Temporal Evolution of the Vela Pulsar's Pulse Profile - Palfreyman et al.

I take note of this very interesting study:
   
Palfreyman, J. L.; Dickey, J. M.; Ellingsen, S. P.; Jones, I. R.; Hotan, A. W.,  February 2016 :

http://arxiv.org/abs/1602.01899

http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1602.01899

23 references at:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2016arXiv160201899P&refs=REFERENCES&db_key=PRE

 Abstract: "The mechanisms of emission and changes in rotation frequency ('glitching') of the Vela pulsar (J0835-4510) are not well understood. Further insight into these mechanisms can be achieved by long-term studies of integrated pulse width, timing residuals, and bright pulse rates. We have undertaken an intensive observing campaign of Vela and collected over 6000 hours of single pulse data. The data shows that the pulse width changes with time, including marked jumps in width after micro-glitches (frequency changes). The abundance of bright pulses also changes after some micro-glitches, but not all. The secular changes in pulse width have three possible cyclic periods, that match with X-ray periodicities of a helical jet that are interpreted as free precession." 

High Time and Frequency Resolution Capabilities of the Murchison Widefield Array - Pulsar observations

Dear Lovers of The Neutron Stars,

Thank you for your FUN work, it keeps me busy when the Sun and Jupiter do not keep me very busy :)

I sometimes wonder what happens at their very center, where temperatures and pressures are truly MONUMENTAL !!

Pulsars were discovered at 81.5 MHz about 50 years ago and I have been studying them since then.

Professor Tremblay at Curtin University in Perth Western Australia, and about 20 of his collaborators around the world, have been doing wonderful things working with the Murchison Widefield Array, a precursor of the Square Kilometer Array.

They have installed equipment to collect time domain data for a total of ~ 31 MHz bandwidth in ~ 1.3 MHz subbands, spread as desired, between 80 and 300 MHz, and observed 10 pulsars.

Read more about it here:

http://arxiv.org/abs/1501.05723

32 references at:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2015PASA...32....5T&refs=REFERENCES&db_key=AST


Abstract: "The science cases for incorporating high time resolution capabilities into modern radio telescopes are as numerous as they are compelling. Science targets range from exotic sources such as pulsars, to our Sun, to recently detected possible extragalactic bursts of radio emission, the so-called fast radio bursts (FRBs). Originally conceived purely as an imaging telescope, the initial design of the Murchison Widefield Array (MWA) did not include the ability to access high time and frequency resolution voltage data. However, the flexibility of the MWA's software correlator allowed an off-the-shelf solution for adding this capability. This paper describes the system that records the 100 micro-second and 10 kHz resolution voltage data from the MWA. Example science applications, where this capability is critical, are presented, as well as accompanying commissioning results from this mode to demonstrate verification."
....

A LOFAR Census of Millisecond Pulsars

With many thanks I refer to:

Kondratiev et al. 2015, "A LOFAR Census of Millisecond Pulsars"

http://arxiv.org/abs/1508.02948

http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1508.02948

Abstract: "We report the detection of 48 millisecond pulsars (MSPs) out of 75 observed thus far using the LOFAR in the frequency range 110-188 MHz. We have also detected three MSPs out of nine observed in the frequency range 38-77 MHz. This is the largest sample of MSPs ever observed at these low frequencies, and half of the detected MSPs were observed for the first time at frequencies below 200 MHz. We present the average pulse profiles of the detected MSPs, their effective pulse widths and flux densities, and compare these with higher observing frequencies. The LOFAR pulse profiles will be publicly available via the EPN Database of Pulsar Profiles. We also present average values of dispersion measures (DM) and discuss DM and profile variations. About 35% of the MSPs show strong narrow profiles, another 25% exhibit scattered profiles, and the rest are only weakly detected. A qualitative comparison of the LOFAR MSP profiles with those at higher radio frequencies shows constant separation between profile components. Similarly, the profile widths are consistent with those observed at higher frequencies, unless scattering dominates at the lowest frequencies. This is very different from what is observed for normal pulsars and suggests a compact emission region in the MSP magnetosphere. The amplitude ratio of the profile components, on the other hand, can dramatically change towards low frequencies, often with the trailing component becoming dominant. As demonstrated by Dyks et al. (2010) this can be caused by aberration and retardation. This data set enables high-precision studies of pulse profile evolution with frequency, dispersion, Faraday rotation, and scattering in the interstellar medium. Characterizing and correcting these systematic effects may improve pulsar-timing precision at higher observing frequencies, where pulsar timing array projects aim to directly detect gravitational waves."

Observations of Crab Giant Pulses in 20-84 MHz using LWA1

With many thanks, I refer to

Ellingson, S. W.; Clarke, T. E.; Craig, J.; Hicks, B. C.; Lazio, T. J. W.; Taylor, G. B.; Wilson, T. L.; Wolfe, C. N.  2013

http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1304.0812

33 references at:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2013ApJ...768..136E&refs=REFERENCES&db_key=AST

4 citations at:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2013ApJ...768..136E&refs=CITATIONS&db_key=AST

Abstract: "We report the detection and observed characteristics of giant pulses from the Crab Nebula pulsar (B0531+21) in four frequency bands covering 20-84 MHz using the recently completed Long Wavelength Array Station 1 (LWA1) radio telescope. In 10 hr of observations distributed over a 72 day period in fall of 2012, 33 giant pulses having peak flux densities between 400 Jy and 2000 Jy were detected. Twenty-two of these pulses were detected simultaneously in channels of 16 MHz bandwidth centered at 44 MHz, 60 MHz, and 76 MHz, including one pulse which was also detected in a channel centered at 28 MHz. We quantify statistics of pulse amplitude and pulse shape characteristics, including pulse broadening. Amplitude statistics are consistent with expectations based on extrapolations from previous work at higher and lower frequencies. Pulse broadening is found to be relatively high, but not significantly greater than expected. We present procedures that have been found to be effective for observing giant pulses in this frequency range."

.....

Observations of Crab giant pulses with 34 meter antenna, 8 GHz bandwidth

 With many thanks, I refer to:

Glenn Jones 2015, "Observations of Radio Giant Pulses with GAVRT"

http://arxiv.org/abs/1507.03864

10 references at:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2011AIPC.1357..281J&refs=REFERENCES&db_key=AST

Abstract: "Radio giant pulses provide a unique opportunity to study the pulsar radio emission mechanism in exquisite detail. Previous studies have revealed a wide range of properties and phenomena, including extraordinarily high brightness temperatures, sub-nanosecond emission features, and banded dynamic spectra. New measurements of giant pulse characteristics can help guide and test theoretical emission models. To this end, an extensive observation campaign has begun which will provide more than 500 hours on the Crab with a 34-meter antenna located in California, USA. The observations are being done as part of an educational outreach program called the Goldstone-Apple Valley Radio Telescope (GAVRT). This antenna has a novel wide bandwidth receiver which provides up to 8 GHz of instantaneous bandwidth in the range of 2.5 to 14 GHz. These observations will provide detailed information about the variability, amplitude distribution, and detailed frequency structure of radio giant pulses. In addition, a database of pulses from these observations and others of the Crab pulsar is being created which will simplify multiwavelength correlation analysis."

Interferometric study of PSR B0329+54 and the interstellar medium, at 324 MHz, with maximum baselines near 1 light second

With many thanks, I refer to:

"PSR B0329+54: Substructure in the scatter-broadened image discovered with RadioAstron on baselines of up to 235,000 km"
   
Popov, M. V.; Andrianov, A. S.; Bartel, N.; Gwinn, C. R.; Johnson, M. D.; Joshi, B. C.; Kardashev, N. S.; Karuppusamy, R.; Kovalev, Y. Y.; Kramer, M.; Rudnitskii, A. G.; Safutdinov, E. R.; Shishov, V. I.; Smirnova, T. V.; Soglasnov, V. A.; Zensus, J. A.; Zhuravlev, V. I.

http://arxiv.org/abs/1501.04449

25 references at:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2015arXiv150104449P&refs=REFERENCES&db_key=PRE

Abstract: "We studied scattering properties of the pulsar PSR B0329+54 with a ground-space radio interferometer RadioAstron which included the 10-m Space Radio Telescope, the 110-m Green Bank Telescope, the 14x25-m Westerbork Synthesis Radio Telescope, and the 64-m Kalyazin Radio Telescope. The observations were performed at 324 MHz on baselines of up to 235,000 km in November 2012 and January 2014. At short ground-space baselines of less than about 20,000 km, the visibility amplitude decreases with the projected baseline length, providing a direct measurement of the diameter of the scattering disk of 4.7±0.9 mas. The size of the diffraction spot near Earth is 15,000±3,000 km. At longer baselines of up to 235,000 km, where no interferometric detection of the scattering disk would be expected, significant visibilities were observed with amplitudes scattered around a constant value. These detections result in a discovery of a substructure in the completely resolved scatter-broadened image of the pointlike source, PSR B0329+54. They fully attribute to properties of the interstellar medium. The visibility function at the longest ground-space baselines in the delay domain consists of many isolated unresolved spikes, in agreement with the amplitude-modulated noise model. Within the assumption of turbulent as well as large-scale irregularities in the plasma of the interstellar medium, we estimate that the effective scattering screen lies 0.35±0.10 of the distance from Earth toward the pulsar."

More on RadioAstron at:

http://herrero-radio-astronomy.blogspot.com/2013/07/the-radioastron-1-light-second-baseline.html

http://herrero-radio-astronomy.blogspot.com/2011/07/10-meter-radioastron-russian-space.html

http://www.asc.rssi.ru/radioastron/

Publications of RadioAstron :
http://www.asc.rssi.ru/radioastron/publications/publ.html

Wikipedia article:
https://en.wikipedia.org/wiki/Spektr-R

"...Spektr-R[2] (or RadioAstron) is a Russian scientific satellite with a 10 m (33 ft) radio telescope on board. It was launched on 18 July 2011,[3] by Zenit-3F launcher, from Baikonur Cosmodrome to perform research on the structure and dynamics of radio sources within and beyond our galaxy. Together with some of the largest ground-based radio telescopes, this telescope forms interferometric baselines extending up to 350,000 km (220,000 mi)..."

...o...

The Ooty Radio Telescope PONDER real time software for pulsar and scintillation observations

With many thanks I refer to:

Arun Naidu, B.C Joshi, P.K Manoharan, M.A Krishnakumar 2015

http://arxiv.org/abs/1503.01405

31 references:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2015ExA....39..319N&refs=REFERENCES&db_key=AST

Abastract: "This paper describes a new real-time versatile backend, the Pulsar Ooty Radio Telescope New Digital Efficient Receiver (PONDER), which has been designed to operate along with the legacy analog system of the Ooty Radio Telescope (ORT). PONDER makes use of the current state of the art computing hardware, a Graphical Processing Unit (GPU) and sufficiently large disk storage to support high time resolution real-time data of pulsar observations, obtained by coherent dedispersion over a bandpass of 16 MHz. Four different modes for pulsar observations are implemented in PONDER to provide standard reduced data products, such as time-stamped integrated profiles and dedispersed time series, allowing faster avenues to scientific results for a variety of pulsar studies. Additionally, PONDER also supports general modes of interplanetary scintillation (IPS) measurements and very long baseline interferometry data recording. The IPS mode yields a single polarisation correlated time series of solar wind scintillation over a bandwidth of about four times larger (16 MHz) than that of the legacy system as well as its fluctuation spectrum with high temporal and frequency resolutions. The key point is that all the above modes operate in real time. This paper presents the design aspects of PONDER and outlines the design methodology for future similar backends. It also explains the principal operations of PONDER, illustrates its capabilities for a variety of pulsar and IPS observations and demonstrates its usefulness for a variety of astrophysical studies using the high sensitivity of the ORT"

 ...o... 

Pulsar Profiles 2015 July

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...NEUTRON STARS...