The radio luminosity distribution of pulsars in 47 Tucanae     

D. McConnell  A. A. Deshpande †  T. Connors ‡  J. G. Ables 《Monthly notices of the Royal Astronomical Society》2004,348(4):1409-1414

  相似文献   

Power spectrum analysis of the timing noise in 18 southern pulsars     

F. D’Alessandro  A. A. Deshpande  P. M. McCulloch 《Journal of Astrophysics and Astronomy》1997,18(1):5-14

Power spectra of the timing noise observed in 18 southern pulsars have been derived using a novel technique, based on the CLEAN algorithm. Most of the spectra are well described by a single- or double-component power-law model. Some of these spectra can be interpreted in the context of one or more of the current timing noise models. The results combined with those obtained from the time-domain analyses of the timing activity in these pulsars are used to assess the viability of the various theoretical models of pulsar timing noise.  相似文献   

p Modes in and Away from a Sunspot     

Kumar  Brajesh  Jain  Rajmal  Tripathy  S.C.  Vats  Hari Om  Deshpande  M.R. 《Solar physics》2000,191(2):293-307

A time series of GONG Dopplergrams for the period 10–14 May 1997 from Udaipur and Big Bear sites has been used to measure the velocity fluctuations in a sunspot (NOAA active region 8038) and quiet photosphere simultaneously. We observe that the power of pre-dominant p mode is reduced in the sunspot as compared to quiet photosphere by 39–52% depending on the location of the sunspot region on the solar disk. We also observe a relative peak frequency deviation of p modes in the sunspot, of the order of 80–310 Hz, which shows a linear dependence on the magnetic field gradient in the active region. The maximum frequency deviation of 310 Hz on 12 May appears to be an influence of a long-duration solar flare that occurred in this active region. We interpret this relative peak frequency deviation as either due to power re-distribution of p modes in the sunspot or a consequence of frequency modulation of these modes along the magnetic flux tubes due to rapidly varying magnetic field structure.  相似文献   

Erratum to: Simulation of monsoon intraseasonal variability in NCEP CFSv2 and its role on systematic bias     

Bidyut B. Goswami  Medha Deshpande  P. Mukhopadhyay  Subodh K. Saha  Suryachandra A. Rao  Raghu Murtugudde  B. N. Goswami 《Climate Dynamics》2015,44(3-4):1171-1171

  相似文献   

The topology and polarization of sub-beams associated with the 'drifting' subpulse emission of pulsar B0943 + 10 – III. Analysis of Pushchino 103/40-MHz observations     

Joanna M. Rankin  †  Svetlana A. Suleymanova  Avinash A. Deshpande ‡ 《Monthly notices of the Royal Astronomical Society》2003,340(4):1076-1086

  相似文献   

Microvariability in Blazars     

M.R. Deshpande  U.C. Joshi  K.S. Baliyan  S. Ganesh 《Astrophysics and Space Science》1997,258(1-2):9-14

Optically violent variable quasars and BL Lac objects, which form a subclass of active galactic nuclei are termed as Blazars. Blazars show high degree variation in their flux and polarization in a relatively shorter period of time. They are strong radio sources with a non-stellar continuum. Most of the BL Lac objects do not show any emission lines though in some cases very weak lines are observed. They harbour in elliptical galaxies. Some BL Lacs show superluminal motion indicating the flow of matter at relativistic speeds close to the line of sight. It is likely that the enormous energy produced by these objects may be due to a massive black hole with an accretion disc system. Some Blazars have been observed to detect short time variations in their flux and polarization in the visual band. These studies are aimed at understanding the physical processes taking place in the central engine. Detecting shorter period variations assumes significance as they impose restrictions on the total volume from where the huge amount of energy is comming out. To date the recorded shortest period variation in visual band is 6.3 min in OJ 287, a BL Lac object. Attempts are being made to detect shorter period variations, which pose observational challenges. It is generally accepted that the central engine of AGN harbours a massive blackhole with an accretion disc surrounding it. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The topology and polarization of sub-beams associated with the 'drifting' sub-pulse emission of pulsar B0943+10 – II. Analysis of Gauribidanur 35-MHz observations     

Ashish Asgekar  Avinash A. Deshpande 《Monthly notices of the Royal Astronomical Society》2001,326(4):1249-1254

In the previous paper of this series, Deshpande & Rankin reported results regarding the sub-pulse drift phenomenon in pulsar B0943+10 at 430 and 111 MHz. This study has led to the identification of a stable system of sub-beams circulating around the magnetic axis of this star. Here, we present a single-pulse analysis of our observations of this pulsar at 35 MHz. The fluctuation properties seen at this low frequency, as well as our independent estimates of the number of sub-beams required and their circulation time, agree remarkably well with the reported behaviour at higher frequencies. We use the 'cartographic' transform mapping technique developed by Deshpande & Rankin in Paper I to study the emission pattern in the polar region of this pulsar. The significance of our results in the context of radio emission mechanisms is also discussed.  相似文献   

Fast Transients with the Square Kilometre Array and its Pathfinders: An Indian Perspective     

Yashwant Gupta  Poonam Chandra  Manjari Bagchi  Niruj M. Ramanujam  Yogesh Maan  Avinash A. Deshpande  Siddhartha Bhattacharyya 《Journal of Astrophysics and Astronomy》2016,37(4):37

In the rapidly developing field of study of the transient sky, fast radio transients are perhaps the most exciting objects of scrutiny at present. The SKA, with its wide field-of-view and significant improvement in sensitivity over existing facilities, is expected to detect a plethora of fast transients which, in addition to help resolve the mysteries surrounding their nature and origin, will also lead to other interesting applications in astrophysics. We explore some of these possibilities here, and also emphasize the current status and future plans of the Indian community working in this area, in the context of ongoing work and extension of this to the SKA.  相似文献   

Spectral Overlap Correction Using Weighted Deconvolution for Improved Dark Object Technique for Correction of EO1-Hyperion Data     

Shailesh S. Deshpande  Arun B. Inamdar  Krishna Mohan Buddhiraju 《Journal of the Indian Society of Remote Sensing》2018,46(3):337-344

We present a critical modification to improved dark object technique for correcting hyperspectral data (EO1-Hyperion). The modification is required in improved dark object technique as the original method does not take into account overlap of spectral response functions of two adjacent bands of hyperspectral sensor. We used weighted deconvolution for correcting the original overlap affected path radiance correction propagation factors. Further, we compared the reduction in correction factors—in different conditions—because of the overlap. We calculated the path radiance for April 22 Hyperion image and compared it with other methods such as 6SV. We found noticeable difference in corrected and uncorrected path radiance propagation factors with “clear” to “very clear” atmospheric models. For the other models (“moderate”, “hazy”, “very hazy”), the difference is negligible and can be ignored and improved dark object technique can be applied without any overlap correction.  相似文献   

Finite element modelling of landslide prone slopes around Rudraprayag and Agastyamuni in Uttarakhand Himalayan terrain     

S. P. Pradhan  Vikram Vishal  T. N. Singh 《Natural Hazards》2018,94(1):181-200

Himalayan mountain chains are neo-tectonically active and significantly susceptible to frequent geohazards like landslides, earthquakes, cloudburst and flash floods, etc. Himalayan slopes are characterized by highly fractured, jointed and sheared rock mass. This affects the strength of the rocks and thus largely influences the stability characteristic of slopes which have been aggravated by human intervention. The ongoing developmental activities, particularly in the last two decades, are responsible for large-scale destabilization of slopes. In rugged terrain, safer designs along hill-cut roads must be ensured. Despite extensive geotechnical works for slope stabilization done in the Himalayan range, slope sections evolve due to various natural and man-made factors are need to be understood in greater details. Proper evaluation and treatment were done on the cut slopes that are severely affected during Kedarnath disaster of June 2013. One of such roads is national highway from Rudraprayag to Gaurikund near Kedarnath. In this study, the stability of vulnerable road cut slopes from Rudraprayag to Agastmuni was investigated. Three key road cut slopes were considered. Finite element analysis was conducted using PLAXIS simulator. Factors of safety, stress, strain, horizontal and vertical displacement have been determined for each slope. The most unstable slope had a factor of safety (FoS) equal to 0.935, while the most stable slope had FoS equal to 2.56. Outcomes from simulation are in good agreement with the prevailing field conditions. Slope stability evaluation must be performed to ensure better safety and to achieve disaster mitigated design.  相似文献