18,673 research outputs found
Sensitivity and pointing accuracy of the NEMO km telescope
n this paper we present the results of Monte Carlo simulation studies on the
capability of the proposed NEMO km3 telescope to detect high energy neutrinos.
We calculated the detector sensitivity to muon neutrinos coming from a generic
point-like source. We also simulated the lack of atmospheric muons in
correspondence to the Moon disk in order to determine the detector angular
resolution and to check the absolute pointing capability.Comment: To be published on VLVNT2 proceedings (Catania, Italy, November 8-11,
2005
X-ray properties of the microquasar GRS 1915+105 during a variability class transition
We present a detailed X-ray study of the microquasar GRS 1915+105 during a
variability class transition observed in 2000 June with the PPCs of the Indian
X-ray Astronomy Experiment. We supplement this observation with data from the
RXTE archives. The source made a transition from a steady low-hard state to a
regular oscillatory behaviour in the light curve known as bursts or class `rho'
(Belloni et al. 2000) between 2000 May 11 and 17 and reverted back to the
low-hard state on 2000 June 27. A gradual change in the burst recurrence time
from about 75 s to about 40 s was observed which then increased to about 120 s
during the ~ 40 days of class `rho'. The regular bursts disappeared from the
X-ray light curves and the class transition was observed to occur within 1.5
hours on 2000 June 27 with the PPCs. A correlation is found between the
observed QPO frequency at 5-8 Hz in the quiescent phase and the average X-ray
intensity of the source during the class `rho'. We notice a strong similarity
between the properties of the source during the class `rho' and those during
the oscillatory phase of the observations of class `alpha'. From the timing and
spectral analysis, it is found that the observed properties of the source over
tens of days during the class `rho' are identical to those over a time scale of
a few hundreds of seconds in the class `alpha'. Examining the light curves from
the beginning of the RXTE/PCA and RXTE/ASM observations, it is found that the
change of state from radio-quiet low-hard state to high state occurs through
the X-ray classes `rho' and `alpha' which appear together during the state
transition. It is further inferred that the source switches from low-hard state
to the class `rho' through the intermediate class `alpha'.Comment: 10 pages with 9 figures, LaTex. To be appeared in MNRA
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