Search

The IceCube report of a excess of 13 ± 5 neutrino events in the direction of the blazar TXS 0506+056 in 2014–2015 and the 2017 detection of a high-energy neutrino event, IceCube-170922A, during a gamma-ray flare from the same blazar, have revived the interest in scenarios for neutrino production in blazars. We perform comprehensive analyses on the long-term electromagnetic emission of TXS 0506+056 using optical, X-ray, and gamma-ray data from the All-Sky Automated Survey for Supernovae, the Neil Gehrels Swift Observatory, Monitor of All-sky X-ray Image, and the Fermi Large Area Telescope. We also perform numerical modeling of the spectral energy distributions (SEDs) in four epochs prior to 2017 with contemporaneous gamma-ray and lower-energy (optical and/or X-ray) data. We find that the multi-epoch SEDs are consistent with a hybrid leptonic scenario, where the gamma-rays are produced in the blazar zone via external inverse Compton scattering of accelerated electrons, and high-energy neutrinos are produced via the photomeson production process of co-accelerated protons. The multi-epoch SEDs can be satisfactorily explained with the same jet parameters and variable external photon density and electron luminosity. Using the maximal neutrino flux derived for each epoch, we put an upper limit of ∼0.4–2 on the muon neutrino number in 10 years of IceCube observations. Our results are consistent with the IceCube-170922A detection, which can be explained as an upper fluctuation from the average neutrino rate expected from the source, but in strong tension with the 2014–2015 neutrino flare. [ABSTRACT FROM AUTHOR]

We report results from the X-ray and optical monitoring of the black hole candidate MAXI J1820+070 (=ASSASN-18ey) over the entire period of its outburst from 2018 March to October. In this outburst, the source exhibited two sets of “fast rise and slow decay”-type long-term flux variations. We found that the 1–100 keV luminosities at two peaks were almost the same, although a significant spectral softening was only seen in the second flux rise. This confirms that the state transition from the low/hard state to the high/soft state is not determined by the mass accretion rate alone. The X-ray spectrum was reproduced with the disk blackbody emission and its Comptonization, and the long-term spectral variations seen in this outburst were consistent with a disk truncation model. The Comptonization component, with a photon index of 1.5–1.9 and electron temperature of ≳40 keV, was dominant during the low/hard state periods, and its contribution rapidly decreased (increased) during the spectral softening (hardening). During the high/soft-state period, in which the X-ray spectrum became dominated by the disk blackbody component, the inner disk radius was almost constant, suggesting that the standard disk was present down to the innermost stable circular orbit. The long-term evolution of optical and X-ray luminosities and their correlation suggest that the jets substantially contributed to the optical emission in the low/hard state, while they are quenched and the outer disk emission dominated the optical flux in the intermediate state and the high/soft state. [ABSTRACT FROM AUTHOR]

We report X-ray, optical, and near-infrared monitoring of the new X-ray transient MAXI J1820+070 discovered with MAXI on 2018 March 11. Its X-ray intensity reached ∼2 crab at 2–20 keV at the end of March, and then gradually decreased until the middle of June. In this period, the X-ray spectrum was described by Comptonization of the disk emission, with a photon index of ∼1.5 and an electron temperature of ∼50 keV, which is consistent with a black hole X-ray binary in the low/hard state. The electron temperature was slightly decreased, and the photon index increased, with increasing flux. The source showed significant X-ray flux variation on a timescale of seconds. This short-term variation was found to be associated with changes in the spectral shape, and the photon index became slightly harder at higher fluxes. This suggests that the variation was produced by a change in the properties of the hot electron cloud responsible for the strong Comptonization. Modeling a multi-wavelength spectral energy distribution around the X-ray flux peak at the end of March, covering the near-infrared to X-ray bands, we found that the optical and near-infrared fluxes were likely contributed substantially by the jet emission. Before this outburst, the source was never detected in the X-ray band with MAXI (with a 3σ upper limit of ∼0.2 mcrab at 4–10 keV, obtained from seven years of data from 2009 to 2016), whereas weak optical and infrared activity was found at flux levels ∼3 orders of magnitude lower than the peak fluxes in the outburst. [ABSTRACT FROM AUTHOR]

We report on the detection and follow-up multi-wavelength observations of the new X-ray transient MAXI J1807+132 with the MAXI/GSC, Swift, and ground-based optical telescopes. The source was first recognized with the MAXI/GSC on 2017 March 13. About a week later, it reached maximum intensity (∼10 mCrab in 2–10 keV), and then gradually faded in ∼10 days by more than one order of magnitude. Time-averaged Swift/X-ray Telescope spectra in the decaying phase can be described by a blackbody with a relatively low temperature (0.1–0.5 keV), plus a hard power-law component with a photon index of ∼2. These spectral properties are similar to those of neutron star low-mass X-ray binaries (LMXBs) in their dim periods. The blackbody temperature and the radius of the emission region varied in a complex manner as the source became dimmer. The source was detected in the optical wavelength on March 27–31 as well. The optical flux decreased monotonically as the X-ray flux decayed. The correlation between the X-ray and optical fluxes is found to be consistent with those of known neutron star LMXBs, supporting the idea that the source is likely to be a transient neutron star LMXB. [ABSTRACT FROM AUTHOR]

A bright long gamma-ray burst GRB 141207A was observed by the Fermi Gamma-ray Space Telescope and detected by both instruments onboard. The observations show that the spectrum in the prompt phase is not well described by the canonical empirical Band function alone, and that an additional power-law component is needed. In the early phase of the prompt emission, a modified blackbody with a hard low-energy photon index (α = +0.2 to +0.4) is detected, which suggests a photospheric origin. In a finely time-resolved analysis, the spectra are also well fitted by the modified blackbody combined with a power-law function. We discuss the physical parameters of the photosphere such as the bulk Lorentz factor of the relativistic flow and the radius. We also discuss the physical origin of the extra power-law component observed during the prompt phase in the context of different models such as leptonic and hadronic scenarios in the internal shock regime and synchrotron emission in the external forward shock. In the afterglow phase, the temporal and spectral behaviors of the temporally extended high-energy emission and the fading X-ray emission detected by the X-Ray Telescope on-board Swift are consistent with synchrotron emission in a radiative external forward shock. [ABSTRACT FROM AUTHOR]

We performed a monitoring observation of a Jupiter-family comet, 17P/Holmes, during its 2014 perihelion passage to investigate its secular change in activity. The comet has drawn the attention of astronomers since its historic outburst in 2007, and this occasion was its first perihelion passage since then. We analyzed the obtained data using an aperture photometry package and derived the parameter, a proxy for the dust-production rate. We found that showed asymmetric properties with respect to the perihelion passage: it increased moderately from 100 cm at the heliocentric distance of rh = 2.6–3.1 AU to a maximal value of 185 cm at rh = 2.2 AU (near the perihelion) during the inbound orbit, while dropping rapidly to 35 cm at rh = 3.2 AU during the outbound orbit. We applied a model for characterizing dust-production rates as a function of rh and found that the fractional active area of the cometary nucleus had dropped from 20%–40% in 2008–2011 (around the aphelion) to 0.1%–0.3% in 2014–2015 (around the perihelion). This result suggests that a dust mantle would have developed rapidly in only one orbital revolution around the Sun. Although a minor eruption was observed on UT 2015 January 26 at rh = 3.0 AU, the areas excavated by the 2007 outburst would be covered with a layer of dust (≲10 cm depth) which would be enough to insulate the subsurface ice and to keep the nucleus in a state of low activity. [ABSTRACT FROM AUTHOR]

The massive flare of 27 December 2004 from the soft?-ray repeater SGR?1806-20, a possible magnetar, saturated almost all?-ray detectors, meaning that the profile of the pulse was poorly characterized. An accurate profile is essential to determine physically what was happening at the source. Here we report the unsaturated?-ray profile for the first 600?ms of the flare, with a time resolution of 5.48?ms. The peak of the profile (of the order of 107?photons?cm-2?s-1) was reached~50?ms after the onset of the flare, and was then followed by a gradual decrease with superposed oscillatory modulations possibly representing repeated energy injections with~60-ms intervals. The implied total energy is comparable to the stored magnetic energy in a magnetar (~1047?erg) based on the dipole magnetic field intensity (~1015?G), suggesting either that the energy release mechanism was extremely efficient or that the interior magnetic field is much stronger than the external dipole field. [ABSTRACT FROM AUTHOR]

We present near-infrared spectroscopy of the host galaxy of the dark gamma-ray burst (GRB) 080325 using Subaru/Multi-Object Infrared Camera and Spectrograph. The obtained spectrum provides a clear detection of Hα emission and marginal [Nii]λ6584. The host is a massive (M* ∼ 1011M⊙), dusty () star-forming galaxy at z = 1.78. The extinction-corrected star formation rate (SFR) calculated from the Hα luminosity (35.6–47.0 M⊙ yr−1) is typical among GRB host galaxies (and star-forming galaxies generally) at z 1; however, the specific SFR is lower than for normal star-forming galaxies at redshift ∼1.6, in contrast to the high specific SFR measured for many of other GRB hosts. The metallicity of the host is estimated to be 12 + log(O/H)KK04 = 8.88. We emphasize that this is one of the most massive host galaxies at z for which metallicity is measured with emission-line diagnostics. The metallicity is fairly high among GRB hosts, however, this is still lower than the metallicity of normal star-forming galaxies of the same mass at z ∼ 1.6. The metallicity offset from normal star-forming galaxies is close to a typical value of other GRB hosts and indicates that GRB host galaxies are uniformly biased toward low metallicity over a wide range of redshifts and stellar masses. The low-metallicity nature of the GRB 080325 host likely cannot be attributed to the fundamental metallicity relation of star-forming galaxies because it is a metal-poor outlier from the relation and has a low specific star formation rate. Thus, we conclude that metallicity is important to the mechanism that produced this GRB. [ABSTRACT FROM AUTHOR]

Multi-wavelength observations of the black widow binary system 2FGL J2339.6-0532 are reported. The Fermi gamma-ray source 2FGL J2339.6-0532 was recently categorized as a black widow in which a recycled millisecond pulsar (MSP) is evaporating the companion star with its powerful pulsar wind. Our optical observations show clear sinusoidal light curves due to the asymmetric temperature distribution of the companion star. Assuming a simple geometry, we constrained the range of the inclination angle of the binary system to , which enables us to discuss the interaction between the pulsar wind and the companion in detail. The X-ray spectrum consists of two components: a soft, steady component that seems to originate from the surface of the MSP, and a hard, variable component from the wind-termination shock near the companion star. The measured X-ray luminosity is comparable to the bolometric luminosity of the companion, meaning that the heating efficiency is less than 0.5. In the companion orbit, 1011 cm from the pulsar, the pulsar wind is already in the particle-dominant stage with a magnetization parameter of . In addition, we precisely investigated the time variations of the X-ray periodograms and detected a weakening of the orbital modulation. The observed phenomenon may be related to unstable pulsar wind activity or weak mass accretion, both of which can result in the temporal extinction of the radio pulse. [ABSTRACT FROM AUTHOR]

Background: 99mTc-sestamibi myocardial perfusion imaging (MIBI) washout is associated wit hmyocardial mitochondrial damage in patients with a successful percutaneous coronary intervention (PCI) following acute myocardial infarction (AMI) and may predict the functional improvement of the left ventricle in follow-ups. Objectives: This study aimed to investigate the clinical efficacy of 99mTc-MIBI washout in patients with AMI by measuring the mean defect area based on 99mTc-MIBI myocardial perfusion-single photon emission computed tomography (MP-SPECT) rest imaging in early and delayed phases and comparing it with the defect area based on 99mTc-MIBI MP-SPECT adenosine stress imaging based on a two-day rest/stress protocol. Patients and Methods: This study was conducted on 29 consecutive patients with AMI (23 males and 6 females; mean age, 71± 8.4 years), who underwent MP-SPECT using a standard two-day rest/stress protocol. The rest 99mTc-MIBI MP-SPECT images were acquired in the early phase at one hour after the injection of 99mTc-MIBI and in the delayed phase at three hours after the early phase. The total perfusion deficit (TPD) score for SPECT was measured to compare the defect area between the rest-early phase, rest-delayed phase, and post-stress imaging conditions. Results: Based on the results, the post-stress TPD score was significantly lower than the rest-delayed phase score (TPD: 22.2% ± 14.3% vs. 27.8% ± 14.0%; P < 0.001). Also, the rest-early phase score was significantly lower than the rest-delayed phase score (TPD: 21.5% ± 14.9% vs. 27.8% ± 14.0%; P < 0.001). However, no significant difference was observed between the post-stress score and the rest-early phase score. Conclusion: The combination of rest-early phase, delayed phase, and post-stress 99mTc-MIBI imaging using a two-day protocol after AMI reperfusion was a clinically useful method, which could identify residual ischemia and predict the left ventricular function improvement in the chronic phase of disease while reducing the exposure dose. [ABSTRACT FROM AUTHOR]

We report on multicolor photometry of WZ Sge-type dwarf novae HVVir and OT J012059.6+325545 during superoutbursts. These systems show early superhumps with mean periods of 0.057093(45) d for HVVir and 0.057147(15) d for OT J012059.6+325545. The observed early superhumps showed a common feature that the brightness minima corresponded to the bluest peaks in color variations, which may be a ubiquitous phenomenon among early superhumps of WZ Sge-type dwarf novae. We confirmed that the amplitudes of early superhumps depend on wavelength: amplitudes with longer bandpass filters show larger values. This indicates that the light source of early superhumps is generated at the outer region of the vertically extended accretion disk. On the other hand, amplitudes of ordinary superhumps are likely to be independent of wavelength. This implies that the superhump light source is geometrically thin. We also examined color variations of ordinary superhumps and found that the bluest peaks in g' - Ic tend to coincide with the brightness minima, particularily in stage B superhumps. This may reflect that the pressure effect plays a dominant role during stage B superhumps. [ABSTRACT FROM AUTHOR]

Background: Magnetic resonance (MR) imaging, have become more frequently used in the diagnosis of ovarian torsion, particularly in subacute cases. Objectives: To assess the characteristic findings and diagnostic performance of preoperative MR imaging for ovarian torsion. Patients and Methods: Twenty-three patients (age range, 10 - 58 years; mean age, 28.4 ± 12.5 years) with suspected ovarian torsion underwent preoperative MR imaging. Fifteen patients exhibited ovarian torsion, whereas the remaining eight did not. Two radiologists evaluated theMRimaging data in relation to six previously-described characteristics associated with ovarian torsion, and the sensitivity, specificity, and accuracy of this approach was determined. Results: Ovarian enlargement (maximum ovarian diameter > 4.0 cm) and a twisted pedicle were significantly more common findings in patients with ovarian torsion compared with those without (regarding ovarian enlargement, P = 0.032 for both readers and considering twisted pedicle, P = 0.0094 for first reader and P = 0.0013 for second reader). The respective sensitivity, specificity, and accuracy of a twisted pedicle for the diagnosis of ovarian torsion were 73%, 88%, and 78%, respectively for reader 1 and 73%, 100%, and 83%, respectively for reader 2. Conclusion: Identifying a twisted pedicle in a patient is therefore, suggestive of ovarian torsion. [ABSTRACT FROM AUTHOR]

Background: Apparent diffusion coefficient (ADC) value measured from diffusion-weighted magnetic resonance (MR) images are highly correlated with pathological T orNstage, tumor differentiation grade, and extramural depth of tumor in patients with rectal cancer. Objectives: To assess the prognostic value of diffusionMRimaging and clinical-pathologic risk factors in patients with rectal cancer. Patients and Methods: This retrospective study was approved by our institutional review board and written informed consent was waived. Sixty-one consecutive patients with rectal cancer (41 men and 20 women; mean age, 64.5 - 12.1 years; range, 32 - 86 years) underwent pelvic MR imaging. Tumor ADC value and clinical-pathologic risk factors were tested as possible risk factors for postoperative local recurrence or distant metastasis (LRDM) as well as disease-free survival outcome. Results: Of 62 tumors, 12 (19.4%) had postoperativeLRDM(median follow-up 38.5 months). Plasmatic CA19-9 level (P = 0.0027), pathological N stage (P = 0.0018), lymphatic invasion (P < 0.0001), and tumor ADC value (P = 0.0076) were independently associated with postoperative LDRM. High plasmatic CA19-9 level (≥ 37 U/mL) (P = 0.010), ly2 (P = 0.020), ly3 (P< 0.0001), pathological N2 (P = 0.006), and low tumor ADC value (< 0.996 x 10-3 mm²/sec) (P = 0.0026) were associated with reduced disease-free survival. Conclusion: Preoperative tumor ADC and plasmatic CA19-9 were significantly associated with postoperative LRDM and disease-free survival in rectal cancer. [ABSTRACT FROM AUTHOR]

The black hole binary V404 Cygni (= GS 2023+338) had an outburst on 2015 June 15 after 26 years of its quiescence. We report on the multi-color optical observation (g', RC, and IC) of this object at the beginning of its outburst performed by the MITSuME 50 cm telescope in Akeno, Yamanashi, and the MURIKABUSHI 105cm telescope at Ishigakijima Astronomical Observatory. Through time domain analysis of the multi-color light curves, we successfully decomposed the optical variations into two components: a highly variable and a less-variable component. The loci of the less-variable component in the color-color diagram are consistent with that of multi-temperature blackbody radiation, while those of the highly variable component trace out a power-law spectrum with a spectral index α ~ 0.6-1.0. For the less-variable component, we argue that an irradiated disk with the innermost temperature higher than ~2.0 × 104 K and the outermost temperature lower than ~6.5 × 103 K is the most plausible source. The gradual rising trend of the light curve during our observation is probably due to the growing of the less-variable component. The observed spectral energy distribution from optical to ultraviolet can be expressed by a model consisting of a power-law component and an irradiated disk component. [ABSTRACT FROM AUTHOR]

Background: Fluorine-18 fluorodeoxyglucose (F-18 FDG)-positron emission tomography/computed tomography (PET/CT) is widely used in most malignancy workups, including detection, differential diagnosis, staging and/or restaging, therapeutic decisionmaking, follow-up, and prognosis. Objectives: The aim of this study was to evaluate the usefulness of F-18 FDG-PET/CT for predicting breast cancer molecular subtypes. Patients and Methods: Sixty-six patients with pathologically proven invasive breast carcinoma (IBC) underwent F-18 FDG-PET/CT imaging for tumor staging. The maximum standardized uptake value (tumor SUVmax) of the IBC and mean SUVs of the liver and spleen (liver and spleen SUVmean) were measured. Molecular subtype was determined according to genomic analysis. The tumor SUVmax, tumor-to-liver SUV ratio, and tumor-to-spleen SUV ratio were correlated with molecular subtype data. Results: Logistic analysis demonstrated that only the tumor-to-liver SUV ratio was a significant parameter for human epidermal growth factor type 2 (HER2)-positive subtype identification (P = 0.0049). The sensitivity, specificity, and area under the receiver-operating-characteristic curve (AUC) of this parameter for HER2-positive subtype detection were 83%, 79%, and 0.87, respectively. Conclusion: The tumor-to-liver SUV ratio appears to be useful for HER2-positive subtype identification, thus indicating the potential use of F-18 FDG-PET/CT as an imaging biomarker that could facilitate the clinical management of patients with breast cancer. [ABSTRACT FROM AUTHOR]

Twenty-three giant flares from thirteen active stars (eight RS CVn systems, one Algol system, three dMe stars, and one young stellar object) were detected during the first two years of our all-sky X-ray monitoring with the gas propotional counters (GSC) of the Monitor of All-sky X-ray Image (MAXI). The observed parameters of all these MAXI/GSC flares are found to be at the upper ends for stellar flares with the luminosity of 1031-34 erg s-1 in the 2-20 keV band, the emission measure of 1054-57 cm-3, the e-folding time of 1 hr to 1.5 d, and the total radiative energy released during the flare of 1034-39 erg. Notably, the peak X-ray luminosity of 5+4-2 x 1033 erg s-1 in the 2-20 keV band was detected in one of the flares on II Peg, which is one of the, or potentially the, largest-ever-observed in stellar flares. X-ray flares were detected from GTMus, V841 Cen, SZ Psc, and TWA-7 for the first time in this survey. Where as most of our detected sources are multiple-star systems, two of them are single stars (YZ CMi and TWA-7). Among the stellar sources within 100 pc distance, the MAXI/GSC sources have larger rotation velocities than the other sources. This suggests that the rapid rotation velocity may play a key role in generating large flares. Combining the X-ray flare data of nearby stars and the sun, taken from literature and our own data, we discovered a universal correlation of τt ∝ LX0.2 for the flare duration τ and the intrinsic X-ray luminosity LX in the 0.1-100 keV band, which holds for 5 and 12 orders of magnitude in τ and LX, respectively. The MAXI/GSC sample is located at the highest ends of the correlation. [ABSTRACT FROM AUTHOR]

We derive the first hard X-ray luminosity function (XLF) of stellar tidal disruption events (TDEs) by supermassive black holes (SMBHs), which gives an occurrence rate of TDEs per unit volume as a function of peak luminosity and redshift, utilizing an unbiased sample observed by the Monitor of All-sky X-ray Image (MAXI). On the basis of the light curves characterized by a power-law decay with an index of -5/3, a systematic search using the MAXI data detected four TDEs in the first 37 months of observations, all of which have been found in the literature. To formulate the TDE XLF, we consider the mass function of SMBHs, that of disrupted stars, the specific TDE rate as a function of SMBH mass, and the fraction of TDEs with relativistic jets. We perform an unbinned maximum likelihood fit to the MAXI TDE list and check the consistency with the observed TDE rate in the ROSAT all-sky survey. The results suggest that the intrinsic fraction of the jet-accompanying events is 0.0007%-34%. We confirm that at z ≲ 1.5 the contamination of the hard X-ray luminosity functions of active galactic nuclei by TDEs is not significant and hence that their contribution to the growth of SMBHs is negligible at the redshifts. [ABSTRACT FROM AUTHOR]

We present our optical follow-up observations to search for an electromagnetic counterpart of the first gravitational wave source GW150914 in the framework of the Japanese collaboration for Gravitational wave ElectroMagnetic follow-up (J-GEM), which is an observing group utilizing optical and radio telescopes in Japan, as well as in New Zealand, China, South Africa, Chile, and Hawaii. We carried out a wide-field imaging survey with the Kiso Wide Field Camera (KWFC) on the 1.05m Kiso Schmidt telescope in Japan and a galaxy-targeted survey with Tripole5 on the B&C 61cm telescope in New Zealand. Approximately 24 deg² regions in total were surveyed in i-band with KWFC and 18 nearby galaxies were observed with Tripole5 in g-, r-, and i-bands 4-12 days after the gravitational wave detection. Median 5 σ depths are i ~ 18.9mag for the KWFC data and g ~ 18.9mag, r ~ 18.7mag, and i ~ 18.3mag for the Tripole5 data. The probability for a counterpart to be in the observed area is 1.2% in the initial skymap and 0.1% in the final skymap. We do not find any transient source associated to an external galaxy with spatial offset from its center, which is consistent with the local supernova rate. [ABSTRACT FROM AUTHOR]

Various transient phenomena on a timescale ranging from seconds to days appear at unexpected sky positions in X-rays. MAXI, Monitor of All-sky X-ray Image, on the International Space Station has been monitoring about 95% of the sky a day and has detected transient objects since 2009 August. Here, we describe quasi-real-time data processing systems of MAXI and a subsequent nova-alert system to find transient objects, and present the capabilities for the nova-alert system to detect transient events with excess fluxes from ≳80 mCrab in a single scan transit to ≳8mCrab for 4 d, and to send prompt alert information to the world in less than 30 s after the onboard detection of a burst, making the best use of the International Space Station (ISS) real-time network. We also report on highlights of scientific results obtained with the system until the end of the first extended mission phase, 2015 March. Including 15 X-ray novae solely or independently discovered, we have reported on 177 transient phenomena, such as X-ray bursts, outbursts, and state transitions of X-ray binaries and X-ray flares from active stars and blazars, via the Astronomer's Telegram, and on 63 burst phenomena of other types via the Gamma-ray Coordinates Network. We summarize the results of these transient sources and phenomena focusing on the detections with the nova-alert system, and some new transients yet unpublished or requiring attention. [ABSTRACT FROM AUTHOR]

We searched for precursive soft X-ray flashes (SXFs) associated with optically discovered classical or recurrent novae in the data of five years' all-sky observations with the Gas Slit Camera (GSC) of theMonitor of All-sky X-ray Image (MAXI).We first developed a tool to measure the fluxes of point sources by fitting the event distribution with a model that incorporates the point-spread function (PSF-fit) to minimize the potential contamination from nearby sources. Then we applied the PSF-fit tool to 40 classical/recurrent novae that were discovered in optical observations from 2009 August to 2014 August. We found no precursive SXFs with significance above the 3σ level in the energy range of 2-4 keV between td - 10 d and td, where td is the date when each nova was discovered. We obtained the upper limits for the bolometric luminosity of SXFs, and compared them with the theoretical prediction and that observed for MAXI J0158-744. This result could constrain the population of massive white dwarfs with a mass of roughly 1.40 solar mass, or larger, in binary systems. [ABSTRACT FROM AUTHOR]

We present a newly developed broadband transient monitor using the Swift Burst Alert Telescope (BAT) and the MAXI Gas Slit Camera (GSC) data. Our broadband transient monitor keeps vigil for high-energy transient sources from 2 keV to 200 keV in seven energy bands by combining the BAT (15-200 keV) and the GSC (2-20 keV) data. Currently, daily and 90-minute (one orbit) averaged light curves are available for 106 high-energy transient sources. This transient monitor is available to the public through our web server, http://yoshidalab.mydns.jp/bat_gsc_trans_mon/, for wider use by the community. We discuss a daily sensitivity of our monitor and possible future improvements on our pipeline. [ABSTRACT FROM AUTHOR]

We have observed the prompt emission of GRB 100418A from its beginning captured by the MAXI SSC (0.7-7 keV) on board the International Space Station followed by the Swift XRT (0.3-10 keV) observation. The light curve can be fitted by a combination of a power-law component and an exponential component (the decay constant is 31.6 ± 1.6 s). The X-ray spectrum is well expressed by the Band function with Ep ⩽ 8.3 keV. This is the brightest gamma-ray burst showing a very low value of Ep. It satisfies the Yonetoku relation (Ep-Lp). It is also consistent with the Amati relation (Ep-Eiso) within a 2.5σ level. [ABSTRACT FROM AUTHOR]

We performed time-lag analysis on the X-ray light curves of Centaurus A (Cen A) obtained by the Gas Slit Camera (GSC) aboard the Monitor of All-sky X-ray Image (MAXI) in three energy bands (2-4 keV, 4-10 keV, and 10-20 keV). We discovered a soft X-ray lag relative to higher energies (soft lag) on a timescale of days in a flaring episode by employing the discrete correlation function (DCF) and the z-transformed discrete correlation function (ZDCF) method. In the episode, a peak and a centroid in the DCF and the ZDCF was observed at a soft lag of ~5 d in 2-4 keV versus 4-10 keV and in 4-10 keV versus 10- 20 keV, and ~10 d in 2-4 keV versus 10-20 keV. We found it difficult to explain the observed X-ray variation by a single energy injection with the one-zone synchrotron self-Compton (SSC) model, in which the soft lags in these three energy bands reflect the different cooling times of the relativistic electrons, by assuming the magnetic field and minimum Lorentz factor estimated from a broad-band spectral energy distribution. Alternatively, if the phenomenon is interpreted as cooling of Comptonizing electrons in a corona covering the accretion disk, the temperature of the corona producing the variable X-rays should be ~10 keV for reconciliation with the soft lag in the energy range of 2-20 keV. [ABSTRACT FROM AUTHOR]

The unprecedentedly bright afterglow of Swift GRB 130606A at z = 5.91 gave us a unique opportunity to probe the reionization era through high-precision analyses of the redward damping wing of Lyα absorption, but the reported constraints on the neutral hydrogen fraction (fHI) in intergalactic medium (IGM) derived from spectra taken by different telescopes are in contradiction to each other. Here we examine the origin of this discrepancy by analyzing the spectrum taken by the Very Large Telescope (VLT) with our own analysis code previously used to fit the Subaru spectrum. Though the VLT team reported no evidence for IGM HI using the VLT spectrum, we confirm our previous result of preferring non-zero IGM HI (the best fit fHI ∼ 0.06, when IGM HI extends to the GRB redshift). The fit residuals of the VLT spectrum using the model without IGM HI show the same systematic trend as the Subaru spectrum. We consider that the likely origin of the discrepancy between the two teams is the difference of the wavelength ranges adopted in the fittings; our wavelength range is wider than that of the VLT team, and also we avoided the shortest wavelength range of deep Lyα absorption (λobs < 8426 A°), because this region is dominated by HI in the host galaxy and the systematic uncertainty about host HI velocity distribution is large. We also study the sensitivity of these results to the adopted Lyα cross-section formulae, ranging from the classical Lorentzian function to the most recent one taking into account fully quantum mechanical scattering. It is found that the preference for non-zero IGM HI is robust against the choice of the cross-section formulae, but it is quantitatively not negligible and hence one should be careful in future analyses. [ABSTRACT FROM AUTHOR]

Background: We describe a case of a very unusual complication following a coiling procedure in which the patient developed transient unique cerebral and cerebellar lesions. Lesions were examined not only by magnetic resonance imaging (MRI) but also by positron emission tomography-computed tomography (PET-CT) and proton magnetic resonance spectroscopy (¹ H-MRS). Case presentation: A 33-year-old woman presented an incidental 3.7 x 3.3-mm unruptured cerebral aneurysm (CAn) in her basilar artery, which was successfully coiled with balloon assistance. A follow-up brain MRI at 1 and 2 months showed a gradual increase in several white matter hyperintense lesions in the left cerebellar, bilateral occipitotemporal and left parietoccipital lobe during fluid-attenuated inversion recovery (FLAIR). These were the only lesions associated with perfused CAn. However, the patient did not show any additional symptoms such as visual disturbance throughout the entire course. 11C-methionine-PET (MET-PET) showed an obvious increase in methionine uptake in the lesion corresponding to enhanced areas with gadolinium-enhanced MRI. MRS showed a decrease in the N-acetylaspartate/ creatine (NAA/cr) ratio and a slight elevation of the choline/creatine (cho/cr) ratio and a lactate peak in the lesion. A follow-up MRI at 6 and 12 months showed a gradual decrease in the initial hyperintense lesions in FLAIR without any treatment. Conclusion: We present a case of an unusual complication after a coiling procedure. Although it is difficult to identify this etiology without a pathological examination, it is importance to increase awareness of such a potential complication arising from coiling procedures, because interventional procedures have become the first choice of treatment for cerebrovascular diseases in many countries. [ABSTRACT FROM AUTHOR]

We here describe the radiologic findings of peritoneal chronic abscess formation due to gallstones lost within the peritoneum during laparoscopic cholecystectomy (LC). A radiologic workup 7 months after LC revealed a soft-tissue mass with contrast enhancement, harboring internal necrosis and punctate calcium located in the Morrison's pouch. The mass exhibited restricted water molecule diffusion, absence of fat deposition, and increased F-18 fluorodeoxy-D-glucose uptake, thus mimicking a malignant tumor. The biopsy revealed an inflammatory granuloma. Another patient with similar findings was treated with percutaneous abscess drainage. Thus, radiologists should be aware of this disease condition and its imaging findings. [ABSTRACT FROM AUTHOR]