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Microcalorimeters have demonstrated success in delivering high spectral resolution, and have paved the path to revolutionary new science possibilities in the coming decade of X-ray astronomy. There are several research areas in compact object science that can only be addressed with energy resolution Delta(E)<~5 eV at photon energies of a few keV, corresponding to velocity resolution of <~a few hundred km/s, to be ushered in by microcalorimeters. Here, we review some of these outstanding questions, focusing on how the research landscape is set to be transformed (i) at the interface between accreting supermassive black holes and their host galaxies, (ii) in unravelling the structures of accretion environments, (iii) in resolving long-standing issues on the origins of energy and matter feedback, and (iv) to test mass-scaled unification of accretion and feedback. The need to learn lessons from Hitomi and to make improvements in laboratory atomic data precision as well as plasma modeling are highlighted., Comment: To appear in Nature Astronomy as a review. Author version, before final editorial and style revisions

We present the catalog of Interplanetary Network (IPN) localizations for 199 short-duration gamma-ray bursts (sGRBs) detected by the Konus-Wind (KW) experiment between 2011 January 1 and 2021 August 31, which extends the initial sample of IPN localized KW sGRBs (arXiv:1301.3740) to 495 events. We present the most comprehensive IPN localization data on these events, including probability sky maps in HEALPix format., Comment: Published in ApJS

We have performed $^{59}$Co NMR measurements of CeCoIn$_5$ down to ultralow temperatures. We find that the temperature dependence of the spin-echo intensity provides a good measure of the sample temperature, enabling us to determine a pulse condition not heating up the sample by the NMR pulses down to ultralow temperatures. From the longitudinal relaxation time ($T_1$) measurements at 5 T applied along the $c$ axis, a pronounced peak in $1/T_1T$ is observed at 20 mK, implying an appearance of magnetic order as suggested by the recent quantum oscillation measurements [H. Shishido {\it et al.}, Phys. Rev. Lett. {\bf 120}, 177201 (2018)]. On the other hand, the NMR spectrum shows no change below 20 mK. Moreover, the peak in $1/T_1 T$ disappears at 6 and 8 T in contrast to the results of the quantum oscillation. We discuss that an antiferromagnetic state with a moment lying in the $a$--$b$ plane can be a possible origin for the peak in $1/T_1 T$ at 5 T., Comment: 9 pages, 10 figures; (v2) texts and figures updated; (v3) typo fixed, DOI and reference added

A new scheme to determine the neutrino mass matrix is proposed using atomic de-excitation between two states of a few eV energy spacing. The determination of the smallest neutrino mass of the order of 1 meV and neutrino mass type, Majorana or Dirac, becomes possible, if one can coherently excite more than 1 gram of atoms using two lasers., Comment: 6 pages, 3 figures

We present the first radio polarimetric observations of a fast-rising blue optical transient, AT2018cow. Two epochs of polarimetry with additional coincident photometry were performed with the Atacama Large Millimeter/submillimeter Array (ALMA). The overall photometric results based on simultaneous observations in the 100 and 230 GHz bands are consistent with the non-thermal radiation model reported by Ho et al. (2019) and indicate that the spectral peaks ($\sim110$ GHz at the first epoch and $\sim67$ GHz at the second epoch) represent the synchrotron self-absorption frequency. The non-detection of linear polarization with $<$0.15% in the 230 GHz band at the phase when the effect of synchrotron self-absorption was quite small in the band may be explained by internal Faraday depolarization with high circumburst density and strong magnetic field. This result supports the stellar explosion scenario rather than the tidal disruption model. The maximum energy of accelerating particles at the shocks of AT2018cow-like objects is also discussed., Comment: 7 pages, 3 figures, 1 table, accepted for publication in ApJL

We report the first detection of radio polarization of a GRB afterglow with the first intensive combined use of telescopes in the millimeter and submillimeter ranges for GRB171205A. The linear polarization degree in the millimeter band at the sub-percent level ($0.27 \pm 0.04\%$) is lower than those observed in late-time optical afterglows (weighted average of $\sim 1\%$). The Faraday depolarization by non-accelerated, cool electrons in the shocked region is one of possible mechanisms for the low value. In this scenario, larger total energy by a factor of $\sim 10$ than ordinary estimate without considering non-accelerated electrons is required. The polarization position angle varies by at least 20 degrees across the millimeter band, which is not inconsistent with this scenario. This result indicates that polarimetry in the millimeter and submillimeter ranges is a unique tool for investigating GRB energetics, and coincident observations with multiple frequencies or bands would provide more accurate measurements of the non-accelerated electron fraction., Comment: Accepted to ApJ Letters; 8 pages, 4 figures, 1 table

ASTRO-H, the sixth Japanese X-ray observatory, which is scheduled to be launched by the end of Japanese fiscal year 2015 has a capability to observe the prompt emission from Gamma-ray Bursts (GRBs) utilizing BGO active shields for the soft gamma-ray detector (SGD). The effective area of the SGD shield detectors is very large and its data acquisition system is optimized for short transients such as short GRBs. Thus, we expect to perform more detailed time-resolved spectral analysis with a combination of ASTRO-H and Fermi LAT/GBM to investigate the gamma-ray emission mechanism of short GRBs. In addition, the environment of the GRB progenitor should be a remarkable objective from the point of view of the chemical evolution of high-z universe. If we can maneuver the spacecraft to the GRBs, we can perform a high-resolution spectroscopy of the X-ray afterglow of GRBs utilizing the onboard micro calorimeter and X-ray CCD camera., Comment: 4 pages, 6 figures, 2014 Fermi Symposium proceedings - eConf C141020.1

In this paper, we demonstrate ASTRO-H's capability to measure the chemical evolution in the high-z (z <~ 3) universe by observing X-ray afterglows of gamma-ray bursts (GRBs) and distant Blazars. Utilizing these sources as background light sources, the excellent energy resolution of ASTRO-H/SXS allows us to detect emission and absorption features from heavy elements in the circumstellar material in the host galaxies, from the intergalactic medium (IGM) and in the ejecta of GRB explosions. In particular, we can constrain the existence of the warm-hot intergalactic material (WHIM), thought to contain most of the baryons at redshift of z < ~3, with a typical exposure of one day for a follow-up observation of a GRB afterglow or 300 ks exposure for several distant Blazars. In addition to the chemical evolution study, the combination of the SGD, HXI, SXI and SXS will measure, for the first time, the temporal behavior of the spectral continuum of GRB afterglows and Blazars over a broad energy range and short time scales allowing detailed modeling of jets. The ability to obtain these data from GRB afterglows will depend critically on the availability of GRB triggers and the capability of ASTRO-H to respond rapidly to targets of opportunity. At the present time it seems as if Swift will still be functioning normally during the first two years of ASTRO-H operations providing the needed triggering capability., Comment: 15 pages, 7 figures, ASTRO-H White Paper

We present optical photometry and spectroscopy of the broad-lined Type Ic supernova (SNIc-BL) PTF10qts, which was discovered as part of the Palomar Transient Factory. The supernova was located in a dwarf galaxy of magnitude $r=21.1$ at a redshift $z=0.0907$. We find that the $R$-band light curve is a poor proxy for bolometric data and use photometric and spectroscopic data to construct and constrain the bolometric light curve. The derived bolometric magnitude at maximum light is $M_{\rm bol} = -18.51\pm0.2$ mag, comparable to that of SN 1998bw ($M_{\rm bol} = -18.7$ mag) which was associated with a gamma-ray burst (GRB). PTF10qts is one of the most luminous SNIc-BL observed without an accompanying GRB. We estimate the physical parameters of the explosion using data from our programme of follow-up observations, finding that it produced a larger mass of radioactive nickel compared to other SNeIc-BL with similar inferred ejecta masses and kinetic energies. The progenitor of the event was likely a $\sim20$M$_{\odot}$ star., Comment: Accepted for publication in MNRAS

Gamma Ray Bursts (GRBs) are characterized by ultra-relativistic outflows, while supernovae are generally characterized by non-relativistic ejecta. GRB afterglows decelerate rapidly usually within days, because their low-mass ejecta rapidly sweep up a comparatively larger mass of circumstellar material. However supernovae, with heavy ejecta, can be in nearly free expansion for centuries. Supernovae were thought to have non-relativistic outflows except for few relativistic ones accompanied by GRBs. This clear division was blurred by SN 2009bb, the first supernova with a relativistic outflow without an observed GRB. Yet the ejecta from SN 2009bb was baryon loaded, and in nearly-free expansion for a year, unlike GRBs. We report the first supernova discovered without a GRB, but with rapidly decelerating mildly relativistic ejecta, SN 2012ap. We discovered a bright and rapidly evolving radio counterpart driven by the circumstellar interaction of the relativistic ejecta. However, we did not find any coincident GRB with an isotropic fluence of more than a sixth of the fluence from GRB 980425. This shows for the first time that central engines in type Ic supernovae, even without an observed GRB, can produce both relativistic and rapidly decelerating outflows like GRBs., Comment: 8 pages, 5 figures, 1 table, accepted for publication in ApJ

Between the launch of the \textit{GGS Wind} spacecraft in 1994 November and the end of 2010, the Konus-\textit{Wind} experiment detected 296 short-duration gamma-ray bursts (including 23 bursts which can be classified as short bursts with extended emission). During this period, the IPN consisted of up to eleven spacecraft, and using triangulation, the localizations of 271 bursts were obtained. We present the most comprehensive IPN localization data on these events. The short burst detection rate, $\sim$18 per year, exceeds that of many individual experiments., Comment: Published version

We present Interplanetary Network (IPN) data for the gamma-ray bursts in the first Fermi Gamma-Ray Burst Monitor (GBM) catalog. Of the 491 bursts in that catalog, covering 2008 July 12 to 2010 July 11, 427 were observed by at least one other instrument in the 9-spacecraft IPN. Of the 427, the localizations of 149 could be improved by arrival time analysis (or triangulation). For any given burst observed by the GBM and one other distant spacecraft, triangulation gives an annulus of possible arrival directions whose half-width varies between about 0.4' and 32 degrees, depending on the intensity, time history, and arrival direction of the burst, as well as the distance between the spacecraft. We find that the IPN localizations intersect the 1 sigma GBM error circles in only 52% of the cases, if no systematic uncertainty is assumed for the latter. If a 6 degree systematic uncertainty is assumed and added in quadrature, the two localization samples agree about 87% of the time, as would be expected. If we then multiply the resulting error radii by a factor of 3, the two samples agree in slightly over 98% of the cases, providing a good estimate of the GBM 3 sigma error radius. The IPN 3 sigma error boxes have areas between about 1 square arcminute and 110 square degrees, and are, on the average, a factor of 180 smaller than the corresponding GBM localizations. We identify two bursts in the IPN/GBM sample that did not appear in the GBM catalog. In one case, the GBM triggered on a terrestrial gamma flash, and in the other, its origin was given as uncertain. We also discuss the sensitivity and calibration of the IPN., Comment: 52 pages, 12 figures, 4 tables. Revised version, resubmitted to the Astrophysical Journal Supplement Series following refereeing. Figures of the localizations in Table 3 may be found on the IPN website, at ssl.berkeley.edu/ipn3/YYMMDD, where YY, MM, and DD are the year, month, and day of the burst, sometimes with suffixes A or B

We present analysis of 4U 1626-67, a 7.7 s pulsar in a low-mass X-ray binary system, observed with the hard X-ray detector of the Japanese X-ray satellite Suzaku in March 2006 for a net exposure of \sim88 ks. The source was detected at an average 10-60 keV flux of \sim4 x10^-10 erg cm^-2 s^-1. The phase-averaged spectrum is reproduced well by combining a negative and positive power-law times exponential cutoff (NPEX) model modified at \sim 37 keV by a cyclotron resonance scattering feature (CRSF). The phase-resolved analysis shows that the spectra at the bright phases are well fit by the NPEX with CRSF model. On the other hand, the spectrum in the dim phase lacks the NPEX high-energy cutoff component, and the CRSF can be reproduced by either an emission or an absorption profile. When fitting the dim phase spectrum with the NPEX plus Gaussian model, we find that the feature is better described in terms of an emission rather than an absorption profile. The statistical significance of this result, evaluated by means of an F-test, is between 2.91 x 10^-3 and 1.53 x 10^-5, taking into account the systematic errors in the background evaluation of HXD-PIN. We find that, the emission profile is more feasible than the absorption one for comparing the physical parameters in other phases. Therefore, we have possibly detected an emission line at the cyclotron resonance energy in the dim phase., Comment: Accepted for publication in ApJ on March 16, 2012. 12 pages, 14 figures

In the first two years of operation of the Fermi GBM, the 9-spacecraft Interplanetary Network (IPN) detected 158 GBM bursts with one or two distant spacecraft, and triangulated them to annuli or error boxes. Combining the IPN and GBM localizations leads to error boxes which are up to 4 orders of magnitude smaller than those of the GBM alone. These localizations comprise the IPN supplement to the GBM catalog, and they support a wide range of scientific investigations., Comment: 2011 Fermi Symposium proceedings - eConf C110509

ORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z=10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to the early Universe ORIGIN will use Gamma-Ray Bursts (GRBs) to study their local environments in their host galaxies. This requires the capability to slew the satellite in less than a minute to the GRB location. By studying the chemical composition and properties of clusters of galaxies we can extend the range of exploration to lower redshifts (z ~ 0.2). For this task we need a high-resolution spectral imaging instrument with a large field of view. Using the same instrument, we can also study the so far only partially detected baryons in the Warm-Hot Intergalactic Medium (WHIM). The less dense part of the WHIM will be studied using absorption lines at low redshift in the spectra for GRBs., Comment: 34 pages, 13 figures. ESA Cosmic Vision medium-class mission (M3) proposal. Accepted for publication in Experimental Astronomy. Including minor corrections in the author list

Soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are thought to be magnetars: neutron stars powered by extreme magnetic fields. These rare objects are characterized by repeated and sometimes spectacular gamma-ray bursts. The burst mechanism might involve crustal fractures and excitation of non-radial modes which would emit gravitational waves (GWs). We present the results of a search for GW bursts from six galactic magnetars that is sensitive to neutron star f-modes, thought to be the most efficient GW emitting oscillatory modes in compact stars. One of them, SGR 0501+4516, is likely ~1 kpc from Earth, an order of magnitude closer than magnetars targeted in previous GW searches. A second, AXP 1E 1547.0-5408, gave a burst with an estimated isotropic energy >10^{44} erg which is comparable to the giant flares. We find no evidence of GWs associated with a sample of 1279 electromagnetic triggers from six magnetars occurring between November 2006 and June 2009, in GW data from the LIGO, Virgo, and GEO600 detectors. Our lowest model-dependent GW emission energy upper limits for band- and time-limited white noise bursts in the detector sensitive band, and for f-mode ringdowns (at 1090 Hz), are 3.0x10^{44} d_1^2 erg and 1.4x10^{47} d_1^2 erg respectively, where d_1 = d_{0501} / 1 kpc and d_{0501} is the distance to SGR 0501+4516. These limits on GW emission from f-modes are an order of magnitude lower than any previous, and approach the range of electromagnetic energies seen in SGR giant flares for the first time., Comment: 9 pages, 3 figures; v2 minor clarifications and new references

We report on the spectral cross-calibration results of the Konus-Wind, the Suzaku/WAM, and the Swift/BAT instruments using simultaneously observed gamma-ray bursts (GRBs). This is the first attempt to use simultaneously observed GRBs as a spectral calibration source to understand systematic problems among the instruments. Based on these joint spectral fits, we find that 1) although a constant factor (a normalization factor) agrees within 20% among the instruments, the BAT constant factor shows a systematically smaller value by 10-20% compared to that of Konus-Wind, 2) there is a systematic trend that the low-energy photon index becomes steeper by 0.1-0.2 and Epeak becomes systematically higher by 10-20% when including the BAT data in the joint fits, and 3) the high-energy photon index agrees within 0.2 among the instruments. Our results show that cross-calibration based on joint spectral analysis is an important step to understanding the instrumental effects which could be affecting the scientific results from the GRB prompt emission data., Comment: 82 pages, 88 figures, accepted for publication in PASJ

Using deep Chandra ACIS observation data for Cygnus A, we report evidence of non-thermal X-ray emission from radio lobes surrounded by a rich intra-cluster medium (ICM). The diffuse X-ray emission, which are associated with the eastern and western radio lobes, were observed in a 0.7--7 keV Chandra$ ACIS image. The lobe spectra are reproduced with not only a single-temperature Mekal model, such as that of the surrounding ICM component, but also an additional power-law (PL) model. The X-ray flux densities of PL components for the eastern and western lobes at 1 keV are derived as 77.7^{+28.9}_{-31.9} nJy and 52.4^{+42.9}_{-42.4} nJy, respectively, and the photon indices are 1.69^{+0.07}_{-0.13} and 1.84^{+2.90}_{-0.12}, respectively. The non-thermal component is considered to be produced via the inverse Compton (IC) process, as is often seen in the X-ray emission from radio lobes. From a re-analysis of radio observation data, the multiwavelength spectra strongly suggest that the seed photon source of the IC X-rays includes both cosmic microwave background radiation and synchrotron radiation from the lobes. The derived parameters indicate significant dominance of the electron energy density over the magnetic field energy density in the Cygnus A lobes under the rich ICM environment., Comment: 8 pages, 5 figures, accepted for publication in ApJ

We are integrating the Fermi Gamma-Ray Burst Monitor (GBM) into the Interplanetary Network (IPN) of Gamma-Ray Burst (GRB) detectors. With the GBM, the IPN will comprise 9 experiments. This will 1) assist the Fermi team in understanding and reducing their systematic localization uncertainties, 2) reduce the sizes of the GBM and Large Area Telescope (LAT) error circles by 1 to 4 orders of magnitude, 3) facilitate the identification of GRB sources with objects found by ground- and space-based observatories at other wavelengths, from the radio to very high energy gamma-rays, 4) reduce the uncertainties in associating some LAT detections of high energy photons with GBM bursts, and 5) facilitate searches for non-electromagnetic GRB counterparts, particularly neutrinos and gravitational radiation. We present examples and demonstrate the synergy between Fermi and the IPN. This is a Fermi Cycle 2 Guest Investigator project., Comment: 5 pages, 11 figures. 2009 Fermi Symposium. eConf Proceedings C091122

One of the most prominent, yet controversial associations derived from the ensemble of prompt-phase observations of gamma-ray bursts (GRBs) is the apparent correlation in the source frame between the peak energy Epeak) of the nu-F(nu) spectrum and the isotropic radiated energy, Eiso. Since most gamma-ray bursts (GRBs) have Epeak above the energy range (15-150 keV) of the Burst Alert Telescope (BAT) on Swift, determining accurate Epeak values for large numbers of Swift bursts has been difficult. However, by combining data from Swift/BAT and the Suzaku Wide-band All-Sky Monitor (WAM), which covers the energy range from 50-5000 keV, for bursts which are simultaneously detected, one can accurately fit Epeak and Eiso and test the relationship between them for the Swift sample. Between the launch of Suzaku in July 2005 and the end of April 2009, there were 48 gamma-ray bursts (GRBs) which triggered both Swift/BAT and WAM and an additional 48 bursts which triggered Swift and were detected by WAM, but did not trigger. A BAT-WAM team has cross-calibrated the two instruments using GRBs, and we are now able to perform joint fits on these bursts to determine their spectral parameters. For those bursts with spectroscopic redshifts, we can also calculate the isotropic energy. Here we present the results of joint Swift/BAT-Suzaku/WAM spectral fits for 91 of the bursts detected by the two instruments. We show that the distribution of spectral fit parameters is consistent with distributions from earlier missions and confirm that Swift bursts are consistent with earlier reported relationships between Epeak and isotropic energy. We show through time-resolved spectroscopy that individual burst pulses are also consistent with this relationship., Comment: Accepted for publication in the Astrophysical Journal

Between 2000 November and 2006 May, one or more spacecraft of the interplanetary network (IPN) detected 226 cosmic gamma-ray bursts that were also detected by the FREGATE experiment aboard the HETE-II spacecraft. During this period, the IPN consisted of up to nine spacecraft, and using triangulation, the localizations of 157 bursts were obtained. We present the IPN localization data on these events., Comment: 37 pages, 3 figures. To be submitted to ApJSS. Table 5 was truncated in the original version, and has been replaced. Revised 9/2010 to correct errors in some ecliptic latitudes in table 5. Also, 3 bursts were added to the catalog

We performed simultaneous multiwavelength observations of OJ 287 with the Nobeyama Millimeter Array for radio, the KANATA telescope and the KVA telescope for optical, the Suzaku satellite for X-ray and the MAGIC telescope for very high energy (VHE) gamma-ray in 2007. The observations were conducted for a quiescent state in April and in a flaring state in November-December. We clearly observed increase of fluxes from radio to X-ray bands during the flaring state while MAGIC could not detect significant VHE gamma-ray emission from the source. We could derive an upper limit (95% confidence level) of 1.7% of the Crab Nebula flux above 150 GeV from about 41.2 hours of the MAGIC observation. A simple SSC model suggests that the observed flaring activity could be caused by evolutions in the distribution of the electron population rather than changes of the magnetic field strength or Doppler beaming factor in the jet., Comment: Contribution to the 31st ICRC, Lodz, Poland, July 2009

The NeXT (New exploration X-ray Telescope), the new Japanese X-ray Astronomy Satellite following Suzaku, is an international X-ray mission which is currently planed for launch in 2013. NeXT is a combination of wide band X-ray spectroscopy (3 - 80 keV) provided by multi-layer coating, focusing hard X-ray mirrors and hard X-ray imaging detectors, and high energy-resolution soft X-ray spectroscopy (0.3 - 10 keV) provided by thin-foil X-ray optics and a micro-calorimeter array. The mission will also carry an X-ray CCD camera as a focal plane detector for a soft X-ray telescope and a non-focusing soft gamma-ray detector. With these instruments, NeXT covers very wide energy range from 0.3 keV to 600 keV. The micro-calorimeter system will be developed by international collaboration lead by ISAS/JAXA and NASA. The simultaneous broad bandpass, coupled with high spectral resolution of Delta E ~ 7 eV by the micro-calorimeter will enable a wide variety of important science themes to be pursued., Comment: 14 pages, 10 figures, Proceedings of the SPIE meeting, "Space Telescopes and Instrumentation II: Ultraviolet to Gamma Ray 2008", Marseille (2008)

The Wide-band All-sky Monitor (WAM) is a function of the large lateral BGO shield of the Hard X-ray Detector (HXD) onboard Suzaku. Its large geometrical area of 800 cm^2 per side, the large stopping power for the hard X-rays and the wide-field of view make the WAM an ideal detector for gamma-ray bursts (GRBs) observations in the energy range of 50-5000 keV. In fact, the WAM has observed 288 GRBs confirmed by other satellites, till the end of May 2007., Comment: 4 pages, 4 figures, to be published in the proceedings of ''Gamma Ray Bursts 2007'', Santa Fe, New Mexico, November 5-9

Aims. Understand the shape and implications of the multiband light curve of GRB 050408, an X-ray rich (XRR) burst. Methods. We present a multiband optical light curve, covering the time from the onset of the gamma-ray event to several months after, when we only detect the host galaxy. Together with X-ray, millimetre and radio observations we compile what, to our knowledge, is the most complete multiband coverage of an XRR burst afterglow to date. Results. The optical and X-ray light curve is characterised by an early flattening and an intense bump peaking around 6 days after the burst onset. We explain the former by an off-axis viewed jet, in agreement with the predictions made for XRR by some models, and the latter with an energy injection equivalent in intensity to the initial shock. The analysis of the spectral flux distribution reveals an extinction compatible with a low chemical enrichment surrounding the burst. Together with the detection of an underlying starburst host galaxy we can strengthen the link between XRR and classical long-duration bursts., Comment: 9 pages, 4 figures, Accepted for publication in A&A Letters

Multi-wavelength B, V, R, I observations of the optical afterglow of GRB 050319 were performed by the 1.05-m telescope at Kiso Observatory and the 1.0-m telescope at Lulin Observatory from 1.31 hours to 9.92 hours after the burst. Our R band lightcurves, combined with other published data, can be described by the smooth broken power-law function, with $\alpha_1$ = -0.84 $\pm$0.02 to $\alpha_2$ = -0.48$\pm$0.03, 0.04 days after the GRB. The optical lightcurves are characterized by shallow decays-- as was also observed in the X-rays-- which may have a similar origin, related to energy injection. However, our observations indicate that there is still a puzzle concerning the chromatic breaks in the R band lightcurve (at 0.04 days) and the X-ray lightcurve (at 0.004 days) that remains to be solved., Comment: 14 pages, 2 figures, accpeted for publication in ApJL

The in-orbit performance and calibration of the Hard X-ray Detector (HXD) on board the X-ray astronomy satellite Suzaku are described. Its basic performances, including a wide energy bandpass of 10-600 keV, energy resolutions of ~4 keV (FWHM) at 40 keV and ~11% at 511 keV, and a high background rejection efficiency, have been confirmed by extensive in-orbit calibrations. The long-term gains of PIN-Si diodes have been stable within 1% for half a year, and those of scintillators have decreased by 5-20%. The residual non-X-ray background of the HXD is the lowest among past non-imaging hard X-ray instruments in energy ranges of 15-70 and 150-500 keV. We provide accurate calibrations of energy responses, angular responses, timing accuracy of the HXD, and relative normalizations to the X-ray CCD cameras using multiple observations of the Crab Nebula., Comment: 45 pages, 40 figures and 9 tables; accepted for Pulications of the Astronomical Society of Japan

The Hard X-ray Detector (HXD) on board Suzaku covers a wide energy range from 10 keV to 600 keV by combination of silicon PIN diodes and GSO scintillators. The HXD is designed to achieve an extremely low in-orbit back ground based on a combination of new techniques, including the concept of well-type active shield counter. With an effective area of 142 cm^2 at 20 keV and 273 cm2 at 150 keV, the background level at the sea level reached ~1x10^{-5} cts s^{-1} cm^{-2} keV^{-1} at 30 keV for the PI N diodes, and ~2x10^{-5} cts s^{-1} cm^{-2} keV^{-1} at 100 keV, and ~7x10^{-6} cts s^{-1} cm^{-2} keV^{-1} at 200 keV for the phoswich counter. Tight active shielding of the HXD results in a large array of guard counters surrounding the main detector parts. These anti-coincidence counters, made of ~4 cm thick BGO crystals, have a large effective area for sub-MeV to MeV gamma-rays. They work as an excellent gamma-ray burst monitor with limited angular resolution (~5 degree). The on-board signal-processing system and the data transmitted to the ground are also described., Comment: 35 pages, 25 figures and 4 tables; acceted for Publication of the Astronomical Society of Japan

We analyze Swift gamma-ray bursts (GRBs) and X-ray afterglows for three GRBs with spectroscopic redshift determinations -- GRB 050401, XRF 050416a, and GRB 050525a. We find that the relation between spectral peak energy and isotropic energy of prompt emissions (the Amati relation) is consistent with that for the bursts observed in pre-Swift era. However, we find that the X-ray afterglow lightcurves, which extend up to 10-70 days, show no sign of the jet break that is expected in the standard framework of collimated outflows. We do so by showing that none of the X-ray afterglow lightcurves in our sample satisfies the relation between the spectral and temporal indices that is predicted for the phase after jet break. The jet break time can be predicted by inverting the tight empirical relation between the peak energy of the spectrum and the collimation-corrected energy of the prompt emission (the Ghirlanda relation). We find that there are no temporal breaks within the predicted time intervals in X-ray band. This requires either that the Ghirlanda relation has a larger scatter than previously thought, that the temporal break in X-rays is masked by some additional source of X-ray emission, or that it does not happen because of some unknown reason., Comment: 24 pages, 6 figures, accepted for publication in ApJ; minor revision

Results are presented of early X-ray afterglow observations of GRB 060105 by Swift and Suzaku. The bright, long gamma-ray burst GRB 060105 triggered the Swift Burst Alert Telescope (BAT) at 06:49:28 on 5 January 2006. The Suzaku team commenced a pre-planned target of opportunity observation at 19 ks (5.3 hr) after the Swift trigger. Following the prompt emission and successive very steep decay, a shallow decay was observed from T_0+187 s to T_0+1287 s. After an observation gap during T_0 +(1.5-3) ks, an extremely early steep decay was observed in T_0+(4-30) ks. The lightcurve flattened again at T_0+30 ks, and another steep decay followed from T_0+50 ks to the end of observations. Both steep decays exhibited decay indices of 2.3 - 2.4. This very early break, if it is a jet break, is the earliest case among X-ray afterglow observations, suggesting a very narrow jet whose opening angle is well below 1 degree. The unique Suzaku/XIS data allow us to set very tight upper limits on line emission or absorption in this GRB. For the reported pseudo-redshift of z=4.0+/-1.3 the upper limit on the iron line equivalent width is 50 eV., Comment: 8 pages, 5 figures, Accepted for publication in PASJ Suzaku Special Issue (vol. 58)

Even with the renaissance in gamma-ray burst (GRB) research fostered by the Swift satellite, few bursts have both contemporaneous observations at long wavelengths and exquisite observations at later times across the electromagnetic spectrum. We present here contemporaneous imaging with the KAIT robotic optical telescope, dense optical sampling with Lulin, and supplemented with infrared data from PAIRITEL and radio to gamma-ray data from the literature. For the first time, we can test the constancy of microphysical parameters in the internal-external shock paradigm and carefully trace the flow of energy from the GRB to the surrounding medium. KAIT data taken <~1 minute after the start of GRB051111 and coinciding with the fading gamma-ray tail of the prompt emission indicate a smooth re-injection of energy into the shock. No color change is apparent in observations beginning ~1.5 minutes after the GRB and lasting for the first hour after the burst. There are achromatic flux modulations about the best-fit model at late (t~10^4 s) times, possibly due to variations in the external density. We find that the host-galaxy extinction is well fit by a curve similar to that ofthe Small Magellanic Cloud. Low visual extinction, A_V~0.2 mag, combined with high column densities determined from the X-ray and optical spectroscopy (N_H> 10^21 cm^-2), indicate a low dust-to-metals ratio and a possible over-abundance of the light metals. An apparent small ratio of total to selective extinction (R_V~2) argues against dust destruction by the GRB. Time constancy of both the IR/optical/UV spectral energy distribution and the soft X-ray absorption suggests that the absorbing material is not local to the GRB., Comment: 21 pages, 6 figures, to Appear in ApJ v653, December, 10 2006

The Soft Gamma-ray Detector (SGD) on board the NeXT (Japanese future high energy astrophysics mission) is a Compton telescope with narrow field of view (FOV), which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor gamma-ray detector which consists of silicon and CdTe (cadmium telluride) detectors. It can detect photons in a wide energy band (0.05-1 MeV) at a background level of 5 x 10^-7 counts/cm^2/s; the silicon layers are required to improve the performance at a lower energy band (<0.3 MeV). Excellent energy resolution is the key feature of the SGD, allowing it to achieve both high angular resolution and good background rejection capability. An additional capability of the SGD, its ability to measure gamma-ray polarization, opens up a new window to study properties of astronomical objects. We will present the development of key technologies to realize the SGD: high quality CdTe, low noise front-end ASIC and bump bonding technology. Energy resolutions of 1.7 keV (FWHM) for CdTe pixel detectors and 1.1 keV for Si strip detectors have been measured. We also present the validation of Monte Carlo simulation used to evaluate the performance of the SGD., Comment: 9 pages, 17 figures, Contributed to IEEE Nuclear Science Symposium, Roma, Italia, October 16-October 22, 2004

The Burst Alert Telescope (BAT) is one of 3 instruments on the Swift MIDEX spacecraft to study gamma-ray bursts (GRBs). The BAT first detects the GRB and localizes the burst direction to an accuracy of 1-4 arcmin within 20 sec after the start of the event. The GRB trigger initiates an autonomous spacecraft slew to point the two narrow field-of-view (FOV) instruments at the burst location within 20-70 sec so to make follow-up x-ray and optical observations. The BAT is a wide-FOV, coded-aperture instrument with a CdZnTe detector plane. The detector plane is composed of 32,768 pieces of CdZnTe (4x4x2mm), and the coded-aperture mask is composed of approximately 52,000 pieces of lead (5x5x1mm) with a 1-m separation between mask and detector plane. The BAT operates over the 15-150 keV energy range with approximately 7 keV resolution, a sensitivity of approximately 10E-8 erg*cm^-2*s^-1, and a 1.4 sr (half-coded) FOV. We expect to detect >100 GRBs/yr for a 2-year mission. The BAT also performs an all-sky hard x-ray survey with a sensitivity of approximately 2 mCrab (systematic limit) and it serves as a hard x-ray transient monitor., Comment: 18 Pages, 12 Figures, To be published in Space Science Reviews

The XMM-Newton observation of the nearby FR-II radio galaxy 3C 98 is reported. In two exposures on the target, faint diffuse X-ray emission associated with the radio lobes was significantly detected, together with a bright X-ray active nucleus, of which the 2 -- 10 keV intrinsic luminosity is (4 -- 8) \times 10^{42} erg s-1. The EPIC spectra of the northern and southern lobes are reproduced by a single power law model modified by the Galactic absorption, with a photon index of 2.2-0.5+0.6 and 1.7-0.6+0.7 respectively. These indices are consistent with that of the radio synchrotron spectrum, 1.73 +- 0.01 The luminosity of the northern and southern lobes are measured to be 8.3-2.6+3.3 \times 10^{40} erg s-1 and 9.2-4.3+5.7 \times 10^{40} erg s-1, respectively, in the 0.7 -- 7 keV range. The diffuse X-ray emission is interpreted as an inverse-Compton emission, produced when the synchrotron-emitting energetic electrons in the lobes scatter off the cosmic microwave background photons. The magnetic field in the lobes is calculated to be about 1.7 \mu G, which is about 2.5 times lower than the value estimated under the minimum energy condition. The energy density of the electrons is inferred to exceed that in the magnetic fields by a factor of 40 -- 50., Comment: 23 pages, 7 figures. Accepted for publication in the Astrophysical Journal

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., Comment: 4 pages, 4 figure. Accepted for publication into "il nuovo cimento". Proceeding of the 4th Rome GRB conference, eds. L. Piro, L. Amati, S. Covino, B. Gendre

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., Comment: 12 pages, 13 figures, to be published in the SPIE proceedings 5488, typo corrected in sec.3

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., Comment: 4 figures, 2 tables, Accepted by ApJL (to appear in the December 1 issue)

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., Comment: 10 pages, 5 figures; accepted for ApJ Letters

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., Comment: 17 pages, 4 figures, 1 table, to appear in ApJ Letter

The high redshift (z=0.997) blazar B2 1308+326 was observed contemporaneously at x-ray, optical and radio wavelengths in June 1996. The x-ray observations were performed with ASCA. The ASCA results were found to be consistent with reanalysed data from two earlier ROSAT observations. The combined ASCA and ROSAT data reveal an x-ray spectrum that is best fit by a broken power law with absorber model. The break in the x-ray spectrum is interpreted, to be the emerging importance of inverse Compton (IC) emission which dominates the ASCA spectrum. The faint optical state reported for these observations (m_V=18.3+/-0.25) is incompatible with the high synchrotron flux previously detected by ROSAT. The IC emission detected by both ROSAT and ASCA was not significantly affected by the large change in the synchrotron component. MgII emission was detected with an equivalent width (EW) significantly different from previously reported values. Absorption at a level of in excess of the Galactic value was detected, indicating the possible presence of a foreground absorber. A gravitational microlensing scenario cannot therefore be ruled out for this blazar. B2 1308+326 could be a typical radio-selected BL Lac in terms of peak synchrotron frequency and optical and radio variability but its high bolometric luminosity, variable line emission and high Doppler boost factor make it appear more like a quasar than a BL Lac. It is suggested that B2 1308+326 be considered as the prototype of this class of composite source., Comment: A&A in press; 11 pages, 5 figures

We conducted a multi-frequency campaign for the TeV blazar Mrk~421 in 1998 April. The campaign started from a pronounced high amplitude flare recorded by SAX and Whipple; ASCA observation started three days later. In the X-ray data, we detected multiple flares, occuring on time scales of about one day. ASCA data clearly reveal spectral variability. The comparison of the data from ASCA, EUVE and RXTE indicates that the variability amplitudes in the low energy synchrotron component are larger at higher photon energies. In TeV Gamma-rays, large intra-day variations -- which were correlated with the X-ray flux -- were observed when results from three Cherenkov telescopes are combined. The RMS variability of TeV Gamma--rays was similar to that observed in hard X-rays, above 10 keV. The X-ray light curve reveals flares which are almost symmetric for most of cases, implying the dominant time scale is the light crossing time through the emitting region. The structure function analysis based on the continuous X-ray light curve of seven days indicates that the characteristic time scale is ~0.5 day. The analysis of ASCA light curves in various energy bands appears to show both soft (positive) and hard (negative) lags. These may not be real, as systematic effects could also produce these lags, which are all much smaller than an orbit. If the lags of both signs are real, these imply that the particle acceleration and X-ray cooling time scales are similar., Comment: 10 pages, 4 figures, accepted for publication in ApJ Letters

The TeV blazar PKS 2155-304 was monitored with the X-ray satellite ASCA in 1994 May, as part of a multiwavelength campaign from the radio to X-ray bands. At the beginning of the two-day continuous observation, we detected a large flare, where the 2-10 keV flux changed by a factor of 2 on a time scale of 3 x 10^4 sec. During the flare, the increase in the hard X-ray flux clearly preceded that observed in the soft X-rays, the spectral evolution tracking a `clockwise loop' in the flux versus photon index plane. Ascribing the energy-dependent variability to differential synchrotron cooling of relativistic electrons, we estimate the magnetic field B in the emission region. We tested two different methods of comparing the time series in various X-ray bands: (i) fitting the light curves to a Gaussian and searching for the time shift of the peak of the flare, and (ii) calculating the discrete correlation function. Both methods yielded a consistent solution of B ~ 0.1 G. We also found that the flare amplitude becomes larger as the photon energy increases, while the duration of the flare stays roughly constant through the ASCA energy band (0.7-7.5 keV). In the framework of the time dependent synchrotron self-Compton model in a homogeneous region, we consider a flare where the maximum Lorentz factor (Gmax) of the injected electrons increases uniformly throughout the emission volume. The temporal evolution of spectra as well as the light curves were reproduced with the physical parameters self-consistently determined from seven observables. We obtain B ~ 0.1-0.2 G and a region size R ~ 10^-2 pc, for relativistic beaming with a Doppler factor of D ~ 20-30. We discuss the significance of light travel time effects., Comment: 43 pages, 8 figures, accepted for publication in the Astrophysical Journal

Radio and optical observations of the possible microlensed BL Lac source MS 0205.7+3509 were obtained simultaneously with ASCA x-ray measurements in February 1997. A single power law model, with a photon index of 2.61, is an adequate fit to the ASCA data, once hydrogenic absorption in excess of the Galactic value is permitted, confirming a previous ROSAT measurement. On the basis of our simultaneous data we have determined MS 0205.7+3509 to be a typical x--ray selected BL Lac, with alpha_xox=-0.82. There is no indication of an inverse Compton (IC) component in the ASCA spectrum up to 10 keV. No evidence for variability on hour-long timescales is present in either the x-ray or the optical data. We discuss these results in the context of a gravitational microlensing scenario for MS 0205.7+3509., Comment: 6 pages, 3 figures, LaTeX2e Accepted for publication in Astronomy and Astrophysics