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DISCOVERY OF AN X-RAY-EMITTING CONTACT BINARY SYSTEM 2MASS J11201034−2201340
Hu, Chin-Ping,Yang, Ting-Chang,Chou, Yi,Liu, L.,Qian, S.-B.,Hui, C. Y.,Kong, Albert K. H.,Lin, L. C. C.,Tam, P. H. T.,Li, K. L.,Ngeow, Chow-Choong,Chen, W. P.,Ip, Wing-Huen American Astronomical Society 2016 The Astronomical journal Vol.151 No.6
<P>We report the detection of orbital modulation, a model solution, and the X-ray properties of a newly discovered contact binary, Two Micron All Sky Survey (2MASS) J11201034-2201340. We serendipitously found this X-ray point source outside the error ellipse when searching for possible X-ray counterparts of 7-ray millisecond pulsars among the unidentified objects detected by the Fermi Gamma-ray Space Telescope. The optical counterpart of the X-ray source (unrelated to the 7-ray source) was then identified using archival databases. The long-term Catalina Real-Time Transient Survey detected a precise signal with a period of P = 0.28876208 (56) days. A follow-up observation made by the Super Light Telescope of Lulin Observatory revealed the binary nature of the object. Utilizing archived photometric data of multi-band surveys, we construct the spectral energy distribution (SED), which is well fit by a K2V spectral template. The fitting result of the orbital profile using the Wilson Devinney code suggests that 2MASS J11201034-2201340 is a short-period A-type contact binary and the more massive component has a cool spot. The X-ray emission was first noted in observations made by Swift, and then further confirmed and characterized by an XMM-Newton observation. The X-ray spectrum can be described by a power law or thermal Bremsstrahlung. Unfortunately, we could not observe significant X-ray orbital modulation. Finally, according to the SED, this system is estimated to be 690 pc from Earth with a calculated X-ray intensity of (0.7 - 1.5) x 10(30) erg s(-1), which is in the expected range of an X-ray emitting contact binary.</P>
K. Karthick,S. Malarvizhi,V. Balasubramanian,S.A. Krishnan,G. Sasikala,Shaju K. Albert 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.1
Modified 9Cr-1Mo ferritic steel is a preferred material for steam generators in nuclear power plants fortheir creep strength and good corrosion resistance. Austenitic stainless steels, such as type 316LN, areused in the high temperature segments such as reactor pressure vessels and primary piping systems. So,the dissimilar joints between these materials are inevitable. In this investigation, dissimilar joints werefabricated by the Shielded Metal Arc Welding (SMAW) process with Inconel 82/182 filler metals. Thenotch tensile properties and Charpy V-notch impact toughness properties of various regions of dissimilarmetal weld joints (DMWJs) were evaluated as per the standards. The microhardness distribution acrossthe DMWJs was recorded. Microstructural features of different regions were characterized by optical andscanning electron microscopy. Inhomogeneous notch tensile properties were observed across theDMWJs. Impact toughness values of various regions of the DMWJs were slightly higher than the prescribedvalue. Formation of a carbon-enriched hard zone at the interface between the ferritic steel andthe buttering material enhanced the notch tensile properties of the heat-affected-zone (HAZ) of P91. Thecomplex microstructure developed at the interfaces of the DMWJs was the reason for inhomogeneousmechanical properties
DISCOVERY OF AN ULTRACOMPACT GAMMA-RAY MILLISECOND PULSAR BINARY CANDIDATE
Kong, Albert K. H.,Jin, Ruolan,Yen, T.-C.,Hu, C.-P.,Hui, C. Y.,Tam, P. H. T.,Takata, J.,Lin, L. C. C.,Cheng, K. S.,Park, S. M.,Kim, C. L. IOP Publishing 2014 ASTROPHYSICAL JOURNAL LETTERS - Vol.794 No.2
<P>We report multi-wavelength observations of the unidentified Fermi object 2FGL J1653.6-0159. With the help of high-resolution X-ray observations, we have identified an X-ray and optical counterpart to 2FGL J1653.6-0159. The source exhibits a periodic modulation of 75 minutes in the optical and possibly also in the X-ray. We suggest that 2FGL J1653.6-0159 is a compact binary system with an orbital period of 75 minutes. Combining the gamma-ray and X-ray properties, 2FGL J1653.6-0159 is potentially a black-widow-/redback-type gamma-ray millisecond pulsar (MSP). The optical and X-ray light curve profiles show that the companion is mildly heated by the high-energy emission and that the X-rays are from intrabinary shock. Although no radio pulsation has yet been detected, we estimated that the spin period of the MSP is similar to 2 ms based on a theoretical model. If pulsation can be confirmed in the future, 2FGL J1653.6-0159 will become the first ultracompact rotation-powered MSP.</P>
STUDYING THE SGR 1806-20/Cl* 1806-20 REGION USING THE<i>FERMI</i>LARGE AREA TELESCOPE
Yeung, Paul K. H.,Kong, Albert K. H.,Tam, P. H. Thomas,Lin, Lupin C. C.,Hui, C. Y.,Hu, Chin-Ping,Cheng, K. S. American Astronomical Society 2016 The Astrophysical journal Vol.827 No.1
<P>The region around SGR 1806-20 and its host stellar cluster Cl* 1806-20 is a potentially important site of particle acceleration. The soft gamma-ray repeater and Cl* 1806-20, which also contains several very massive stars including a luminous blue variable hypergiant LBV 1806-20, are capable of depositing a large amount of energy to the surroundings. Using the data taken with the Fermi Large Area Telescope (LAT), we identified an extended LAT source to the southwest of Cl* 1806-20. The centroid of the 1-50 GeV emission is consistent with that of HESS J1808-204 (until now unidentified). The LAT spectrum is best-fit by a broken power law with the break energy E-b = 297 +/- 15 MeV. The index above E-b is 2.60 +/- 0.04 and is consistent with the flux and spectral index above 100 GeV for HESS J1808-204, suggesting an association between the two sources. Meanwhile, the interacting supernova remnant SNR G9.7-0.0 is also a potential contributor to the LAT flux. A tentative flux enhancement at the MeV band during a 45 day interval (2011 January 21-March 7) is also reported. We discuss possible origins of the extended LAT source in the context of both leptonic and hadronic scenarios.</P>
Yeung, Paul K. H.,Kong, Albert K. H.,Tam, P. H. Thomas,Hui, C. Y.,Takata, Jumpei,Cheng, K. S. American Astronomical Society 2017 The Astrophysical journal Vol.837 No.1
<P>The supernova remnant (SNR) Kes 73 and/or the magnetar 1E 1841-045 at its center can deposit a large amount of energy to the surroundings and is potentially responsible for particle acceleration. Using the data taken with the Fermi Large Area Telescope (LAT), we confirmed the presence of an extended source whose centroid position is highly consistent with this magnetar/SNR pair. Its emission is intense from 100 MeV to > 100 GeV. Its LAT spectrum can be decoupled into two components, which are respectively governed by two different mechanisms. According to the young age of this system, the magnetar is seemingly a necessary and sufficient source for the downward-curved spectrum below 10 GeV, as the observed < 10 GeV flux is too high for the SNR to account for. On the other hand, the SNR is reasonably responsible for the hard spectrum above 10 GeV. Further studies of this region in the TeV regime is required. so that we can perform physically meaningful comparisons of the > 10 GeV spectrum and the TeV spectrum.</P>
Evidence of electron neutrino appearance in a muon neutrino beam
Abe, K.,Abgrall, N.,Aihara, H.,Akiri, T.,Albert, J. B.,Andreopoulos, C.,Aoki, S.,Ariga, A.,Ariga, T.,Assylbekov, S.,Autiero, D.,Barbi, M.,Barker, G. J.,Barr, G.,Bass, M.,Batkiewicz, M.,Bay, F.,Bentham American Physical Society 2013 PHYSICAL REVIEW D - Vol.88 No.3
M. Zubairuddin,S. K. Albert,S. Mahadevan,M. Vasudevan,V. Chaudhari,V. K. Suri 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.12
In this paper, investigation of residual stress and distortion induced in 3 mm thick Modified 9Cr-1Mo steel plates during GTA weldingis carried out. SYSWELD software is used for the thermo-mechanical analysis. A 3D meshed model is created for the simulation anddouble ellipsoidal heat source distribution is used for the thermal analysis. Thermal cycles predicted near the fusion zone are comparedwith experimentally measured thermal cycles using thermocouples. Predicted residual stress profile across the fusion zone is comparedwith the measured profile using X-ray diffraction method. There is a good agreement between measured and predicted thermal cyclesand residual stress profile. Distortion of the weld joint is measured using vertical electronic height gauge. Finite element analysis of distortionof the weld joint is carried out by applying both large and small distortion theories. Comparison of experimental and numericalresults showed better accuracy if large distortion theory is applied.
Weldability Study on SS 304B4 Joined using Boron Containing Austenitic Stainless Steel Consumable
M. Divya,S. K. Albert 대한용접접합학회 2018 대한용접·접합학회지 Vol.36 No.6
304B4 stainless steel contains ~1.2 wt.% of boron intentionally added for neutron shielding purposes in nuclear power plants and nuclear waste storage applications. Weldabilty of 304B4 stainless steel is generally considered to be poor because boron is almost insoluble in austenite phase and has a tendency to segregate in the liquid phase during solidification. This results in formation of different types of borides in the eutectic which melts at low temperature and makes the steel susceptible to cracking. Among the welding consumables specified in standards and codes, E309 consumable is the one generally recommended for this steel, but electrodes with controlled addition of boron (E308BRN) is also available. A systematic study on solidification cracking susceptibility of 304B4 stainless steel weld joint prepared using E308BRN containing ~1 wt.% B has been carried out. Further, mechanical properties of weld joints made with this electrode are compared with that made from E309 electrode. Results show that E308BRN electrode can be chosen for applications involving low restraint forces to produce crack free joints. Mechanical properties of the joints made with both E308BRN and E309 are poor when compared to the base metal. This is attributed to continuous network of eutectic borides present in the interdendritic regions of fusion zone and partially melted zones of the weld joints.