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تسجيل مستخدم جديدPolarization studies with NuSTAR
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The capability of NuSTAR to detect polarization in the Compton scattering regime (>50 keV) has been investigated. The NuSTAR mission, flown on June 2012 a Low Earth Orbit (LEO), provides a unique possibility to confirm the findings of INTEGRAL on the polarization of cosmic sources in the hard X-rays. Each of the two focal plane detectors are high resolution pixellated CZT arrays, sensitive in the energy range ~ 3 - 80 keV. These units have intrinsic polarization capabilities when the proper information on the double events is transmitted on ground. In this case it will be possible to detect polarization from bright sources on timescales of the order of 10^5s
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The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 13 June 2012, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates in the band from 3 -- 79 keV, extending the sensitivity of focusing far beyond the ~10 k
eV high-energy cutoff achieved by all previous X-ray satellites. The inherently low-background associated with concentrating the X-ray light enables NuSTAR to probe the hard X-ray sky with a more than one-hundred-fold improvement in sensitivity over the collimated or coded-mask instruments that have operated in this bandpass. Using its unprecedented combination of sensitivity, spatial and spectral resolution, NuSTAR will pursue five primary scientific objectives, and will also undertake a broad program of targeted observations. The observatory consists of two co-aligned grazing-incidence X-ray telescopes pointed at celestial targets by a three-axis stabilized spacecraft. Deployed into a 600 km, near-circular, 6degree inclination orbit, the Observatory has now completed commissioning, and is performing consistent with pre-launch expectations. NuSTAR is now executing its primary science mission, and with an expected orbit lifetime of ten years, we anticipate proposing a guest investigator program, to begin in Fall 2014.
Observations with modern radio telescopes have revealed that classical novae are far from the simple, spherically symmetric events they were once assumed to be. It is now understood that novae provide excellent laboratories to study several astrophys
ical properties including binary interactions, stellar outflows, and shock physics. The ngVLA will provide unprecedented opportunities to study these events. It will enable us to observe more distant and fainter novae than we can today. It will allow us to simultaneously resolve both the thermal and non-thermal components in the ejecta. Finally, monitoring novae with the ngVLA will reveal the evolution of the ejecta in better detail than is possible with any current instrument.
The Nuclear Spectroscopic Telescope Array (NuSTAR) mission is the first focusing X-ray telescope in the hard X-ray (3-79 keV) band. Among the phenomena that can be studied in this energy band, some require high time resolution and stability: rotation
-powered and accreting millisecond pulsars, fast variability from black holes and neutron stars, X-ray bursts, and more. Moreover, a good alignment of the timestamps of X-ray photons to UTC is key for multi-instrument studies of fast astrophysical processes. In this Paper, we describe the timing calibration of the NuSTAR mission. In particular, we present a method to correct the temperature-dependent frequency response of the on-board temperature-compensated crystal oscillator. Together with measurements of the spacecraft clock offsets obtained during downlinks passes, this allows a precise characterization of the behavior of the oscillator. The calibrated NuSTAR event timestamps for a typical observation are shown to be accurate to a precision of ~65 microsec.
This paper describes the Polarization Spectroscopic Telescope Array (PolSTAR), a mission proposed to NASAs 2014 Small Explorer (SMEX) announcement of opportunity. PolSTAR measures the linear polarization of 3-50 keV (requirement; goal: 2.5-70 keV) X-
rays probing the behavior of matter, radiation and the very fabric of spacetime under the extreme conditions close to the event horizons of black holes, as well as in and around magnetars and neutron stars. The PolSTAR design is based on the technology developed for the Nuclear Spectroscopic Telescope Array (NuSTAR) mission launched in June 2012. In particular, it uses the same X-ray optics, extendable telescope boom, optical bench, and CdZnTe detectors as NuSTAR. The mission has the sensitivity to measure ~1% linear polarization fractions for X-ray sources with fluxes down to ~5 mCrab. This paper describes the PolSTAR design as well as the science drivers and the potential science return.
The Simons Observatory (SO) will observe the temperature and polarization anisotropies of the cosmic microwave background (CMB) over a wide range of frequencies (27 to 270 GHz) and angular scales by using both small (0.5 m) and large (6 m) aperture t
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