arXiv subjects

K. Makishima

Publications and source records attributed to K. Makishima.

At least 73 records · Page 4Linked to original sources

arXiv2005

GRBs Optical follow-up observation at Lulin observatory, Taiwan

The Lulin GRB program, using the Lulin One-meter Telescope (LOT) in Taiwan started in July 2003. Its scientific aims are to discover optical counterparts of XRFs and short and long GRBs, then to quickly observe them in multiple bands. Thirteen follow-up observations were provided by LOT between July 2003 and Feb. 2005. One host galaxy was found at GRB 031203. Two optical afterglows were detected for GRB 040924 and GRB 041006. In addition, the optical observations of GRB 031203 and a discussion of the non-detection of the optical afterglow of GRB 031203 are also reported in this article.

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arXiv2005

The search for optical emission on and before the GRB trigger with the WIDGET telescope

WIDGET is a robotic telescope for monitoring the HETE-2 field-of-view to detect Gamma-ray Burst optical flashes or possible optical precursors. The system has 62degx62deg wide field-of-view which covers about 80% of HETE-2 one with a 2kx2k Apogee U10 CCD camera and a Canon EF 24mm f/1.4 wide-angle lens without a bandpass filter. WIDGET has been in operation since June 2004 at Akeno observing site where is about 200 km apart from Tokyo. Typical limiting magnitude with S/N=3 at the site is V=10mag for 5 seconds exposure and V=11mag for 30 seconds exposure. We had already six coincident observations with HETE-2 position alerts. It was, however, cloudy for all cases due to rainy season in Japan. Expected number of coincident observations under clear sky is about 5 events per year. We will extend the system in early 2005 for Swift era to monitor optical transients in wider field-of-view, multi-color or polarization modes.

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arXiv2005

GRB follow-up observations in the East-Asian region

In 2004, we established a Japan-Taiwan-China collaboration for GRB study in the East-Asian region. This serves as a valuable addition to the world-wide optical and infrared follow-up network, because the East-Asia region would otherwise be blank. We have been carrying out imaging and spectroscopic follow-up observations at Lulin (Taiwan), Kiso (Japan), WIDGET (Japan) and Xinglong (China). From Xinglong and Kiso, we can locate candidates and obtain early time spectra for afterglows. While WIDGET provides early time observations before the burst, the high-time resolution for multi-band light curves can be obtained at Lulin. With the data from these sites, we can obtain detailed information about the light curve and redshift of GRBs, which are important to understand the mechanism of the afterglows. Up to March 2005, ten follow-up observations have been provided by this East-Asia cooperation. Two optical afterglows were detected, GRB 040924 and GRB 041006. The results of the two detected afterglows are reported in this article.

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arXiv2005

Kiso observations for 20 GRBs in HETE-2 era

We have established a GRB follow-up observation system at Kiso observatory (Japan) in 2001. Since the east Asian area had been blank for the GRB follow-up observational network, this observational system is very important in studying the temporal and spectral evolution of early afterglows. Using this system, we have performed quick observations for optical afterglows from early phase based on HETE-2 and INTEGRAL alerts. Thanks to the quick follow-up observation system, we have been able to use the Kiso observatory in 20 events, and conduct their follow-up observations in optical and near infrared wavelengths.

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arXiv2004

Wide band X-ray Imager (WXI) and Soft Gamma-ray Detector (SGD) for the NeXT Mission

The NeXT mission has been proposed to study high-energy non-thermal phenomena in the universe. The high-energy response of the super mirror will enable us to perform the first sensitive imaging observations up to 80 keV. The focal plane detector, which combines a fully depleted X-ray CCD and a pixellated CdTe detector, will provide spectra and images in the wide energy range from 0.5 keV to 80 keV. In the soft gamma-ray band up to ~1 MeV, a narrow field-of-view Compton gamma-ray telescope utilizing several tens of layers of thin Si or CdTe detector will provide precise spectra with much higher sensitivity than present instruments. The continuum sensitivity will reach several times 10^(-8) photons/s/keV/cm^(2) in the hard X-ray region and a few times10^(-7) photons/s/keV/cm^(2) in the soft gamma-ray region.

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arXiv2004

INTEGRAL/SPI Limits on Electron-Positron Annihilation Radiation from the Galactic Plane

The center of our Galaxy is a known strong source of electron-positron 511-keV annihilation radiation. Thus far, however, there have been no reliable detections of annihilation radiation outside of the central radian of our Galaxy. One of the primary objectives of the INTEGRAL (INTErnational Gamma-RAy Astrophysics Laboratory) mission, launched in Oct. 2002, is the detailed study of this radiation. The Spectrometer on INTEGRAL (SPI) is a high resolution coded-aperture gamma-ray telescope with an unprecedented combination of sensitivity, angular resolution and energy resolution. We report results from the first 10 months of observation. During this period a significant fraction of the observing time was spent in or near the Galactic Plane. No positive annihilation flux was detected outside of the central region (|l| > 40 deg) of our Galaxy. In this paper we describe the observations and data analysis methods and give limits on the 511-keV flux.

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arXiv2004

A search for cyclotron resonance features with INTEGRAL

We present an INTEGRAL observation of the Cen-Crux region in order to search the electron cyclotron resonance scattering features from the X-ray binary pulsars. During the AO1 200ks observation, we clearly detected 4 bright X-ray binaries, 1 Seyfert Galaxy, and 4 new sources in the field of view. Especially from GX301-2, the cyclotron resonance feature is detected at about 37 keV, and width of 3--4 keV. In addition, the depth of the resonance feature strongly depends on the X-ray luminosity. This is the first detection of luminosity dependence of the resonance depth. The cyclotron resonance feature is marginally detected from 1E1145.1-6141. Cen X-3 was very dim during the observation and poor statistics disable us to detect the resonance features.These are first INTEGRAL results of searching for the cyclotron resonance feature.

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arXiv2003

Early ($<$0.3 day) R-band light curve of the optical afterglow of GRB030329

We observed the optical afterglow of the bright gamma-ray burst GRB030329 on the nights of 2003 March 29, using the Kiso observatory (the University of Tokyo) 1.05 m Schmidt telescope. Data were taken from March 29 13:21:26 UT to 17:43:16 (0.072 to 0.253 days after the burst), using an $Rc$-band filter. The obtained $Rc$-band light curve has been fitted successfully by a single power law function with decay index of $0.891\pm0.004$. These results remain unchanged when incorporating two early photometric data points at 0.065 and 0.073 days, reported by Price et al.(2003) using the SSO 40 inch telescope, and further including RTT150 data (Burenin et al. 2003) covering at about 0.3 days. Over the period of 0.065-0.285 days after the burst, any deviation from the power-law decay is smaller than $\pm$0.007 mag. The temporal structure reported by Uemura et al. (2003) does not show up in our $R$-band light curve.

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arXiv2003

Multi-band optical follow-up observations of GRB 020813 at KISO and Bisei observatories

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 $\sim$0.2 days, respectively. The optical spectral index stayed approximately constant at $\sim$0.9 over 0.17 $\sim$ 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.

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arXiv2003

XMM-Newton Survey of a Distance-limited Sample of Seyfert Galaxies: Preliminary Spectral Results

An unbiased estimate of the average intrinsic X-ray properties and column density distribution of Seyfert galaxies in the local Universe is crucial to validate unified models of active galactic nuclei (AGNs) and to synthesis models for the X-ray background. We present here preliminary results obtained from an on-going XMM-Newton study (~250 ks awarded in the EPIC GT) on a well-defined, statistically complete, and significant sample of nearby Seyfert galaxies.

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arXiv2002

High resolution soft X-ray spectroscopy of the elliptical galaxy NGC 5044. Results from the reflection grating spectrometer on-board XMM-Newton

The results from an X-ray spectroscopic study of the giant elliptical galaxy NGC5044 in the center of a galaxy group are presented. The line dominated soft X-ray spectra (mainly Fe-L and O VIII Ly_a) from the diffuse gas are resolved for the first time in this system with the Reflection Grating Spectrometers on-board XMM-Newton and provide a strong constraint on the temperature structure. The spectra integrated over 2' (\sim 20kpc) in full-width can be described by a two temperature plasma model of 0.7keV and 1.1keV. Most of the latter component is consistent with originating from off-center regions. Compared to the isobaric cooling flow prediction, the observation shows a clear cut-off below a temperature of 0.6 +-0.1keV. Furthermore, the Fe and O abundances within the central 10--20kpc in radius are accurately measured to be 0.55+-0.05 and 0.25+-0.1 times the solar ratios, respectively. The observed cut-off temperature of this galaxy and other central galaxies in galaxy groups and clusters are compared with the scale of the galaxy and properties of the surrounding intra-cluster medium. Based on this comparison, the origin of the lack of predicted cool emission is discussed.

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arXiv2002

A Chandra detection of diffuse hard X-ray emission associated with the lobes of the radio galaxy 3C 452

An 80 ksec Chandra ACIS observation of the radio galaxy 3C 452 is reported. A diffuse X-ray emission associated with the lobes has been detected with high statistical significance, together with the X-ray nucleus of the host galaxy. The 0.5--5 keV ACIS spectrum of the diffuse emission is described by a two-component model, consisting of a soft thermal plasma emission from the host galaxy halo and a hard non-thermal power-law component. The hard component is ascribed to the inverse Comptonization of cosmic microwave background photons by the synchrotron emitting electrons in the lobes, because its spectral energy index, 0.68+-0.28, is consistent with the radio synchrotron index, 0.78. These results reveal a significant electron dominance in the lobes. The electrons are inferred to have a relatively uniform distribution, while the magnetic field is compressed toward the lobe periphery.

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arXiv2002

First Results from a XMM-Newton Survey of a Distance-Limited (D<22 Mpc) Sample of Seyfert Galaxies: I- the Agns

We report here preliminary results from a survey of nearby Seyfert galaxies using the EPIC CCDs on board XMM-Newton. The total sample consists of 28 Seyfert galaxies, and constitute a well-defined, complete (B<12.5 mag), and volume-limited (D<22 Mpc) sample of Seyfert galaxies in the northern (Delta > 0 deg.) hemisphere. The survey has been initiated in June, 2001, and we report here the results for the 6 objects analyzed so far, namely: NGC3185, NGC3486, NGC3941, NGC4138, NGC4565, and NGC5033. The main goal of this survey is to obtain a better and unbiased understanding of the ``typical'' Seyfert X-ray spectrum (e.g. the distribution of their absorption column density) in the local Universe. This is crucial to verify the predictions and, thus, to validate unified models, and is a fundamental parameter of synthesis models for the X-ray background. A companion poster (paper II: L. Foschini et al., these proceedings) illustrates how this survey will also allow a comprehensive spectral study of the brightest (highest-luminosity) off-nuclear sources in the galaxies.

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arXiv2001

High Resolution Observations of the Elliptical Galaxy NGC 4636 with the Reflection Grating Spectrometer On-Board XMM-Newton

We present the first high spectral resolution X-ray observation of the giant elliptical galaxy NGC 4636, obtained with the Reflection Grating Spectrometer on-board the XMM-Newton Observatory. The resulting spectrum contains a wealth of emission lines from various charge states of oxygen, neon, magnesium, and iron. Examination of the cross-dispersion profiles of several of these lines provides clear, unambiguous evidence of resonance scattering by the highest oscillator strength lines, as well as a weak temperature gradient in the inner regions of the interstellar medium. We invoke a sophisticated new Monte Carlo technique which allows us to properly account for these effects in performing quantitative fits to the spectrum. Our spectral fits are not subject to many of the systematics that have plagued earlier investigations. The derived metal abundances are higher than have been inferred from prior, lower spectral resolution observations of this source (Awaki et al. 1994), but are still incompatible with conventional chemical enrichment models of elliptical galaxies. In addition, our data are incompatible with standard cooling flow models for this system - our derived upper limit to the mass deposition rate is below the predicted value by a factor of 3--5.

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arXiv2001

A Possible X-Ray Periodicity at Several Tens Hours of a Ultra-Luminous Compact X-Ray Source in IC 342

A long (155 hours) ASCA observation was performed of two ultra luminous compact X-ray sources, Source 1 and Source 2, in the spiral galaxy IC 342. While Source 1 that was in a hard spectral state varied little, Source 2 that was in its soft spectral state varied significantly on a time scale of about one day. The rms variation amplitude amounts to 5% in the 2-10 keV band, but is less than 4% in 0.7-2 keV. The variation involves statistically significant changes in the parameters describing multi-color disk blackbody emission from this source. The variation is possibly periodic, with a period of either 31 $\pm$ 2, hours or 41 $\pm$ 3 hours. Both are consistent with the orbital period of a semi-detached binary formed by a black hole and a main-sequence star of several tens solar masses. These results reinforce the interpretation of these X-ray objects in terms of accreting massive stellar black holes.

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arXiv2001

X-Ray Beaming due to Resonance Scattering in the Accretion Column of Magnetic Cataclysmic Variables

Extremely strong ionized Fe emission lines, with the equivalent width reaching about 4000 eV, were discovered with ASCA from a few Galactic compact objects, including AX J2315-0592, RX J1802.1+1804 and AX J1842.8-0423. These objects are thought to be binary systems containing magnetized white dwarfs (WDs). A possible interpretation of the strong Fe-K line is the line-photon collimation in the WD accretion column, due to resonance scattering of line photons. The collimation occurs when the accretion column has a flat shape, and the effect is augmented by the vertical velocity gradient there, which reduces the resonant trapping of resonant photons along the magnetic field lines. This effect was quantitatively confirmed with Monte-Carlo simulations. Furthermore, with ASCA observations of the polar V834 Centauri, this collimation effect was clearly detected as a rotational modulation of the equivalent width of the Fe-K emission line. Extremely strong emission lines mentioned above can be explained by our interpretation consistently. Combing this effect with other X-ray information, the geometry and plasma parameters in the accretion column were determined.

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arXiv2001

Spectral variability of Ultra Luminous Compact X-ray Sources in Nearby Spiral Galaxies

Using the X-ray data taken with ASCA, a detailed analysis was made of intensity and spectral variations of three ultra-luminous extra-galactic compact X-ray sources (ULXs); IC 342 source 1, M81 X-6, and NGC 1313 source B, all exhibiting X-ray luminosity in the range 10^{39}-1.5x10^{40} erg s^{-1}. As already reported, IC 342 source 1 showed short-term X-ray intensity variability by a factor of 2.0 on a typical time scale of 10 ks. M81 X-6 varied by a factor of 1.6 across seven observations spanning 3 years, while NGC 1313 source B varied by a factor of 2.5 between two observations conducted in 1993 July and 1995 November. The ASCA spectra of these sources, acquired on these occasions, were all described successfully as optically-thick emission from standard accretion disks around black holes. This confirms previous ASCA works which explained ULXs as mass-accreting massive black-hole binaries. In all three sources, the disk color temperature was uncomfortably high at T_{in}=1.0-2.0 keV, and was found to vary in proportion to the square-root of the source flux. The apparent accretion-disk radius is hence inferred to change as inversely proportional to T_{in}. This suggests a significant effect of advection in the accretion disk. However, even taking this effect fully into account, the too high values of T_{in} of ULXs cannot be explained. Further invoking the rapid black-hole rotation may give a solution to this issue.

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arXiv2000

X-ray measurements of the field and particle energy distributions in the west lobe of the radio galaxy NGC 1316 (Fornax A)

A follow-up X-ray study was made of the west lobe of the radio galaxy Fornax A, (NGC 1316) based on new ASCA observations made in 1997 for 98 ks, and incorporating the previous observation in 1994 for 39 ks. The 0.7--10 keV spectrum of the emission can be described by a power-law of energy index 0.74 +/- 0.10, which agrees with the synchrotron radio index of 0.9 +/- 0.2. Therefore, the X-rays are reconfirmed to arise via inverse-Compton scattering of the cosmic microwave photons, as Kaneda et al. (1995) and Feigelson et al. (1995) concluded. The surface brightness of the inverse-Compton X-rays exhibits a relatively flat distribution over the west lobe, indicative of an approximately spherical emissivity distribution with a radius of ~11' (75 kpc). n contrast, the 1.4 GHz radio image by Ekers et al. (1983) exhibits a rim- brightened surface brightness, consistentwith a shell-like emissivity distribution whose inner and outer boundaries are 4' and 11', respectively. These morphological differences between radio and X-rays suggest that the relativistic electrons are distributed homogeneously over the lobe volume, whereas the magnetic field is amplified toward the lobe rim region.

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