NuSTAR View of TeV Blazar Mrk 501

We report the results of flux and spectral variability studies of all seven {\it Nuclear Spectroscopic Telescope Array (NuSTAR)} observations of TeV $\gamma-$ray emitting blazar Markarian (or Mrk) 501. We found strong evidence of intraday variability in 3-79 keV X-ray light curves (LCs) of Mrk 501 during four out of these seven observations. We examined spectral variability using a model-independent hardness-ratio analysis and found a general "harder-when-brighter" behaviour in two observations. We also investigated the nature of 3-79 keV X-ray spectra of TeV blazar Mrk 501 and found that five out of seven spectra are well described by the curved log-parabola models with photon indices (at 10 keV) $\alpha \sim$ 2.12-2.32 and a curvature $\beta \sim$ 0.15-0.28. The two other spectra are somewhat better represented by simple power-law models with photon indices 2.70 and 2.75. We briefly discuss available physical models to explain our results.Comment: 13 pages, 3 figures, 3 tables, published in special issue "X-Ray Flux and Spectral Variability of Blazars" of Galaxies journa

X-ray Intraday Variability of Five TeV Blazars with NuSTAR

We have examined 40 NuSTAR light curves (LCs) of five TeV emitting high synchrotron peaked blazars: 1ES 0229+200, Mrk 421, Mrk 501, 1ES 1959+650 and PKS 2155-304. Four of the blazars showed intraday variability in the NuSTAR energy range of 3-79 keV. Using an auto correlation function analysis we searched for intraday variability timescales in these LCs and found indications of several between 2.5 and 32.8 ks in eight LCs of Mrk 421, a timescale around 8.0 ks for one LC of Mrk 501, and timescales of 29.6 ks and 57.4 ks in two LCs of PKS 2155-304. The other two blazars' LCs do not show any evidence for intraday variability timescales shorter than the lengths of those observations, however, the data was both sparser and noisier, for them. We found positive correlations with zero lag between soft (3-10 keV) and hard (10-79 keV) bands for most of the LCs, indicating that their emissions originate from the same electron population. We examined spectral variability using a hardness ratio analysis and noticed a general "harder-when-brighter" behavior. The 22 LCs of Mrk 421 observed between July 2012 and April 2013 show that this source was in a quiescent state for an extended period of time and then underwent an unprecedented double peaked outburst while monitored on a daily basis during 10 - 16 April 2013. We briefly discuss models capable of explaining these blazar emissions.Comment: 21 pages, 4 figures, 4 tables, Accepted for Publication in Ap

In vitro evaluation of Trichoderma species for virulence efficacy on Botryodiplodia palmarum

Trichoderma species are well known for their antagonistic activity against number of phytopathogens. They restrict the growth of pathogens by variety of means like parasitism, release of antibiotic volatile and non-volatile metabolites. The studies aimed to screen and evaluate the growth inhibition potential of six Trichoderma species against Botryodiplodia palmarum under laboratory conditions. The results revealed 37.56-61.95% growth inhibition of B. palmarum in dual culture, 12.59-43.46% and 4.38-78.08% respectively by the release of volatile and non-volatile metabolites. The growth inhibition was increased with period of incubation and concentration of culture filtrate of Trichoderma species in the culture media. Trichoderma harzianum was most effective among the selected species

Spectral Characterization of Himalayan Near-Fault Ground Motion

Near-Fault Ground Motion (NFGM) spectral characteristics of three moderate-sized Himalayan earthquakes, viz., the 1986 Dharamsala earthquake (Mw = 5:5), the 1991 Uttarkashi earthquake (Mw = 6:8), and the 1999 Chamoli earthquake (Mw = 6:5) have been studied from the 33 available strong ground motion recordings. Pulse characteristics of fault-normal components in terms of pulse-periods and pulse-indicators have been extracted adopting wavelet analysis. Seven mother wavelets were used in the analysis, and it was found that db4 and db7 mother wavelets were more efficient in extracting the pulse-type characteristics. NFGM spectra, at Bhatwari and Gopeshwar stations, showed higher spectral amplitudes in the velocity-sensitive and acceleration-sensitive regions compared to Indian codal response spectra. This is attributed to high PGV/PGA ratios. The study shows that NFGM leads to widening of acceleration-sensitive region, and the structures that are designed according to the Indian seismic code as flexible structures shall behave as stiff structures when subjected to NFGM

Electronic states of PrCoO3_3: X-ray photoemission spectroscopy and LDA+U density of states studies

Electronic states of PrCoO$_3$ are studied using x-ray photoemission spectroscopy. Pr 3d$_{5/2}$ core level and valence band (VB) were recorded using Mg K$_\beta$ source. The core level spectrum shows that the 3d$_{5/2}$ level is split into two components of multiplicity 4 and 2, respectively due to coupling of the spin states of the hole in 3d$_{5/2}$ with Pr 4f holes spin state. The observed splitting is 4.5 eV. The VB spectrum is interpreted using density of states (DOS) calculations under LDA and LDA+U. It is noted that LDA is not sufficient to explain the observed VB spectrum. Inclusion of on-site Coulomb correlation for Co 3d electrons in LDA+U calculations gives DOS which is useful in qualitative explanation of the ground state. However, it is necessary to include interactions between Pr 4f electrons to get better agreement with experimental VB spectrum. It is seen that the VB consists of Pr 4f, Co 3d and O 2p states. Pr 4f, Co 3d and O 2p bands are highly mixed indicating strong hybridization of these three states. The band near the Fermi level has about equal contributions from Pr 4f and O 2p states with somewhat smaller contribution from Co 3d states. Thus in the Zaanen, Sawatzky, and Allen scheme PrCoO$_3$ can be considered as charge transfer insulator. The charge transfer energy $\Delta$ can be obtained using LDA DOS calculations and the Coulomb-exchange energy U' from LDA+U. The explicit values for PrCoO$_3$ are $\Delta$ = 3.9 eV and U' = 5.5 eV; the crystal field splitting and 3d bandwidth of Co ions are also found to be 2.8 and 1.8 eV, respectively.Comment: 12 pages, 7 figures; to appear J. Phys.: Condens. Matte