on the origin of the cosmic X-rays., 4 pages, 3 postscript figures

We report here the discovery of a 65 ms X-ray pulsar in the supernova remnant G11.2-0.3 with ASCA. The object is known to be a composite supernova remnant that shows both an extended shell component and a compact plerionic component. We have detected a sinusoidal pulsation with an amplitude of ~19% in the hard X-ray band (3-10 keV). The object has been proposed to be the historical remnant of the supernova of A.D. 386, which makes it the second candidate for the secure association of a pulsar and a historical supernova after the Crab Nebula and its pulsar.

We report early BVRcIc imaging of the INTEGRAL GRB 041218. The observation started 129 s after the burst and a sequence of exposures in V, Rc, Ic, and B bands were repeated. The optical afterglow is detected in Rc and Ic bands while it was not detected in B and V. We find that the early afterglow deviates from a single power law decay and identify two characteristic timescales (breaks). Such breaks are theoretically expected from synchrotron cooling in the relativistic fireball (Sari et al. 1998) and we crudely constrain the physical condition of the relativistic shock.

We report time-resolved CCD photometry of the cataclysmic variable EG Aquarii during the 2006 November outburst During the outburst, superhumps were unambiguously detected with a mean period of 0.078828(6) days, firstly classifying the object as an SU UMa-type dwarf nova. It also turned out that the outburst contained a precursor. At the end of the precursor, immature profiles of humps were observed. By a phase analysis of these humps, we interpreted the features as superhumps. This is the second example that the superhumps were shown during a precursor. Near the maximum stage of the outburst, we discovered an abrupt shift of the superhump period by ${\sim}$ 0.002 days. After the supermaximum, the superhump period decreased at the rate of $\dot{P}/P$=$-8.2{\times}10^{-5}$, which is typical for SU UMa-type dwarf novae. Although the outburst light curve was characteristic of SU UMa-type dwarf novae, long-term monitoring of the variable shows no outbursts over the past decade. We note on the basic properties of long period and inactive SU UMa-type dwarf novae., 9 pages, 7 figures, accepted for PASJ

The energy resolution of the X-ray CCDs onboard the Suzaku satellite (X-ray Imaging Spectrometer; XIS) has been degraded since the launch due to radiation damage. To recover from this, we have applied a spaced-row charge injection (SCI) technique to the Suzaku XIS in orbit. By injecting charge into CCD rows periodically, the energy resolution 14 months after launch is improved from 210 eV to 150 eV at 5.9 keV, which is close to the resolution just after the launch (140 eV). Additional information on these results is given in a companion paper by the XIS team. In this paper, we report the details of CCD charge transfer inefficiency (CTI) in the SCI mode, the correction method, and the implementation of it in ground analysis software for XIS data. In the SCI mode, CTI depends on the distance of a charge packet from the nearest charge-injected row, and the gain shows a periodic non-uniformity. Using flight data obtained with the onboard calibration sources, as well as a cosmic source (the Perseus cluster of galaxies), we studied the non-uniformity in detail. We developed a method to correct for the non-uniformity that will be valuable as the radiation damage progresses in future.

The CCD detectors in the X-ray Imaging Spectrometers (XIS) aboard Suzaku have been equipped with a precision charge injection capability. The purposes of this capability are to measure and reduce the detector degradation caused by charged particle radiation encountered on-orbit. Here we report the first results from routine operation of the XIS charge injection function. After 12 months' exposure of the XIS to the on-orbit charged particle environment, charge injection already provided measurable improvements in detector performance: the observed width of the 5.9 keV line from the onboard calibration source was reduced from 205 eV to less than 145 eV. The rate of degradation is also significantly smaller with charge injection, so its benefit will increase as the mission progresses. Measured at 5.9 keV, the radiation-induced rate of gain degradation is reduced by a factor of 4.3 ± 0.1 in the front-illuminated sensors when injecting charge greater than 6 keV equivalent per pixel. The corresponding rate of degradation in spectral resolution is reduced by a factor 6.5 ± 0.3. Injection of a smaller quantity of injected charge in the back-illuminated XIS sensor produces commensurately smaller improvement factors. Excellent uniformity of the injected charge pattern is essential to the effectiveness of charge injection in the XIS.

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We report on time-resolved CCD photometry of four outbursts of a short-period SU UMa-type dwarf nova, V844 Herculis. We successfully determined the mean superhump periods to be 0.05584(64) days, and 0.055883(3) for the 2002 May superoutburst, and the 2006 April-May superoutburst, respectively. During the 2002 October observations, we confirmed that the outburst is a normal outburst, which is the first recorded normal outburst in V844 Her. We also examined superhump period changes during 2002 May and 2006 April-May superoutbursts, both of which showed increasing superhump period over the course of the plateau stage. In order to examine the long-term behavior of V844 Her, we analyzed archival data over the past ten years since the discovery of this binary. Although photometry is not satisfactory in some superoutbursts, we found that V844 Her showed no precursors and rebrightenings. Based on the long-term light curve, we further confirmed V844 Her has shown almost no normal outbursts despite the fact that the supercycle of the system is estimated to be about 300 days. In order to explain the long-term light curves of V844 Her, evaporation in the accretion disk may play a role in the avoidance of several normal outbursts, which does not contradict with the relatively large X-ray luminosity of V844 Her., Comment: 10 pages, 11 figures, accepted for PASJ

We report in-flight status of the X-ray detectors on board the Suzaku observatory, the 5th X-ray astronomy satellite of Japan launched on July 10, 2005. Suzaku is equipped with two types of instruments: one is the X-ray imaging spectrometers (XISs) and the other is hard X-ray detector (HXD). XIS utilizes the X-ray CCD camera in combination with the grazing-incidence X-ray telescope. HXD is a non-imaging, hybrid detector utilizing Si PIN diodes and GSO/BGO phoswich counters. Suzaku takes a low-earth, circular orbit with an altitude of 560 km and an inclination of 31 deg. This means that Suzaku goes through the south atlantic anomaly about 1/3 of its revolutions. This has a large impact on the in-flight performance of XIS and HXD, which is reported in detail in the present paper.

The X-ray Imaging Spectrometer on the Suzaku satellite consists three front-illuminated (FI) and one back-illuminated (BI) CCD cameras. Using ground calibration data taken at Kyoto University and Osaka University, we obtained the energy response of the XIS, which consists of at least six components: 1. a main peak, 2. a sub peak, 3. a triangle component, 4. a Si escape, 5. a Si line, and 6. a constant component. The relation between the energy and the pulse height was also estimated, which is called as a gain. The relation cannot be represented with a single linear function. Then we divided the gain into two parts at the Si edge (1.839 keV) and each part can be described with a single linear function. Thus there is a discontinuity at 1.839 keV in the XIS gain. We have monitored the variation of the gain and energy resolution in orbit by observing the calibration source of 55Fe illuminating two corners of each CCD.

Suzaku is the fifth Japanese X-ray astronomical satellite and it was launched in July 2005. The Suzaku X-ray Imaging Spectrometers (XISs) consist of four X-ray Charge-Coupled Device (CCD) cameras. Three of them are front-illuminated (FI) CCD, and the other is back-illuminated (BI) CCD. The strong points of the XIS are a high energy resolution, a large effective area, and a low and stable background. In particular, the background level of the Suzaku/XIS is much lower than the other X-ray satellites, XMM-Newton/EPIC and Chandra/ACIS. We investigated the background property of the XIS using the data obtained when the satellite is looking at the night earth, and proved the low level and the stability of the XIS background. Non X-ray background (NXB) consists of continuum component and some emission lines. The continuum component is very different between the FI-CCD and the BI-CCD. We discussed the positional dependence of the continuum component and the line components, and proved that the flux of the line components of the NXB is higher in the frame-store region than the imaging area. Finally, we investigated the effects of magnetic cut-off rigidity (COR) upon the count rate of NXB.