- ID:
- ivo://CDS.VizieR/J/A+A/513/A65
- Title:
- Rotation measures in the fourth Galactic quadrant
- Short Name:
- J/A+A/513/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have re-examined the published rotation measures (RMs) of extragalactic point sources and pulsars with |b|<3{deg} to study the magnetic field in the fourth Galactic quadrant. We reduced the influence of structure in electron density as much as possible by excluding objects for which H{alpha}-data indicate large fluctuations in n_e_ somewhere along the line of sight. We also excluded objects for which the RM may have been significantly "corrupted" by an intervening supernova remnant. We modelled RM(l), the longitude dependence of RM of the unaffected extragalactic sources and pulsars. We assumed several geometries for the large-scale field. All but one of those are based on logarithmic spiral arms (with various pitch angles and widths), while one has circular symmetry. We also made different assumptions about the large-scale n_e_-distribution.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/4371
- Title:
- Sample of faint X-ray pulsators
- Short Name:
- J/MNRAS/462/4371
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the discovery of 41 new pulsating sources in the data of the Chandra Advanced CCD Imaging Spectrometer, which is sensitive to X-ray photons in the 0.3-10 keV band. The archival data of the first 15 yr of Chandra observations were retrieved and analysed by means of fast Fourier transforms, employing a peak-detection algorithm able to screen candidate signals in an automatic fashion. We carried out the search for new X-ray pulsators in light curves with more than 50 photons, for a total of about 190000 light curves out of about 430000 extracted. With these numbers, the ChAndra Timing Survey at Brera And Roma astronomical observatories (CATS @ BAR) - as we called the project - represents the largest ever systematic search for coherent signals in the classic X-ray band. More than 50 per cent of the signals were confirmed by further Chandra (for those sources with two or more pointings), XMM-Newton or ROSAT data. The period distribution of the new X-ray pulsators above ~2000s resembles that of cataclysmic variables, while there is a paucity of sources with shorter period and low fluxes. Since there is not an obvious bias against these detections, a possible interpretation is in terms of a magnetic gating mechanism in accreting neutron stars. Finally, we note that CATS @ BAR is a living project and the detection algorithm will continue to be routinely applied to the new Chandra data as they become public. Based on the results obtained so far, we expect to discover about three new pulsators every year.
- ID:
- ivo://CDS.VizieR/J/AZh/84/685
- Title:
- Scattering of pulsar radio emission
- Short Name:
- J/AZh/84/685
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Measurements of the broadening of pulsar pulses by scattering in the interstellar medium are presented for a complete sample of 100 pulsars with Galactic longitudes from 6{deg} to 311{deg} and distances to three kiloparsec. The dependences of the scattering on the dispersion measure (tau_sc_(DM){prop.to}DM^alpha^), frequency (tau_sc_(nu){prop.to}nu^-gamma^), Galactic longitude, and distance to the pulsar are analyzed.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/66
- Title:
- Search for extraterrestrial intelligence with ATA
- Short Name:
- J/ApJ/869/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a novel radio autocorrelation search for extraterrestrial intelligence. For selected frequencies across the terrestrial microwave window (1-10GHz), observations were conducted at the Allen Telescope Array to identify artificial non-sinusoidal periodic signals with radio bandwidths greater than 4Hz, which are capable of carrying substantial messages with symbol rates from 4 to 10^6^Hz. Out of 243 observations, about half (101) were directed toward sources with known continuum flux >~1Jy over the sampled bandwidth (quasars, pulsars, supernova remnants, and masers), based on the hypothesis that they might harbor heretofore undiscovered natural or artificial repetitive, phase or frequency modulation. The rest of the observations were directed mostly toward exoplanet stars with no previously discovered continuum flux. No signals attributable to extraterrestrial technology were found in this study. We conclude that the maximum probability that future observations like the ones described here will reveal repetitively modulated emissions is less than 5% for continuum sources and exoplanets alike. The paper concludes by describing a new approach to expanding this survey to many more targets and much greater sensitivity using archived data from interferometers all over the world.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A13
- Title:
- Second AGILE catalogue of gamma-ray sources
- Short Name:
- J/A+A/627/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the second AGILE-GRID catalogue (2AGL) of gamma-ray sources in the energy range 100MeV-10GeV. With respect to previous AGILE-GRID catalogues, the current 2AGL catalogue is based on the first 2.3 years of science data from the AGILE mission (the so-called pointing mode) and incorporates more data and several analysis improvements, including better calibrations at the event reconstruction level, an updated model for the Galactic diffuse gamma-ray emission, a refined procedure for point-like source detection, and the inclusion of a search for extended gamma-ray sources. The 2AGL catalogue includes 175 high-confidence sources (above 4{sigma} significance) with their location regions and spectral properties and a variability analysis with four-day light curves for the most significant. Relying on the error region of each source position, including systematic uncertainties, 122 sources are considered as positionally associated with known counterparts at different wavelengths or detected by other gamma-ray instruments. Among the identified or associated sources, 62 are active galactic nuclei (AGNs) of the blazar class. Pulsars represent the largest Galactic source class, with 41 associated pulsars, 7 of which have detected pulsation; 8 supernova remnants and 4 high-mass X-ray binaries have also been identified. A substantial number of 2AGL sources are unidentified: for 53 sources no known counterpart is found at different wavelengths. Among these sources, we discuss a subclass of 29 AGILE-GRID-only gamma-ray sources that are not present in 1FGL, 2FGL, or 3FGL catalogues; the remaining sources are unidentified in both 2AGL and 3FGL catalogues. We also present an extension of the analysis of 2AGL sources detected in the energy range 50-100MeV.
- ID:
- ivo://CDS.VizieR/J/ApJS/232/17
- Title:
- Spectral properties of magnetar bursts
- Short Name:
- J/ApJS/232/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our broadband (2-250keV) time-averaged spectral analysis of 388 bursts from SGR J1550-5418, SGR 1900+14, and SGR 1806-20 detected with the Rossi X-ray Timing Explorer (RXTE) here and as a database in a companion web-catalog. We find that two blackbody functions (BB+BB), the sum of two modified blackbody functions (LB+LB), the sum of a blackbody function and a power-law function (BB+PO), and a power law with a high-energy exponential cutoff (COMPT) all provide acceptable fits at similar levels. We performed numerical simulations to constrain the best fitting model for each burst spectrum and found that 67.6% of burst spectra with well-constrained parameters are better described by the Comptonized model. We also found that 64.7% of these burst spectra are better described with the LB+LB model, which is employed in the spectral analysis of a soft gamma repeater (SGR) for the first time here, than with the BB+BB and BB+PO models. We found a significant positive lower bound trend on photon index, suggesting a decreasing upper bound on hardness, with respect to total flux and fluence. We compare this result with bursts observed from SGR and AXP (anomalous X-ray pulsar) sources and suggest that the relationship is a distinctive characteristic between the two. We confirm a significant anticorrelation between burst emission area and blackbody temperature, and find that it varies between the hot and cool blackbody temperatures differently than previously discussed. We expand on the interpretation of our results in the framework of a strongly magnetized neutron star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/4436
- Title:
- Spectral properties of 441 radio pulsars
- Short Name:
- J/MNRAS/473/4436
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the spectral properties of 441 pulsars observed with the Parkes radio telescope near the centre frequencies of 728, 1382 and 3100MHz. The observations at 728 and 3100MHz were conducted simultaneously using the dual-band 10-50cm receiver. These high-sensitivity, multifrequency observations provide a systematic and uniform sample of pulsar flux densities. We combine our measurements with spectral data from the literature in order to derive the spectral properties of these pulsars. Using techniques from robust regression and information theory, we classify the observed spectra in an objective, robust and unbiased way into five morphological classes: simple or broken power law, power law with either low- or high-frequency cut-off and log-parabolic spectrum. While about 79 per cent of the pulsars that could be classified have simple power-law spectra, we find significant deviations in 73 pulsars, 35 of which have curved spectra, 25 with a spectral break and 10 with a low-frequency turn-over. We identify 11 gigahertz-peaked spectrum (GPS) pulsars, with 3 newly identified in this work and 8 confirmations of known GPS pulsars; 3 others show tentative evidence of GPS, but require further low-frequency measurements to support this classification. The weighted mean spectral index of all pulsars with simple power-law spectra is -1.60+/-0.03. The observed spectral indices are well described by a shifted log-normal distribution. The strongest correlations of spectral index are with spin-down luminosity, magnetic field at the light-cylinder and spin-down rate. We also investigate the physical origin of the observed spectral features and determine emission altitudes for three pulsars.
- ID:
- ivo://CDS.VizieR/J/ApJ/854/99
- Title:
- The Einstein@Home gamma-ray pulsar survey. II.
- Short Name:
- J/ApJ/854/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the analysis of 13 gamma-ray pulsars discovered in the Einstein@Home blind search survey using Fermi Large Area Telescope (LAT) Pass 8 data. The 13 new gamma-ray pulsars were discovered by searching 118 unassociated LAT sources from the third LAT source catalog (3FGL), selected using the Gaussian Mixture Model machine-learning algorithm on the basis of their gamma-ray emission properties being suggestive of pulsar magnetospheric emission. The new gamma-ray pulsars have pulse profiles and spectral properties similar to those of previously detected young gamma-ray pulsars. Follow-up radio observations have revealed faint radio pulsations from two of the newly discovered pulsars and enabled us to derive upper limits on the radio emission from the others, demonstrating that they are likely radio-quiet gamma-ray pulsars. We also present results from modeling the gamma-ray pulse profiles and radio profiles, if available, using different geometric emission models of pulsars. The high discovery rate of this survey, despite the increasing difficulty of blind pulsar searches in gamma rays, suggests that new systematic surveys such as presented in this article should be continued when new LAT source catalogs become available.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/33
- Title:
- The Fermi LAT fourth source catalog (4FGL)
- Short Name:
- J/ApJS/247/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the fourth Fermi Large Area Telescope catalog (4FGL) of {gamma}-ray sources. Based on the first eight years of science data from the Fermi Gamma-ray Space Telescope mission in the energy range from 50MeV to 1TeV, it is the deepest yet in this energy range. Relative to the 3FGL catalog, the 4FGL catalog has twice as much exposure as well as a number of analysis improvements, including an updated model for the Galactic diffuse {gamma}-ray emission, and two sets of light curves (one-year and two-month intervals). The 4FGL catalog includes 5064 sources above 4{sigma} significance, for which we provide localization and spectral properties. Seventy-five sources are modeled explicitly as spatially extended, and overall, 358 sources are considered as identified based on angular extent, periodicity, or correlated variability observed at other wavelengths. For 1336 sources, we have not found plausible counterparts at other wavelengths. More than 3130 of the identified or associated sources are active galaxies of the blazar class, and 239 are pulsars.
- ID:
- ivo://CDS.VizieR/J/ApJ/706/L7
- Title:
- The Fermi LAT sky as seen by INTEGRAL/IBIS
- Short Name:
- J/ApJ/706/L7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this Letter we present the result of the cross correlation between the fourth INTEGRAL/IBIS soft gamma-ray catalog, in the range 20-100keV, and the Fermi LAT bright source list of objects emitting in the 100MeV-100GeV range. The main result is that only a minuscule part of the more than 720 sources detected by INTEGRAL and the population of 205 Fermi LAT sources are detected in both spectral regimes. This is in spite of the mCrab INTEGRAL sensitivity for both galactic and extragalactic sources and the breakthrough, in terms of sensitivity, achieved by Fermi at MeV-GeV energies. The majority of the 14 Fermi LAT sources clearly detected in the fourth INTEGRAL/IBIS catalog are optically identified active galactic nuclei (10) complemented by two isolated pulsars (Crab and Vela) and two high-mass X-ray binaries (LS I +61 303 and LS 5039). Two more possible associations have been found: one is 0FGL J1045.6-5937, possibly the counterpart at high energy of the massive colliding wind binary system Eta Carinae, discovered to be a soft gamma ray emitter by recent INTEGRAL observations and 0FGL J1746.0-2900 coincident with IGR J17459-2902, but still not identified with any known object at lower energy. For the remaining 189 Fermi LAT sources no INTEGRAL counterpart was found and we report the 2{sigma} upper limit in the energy band 20-40keV.
