Variations in the Cyclotron Resonant Scattering Features during 2011 outburst of 4U 0115+63

We study the variations in the Cyclotron Resonant Scattering Feature (CRSF) during 2011 outburst of the high mass X-ray binary 4U 0115+63 using observations performed with Suzaku, RXTE, Swift and INTEGRAL satellites. The wide-band spectral data with low energy coverage allowed us to characterize the broadband continuum and detect the CRSFs. We find that the broadband continuum is adequately described by a combination of a low temperature (kT ~ 0.8 keV) blackbody and a power-law with high energy cutoff (Ecut ~ 5.4 keV) without the need for a broad Gaussian at ~ 10 keV as used in some earlier studies. Though winds from the companion can affect the emission from the neutron star at low energies (< 3 keV), the blackbody component shows a significant presence in our continuum model. We report evidence for the possible presence of two independent sets of CRSFs with fundamentals at ~ 11 keV and ~ 15 keV. These two sets of CRSFs could arise from spatially distinct emitting regions. We also find evidence for variations in the line equivalent widths, with the 11 keV CRSF weakening and the 15 keV line strengthening with decreasing luminosity. Finally, we propose that the reason for the earlier observed anti-correlation of line energy with luminosity could be due to modelling of these two independent line sets (~ 11 keV and ~ 15 keV) as a single CRSF.Comment: 12 pages, 8 figures (4 in colour), 6 tables. Accepted for publication in MNRAS. Typos corrected, Figure 8 changed and some changes to draf

The Frenet Serret Description of Gyroscopic Precession

The phenomenon of gyroscopic precession is studied within the framework of Frenet-Serret formalism adapted to quasi-Killing trajectories. Its relation to the congruence vorticity is highlighted with particular reference to the irrotational congruence admitted by the stationary, axisymmetric spacetime. General precession formulae are obtained for circular orbits with arbitrary constant angular speeds. By successive reduction, different types of precessions are derived for the Kerr - Schwarzschild - Minkowski spacetime family. The phenomenon is studied in the case of other interesting spacetimes, such as the De Sitter and G\"{o}del universes as well as the general stationary, cylindrical, vacuum spacetimes.Comment: 37 pages, Paper in Late

Impacts of the 20th January 2005 solar proton event on the ozone concentration of Indian cities

The ozone data obtained from Nimbus-7 and Earth probe Total Ozone Mapping Spectrometer (TOMS) has been used to study the impact of coronal mass ejection (CME) on the columnar ozone concentration in India. A comparison of columnar ozone values for different solar proton events (SPE) observed at Srinagar indicates that although the 20th Jan., 2005 SPE was the most intense in the last 15 years, the ozone depletion was found to be maximum in the 23rd March, 1991 event followed by 20th Jan., 2005, 4th Nov., 2001, 19th Oct., 1989 and 28th Oct., 2003 events. A comparison between the ozone levels observed in different Indian cities for a few days after the 20th Jan., 2005 SPE indicates that the ozone values were found to decrease sharply at higher latitudes compared to places located in the tropics .The ozone values measured by TOMS, Dobson Spectrometer and AURA Ozone Monitoring Instrument (OMI) were found to decrease for a short period from 20th January to 25th January after which the ozone levels started recovering to normal values. The vertical ozone profiles obtained from Microwave Limb Sounder for New Delhi, indicate that the ozonemixing ratio in the 3.0 to 10.0 hPa pressure range decreased consistently from 21st Jan., 2005 to 25th Jan., 2005 and thereafter, recovered by the 31st January, 2005.Impacts of the 20th January 2005 solar proton event on the ozone concentration of Indian cities Nandita D Ganguly 1* and K N Iyer 2 1 Department of Physics, St.Xavier’s College, Ahmedabad-380 009, Gujarat, India 2 Department of Physics, Saurashtra University, Rajkot-360 005, Gujarat, India E–mail: [email protected] Received 1 December 2005, accepted 27 February 20061 Department of Physics, St.Xavier’s College, Ahmedabad-380 009, Gujarat, India 2 Department of Physics, Saurashtra University, Rajkot-360 005, Gujarat, Indi

Magnetic behavior of nanocrystalline ErCo2

We have investigated the magnetic behavior of the nanocrystalline form of a well-known Laves phase compound, ErCo2 - the bulk form of which has been known to undergo an interesting first-order ferrimagnetic ordering near 32 K - synthesized by high-energy ball-milling. It is found that, in these nanocrystallites, Co exhibits ferromagnetic order at room temperature as inferred from the magnetization data. However, the magnetic transition temperature for Er sublattice remains essentially unaffected as though the (Er)4f-Co(3d) coupling is weak on Er magnetism. The net magnetic moment as measured at high fields, sat at 120 kOe, is significantly reduced with respect to that for the bulk in the ferrimagnetically ordered state and possible reasons are outlined. We have also compared the magnetocaloric behavior for the bulk and the nano particles.Comment: JPCM, in pres

Detection and localization of speech in the presence of competing speech signals

Presented at the 12th International Conference on Auditory Display (ICAD), London, UK, June 20-23, 2006.Auditory displays are often used to convey important information in complex operational environments. One problem with these displays is that potentially critical information can be corrupted or lost when multiple warning sounds are presented at the same time. In this experiment, we examined a listener's ability to detect and localize a target speech token in the presence of from 1 to 5 simultaneous competing speech tokens. Two conditions were examined: a condition in which all of the speech tokens were presented from the same location (the `co-located' condition) and a condition in which the speech tokens were presented from different random locations (the `spatially separated' condition). The results suggest that both detection and localization degrade as the number of competing sounds increases. However, the changes in detection performance were found to be surprisingly small and there appeared to be little or no benefit of spatial separation for detection. Localization, on the other hand, was found to degrade substantially and systematically as the number of competing speech tokens increased. Overall, these results suggest that listeners are able to extract substantial information from these speech tokens even when the target is presented with 5 competing simultaneous sounds

The Dirac Equation Is Separable On The Dyon Black Hole Metric

Using the tetrad formalism, we carry out the separation of variables for the massive complex Dirac equation in the gravitational and electromagnetic field of a four-parameter (mass, angular momentum, electric and magnetic charges) black hole.Comment: 13 page

One-loop Renormalization of Black Hole Entropy Due to Non-minimally Coupled Matter

The quantum entanglement entropy of an eternal black hole is studied. We argue that the relevant Euclidean path integral is taken over fields defined on $\alpha$-fold covering of the black hole instanton. The statement that divergences of the entropy are renormalized by renormalization of gravitational couplings in the effective action is proved for non-minimally coupled scalar matter. The relationship of entanglement and thermodynamical entropies is discussed.Comment: 17 pages, latex, no figure

Conical geometry and quantum entropy of a charged Kerr black hole

We apply the method of conical singularities to calculate the tree-level entropy and its one-loop quantum corrections for a charged Kerr black hole. The Euclidean geometry for the Kerr-Newman metric is considered. We show that for an arbitrary periodization in Euclidean space there exists a conical singularity at the horizon. Its $\delta$-function like curvatures are calculated and are shown to behave similar to the static case. The heat kernel expansion for a scalar field on this conical space background is derived and the (divergent) quantum correction to the entropy is obtained. It is argued that these divergences can be removed by renormalization of couplings in the tree-level gravitational action in a manner similar to that for a static black hole.Comment: 22 pages, latex, no figures; minor corrections mad