333 research outputs found
Knowledge of IPM Practices among Cotton Growers of Sabarkantha District; Gujarat, India
India is the pioneer country for the commercial cultivation of hybrid cotton. Cotton is one of the principal commercial crops and has been one of the main sources of Indias economic growth and foreign exchange earner. Gujarat is the second largest cotton producing state of India. In Gujarat state Sabarkantha is also has major area under cotton crop. The study was conducted in Sabarkantha District of Gujarat State. Sabarkantha district was selected purposively on the basis of leading hybrid cotton growing area. Total sample size 240 respondents of cotton growers were selected from twelve villages of the district. The cotton crop is attacked by a number of insect, pests, diseases, nematodes and weeds. So, the aims of the study were to study the knowledge of cotton growers about IPM technology and find correlation between selected personal, socio-economic and psychological characteristics of cotton growers and their knowledge of IPM technology. A perusal of the data indicated that cotton growers had medium level of knowledge regarding IPM technology in cotton, In case of independent variable like age and land holding was found no-significant relationship with their knowledge level while selected remaining independent variables were found significant relationship with their knowledge level of farmer regarding IPM technology.
DOI: 10.17762/ijritcc2321-8169.15020
Fading of the Transient Anomalous X-ray Pulsar XTE J1810-197
Three observations of the 5.54 s Transient Anomalous X-ray Pulsar XTE
J1810-197 obtained over 6 months with the Newton X-Ray Multi-Mirror Mission
(XMM-Newton) are used to study its spectrum and pulsed light curve as the
source fades from outburst. The decay is consistent with an exponential of time
constant 300 days, but not a power law as predicted in some models of sudden
deep crustal heating events. All spectra are well fitted by a blackbody plus a
steep power law, a problematic model that is commonly fitted to anomalous X-ray
pulsars (AXPs). A two-temperature blackbody fit is also acceptable, and better
motivated physically in view of the faint optical/IR fluxes, the X-ray pulse
shapes that weakly depend on energy in XTE J1810-197, and the inferred emitting
areas that are less than or equal to the surface area of a neutron star. The
fitted temperatures remained the same while the flux declined by 46%, which can
be interpreted as a decrease in area of the emitting regions. The pulsar
continues to spin down, albeit at a reduced rate of (5.1+/-1.6)x10^{-12} s
s^{-1}. The inferred characteristic age Tau_c = P/2Pdot ~17,000 yr, magnetic
field strength B_s ~1.7x10^{14} G, and outburst properties are consistent with
both the outburst and quiescent X-ray luminosities being powered by magnetic
field decay, i.e., XTE J1810-197 is a magnetar.Comment: 10 pages, 5 figures, accepted by Ap.
X-ray Spectrum and Pulsations of the Vela Pulsar
We report the results of the spectral and timing analysis of observations of
the Vela pulsar with the Chandra X-ray Observatory. The spectrum shows no
statistically significant spectral lines in the observed 0.25--8.0 keV band. It
consists of two distinct continuum components. The softer component can be
modeled as either a magnetic hydrogen atmosphere spectrum with kT = 59 +- 3 eV,
R = 15.5 +- 1.5 km, or a standard blackbody with kT = 129 +- 4 eV, R = 2.1 +-
0.2 km (the radii are for a distance of 250 pc). The harder component, modeled
as a power-law spectrum, gives photon indices depending on the model adopted
for the soft component: gamma = 1.5 +- 0.3 for the magnetic atmosphere soft
component, and gamma = 2.7 +- 0.4 for the blackbody soft component. Timing
analysis shows three peaks in the pulse profile, separated by about 0.3 in
phase. Energy-resolved timing provides evidence for pulse profile variation
with energy. The higher energy (E > 1.8 keV) profile shows significantly higher
pulsed fraction.Comment: 4 pages, 2 figures, To appear in "Neutron Stars in Supernova
Remnants" (ASP Conference Proceedings), eds P. O. Slane and B. M. Gaensler
Corrected TYPO
Deep infrared observations of the puzzling central X-ray source in RCW103
1E 161348-5055 (1E 1613) is a point-like, soft X-ray source originally
identified as a radio-quiet, isolated neutron star, shining at the center of
the 2000 yr old supernova remnant RCW103. 1E 1613 features a puzzling 6.67 hour
periodicity as well as a dramatic variability over a time scale of few years.
Such a temporal behavior, coupled to the young age and to the lack of an
obvious optical counterpart, makes 1E 1613 a unique source among all compact
objects associated to SNRs. It could either be the first low-mass X-ray binary
system discovered inside a SNR, or a peculiar isolated magnetar with an
extremely slow spin period. Analysis of archival IR observations, performed in
2001 with the VLT/ISAAC instrument, and in 2002 with the NICMOS camera onboard
HST unveils a very crowded field. A few sources are positionally consistent
with the refined X-ray error region that we derived from the analysis of 13
Chandra observations. To shed light on the nature of 1E 1613, we have performed
deep IR observations of the field with the NACO instrument at the ESO/VLT,
searching for variability. We find no compelling reasons to associate any of
the candidates to 1E 1613. On one side, within the frame of the binary system
model for the X-ray source, it is very unlikely that one of the candidates be a
low-mass companion star to 1E 1613. On the other side, if the X-ray source is
an isolated magnetar surrounded by a fallback disc, we cannot exclude that the
IR counterpart be hidden among the candidates. If none of the potential
counterparts is linked to the X-ray source, 1E 1613 would remain undetected in
the IR down to Ks>22.1. Such an upper limit is consistent only with an
extremely low-mass star (an M6-M8 dwarf) at the position of 1E 1613, and makes
rather problematic the interpretation of 1E 1613 as an accreting binary system.Comment: 26 pages, 5 figures. Accepted for publication in Ap
Chandra Observations of 1RXS J141256.0+792204 (Calvera)
We report the results of a 30 ks Chandra ACIS-S observation of the isolated
compact object 1RXS J141256.0+792204 (Calvera). The X-ray spectrum is
adequately described by an absorbed neutron star hydrogen atmosphere model with
an effective temperature at infinity of 88.3 +/- 0.8 eV and radiation radius at
infinity of 4.1 +/- 0.1 km/kpc. The best-fit blackbody spectrum yields
parameters consistent with previous measurements; although the fit itself is
not statistically acceptable, systematic uncertainties in the pile-up
correction may contribute to this. We find marginal evidence for narrow
spectral features in the X-ray spectrum between 0.3 and 1.0 keV. In one
interpretation, we find evidence at 81%-confidence for an absorption edge at
0.64 (+0.08) (-0.06) keV with an equivalent width of ~70 eV; if this feature is
real, it is reminiscent of features seen in the isolated neutron stars RX
J1605.3+3249, RX J0720.4-3125, and 1RXS J130848.6+212708 (RBS 1223). In an
alternative approach, we find evidence at 88%-confidence for an unresolved
emission line at energy 0.53 +/- 0.02 keV, with an equivalent width of ~28 eV;
the interpretation of this feature, if real, is uncertain. We search for
coherent pulsations up to the Nyquist frequency of 1.13 Hz and set an upper
limit of 8.0% rms on the strength of any such modulation. We derive an improved
position for the source and set the most rigorous limits to-date on any
associated extended emission on arcsecond scales. Our analysis confirms the
basic picture of Calvera as the first isolated compact object in the
ROSAT/Bright Source Catalog discovered in six years, the hottest such object
known, and an intriguing target for multiwavelength study.Comment: Submitted to ApJ. AASTeX, 19 pages, 2 figure
The Chemical Compositions of the Type II Cepheids -- The BL Her and W Vir Variables
Abundance analyses from high-resolution optical spectra are presented for 19
Type II Cepheids in the Galactic field. The sample includes both short-period
(BL Her) and long-period (W Vir) stars. This is the first extensive abundance
analysis of these variables. The C, N, and O abundances with similar spreads
for the BL Her and W Vir show evidence for an atmosphere contaminated with
-process and CN-cycling products. A notable anomaly of the BL Her
stars is an overabundance of Na by a factor of about five relative to their
presumed initial abundances. This overabundance is not seen in the W Vir stars.
The abundance anomalies running from mild to extreme in W Vir stars but not
seen in the BL Her stars are attributed to dust-gas separation that provides an
atmosphere deficient in elements of high condensation temperature, notably Al,
Ca, Sc, Ti, and -process elements. Such anomalies have previously been seen
among RV Tau stars which represent a long-period extension of the variability
enjoyed by the Type II Cepheids. Comments are offered on how the contrasting
abundance anomalies of BL Her and W Vir stars may be explained in terms of the
stars' evolution from the blue horizontal branch.Comment: 41 pages including 11 figures and 4 tables; Accepted for publication
in Ap
X-Ray Observations of the supernova remnant G21.5-0.9
We present the analysis of archival X-ray observations of the supernova
remnant (SNR) G21.5-0.9. Based on its morphology and spectral properties,
G21.5-0.9 has been classified as a Crab-like SNR. In their early analysis of
the CHANDRA calibration data, Slane et al. (2000) discovered a
low-surface-brightness, extended emission. They interpreted this component as
the blast wave formed in the supernova (SN) explosion. In this paper, we
present the CHANDRA analysis using a total exposure of ~150 ksec. We also
include ROSAT and ASCA observations. Our analysis indicates that the extended
emission is non-thermal -- a result in agreement with XMM observations. The
entire remnant of radius ~ 2'.5 is best fitted with a power law model with a
photon index steepening away from the center. The total unabsorbed flux in the
0.5-10 keV is 1.1E-10 erg/cm2/s with an 85% contribution from the 40" radius
inner core. Timing analysis of the High-Resolution Camera (HRC) data failed to
detect any pulsations. We put a 16% upper limit on the pulsed fraction. We
derive the physical parameters of the putative pulsar and compare them with
those of other plerions (such as the Crab and 3C 58). G21.5-0.9 remains the
only plerion whose size in X-rays is bigger than in the radio. Deep radio
observations will address this puzzle.Comment: 23 pages including 11 figures and 3 tables; accepted by ApJ June 22,
2001; to appear in Oct 20, 2001 issue of Ap
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