| 1. |
- Abdo, A. A., et al.
(författare)
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The second Fermi large area telescope catalog of gamma-ray pulsars
- 2013
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 208:2, s. 17-
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Tidskriftsartikel (refereegranskat)abstract
- This catalog summarizes 117 high-confidence ≥0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.
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| 2. |
- Abdo, A. A., et al.
(författare)
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The first fermi large area telescope catalog of gamma-ray pulsars
- 2010
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 187:2, s. 460-494
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Tidskriftsartikel (refereegranskat)abstract
- The dramatic increase in the number of known gamma-ray pulsars since the launch of the Fermi Gamma-ray Space Telescope (formerly GLAST) offers the first opportunity to study a sizable population of these high-energy objects. This catalog summarizes 46 high-confidence pulsed detections using the first six months of data taken by the Large Area Telescope (LAT), Fermi's main instrument. Sixteen previously unknown pulsars were discovered by searching for pulsed signals at the positions of bright gamma-ray sources seen with the LAT, or at the positions of objects suspected to be neutron stars based on observations at other wavelengths. The dimmest observed flux among these gamma-ray-selected pulsars is 6.0 x 10(-8) ph cm(-2) s(-1) (for E > 100 MeV). Pulsed gamma-ray emission was discovered from 24 known pulsars by using ephemerides (timing solutions) derived from monitoring radio pulsars. Eight of these new gamma-ray pulsars are millisecond pulsars. The dimmest observed flux among the radio-selected pulsars is 1.4 x 10(-8) ph cm(-2) s(-1) (for E > 100 MeV). The remaining six gamma-ray pulsars were known since the Compton Gamma Ray Observatory mission, or before. The limiting flux for pulse detection is non-uniform over the sky owing to different background levels, especially near the Galactic plane. The pulsed energy spectra can be described by a power law with an exponential cutoff, with cutoff energies in the range similar to 1-5 GeV. The rotational energy-loss rate ((E) over dot) of these neutron stars spans five decades, from similar to 3 x 10(33) erg s(-1) to 5 x 10(38) erg s(-1), and the apparent efficiencies for conversion to gammaray emission range from similar to 0.1% to similar to unity, although distance uncertainties complicate efficiency estimates. The pulse shapes show substantial diversity, but roughly 75% of the gamma-ray pulse profiles have two peaks, separated by greater than or similar to 0.2 of rotational phase. For most of the pulsars, gamma-ray emission appears to come mainly from the outer magnetosphere, while polar-cap emission remains plausible for a remaining few. Spatial associations imply that many of these pulsars power pulsar wind nebulae. Finally, these discoveries suggest that gamma-ray-selected young pulsars are born at a rate comparable to that of their radio-selected cousins and that the birthrate of all young gamma-ray-detected pulsars is a substantial fraction of the expected Galactic supernova rate.
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| 3. |
- Weltevrede, P., et al.
(författare)
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Gamma-ray and radio properties of six pulsars detected by the Fermi large area telescope
- 2010
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 708:2, s. 1426-1441
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Tidskriftsartikel (refereegranskat)abstract
- We report the detection of pulsed gamma-rays for PSRs J0631+1036, J0659+1414, J0742-2822, J1420-6048, J1509-5850, and J1718-3825 using the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (formerly known as GLAST). Although these six pulsars are diverse in terms of their spin parameters, they share an important feature: their gamma-ray light curves are (at least given the current count statistics) single peaked. For two pulsars, there are hints for a double-peaked structure in the light curves. The shapes of the observed light curves of this group of pulsars are discussed in the light of models for which the emission originates from high up in the magnetosphere. The observed phases of the gamma-ray light curves are, in general, consistent with those predicted by high-altitude models, although we speculate that the gamma-ray emission of PSR J0659+1414, possibly featuring the softest spectrum of all Fermi pulsars coupled with a very low efficiency, arises from relatively low down in the magnetosphere. High-quality radio polarization data are available showing that all but one have a high degree of linear polarization. This allows us to place some constraints on the viewing geometry and aids the comparison of the gamma-ray light curves with high-energy beam models.
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| 4. |
- Freire, P. C. C., et al.
(författare)
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Fermi Detection of a Luminous gamma-Ray Pulsar in a Globular Cluster
- 2011
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 334:6059, s. 1107-1110
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Tidskriftsartikel (refereegranskat)abstract
- We report on the Fermi Large Area Telescope's detection of gamma-ray (>100 mega-electron volts) pulsations from pulsar J1823-3021A in the globular cluster NGC 6624 with high significance (similar to 7 sigma). Its gamma-ray luminosity, L(gamma) = (8.4 +/- 1.6) x 10(34) ergs per second, is the highest observed for any millisecond pulsar (MSP) to date, and it accounts for most of the cluster emission. The nondetection of the cluster in the off-pulse phase implies that it contains <32 gamma-ray MSPs, not similar to 100 as previously estimated. The gamma-ray luminosity indicates that the unusually large rate of change of its period is caused by its intrinsic spin-down. This implies that J1823-3021A has the largest magnetic field and is the youngest MSP ever detected and that such anomalous objects might be forming at rates comparable to those of the more normal MSPs.
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| 5. |
- Noutsos, A., et al.
(författare)
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Radio and γ-ray constraints on the emission geometry and birthplace of PSR j2043+2740
- 2011
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 728:2, s. 77-
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first year of Fermi γ-ray observations of pulsed high-energy emission from the old PSR J2043 + 2740. The study of the γ-ray efficiency of such old pulsars gives us an insight into the evolution of pulsars' ability to emit in γ rays as they age. The y-ray light curve of this pulsar above 0.1 GeV is clearly defined by two sharp peaks, 0.353 ± 0.035 periods apart. We have combined the γ-ray profile characteristics of PSR J2043 + 2740 with the geometrical properties of the pulsar's radio emission, derived from radio-polarization data, and constrained the pulsar-beam geometry in the framework of a two-pole caustic (TPC) and an outer gap (OG) model. The ranges of magnetic inclination and viewing angle were determined to be {α, ζ} ∼ {52°-57°, 61°-68°} for the TPC model, and {α, ζ} ∼ {62°-73°, 74°-81°} and {α, ζ,} ∼ {72°-83°, 60°-75°} for the OG model. Based on this geometry, we assess possible birth locations for this pulsar and derive a likely proper motion, sufficiently high to be measurable with VLBI. At a characteristic age of 1.2 Myr, PSR J2043 + 2740 is the third oldest of all discovered, non-recycled, γ-ray pulsars: it is twice as old as the next oldest, PSR J0357 + 32, and younger only than the recently discovered PSR J1836 + 5925 and PSR J2055 + 25, both of which are at least five and ten times less energetic, respectively.
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| 6. |
- Ardo, A. A., et al.
(författare)
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FERMI LARGE AREA TELESCOPE OBSERVATIONS OF GAMMA-RAY PULSARS PSR J1057-5226, J1709-4429, AND J1952+3252
- 2010
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 720:1, s. 26-40
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Tidskriftsartikel (refereegranskat)abstract
- The Fermi Large Area Telescope (LAT) data have confirmed the pulsed emission from all six high-confidence gamma-ray pulsars previously known from the EGRET observations. We report results obtained from the analysis of 13 months of LAT data for three of these pulsars (PSR J1057-5226, PSR J1709-4429, and PSR 11952+3252) each of which had some unique feature among the EGRET pulsars. The excellent sensitivity of LAT allows more detailed analysis of the evolution of the pulse profile with energy and also of the variation of the spectral shape with phase. We measure the cutoff energy of the pulsed emission from these pulsars for the first time and provide a more complete picture of the emission mechanism. The results confirm some, but not all, of the features seen in the EGRET data.
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| 7. |
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| 9. |
- Gomez-Gallego, F, et al.
(författare)
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Are elite endurance athletes genetically predisposed to lower disease risk?
- 2010
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Ingår i: Physiological genomics. - : American Physiological Society. - 1531-2267 .- 1094-8341. ; 41:1, s. 82-90
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Tidskriftsartikel (refereegranskat)abstract
- We compared a polygenic profile that combined 33 disease risk-related mutations and polymorphisms among nonathletic healthy control subjects and elite endurance athletes. The study sample comprised 100 healthy Spanish male nonathletic (sedentary) control subjects and 100 male elite endurance athletes. We analyzed 33 disease risk-related mutations and polymorphisms. We computed a health-related total genotype score (TGS, 0–100) from the accumulated combination of the 33 variants. We did not observe significant differences in genotype or allele distributions among groups, except for the rs4994 polymorphism ( P < 0.001). The computed health-related TGS was similar among groups (23.8 ± 1.0 vs. 24.2 ± 0.8 in control subjects and athletes, respectively; P = 0.553). Similar results were obtained when computing specific TGSs for each main disease category (cardiovascular disease and cancer). We observed no evidence that male elite endurance athletes are genetically predisposed to have lower disease risk than matched nonathletic control subjects.
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| 10. |
- Kirsten, F., et al.
(författare)
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Precision astrometry of pulsars and other compact radio sources in the globular cluster M15
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 565
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Tidskriftsartikel (refereegranskat)abstract
- The globular cluster (GC) M15 (NGC 7078) is host to at least eight pulsars and two low mass X-ray binaries (LMXBs), one of which is also visible in the radio regime. Here we present the results of a multi-epoch global very long baseline interferometry (VLBI) campaign aiming at i) measuring the proper motion of the known compact radio sources; ii) finding and classifying thus far undetected compact radio sources in the GC; and iii) detecting a signature of the putative intermediate mass black hole (IMBH) proposed to reside at the core of M15. We measure the sky motion in right ascension (mu(alpha),) and declination (mu(delta)) of the pulsars M15A and M15C and of the LMXB AC211 to be (mu(alpha), mu(delta))(M15A) = (-0.54 +/- 0.14, -4.33 +/- 0.25) mas yr(-1), (mu(alpha), mu(delta))(M15A) = (-0.75 +/- 0.09, -3.52 +/- 0.13) mas yr(-1), and (mu(alpha), mu(delta))(AC211) = (-0.46 0.08, 4.31 0.20) mas yr-I, respectively. Based on these measurements we estimate the global proper motion of M15 to be (mu(alpha), mu(delta)) = (-0.58 +/- 0.18, -4.05 +/- 0.34) mas yr(-1). We detect two previously known but unclassified compact sotirces within our field of view. Our observations indicate that one them is of extragalactic origin while the other one is a foreground source, quite likely an LMXB. The double neutron star system M15C became fainter during the observations, disappeared for one year and is now observable again - an effect possibly caused by geodetic precession. The LMXB AC211 shows a double lobed structure in one of the observations indicative of an outburst during this campaign. With the inclusion of the last two of a total of seven observations we confirm the upper mass limit for a putative IMBH to be M-circle dot tau
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