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Outbursts from IGR J17473-2721
We have investigated the outbursts of IGR J17473-2721. We analyzed all
available observations carried out by RXTE on IGR J17473-2721 during its later
outburst and as well all the available SWIFT/BAT data. The flux of the latter
outburst rose in ~ one month and then kept roughly constant for the following ~
two months. During this time period, the source was in a low/hard state. The
source moved to a high/soft state within the following three days, accompanied
by the occurrence of an additional outburst at soft X-rays and the end of the
preceding outburst in hard X-rays. During the decay of this soft outburst, the
source went back to a low/hard state within 6 days, with a luminosity 4 times
lower than the first transition. This shows a full cycle of the hysteresis in
transition between the hard and the soft states. The fact that the flux
remained roughly constant for ~ two months at times prior to the spectral
transition to a high/soft state might be regarded as the result of balancing
the evaporation of the inner disk and the inward accretion flow, in a model in
which the state transition is determined by the mass flow rate. Such a balance
might be broken via an additional mass flow accreting onto the inner disk,
which lightens the extra soft outburst and causes the state transition.
However, the possibility of an origin of the emission from the jet during this
time period cannot be excluded. The spectral analysis suggests an inclined XRB
system for IGR J17473-2721. Such a long-lived preceding low/hard state makes
IGR J17473-2721 resemble the behavior of outbursts seen in black hole X-ray
binaries like GX 339-4.Comment: A&A in pres
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Politics, Portraiture and Power: Reassessing the Public Image of William Ewart Gladstone
Time of life as it is in LiFeAs
The time of life of fermionic quasiparticles, the distribution of which in
the momentum-energy space can be measured by angle resolved photoemission
(ARPES), is the first quantity to look for fingerprints of interaction
responsible for the superconducting pairing. Such an approach has been recently
used for superconducting cuprates, but its direct application to pnictides was
not possible due to essential three-dimensionality of the electronic band
structure and magnetic ordering. Here, we report the investigation of the
quasiparticle lifetime in LiFeAs, a non-magnetic stoichiometric superconductor
with a well separated two-dimensional band. We have found two energy scales:
the lower one contains clear fingerprints of optical phonon modes while the
higher scale indicates a presence of strong electron-electron interaction. The
result suggests that LiFeAs is a phonon mediated superconductor with strongly
enhanced electronic density of states at the Fermi level.Comment: reevaluated electron-phonon coupling strength, added reference
Jupiter's X-ray and EUV auroras monitored by Chandra, XXM-Newton, and Hisaki satellite
Jupiter's X-ray auroral emission in the polar cap region results from particles which have undergone strong field-aligned acceleration into the ionosphere. The origin of precipitating ions and electrons and the time variability in the X-ray emission are essential to uncover the driving mechanism for the high-energy acceleration. The magnetospheric location of the source field line where the X-ray is generated is likely affected by the solar wind variability. However, these essential characteristics are still unknown because the long-term monitoring of the X-rays and contemporaneous solar wind variability has not been carried out. In April 2014, the first long-term multiwavelength monitoring of Jupiter's X-ray and EUV auroral emissions was made by the Chandra X-ray Observatory, XMM-Newton, and Hisaki satellite. We find that the X-ray count rates are positively correlated with the solar wind velocity and insignificantly with the dynamic pressure. Based on the magnetic field mapping model, a half of the X-ray auroral region was found to be open to the interplanetary space. The other half of the X-ray auroral source region is magnetically connected with the prenoon to postdusk sector in the outermost region of the magnetosphere, where the Kelvin-Helmholtz (KH) instability, magnetopause reconnection, and quasiperiodic particle injection potentially take place. We speculate that the high-energy auroral acceleration is associated with the KH instability and/or magnetopause reconnection. This association is expected to also occur in many other space plasma environments such as Saturn and other magnetized rotators
The CUORE Cryostat: A 1-Ton Scale Setup for Bolometric Detectors
The cryogenic underground observatory for rare events (CUORE) is a 1-ton
scale bolometric experiment whose detector consists of an array of 988 TeO2
crystals arranged in a cylindrical compact structure of 19 towers. This will be
the largest bolometric mass ever operated. The experiment will work at a
temperature around or below 10 mK. CUORE cryostat consists of a cryogen-free
system based on pulse tubes and a custom high power dilution refrigerator,
designed to match these specifications. The cryostat has been commissioned in
2014 at the Gran Sasso National Laboratories and reached a record temperature
of 6 mK on a cubic meter scale. In this paper, we present results of CUORE
commissioning runs. Details on the thermal characteristics and cryogenic
performances of the system will be also given.Comment: 7 pages, 2 figures, LTD16 conference proceedin
The price of rapid exit in venture capital-backed IPOs
This paper proposes an explanation for two empirical puzzles surrounding initial public offerings (IPOs). Firstly, it is well documented that IPO underpricing increases during “hot issue” periods. Secondly, venture capital (VC) backed IPOs are less underpriced than non-venture capital backed IPOs during normal periods of activity, but the reverse is true during hot issue periods: VC backed IPOs are more underpriced than non-VC backed ones. This paper shows that when IPOs are driven by the initial investor’s desire to exit from an existing investment in order to finance a new venture, both the value of the new venture and the value of the existing firm to be sold in the IPO drive the investor’s choice of price and fraction of shares sold in the IPO. When this is the case, the availability of attractive new ventures increases equilibrium underpricing, which is what we observe during hot issue periods. Moreover, I show that underpricing is affected by the severity of the moral hazard problem between an investor and the firm’s manager. In the presence of a moral hazard problem the degree of equilibrium underpricing is more sensitive to changes in the value of the new venture. This can explain why venture capitalists, who often finance firms with more severe moral hazard problems, underprice IPOs less in normal periods, but underprice more strongly during hot issue periods. Further empirical implications relating the fraction of shares sold and the degree of underpricing are presented
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