ترغب بنشر مسار تعليمي؟ اضغط هنا

The stationary phase point method for transitional scattering: diffractive radio scintillation for pulsar

39   0   0.0 ( 0 )
 نشر من قبل Chengmin Zhang
 تاريخ النشر 2007
  مجال البحث فيزياء
والبحث باللغة English
 تأليف C.M. Zhang




اسأل ChatGPT حول البحث

The stationary phase point (SPP) method in one-dimensional case is introduced to treat the diffractive scintillation. From weak scattering, where the SPP number N=1, to strong scattering (N$gg$1), via transitional scattering regime (N$sim$2,3), we find that the modulation index of intensity experiences the monotonically increasing from 0 to 1 with the scattering strength, characterized by the ratio of Fresnel scale $rf$ to diffractive scale $rdiff$.

قيم البحث

اقرأ أيضاً

We present a stroboscopic system developed for optical observations of pulsars and its application in the CLYPOS survey. The stroboscopic device is connected to a GPS clock and provides absolute timing to the stroboscopic shutter relative to the puls ars radio ephemerides. By changing the phase we can examine the pulsars light curve. The precisely timed stroboscope in front of the CCD camera can perform highly accurate time resolved pulsar photometry and offers the advantages of CCD cameras, which are high quantum efficiency as well as relatively large field of view, which is important for flux calibrations. CLYPOS (Cananea Ljubljana Young Pulsar Optical Survey) is an extensive search for optical counterparts of about 30 northern hemisphere radio pulsars. It is a collaboration between the INAOE, Mexico and the Faculty of Mathematics and Physics of the University of Ljubljana. Stroboscopic observations were done between December 1998 and November 2000 at the 2.12 m telescope of the Observatory Guillermo Haro in Cananea, Sonora. The first results of the survey are presented. Analyzed data indicate that there is no optical counterpart brighter than ~22.
114 - Alex E. Bernardini 2008
The stationary phase method is often employed for computing tunneling {em phase} times of analytically-continuous {em gaussian} or infinite-bandwidth step pulses which collide with a potential barrier. The indiscriminate utilization of this method wi thout considering the barrier boundary effects leads to some misconceptions in the interpretation of the phase times. After reexamining the above barrier diffusion problem where we notice the wave packet collision necessarily leads to the possibility of multiple reflected and transmitted wave packets, we study the phase times for tunneling/reflecting particles in a framework where an idea of multiple wave packet decomposition is recovered. To partially overcome the analytical incongruities which rise up when tunneling phase time expressions are obtained, we present a theoretical exercise involving a symmetrical collision between two identical wave packets and a one dimensional squared potential barrier where the scattered wave packets can be recomposed by summing the amplitudes of simultaneously reflected and transmitted waves.
We present ULTRACAM multiband optical photometry of two transitional millisecond pulsars, PSR J1023+0038 and PSR J1227$-$4853, taken while both were in their radio pulsar states. The light curves show significant asymmetry about the flux maxima in al l observed bands, suggesting an asymmetric source of heating in the system. We model the light curves using the Icarus binary code, using models with an additional hot spot heating contribution and an anisotropic heat redistribution model to treat the asymmetry. Our modelling reveals companion stars with under-filled Roche lobes in both PSRs J1023+0038 and J1227$-$4853, with Roche lobe filling factors in the range $f sim 0.82-0.92$. While the volume-averaged filling factors are closer to unity, significant under-filling is unexpected from tMSPs as they must rapidly over-fill their Roche lobes to start transferring mass, which occurs on timescale of weeks or months. We discuss the motivation and validity of our extensions to the models and the implications of the under-filled Roche lobe, and suggest future work to further investigate the role of the filling factor in the tMSP cycle.
GRO J1744-28 (the Bursting Pulsar) is a neutron star LMXB which shows highly structured X-ray variability near the end of its X-ray outbursts. In this letter we show that this variability is analogous to that seen in Transitional Millisecond Pulsars such as PSR J1023+0038: missing link systems consisting of a pulsar nearing the end of its recycling phase. As such, we show that the Bursting Pulsar may also be associated with this class of objects. We discuss the implications of this scenario; in particular, we discuss the fact that the Bursting Pulsar has a significantly higher spin period and magnetic field than any other known Transitional Pulsar. If the Bursting Pulsar is indeed transitional, then this source opens a new window of opportunity to test our understanding of these systems in an entirely unexplored physical regime.
We report the discovery of a new low-mass X-ray binary near the center of the unassociated Fermi GeV gamma-ray source 4FGL J0540.0-7552. The source shows the persistent presence of an optical accretion disk and exhibits extreme X-ray and optical vari ability. It also has an X-ray spectrum well-fit by a hard power law with a Gamma = 1.8 and a high ratio of X-ray to gamma-ray flux. Together, these properties are consistent with the classification of the binary as a transitional millisecond pulsar (tMSP) in the sub-luminous disk state. Uniquely among the candidate tMSPs, 4FGL J0540.0-7552 shows consistent optical, X-ray, and gamma-ray evidence for having undergone a state change, becoming substantially brighter in the optical and X-rays and fainter in GeV gamma-rays sometime in mid-2013. In its current sub-luminous disk state, and like one other candidate tMSP in the Galactic field, 4FGL J0540.0-7552 appears to always be in an X-ray flare mode, indicating that this could be common phenomenology for tMSPs.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا