An Arecibo follow-up study of seven pulsars discovered by Five-hundred-meter Aperture Spherical radio Telescope (FAST)

2021 ◽  
Vol 21 (10) ◽  
pp. 251
Author(s):  
Shen Wang ◽  
Wei-Wei Zhu ◽  
Di Li ◽  
Zhi-Chen Pan ◽  
Pei Wang ◽  
...  
Keyword(s):  
Electron Density ◽  
Radio Telescope ◽  
Free Electron ◽  
Single Pulse ◽  
Dispersion Measure ◽  
Radiation Mechanism ◽  
Free Electron Density ◽  
Pulsar Radiation ◽  
Show Evidence

Abstract We present Arecibo 327 MHz confirmation and follow-up studies of seven new pulsars discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). These pulsars are discovered in a pilot program of the Commensal Radio Astronomy FAST Survey (CRAFTS) with the ultra-wide-bandwidth commissioning receiver. Five of them are normal pulsars and two are extreme nulling slow pulsars. PSR J2111+2132’s dispersion measure(DM: 78.5 pc cm−3) is above the upper limits of the two Galactic free electron density models, NE2001 and YMW16, and PSR J2057+2133’s position is out of the Scutum-Crux Arm, making them uniquely useful for improving the Galactic free electron density model in their directions. We present a detailed single pulse analysis for the slow nulling pulsars. We show evidence that PSR J2323+1214’s main pulse component follows a non-Poisson distribution and marginal evidence for a sub-pulse-drift or recurrent period of 32.3±0.4 rotations from PSR J0539+0013. We discuss the implication of our finding to the pulsar radiation mechanism.

Transition from a Bloch-Wilson to a free-electron density of states in Znn− clusters

2005 ◽  
Vol 123 (22) ◽  
pp. 221102 ◽  
Author(s):  
Oleg Kostko ◽  
Gert Wrigge ◽  
Ori Cheshnovsky ◽  
Bernd v. Issendorff
Keyword(s):  
Electron Density ◽  
Density Of States ◽  
Free Electron ◽  
Free Electron Density ◽  
Electron Density Of States

Evidence for non-equilibrium free electron density in AlGaAs at low temperatures

1991 ◽  
Vol 78 (2) ◽  
pp. 159-162 ◽  
Author(s):  
C. Ghezzi ◽  
R. Mosca ◽  
A. Bosacchi ◽  
S. Franchi ◽  
E. Gombia ◽  
...  
Keyword(s):  
Electron Density ◽  
Free Electron ◽  
Low Temperatures ◽  
Free Electron Density ◽  
Non Equilibrium

Analysis of USP Laser Induced Ablation Threshold in Transparent Aqueous Tissue

2012 ◽  
Author(s):  
Jian Jiao ◽  
Zhixiong Guo
Keyword(s):  
Electron Density ◽  
Free Electron ◽  
Present Model ◽  
Ablation Threshold ◽  
Ablation Process ◽  
Free Electrons ◽  
Free Electron Density ◽  
Avalanche Ionization ◽  
Transparent Media ◽  
First Time

The ultrashort pulsed (USP) laser induced plasma-mediated ablation in transparent media is modeled and studied in this work. We propose that a certain number of free electrons are required to trigger the avalanche ionization for the first time. Based on this assumption, the ablation process is postulated as two separate processes — the multiphoton and avalanche ionizations. For USP laser induced ablation in the transparent corneal epithelium at 800 nm, the critical seed free-electron density and the time to initialize the avalanche ionization for pulse widths from picoseconds down to the femtoseconds range are calculated. It is found that the critical seed free-electron density decreases as the pulse width increases, obeying a tp−5.65 rule. Moreover, this model is also extended to the estimation of crater sizes in USP laser ablation of polydimethylsiloxane (PDMS). The crater sizes ablated in a PDMS by a 900 fs pulsed laser at wavelength 1552 nm are modeled using the present model, and the results match with the existing experimental measurements.

scholarly journals FAST early pulsar discoveries: Effelsberg follow-up

2021 ◽  
Author(s):  
M Cruces ◽  
D J Champion ◽  
D Li ◽  
M Kramer ◽  
W W Zhu ◽  
...  
Keyword(s):  
Electron Density ◽  
Radio Telescope ◽  
White Dwarf ◽  
Wide Band ◽  
Mass Function ◽  
Ultra Wide Band ◽  
Linearly Polarized ◽  
Drift Scan ◽  
L Band

Abstract We report the follow-up of 10 pulsars discovered by the Five-hundred-meter Aperture Spherical radio-Telescope (FAST) during its commissioning. The pulsars were discovered at a frequency of 500-MHz using the ultra-wide-band (UWB) receiver in drift-scan mode, as part of the Commensal Radio Astronomy FAST Survey (CRAFTS). We carried out the timing campaign with the 100-m Effelsberg radio-telescope at L-band around 1.36 GHz. Along with 11 FAST pulsars previously reported, FAST seems to be uncovering a population of older pulsars, bordering and/or even across the pulsar death-lines. We report here two sources with notable characteristics. PSR J1951+4724 is a young and energetic pulsar with nearly 100 per cent of linearly polarized flux density and visible up to an observing frequency of 8 GHz. PSR J2338+4818, a mildly recycled pulsar in a 95.2-d orbit with a Carbon-Oxygen white dwarf (WD) companion of $\gtrsim 1\, \rm {M}_{\odot }$, based on estimates from the mass function. This system is the widest WD binary with the most massive companion known to-date. Conspicuous discrepancy was found between estimations based on NE2001 and YMW16 electron density models, which can be attributed to under-representation of pulsars in the sky region between Galactic longitudes 70○ < l < 100○. This work represents one of the early CRAFTS results, which start to show potential to substantially enrich the pulsar sample and refine the Galactic electron density model.

Materials Removals During Femtosecond Laser Non-Thermal Ablation of Dielectrics

2006 ◽  
Author(s):  
Lan Jiang ◽  
Hai-Lung Tsai
Keyword(s):  
Experimental Data ◽  
Laser Ablation ◽  
Femtosecond Laser ◽  
Electron Density ◽  
Free Electron ◽  
Femtosecond Laser Ablation ◽  
Threshold Fluence ◽  
Plasma Model ◽  
Free Electron Density ◽  
Two Temperature

It remains a big challenge to theoretically predict the material removals mechanism in femtosecond laser ablation. To bypass this unresolved problem, many calculations of femtosecond laser ablation of non-metals have been based on free electron density distribution without the actual consideration of the phase change mechanism. However, this widely-used key assumption needs further theoretical and experimental confirmations. By combining the plasma model and improved two-temperature model developed by the authors, this study focuses on investigating ablation threshold fluence, depth, and shape during femtosecond laser ablation of dielectrics through non-thermal processes (the Coulomb explosion and electrostatic ablation). The predicted ablation depths and shapes in fused silica, by using 1) the plasma model only and 2) the plasma model plus the two-temperature equation, are both in agreement with published experimental data. The widely-used assumptions for threshold fluence, ablation depth, and shape in the plasma model based on free electron density are validated by the comparison study and experimental data.

Free electron density and mobility in high-quality 4H–SiC

2000 ◽  
Vol 77 (26) ◽  
pp. 4359-4361 ◽  
Author(s):  
J. Pernot ◽  
S. Contreras ◽  
J. Camassel ◽  
J. L. Robert ◽  
W. Zawadzki ◽  
...  
Keyword(s):  
Electron Density ◽  
Free Electron ◽  
High Quality ◽  
Free Electron Density
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