Detection of 25 new rotating radio transients at 111 MHz

Nearly all fast radio RRAT-type transients that are pulsars with rare pulses have been previously detected using decimetre wavelengths. We present here 34 transients detected at metre wavelengths in our daily monitoring at declinations -9o < decl. < +42o. 25 transients are new RRATs. We confirmed the detection of 7 RRATs based on our early observations. One of the 34 detected transients was determined to be a new pulsar J1326+3346. At the same time, out of 35 RRATs detected at the decimetre wavelengths and included in the studied area, only one was detected by us J1848+1518. The periods of 6 RRATs were found from the time of arrival of single pulses. Three quarters of all RRATs were observed more than once and the total number of RRATs in the area studied has doubled.Comment: 6 pages, 3 figures, 1 table; Astronomy and Astrophysics in pres

Optical identification of the 3C 58 pulsar wind nebula

We have performed a deep optical imaging of 3C 58 SNR with the NOT in the B and V bands to detect the optical counterpart of the associated pulsar J0295+6449 and its torus-like wind nebula visible in X-rays. We analyzed our data together with the archival data obtained with the Chandra in X-rays and with the Spitzer in the mid-IR. We detect a faint extended elliptical object with B=24.06 and V=23.11 whose peak brightness and center position are consistent at the sub-arcsecond level with the position of the pulsar. Its morphology and orientation are in excellent agreement with the torus-like pulsar nebula, seen almost edge on in X-rays although its extension is only about a half of that in X-rays. In the optical we likely see only the brightest central part of the torus with the pulsar. The object is identical to the counterpart of the torus recently detected in the mid-IR. The estimated pulsar contribution to the optical flux is less than 10%. Combinig the optical/mid-IR fluxes and X-ray power-law spectrum extracted from the spatial region constrained by the optical/IR source extent we compile a tentative multi-wavelength spectrum of the central part of the nebula. Within uncertainties of the interstellar extinction it is reminiscent of either the Crab or B0540-69 pulsar wind nebula spectra. The properties of the object strongly suggest it to be the optical counterpart of the 3C 58 pulsar + its wind nebula system, making 3C 58 the third member of such a class of the torus-like systems identified in the optical and mid-IR.Comment: 12 pages including 7 figures, submitted for publication in A&A. For high resolution images, see http://www.ioffe.ru/astro/NSG/obs/3C58

Radio Astronomical Monitoring in Virtual Environment

We present StarWatch, our application for real-time analysis of radio astronomical data in Virtual Environment. Serving as an interface to radio astronomical databases or being applied to live data from the radio telescopes, the application supports various data filters measuring signal-to-noise ratio (SNR), Doppler's drift, degree of signal localization on celestial sphere and other useful tools for signal extraction and classification. Originally designed for the database of narrow band signals from SETI Institute (setilive.org), the application has been recently extended for the detection of wide band periodic signals, necessary for the search of pulsars. We will also address the detection of week signals possessing arbitrary waveforms and present several data filters suitable for this purpose

Radio Astronomical Monitoring in Virtual Environment

AbstractWe present StarWatch, our application for real-time analysis of radio astronomical data in Virtual Environment. Serving as an interface to radio astronomical databases or being applied to live data from the radio telescopes, the application supports various data filters measuring signal-to-noise ratio (SNR), Doppler's drift, degree of signal localization on celestial sphere and other useful tools for signal extraction and classification. Originally designed for the database of narrow band signals from SETI Institute (setilive.org), the application has been recently extended for the detection of wide band periodic signals, necessary for the search of pulsars. We will also address the detection of week signals possessing arbitrary waveforms and present several data filters suitable for this purpose

Radio spectrum of the AXP J1810-197 and of its profile components

As part of a European Pulsar Network (EPN) multi-telescope observing campaign, we performed simultaneous multi-frequency observations at 1.4, 4.9 and 8.4 GHz during July 2006 and quasi-simultaneous multi-frequency observations from Decem- ber 2006 until July 2007 at 2.7, 4.9, 8.4, 14.6 and 32 GHz, in order to obtain flux density measurements and spectral features of the 5.5-sec radio-emitting magnetar AXP J1810-197. We monitored the spectral evolution of its pulse shape which consists of a main pulse (MP) and an interpulse (IP). We present the flux density spectrum of the average profile and of the separate pulse components of this first-known radio-emitting transient anomalous X-ray pulsar. We observe a decrease of the flux density by a factor of 10 within 8 months and follow the disappearance of one of the two main components. Although the spectrum is generally flat, we observe large fluctuations of the spectral index with time. For that reason we have made some measurements of modulation indices for individual pulses in order to also investigate the origin of these fluctuations.Comment: accepted for publication in MNRAS, 9 pages, 7 figures, 5 table

Formation of "Lightnings" in a Neutron Star Magnetosphere and the Nature of RRATs

The connection between the radio emission from "lightnings" produced by the absorption of high-energy photons from the cosmic gamma-ray background in a neutron star magnetosphere and radio bursts from rotating radio transients (RRATs) is investigated. The lightning length reaches 1000 km; the lightning radius is 100 m and is comparable to the polar cap radius. If a closed magnetosphere is filled with a dense plasma, then lightnings are efficiently formed only in the region of open magnetic field lines. For the radio emission from a separate lightning to be observed, the polar cap of the neutron star must be directed toward the observer and, at the same time, the lightning must be formed. The maximum burst rate is related to the time of the plasma outflow from the polar cap region. The typical interval between two consecutive bursts is ~100 s. The width of a single radio burst can be determined both by the width of the emission cone formed by the lightning emitting regions at some height above the neutron star surface and by a finite lightning lifetime. The width of the phase distribution for radio bursts from RRATs, along with the integrated pulse width, is determined by the width of the bundle of open magnetic field lines at the formation height of the radio emission. The results obtained are consistent with the currently available data and are indicative of a close connection between RRATs, intermittent pulsars, and extreme nullers.Comment: 24 pages, no figures, references update

Diffractive and refractive timescales at 4.8 GHz in PSR B0329+54

We present the results of flux density monitoring of PSR B0329+54 at the frequency of 4.8 GHz using the 32-meter TCfA radiotelescope. The observations were conducted between 2002 and 2005. The main goal of the project was to find interstellar scintillation (ISS) parameters for the pulsar at the frequency at which it was never studied in detail. To achieve this the 20 observing sessions consisted of 3-minute integrations which on average lasted 24 hours. Flux density time series obtained for each session were analysed using structure functions. For some of the individual sessions as well as for the general average structure function we were able to identify two distinctive timescales present, the timescales of diffractive and refractive scintillations. To the best of our knowledge, this is the first case when both scintillation timescales, t_DISS=42.7 minutes and t_RISS=305 minutes, were observed simultaneously in a uniform data set and estimated using the same method. The obtained values of the ISS parameters combined with the data found in the literature allowed us to study the frequency dependence of these parameters over a wide range of observing frequencies, which is crucial for understanding the ISM turbulence. We found that the Kolmogorov spectrum is not best suited for describing the density fluctuations of the ISM, and a power-law spectrum with beta =4 seems to fit better with our results. We were also able to estimate the transition frequency (transition from strong to weak scintillation regimes) as 10.1 GHz, much higher than was previously predicted. We were also able to estimate the strength of scattering parameter u=2.67$ and the Fresnel scale as 6.7x10^8 meters.Comment: 11 pages, 4 figures, accepted for publication in: Astronomy and Astrophysic

Morphology and characteristics of radio pulsars

This review describes the observational properties of radio pulsars, fast rotating neutron stars, emitting radio waves. After the introduction we give a list of milestones in pulsar research. The following chapters concentrate on pulsar morphology: the characteristic pulsar parameters such as pulse shape, pulsar spectrum, polarization and time dependence. We give information on the evolution of pulsars with frequency since this has a direct connection with the emission heights, as postulated in the radius to frequency mapping (RFM) concept. We deal successively with the properties of normal (slow) pulsars and of millisecond (fast-recycled) pulsars. The final chapters give the distribution characteristics of the presently catalogued 1300 objects.Comment: 33 pages, PDF with 30 PostScript figures, see http://springerlink.metapress.com/link.asp?id=d6k3a6wunb138dpl Accepted by Astronomy & Astrophysivs Review