共查询到20条相似文献，搜索用时 62 毫秒
1.
We summarize our current state of knowledge of fast radio bursts (FRBs) which were first discovered a decade ago. Following an introduction to radio transients in general, including pulsars and rotating radio transients, we discuss the discovery of FRBs. We then discuss FRB follow-up observations in the context of repeat bursts before moving on to review propagation effects on FRB signals, FRB progenitor models and an outlook on FRBs as potential cosmological tools. 相似文献
2.
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 ratio 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. 相似文献
3.
O. Reimer P. F. Michelson R. A. Cameron S. W. Digel D. J. Thompson K. S. Wood 《Astrophysics and Space Science》2007,309(1-4):523-526
Gamma-ray astrophysics depends in many ways on multiwavelength studies. The Gamma-ray Large Area Space Telescope (GLAST) Large
Area Telescope (LAT) Collaboration has started multiwavelength planning well before the scheduled 2007 launch of the observatory.
Some of the high-priority multiwavelength needs include: (1) availability of contemporaneous radio and X-ray timing of pulsars;
(2) expansion of blazar catalogs, including redshift measurements; (3) improved observations of molecular clouds, especially
at high galactic latitudes; (4) simultaneous broad-band blazar monitoring; (5) characterization of gamma-ray transients, including
gamma ray bursts; (6) radio, optical, X-ray and TeV counterpart searches for reliable and effective sources identification
and characterization. Several of these activities are needed to be in place before launch.
相似文献
4.
S.B. Popov 《Astronomische Nachrichten》2008,329(1):15-19
In this short note I discuss the hypothesis that bursting activity of magnetars evolves in time analogously to the glitching activity of normal radio pulsars (i.e. sources are more active at smaller ages), and that the increase of the burst rate follows one of the laws established for glitching radio pulsars. If the activity of soft gamma repeaters decreases in time in the way similar to the evolution of core‐quake glitches (∝t5/2), then it is more probable to find the youngest soft gamma repeaters, but the energy of giant flares from these sources should be smaller than observed 1044–1046 erg as the total energy stored in a magnetar's magnetic field is not enough to support thousands of bursts similar to the prototype 1979 March 5 flare. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
I. F. Malov 《Astronomy Letters》2008,34(10):699-703
At present, it is widely believed that anomalous X-ray pulsars (AXPs), soft gamma-ray repeaters (SGRs), rotational radio transients (RRATs), compact central objects (CCOs) in supernova remnants, and X-ray dim isolated neutron stars (XDINSs) belong to different classes of anomalous objects in which the central bodies are isolated neutron stars. Previously, we have shown that AXPs and SGRs can be described in terms of the drift model for parameters of the central neutron star typical of radio pulsars (rotation periods P ～ 0.1–1 s and surface magnetic fields B ～ 1011–1013 G). Here, we show that some of the peculiarities of the sources under consideration can be explained by their geometry (in particular, by the angle β between the rotation axis and the magnetic moment). If β ? 10° (an aligned rotator), the drift waves in the outer layers of the neutron star magnetosphere can account for the observed periodicity in the radiation. For large β (a nearly orthogonal rotator), the observed modulation of the radiation and its short bursts can be explained by mass accretion from the ambient medium (e.g., a relic disk). 相似文献
6.
We discuss a possible generation of radio bursts preceding final stages of binary neutron star mergings which can be accompanied
by short gamma-ray bursts. Detection of such bursts appear to be advantageous in the low-frequency radio band due to a time
delay of ten to several hundred seconds required for radio signal to propagate in the ionized intergalactic medium. This delay
makes it possible to use short gamma-ray burst alerts to promptly monitor specific regions on the sky by low-frequency radio
facilities, especially by LOFAR. To estimate the strength of the radio signal, we assume a power-law dependence of the radio
luminosity on the total energy release in a magnetically dominated outflow, as found in millisecond pulsars. Based on the
planned LOFAR sensitivity at 120 MHz, we estimate that the LOFAR detection rate of such radio transients could be about several
events per month from redshifts up to z∼1.3 in the most optimistic scenario. The LOFAR ability to detect such events would crucially depend on exact efficiency of
low-frequency radio emission mechanism. 相似文献
7.
Marta Burgay Nanda Rea GianLuca Israel Andrea Possenti Luciano Burderi Tiziana Di Salvo Nichi D’Amico Luigi Stella Elisa Nichelli 《Astrophysics and Space Science》2007,308(1-4):531-534
We have performed deep searches for radio pulsations from four southern anomalous X-ray pulsars (AXPs) to investigate their
physical nature in comparison with the rotation powered pulsars. The data were acquired using the Parkes radio telescope with
the 1.4 GHz multibeam receiver. No pulsed emission with periodicity matching the X-ray ephemeris have been found in the observed
targets down to a limit of ∼0.1 mJy. A blind search has also been performed on all the 13 beams of the multibeam receiver
(the central beam being pointed on the target AXP), leading to the serendipitous discovery of two new radio pulsars and to
the further detection of 18 pulsars. Also a search for single dispersed pulses has been performed in the aim to detect signals
similar to those of the recently discovered rotating radio transients.
相似文献
8.
Brad M. S. Hansen † Maxim Lyutikov† 《Monthly notices of the Royal Astronomical Society》2001,322(4):695-701
We describe the possible electromagnetic signals expected from the magnetospheric interactions of a neutron star binary prior to merger. We find that both radio and X-ray signals of detectable strength are possible. We discuss possible links with the phenomenon of gamma-ray bursts (GRBs) and describe the prospects for direct detection of these signals in searches for radio and X-ray transients. 相似文献
9.
M. Serylak B. W. Stappers P. Weltevrede M. Kramer A. Jessner A. G. Lyne C. A. Jordan K. Lazaridis J. A. Zensus 《Monthly notices of the Royal Astronomical Society》2009,394(1):295-308
We have used the 76-m Lovell, 94-m equivalent Westerbork Synthesis Radio Telescope (WSRT) and 100-m Effelsberg radio telescopes to investigate the simultaneous single-pulse properties of the radio emitting magnetar Anomalous X-ray Pulsar (AXP) XTE J1810−197 at frequencies of 1.4, 4.8 and 8.35 GHz during 2006 May and July. We study the magnetar's pulse-energy distributions which are found to be very peculiar as they are changing on time-scales of days and cannot be fit by a single statistical model. The magnetar exhibits strong spiky single giant-pulse-like subpulses, but they do not fit the definition of the giant pulse or giant micropulse phenomena. Measurements of the longitude-resolved modulation index reveal a high degree of intensity fluctuations on day-to-day time-scales and dramatic changes across pulse phase. We find the frequency evolution of the modulation index values differs significantly from what is observed in normal radio pulsars. We find that no regular drifting subpulse phenomenon is present at any of the observed frequencies at any observing epoch. However, we find a quasi-periodicity of the subpulses present in the majority of the observing sessions. A correlation analysis indicates a relationship between components from different frequencies. We discuss the results of our analysis in light of the emission properties of normal radio pulsars and a recently proposed model which takes radio emission from magnetars into consideration. 相似文献
10.
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.Received: 5 December 2003, Published online: 15 April 2004
Correspondence to: Richard Wielebinski 相似文献
11.
W. Pietsch 《Astronomische Nachrichten》2008,329(2):170-173
First studies of the X‐ray source population of M 31 were performed with the Einstein Observatory and ROSAT. High resolution Chandra Observatory images not only spatially resolved the center area but also supernova remnants (SNRs) in the galaxy. Source catalogues of restricted areas were presented with high astrometric accuracy. Also luminosity function studies and studies of individual sources based on Chandra and XMM‐Newton observations led to a better knowledge of the X‐ray source population. An XMM‐Newton source catalog based on archival observations revealed more than 850 sources down to a 0.2–4.5 keV luminosity of 1035 erg s–1. EPIC hardness ratios as well as informations from earlier X‐ray, optical, and radio catalogues were used to distinguish between different source classes (SNRs, supersoft sources (SSSs), X‐ray binaries (XRBs), globular cluster sources within M 31, and foreground stars and objects in the background). However, many sources could only be classified as “hard”. These sources may either be XRBs or Crab‐like SNRs in M 31 or background sources. Two of the globular cluster sources could be identified as low mass XRBs with a neutron star as compact object as they showed type I X‐ray bursts. Many of the SSSs were identified as optical novae. Inspired by these results an XMM‐Newton survey of the entire D25 disk of M 31 and a dedicated program to monitor X‐ray counterparts of optical novae in M 31 was started. We discuss implications for further nearby galaxy studies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
12.
A.A. Stanislavsky A.A. Konovalenko H.O. Rucker E.P. Abranin M.L. Kaiser V.V. Dorovskyy V.N. Mel'nik A. Lecacheux 《Astronomische Nachrichten》2009,330(7):691-697
Decameter wavelength radio emission is finely structured in solar bursts. For their research it is very important to use a sufficient sensitivity of antenna systems. In this paper we study an influence of the radiotelescope‐antenna effective area on the results of decameter solar radio observations. For this purpose we compared the solar bursts received by the array of 720 ground‐based dipoles and the single dipole of the radiotelescope UTR‐2. It is shown that a larger effective area of the ground‐based antenna allows us to measure a weaker solar emission and to distinguish a fine structure of strong solar events. This feature has been also verified by simultaneous ground‐ and space‐based observations in the overlapping frequency range (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
G. Pühlhofer 《Astronomische Nachrichten》2008,329(2):186-190
Very high energy (VHE) γ‐ray observations have proven to be very successful in localizing Galactic acceleration sites of VHE particles. Observations of shell‐type supernova remnants have confirmed that particles are accelerated to VHE energies in supernova blast waves; the interpretation of the γ‐ray data in terms of hadronic or leptonic particle components in these objects relies nevertheless strongly on input from X‐ray observations. The largest identified Galactic VHE source class consists of pulsar wind nebulae, as detected in X‐rays. Many of the remaining VHE sources remain however unidentified until now. With X‐ray observations of these enigmatic “dark” objects one hopes to solve the following questions: What is the astrophysical nature of these sources? Are they predominantly electron or hadron accelerators? And what is their contribution to the overall cosmic ray energy budget? The paper aims to provide an overview over the identification status of the Galactic VHE source population. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
14.
It is proposed that radiation belts similar to the ones in the planetary magnetosphere can exist for a pulsar with a relatively long period and a strong magnetic field. In the belts located in the closed field line region near the light cylinder relativistic pairs are trapped and maintained at a density substantially higher than the local Goldreich–Julian corotation density. The trapped plasma can be supplied and replenished by either direct injection of relativistic pairs from acceleration of externally supplied particles in a dormant outer gap or in situ ionization of the accreted neutral material in the trapping region. The radiation belts can be disrupted by waves that are excited in the region as the result of plasma instabilities or emitted from the surface due to starquakes or stellar oscillations. The disruption can cause an intermittent particle precipitation towards the star producing radio bursts. It is suggested that such bursts may be seen as rotating radio transients. 相似文献
15.
M. Bouwhuis 《Astronomische Nachrichten》2008,329(3):334-336
The real‐time distribution of alert messages from satellites that detect gamma‐ray bursts are of key importance to neutrino telescopes.We describe how the distribution network of these alert messages is used by the ANTARES neutrino telescope, and the resulting increase in detection efficiency for neutrinos from gamma‐ray bursts. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
16.
R. N. Manchester 《Astrophysics and Space Science》2005,297(1-4):101-108
A total of eight gamma-ray sources are identified with pulsars and these include some of the strongest gamma-ray sources in
the sky. About 20 of the unidentified gamma-ray sources are very likely to be associated with currently known pulsars and
there is little doubt that many of the others, at least those at low Galactic latitudes, will ultimately be identified with
pulsars. How many of these and future gamma-ray detections will be detectable at radio wavelengths depends on the details
of the radio and gamma-ray beaming. There is good evidence that the radio beams in young and millisecond pulsars are very
wide, implying that most gamma-ray pulsars will be detectable in the radio band. 相似文献
17.
S. Campana M. Colpi S. Mereghetti L. Stella M. Tavani 《Astronomy and Astrophysics Review》1998,8(4):279-316
Summary. Soft X–ray Transients (SXRTs) have long been suspected to contain old, weakly magnetic neutron stars that have been spun
up by accretion torques. After reviewing their observational properties, we analyse the different regimes that likely characterise
the neutron stars in these systems across the very large range of mass inflow rates, from the peak of the outbursts to the
quiescent emission. While it is clear that close to the outburst maxima accretion onto the neutron star surface takes place,
as the mass inflow rate decreases, accretion might stop at the magnetospheric boundary because of the centrifugal barrier
provided by the neutron star. For low enough mass inflow rates (and sufficiently short rotation periods), the radio pulsar
mechanism might turn on and sweep the inflowing matter away. The origin of the quiescent emission, observed in a number of
SXRTs at a level of , plays a crucial role in constraining the neutron star magnetic field and spin period. Accretion onto the neutron star surface
is an unlikely mechanism for the quiescent emission of SXRTs, as it requires very low magnetic fields and/or long spin periods.
Thermal radiation from a cooling neutron star surface in between the outbursts can be ruled out as the only cause of the quiescent
emission.
We find that accretion onto the neutron star magnetosphere and shock emission powered by an enshrouded radio pulsar provide
far more plausible models. In the latter case the range of allowed neutron star spin periods and magnetic fields is consistent
with the values recently inferred from the properties of kHz quasi-periodic oscillation in low mass X–ray binaries. If quiescent
SXRTs contain enshrouded radio pulsars, they provide a missing link between X–ray binaries and millisecond pulsars.
Received 4 November 1997; Accepted 15 April 1998 相似文献
18.
The possible low-frequency radio emission from the progenitors of gamma ray bursts can experience a delay from tens of seconds to hours on the way to the observer due to the dispersion in galactic and extragalactic plasma, and thus reach the observer as a radio afterglow of the burst. This opens a unique possibility (peculiar “time machine”) of seeing what happened at that place before the catastrophe. 相似文献
19.
The rotation periods, surface magnetic field strengths, as well as the spatial distribution of the several kinds of pulsars discovered sofar are analyzed statistically. It is revealed that the spatial distribution of the millisecond pulsars is more dispersive than that of the normal radio pulsars. And that the spatial distribution of the pulsars in low-mass X-ray binaries (LMXBs) is also more dispersive than that of the pulsars in high-mass X-ray binaries (HMXBs). The distribution of rotation periods of the isolated millisecond pulsars has a peak at 4.7ms, and the corresponding peak values for the normal radio pulsars and the millisecond pulsars in binaries are 0.6 s and 3.5ms, respectively. The surface magnetic field strengths of the FERMI pulsars (the gamma-ray pulsars observed by the Large Area Telescope/Fermi Gamma-ray Space Telescope) and normal pulsars are all concentrated around 1012 Gs. It is found also that some young high-energy pulsars are associated with supernova remnants. In combination with the formation and evolution models of pulsars, we have made some remarks on the characteristics of these distributions. 相似文献