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.
The Swift and Fermi satellites have been observing gamma-ray bursts (GRBs), which are short-lived and intense flashes of gamma-rays associated with the death/explosion of massive stars and/or compact ...binary mergers, for nearly a decade in space since their launch in 2004 and 2008, respectively. ...P. Chandra discusses GRBs from the radio perspective, which is very important for studies of GRBs related to their calorimetry, reverse-shock emission, and circumburst environments.
The difference of photon arrival time, which is known as spectral lag, is well known characteristics of gamma-ray bursts (GRBs). In particular, long duration GRBs show a soft lag which means that ...high energy photons arrive earlier than soft photons. The lag-luminosity relation is the empirical relationship between the isotropic peak luminosity and the spectral lag. We calculated the spectral lags for 40 known redshift GRBs observed by Swift addition to the previous 31 GRB samples. We confirmed that most of our samples follow the lag-luminosity relation. However, we noticed that there are some GRBs which show a significant scatter from the relation. We also confirm that the relationship between the break time and the luminosity of the X-ray afterglow (so-called Dainotti relation) extends up to the lag-luminosity relation.
Swift/BAT and MAXI/GSC broadband transient monitor Sakamoto, Takanori; Oda, Ryoma; Mihara, Tatehiro ...
Publications of the Astronomical Society of Japan,
06/2016, Volume:
68, Issue:
SP1
Journal Article
Peer reviewed
Open access
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.
The fastest-rotating magnetar 1E 1547.0
$-$
5408 was observed in broad-band X-rays with Suzaku for 33 ks on 2009 January 28–29, 7 d after the onset of its latest bursting activity. After removing ...burst events, the absorption-uncorrected 2–10 keV flux of the persistent emission was measured with the XIS as 5.7
$\times$
10
$^{-11} $
erg cm
$^{-2} $
s
$^{-1}$
, which is 1–2 orders of magnitude higher than was measured in 2006 and 2007 when the source was less active. This persistent emission was also detected significantly with the HXD in
$> $
10 keV up to at least
$\sim $
110 keV, with an even higher flux of 1.3
$\times$
10
$^{-10} $
erg cm
$^{-2} $
s
$^{-1}$
in 20–100 keV. The pulsation was detected at least up to 70 keV for a period of 2.072135
$ \pm $
0.00005 s, with a deeper modulation than was measured in a fainter state. The phase-averaged 0.7–114 keV spectrum was reproduced by an absorbed blackbody emission with a temperature of 0.65
$ \pm $
0.02 keV, plus a hard power-law with a photon index of
$\sim $
1.5. At a distance of 9 kpc, the bolometric luminosity of the blackbody and the 2–100 keV luminosity of the hard power-law are estimated to be (6.2
$ \pm $
1.2)
$\times$
10
$^{35} $
erg s
$^{-1}$
and 1.9
$\times$
10
$^{36} $
erg s
$^{-1}$
, respectively, while the blackbody radius becomes
$\sim $
5 km. Although the source has not been detected significantly in hard X-rays during the past fainter states, a comparison of the present and past spectra at energies below 10 keV suggests that the hard component is more enhanced than the soft X-ray component during the period of persistent activity.
MAXI observations of gamma-ray bursts Serino, Motoko; Sakamoto, Takanori; Kawai, Nobuyuki ...
Publications of the Astronomical Society of Japan,
10/2014, Volume:
66, Issue:
5
Journal Article
Peer reviewed
Open access
Abstract
The Monitor of All-sky X-ray Image (MAXI) Gas Slit Camera (GSC) detects gamma-ray bursts (GRBs), including bursts with soft spectra, such as X-ray flashes (XRFs). MAXI/GSC is sensitive to ...the energy range from 2 to 30 keV. This energy range is lower than other currently operating instruments which are capable of detecting GRBs. Since the beginning of the MAXI operation on 2009 August 15, GSC observed 35 GRBs up to the middle of 2013. One third of them were also observed by other satellites. The rest of them show a trend to have soft spectra and low fluxes. Because of the contribution of those XRFs, the MAXI GRB rate is about three times higher than those expected from the BATSE log N–log P distribution. When we compare it to the observational results of the Wide-field X-ray Monitor on the High Energy Transient Explorer 2, which covers the the same energy range as that of MAXI/GSC, we find the possibility that many of the MAXI bursts are XRFs with Epeak lower than 20 keV. We discuss the source of soft GRBs observed only by MAXI. The MAXI log N–log S distribution suggests that the MAXI XRFs are distributed over a closer distance than hard GRBs. Since the distributions of the hardness of galactic stellar flares and X-ray bursts overlap with those of MAXI GRBs, we discuss the possibility of confusion of such galactic transients with the MAXI GRB samples.
Abstract A new type of cosmological transient, dubbed fast radio bursts (FRBs), was recently discovered. The source of FRBs is still unknown. One possible scenario of an FRB is the collapse of a ...spinning supra-massive neutron star. Zhang (2014, ApJ, 780, L21) suggests that the collapse can happen shortly (hundreds to thousands of seconds) after the birth of supra-massive neutron stars. The signatures can be visible in X-ray afterglows of long and short gamma-ray bursts (GRBs). For instance, a sudden drop (decay index steeper than $-3$ to $-9$) from a shallow decay (decay index shallower than $-1$) in the X-ray afterglow flux can indicate such an event. We selected the X-ray afterglow light curves with a steep decay after the shallow decay phase from the Swift/XRT GRB catalog. We analyzed when the decay index changed suddenly by fitting these light curves to double power-law functions and compared them with the onset of FRBs. We found that none of our GRB samples match the onset of FRBs.
Double-layer TiN/PSZ coatings approximately 2 micron thick were deposited on Si wafers and WC-Co cutting tools from Ti-, Zr-, and Y-alkoxide solutions by Ar/H2/N2 thermal plasma chemical vapour ...deposition with water functioning as an oxidant. A PSZ layer was deposited on TiN films after oxidation of Zr- and Y-alkoxides by H2O. The double-layer coatings were characterised by XRD, SEM, TEM, in-depth glow discharge optical emission spectrometry, and cutting tests. Two H2O supply methods, two-stage pulse and five-step-wise supply methods, were shown to be suitable for the formation of the double-layer coatings by SEM and TEM observation of surface and cross-sectional microstructures. Cutting tests for the double-layer coatings deposited on WC?Co cutting tools prepared by the above two H2O supply methods were carried out to evaluate their wear resistance.
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
$E_{\rm peak}$
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 that could be affecting the scientific results from the GRB prompt emission data.
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