We report on the discovery of gamma-ray pulsations from five millisecond pulsars (MSPs) using the Fermi Large Area Telescope (LAT) and timing ephemerides provided by various radio observatories. We ...also present confirmation of the gamma-ray pulsations from a sixth source, PSR J2051−0827. Five of these six MSPs are in binary systems: PSRs J1713+0747, J1741+1351, J1600−3053 and the two black widow binary pulsars PSRs J0610−2100 and J2051−0827. The only isolated MSP is the nearby PSR J1024−0719, which is also known to emit X-rays. We present X-ray observations in the direction of PSRs J1600−3053 and J2051−0827. While PSR J2051−0827 is firmly detected, we can only give upper limits for the X-ray flux of PSR J1600−3053. There are no dedicated X-ray observations available for the other three objects.
The MSPs mentioned above, together with most of the MSPs detected by Fermi, are used to put together a sample of 30 gamma-ray MSPs. This sample is used to study the morphology and phase connection of radio and gamma-ray pulse profiles. We show that MSPs with pulsed gamma-ray emission which is phase-aligned with the radio emission present the steepest radio spectra and the largest magnetic fields at the light cylinder among all MSPs. Also, we observe a trend towards very low, or undetectable, radio linear polarization levels. These properties could be attributed to caustic radio emission produced at a range of different altitudes in the magnetosphere. We note that most of these characteristics are also observed in the Crab pulsar, the only other radio pulsar known to exhibit phase-aligned radio and gamma-ray emission.
A precise mass measurement of PSR J2045 + 3633 McKee, J W; Freire, P C C; Berezina, M ...
Monthly notices of the Royal Astronomical Society,
12/2020, Letnik:
499, Številka:
3
Journal Article
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ABSTRACT
We present the results of a timing analysis undertaken with the goal of obtaining an improved mass measurement of the recycled pulsar J2045 + 3633. Using regular high-cadence observations ...with the Effelsberg, Nançay, and Lovell radio telescopes, together with targeted campaigns with the Arecibo Telescope and Effelsberg, we have assembled a 6-yr timing data set for this pulsar. We measure highly significant values for the proper motion and the related rate of change of orbital semimajor axis ($\dot{x}$), and have obtained high-precision values of the rate of advance of periastron time ($\dot{\omega }$), and two of the Shapiro delay parameters (h3 and ς). This has allowed us to improve the measurements of the pulsar and companion masses by an order of magnitude, yielding (with 1σ uncertainties) $1.251^{+0.021}_{-0.021}\, \text{M}_{\odot }$ for PSR J2045 + 3633, and $0.873^{+0.016}_{-0.014}\, \text{M}_{\odot }$ for its white dwarf companion, and has allowed us to place improved constraints on the geometrical orientation of the binary system. Using our measurements of the binary component masses and the orbital size, we consider possible evolutionary scenarios for the system.
The paucity of observed supermassive black hole binaries (SMBHBs) may imply that the gravitational wave background (GWB) from this population is anisotropic, rendering existing analyses suboptimal. ...We present the first constraints on the angular distribution of a nanohertz stochastic GWB from circular, inspiral-driven SMBHBs using the 2015 European Pulsar Timing Array data. Our analysis of the GWB in the ~2-90 nHz band shows consistency with isotropy, with the strain amplitude in l>0 spherical harmonic multipoles ≲40% of the monopole value. We expect that these more general techniques will become standard tools to probe the angular distribution of source populations.
Context.
With the advent of multi-wavelength electromagnetic observations of neutron stars – spanning many decades in photon energies – from radio wavelengths up to X-rays and
γ
-rays, it has become ...possible to significantly constrain the geometry and the location of the associated emission regions.
Aims.
In this work, we use results from the modelling of thermal X-ray observations of PSR J0030+0451 from the Neutron Star Interior Composition Explorer (NICER) mission and phase-aligned radio and
γ
-ray pulse profiles to constrain the geometry of an off-centred dipole that is able to reproduce the light curves in these respective bands simultaneously.
Methods.
To this aim, we deduced a configuration with a simple dipole off-centred from the location of the centre of the thermal X-ray hot spots. We show that the geometry is compatible with independent constraints from radio and
γ
-ray pulsations only, leading to a fixed magnetic obliquity of
α
≈ 75° and a line-of-sight inclination angle of
ζ
≈ 54°.
Results.
We demonstrate that an off-centred dipole cannot be rejected by accounting for the thermal X-ray pulse profiles. Moreover, the crescent shape of one spot is interpreted as the consequence of a small-scale surface dipole on top of the large-scale off-centred dipole.
We observed the young (∼1700 yr) pulsar PSR B0540−69 in the ultraviolet for the first time with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. Imaging observations with ...the NUV-MAMA and ultraviolet FUV-MAMA detectors in TIME-TAG mode allowed us to clearly detect the pulsar in two bands around 2350 and 1590 , with magnitudes mNUV = 21.45 0.02 and mFUV = 21.83 0.10. We also detected the pulsar wind nebula in the NUV-MAMA image, with a morphology similar to that observed in the optical and near-infrared (IR). The extinction-corrected NUV and FUV pulsar fluxes are compatible with a very steep power-law spectrum with spectral index UV ∼ 3, and incompatible with a Rayleigh-Jeans spectrum, indicating a non-thermal origin of the emission. The comparison with the optical/near-IR power-law spectrum (spectral index O,nIR ∼ 0.7), indicates an abrupt turnover at wavelengths below 2500 , not yet observed in other pulsars. We detected pulsations in both the NUV and FUV data at the 50 ms pulsar period. In both cases, the folded light curve features a broad pulse with two peaks closely spaced in phase, as observed in the optical and X-ray light curves. The NUV/FUV peaks are also aligned in phase with those observed in the radio (1.4 GHz), optical, X-ray, and γ-ray light curves, as in the Crab pulsar, implying a similar beaming geometry across all wavelengths. PSR B0540−69 is now the fifth isolated pulsar, together with Crab, Vela, PSR B0656+14, and the radio-quiet Geminga, detected in the optical, UV, near-IR, X-rays, and γ-rays, and seen to pulsate in at least four of these energy bands.
Here, we present precise phase-connected pulse timing solutions for 16 γ-ray-selected pulsars recently discovered using the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope plus one ...very faint radio pulsar (PSR J1124–5916) that is more effectively timed with the LAT. We describe the analysis techniques including a maximum likelihood method for determining pulse times of arrival from unbinned photon data. A major result of this work is improved position determinations, which are crucial for multiwavelength follow-up. For most of the pulsars, we overlay the timing localizations on X-ray images from Swift and describe the status of X-ray counterpart associations. We report glitches measured in PSRs J0007+7303, J1124–5916, and J1813–1246. We analyze a new 20 ks Chandra ACIS observation of PSR J0633+0632 that reveals an arcminute-scale X-ray nebula extending to the south of the pulsar. We were also able to precisely localize the X-ray point source counterpart to the pulsar and find a spectrum that can be described by an absorbed blackbody or neutron star atmosphere with a hard power-law component. Another Chandra ACIS image of PSR J1732–3131 reveals a faint X-ray point source at a location consistent with the timing position of the pulsar. Finally, we present a compilation of new and archival searches for radio pulsations from each of the γ-ray-selected pulsars as well as a new Parkes radio observation of PSR J1124–5916 to establish the γ-ray to radio phase offset.
21 year timing of the black-widow pulsar J2051−0827 Shaifullah, G; Verbiest, J. P. W; Freire, P. C. C ...
Monthly notices of the Royal Astronomical Society,
10/2016, Letnik:
462, Številka:
1
Journal Article
Recenzirano
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Timing results for the black-widow pulsar J2051−0827 are presented, using a 21 year data set from four European Pulsar Timing Array telescopes and the Parkes radio telescope. This data set, which is ...the longest published to date for a black-widow system, allows for an improved analysis that addresses previously unknown biases. While secular variations, as identified in previous analyses, are recovered, short-term variations are detected for the first time. Concurrently, a significant decrease of ∼ 2.5 × 10− 3 cm− 3 pc in the dispersion measure associated with PSR J2051−0827 is measured for the first time and improvements are also made to estimates of the proper motion. Finally, PSR J2051−0827 is shown to have entered a relatively stable state suggesting the possibility of its eventual inclusion in pulsar timing arrays.
The Vela supernova remnant (SNR) is the closest SNR to Earth containing an active pulsar, the Vela pulsar (PSR B0833-45). This pulsar is an archetype of the middle-aged pulsar class and powers a ...bright pulsar wind nebula (PWN), Vela-X, spanning a region of 2degrees x 3degrees south of the pulsar and observed in the radio, X-ray, and very high energy gamma -ray domains. The detection of the Vela-X PWN by the Fermi Large Area Telescope (LAT) was reported in the first year of the mission. Subsequently, we have reinvestigated this complex region and performed a detailed morphological and spectral analysis of this source using 4 yr of Fermi-LAT observations. This study lowers the threshold for morphological analysis of the nebula from 0.8 GeV to 0.3 GeV, allowing for the inspection of distinct energy bands by the LAT for the first time. We describe the recent results obtained on this PWN and discuss the origin of the newly detected spatial features.
Using the Parkes Radio Telescope, we have carried out deep observations of 11 unassociated gamma-ray sources. Periodicity searches of these data have discovered two millisecond pulsars, PSR ...J1103−5403 (1FGL J1103.9−5355) and PSR J2241−5236 (1FGL J2241.9−5236), and a long-period pulsar, PSR J1604−44 (1FGL J1604.7−4443). In addition, we searched for but did not detect any radio pulsations from six gamma-ray pulsars discovered by the Fermi satellite to a level of ∼0.04 mJy (for pulsars with a 10 per cent duty cycle).
The timing of the millisecond pulsar PSR J1103−5403 has shown that its position is 9 arcmin from the centroid of the gamma-ray source. Since these observations were carried out, independent evidence has shown that 1FGL J1103.9−5355 is associated with the flat spectrum radio source PKS 1101−536. It appears certain that the pulsar is not associated with the gamma-ray source, despite the seemingly low probability of a chance detection of a radio millisecond pulsar. We consider that PSR J1604−44 is a chance discovery of a weak, long-period pulsar and is unlikely to be associated with 1FGL J1604.7−4443. PSR J2241−5236 has a spin period of 2.2 ms and orbits a very low mass companion with a 3.5-h orbital period. The relatively high flux density and low dispersion measure of PSR J2241−5236 make it an excellent candidate for high precision timing experiments. The gamma rays of 1FGL J2241.9−5236 have a spectrum that is well modelled by a power law with an exponential cut-off, and phase binning with the radio ephemeris results in a multipeaked gamma-ray pulse profile. Observations with Chandra have identified a coincident X-ray source within 0.1 arcsec of the position of the pulsar obtained by radio timing.
Context. The 11.99 ms pulsar PSR J1618−3921 orbits a He white dwarf companion of probably low mass with a period of 22.7 d. The pulsar was discovered in a survey of the intermediate Galactic ...latitudes at 1400 MHz that was conducted with the Parkes radio telescope in the late 1990s. Although PSR J1618−3921 was discovered more than 15 years ago, only limited information has been published about this pulsar, which has a surprisingly high orbital eccentricity (e ≃ 0.027) considering its high spin frequency and the likely low mass of the companion. Aims. The focus of this work is a precise measurement of the spin and the astrometric and orbital characteristics of PSR J1618−3921. This was done with timing observations made at the Nançay Radio Telescope from 2009 to 2017. Methods. We analyzed the timing data recorded at the Nançay Radio Telescope over several years to characterize the properties of PSR J1618−3921. A rotation ephemeris for this pulsar was obtained by analyzing the arrival times of the radio pulses at the telescope. Results. We confirm the unusual eccentricity of PSR J1618−3921 and discuss several hypotheses regarding its formation in the context of other discoveries of recycled pulsars in eccentric orbits.
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