| 1. |
- Abdo, A. A., et al.
(författare)
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FERMI LARGE AREA TELESCOPE DETECTION OF PULSED gamma-RAYS FROM THE VELA-LIKE PULSARS PSR J1048-5832 AND PSR J2229+6114
- 2009
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 706:2, s. 1331-1340
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Tidskriftsartikel (refereegranskat)abstract
- We report the detection of gamma-ray pulsations (>= 0.1GeV) from PSR J2229+ 6114 and PSR J1048-5832, the latter having been detected as a low-significance pulsar by EGRET. Data in the gamma-ray band were acquired by the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope, while the radio rotational ephemerides used to fold the gamma-ray light curves were obtained using the Green Bank Telescope, the Lovell telescope at Jodrell Bank, and the Parkes Telescope. The two young radio pulsars, located within the error circles of the previously unidentified EGRET sources 3EG J1048-5840 and 3EG J2227+6122, present spin-down characteristics similar to the Vela pulsar. PSR J1048-5832 shows two sharp peaks at phases 0.15 +/- 0.01 and 0.57 +/- 0.01 relative to the radio pulse confirming the EGRET light curve, while PSR J2229+ 6114 presents a very broad peak at phase 0.49 +/- 0.01. The gamma-ray spectra above 0.1 GeV of both pulsars are fit with power laws having exponential cutoffs near 3 GeV, leading to integral photon fluxes of (2.19 +/- 0.22 +/- 0.32) x 10(-7) cm(-2) s(-1) for PSR J1048-5832 and (3.77 +/- 0.22 +/- 0.44) x 10(-7) cm(-2) s(-1) for PSR J2229+6114. The first uncertainty is statistical and the second is systematic. PSR J1048-5832 is one of the two LAT sources whichwere entangled together as 3EG J1048-5840. These detections add to the growing number of young gamma-ray pulsars that make up the dominant population of GeV gamma-ray sources in the Galactic plane.
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| 2. |
- Abdo, A. A., et al.
(författare)
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FERMI LARGE AREA TELESCOPE GAMMA-RAY DETECTION OF THE RADIO GALAXY M87
- 2009
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 707:1, s. 55-60
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Tidskriftsartikel (refereegranskat)abstract
- We report the Fermi Large Area Telescope (LAT) discovery of high-energy (MeV/GeV) gamma-ray emission positionally consistent with the center of the radio galaxy M87, at a source significance of over 10 sigma in 10 months of all-sky survey data. Following the detections of Cen A and Per A, this makes M87 the third radio galaxy seen with the LAT. The faint point-like gamma-ray source has a >100 MeV flux of 2.45 (+/-0.63) x 10(-8) photons cm(-2) s(-1) (photon index = 2.26 +/- 0.13) with no significant variability detected within the LAT observation. This flux is comparable with the previous EGRET upper limit (<2.18 x 10-8 photons cm(-2) s(-1), 2 sigma), thus there is no evidence for a significant MeV/GeV flare on decade timescales. Contemporaneous Chandra and Very Long Baseline Array data indicate low activity in the unresolved X-ray and radio core relative to previous observations, suggesting M87 is in a quiescent overall level over the first year of Fermi-LAT observations. The LAT gamma-ray spectrum is modeled as synchrotron self-Compton (SSC) emission from the electron population producing the radio-to-X-ray emission in the core. The resultant SSC spectrum extrapolates smoothly from the LAT band to the historical-minimum TeV emission. Alternative models for the core and possible contributions from the kiloparsec-scale jet in M87 are considered, and cannot be excluded.
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| 3. |
- Abdo, A. A., et al.
(författare)
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MULTIWAVELENGTH MONITORING OF THE ENIGMATIC NARROW-LINE SEYFERT 1 PMN J0948+0022 IN 2009 MARCH-JULY
- 2009
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 707:1, s. 727-737
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Tidskriftsartikel (refereegranskat)abstract
- Following the recent discovery of gamma rays from the radio-loud narrow-line Seyfert 1 galaxy PMN J0948+0022 (z = 0.5846), we started a multiwavelength campaign from radio to gamma rays, which was carried out between the end of 2009 March and the beginning of July. The source displayed activity at all the observed wavelengths: a general decreasing trend from optical to gamma-ray frequencies was followed by an increase of radio emission after less than two months from the peak of the gamma-ray emission. The largest flux change, about a factor of about 4, occurred in the X-ray band. The smallest was at ultraviolet and near-infrared frequencies, where the rate of the detected photons dropped by a factor 1.6-1.9. At optical wavelengths, where the sampling rate was the highest, it was possible to observe day scale variability, with flux variations up to a factor of about 3. The behavior of PMN J0948+0022 observed in this campaign and the calculated power carried out by its jet in the form of protons, electrons, radiation, and magnetic field are quite similar to that of blazars, specifically of flat-spectrum radio quasars. These results confirm the idea that radio-loud narrow-line Seyfert 1 galaxies host relativistic jets with power similar to that of average blazars.
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| 4. |
- Abdo, A. A., et al.
(författare)
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PULSED GAMMA RAYS FROM THE MILLISECOND PULSAR J0030+0451 WITH THE FERMI LARGE AREA TELESCOPE
- 2009
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 699:2, s. 1171-1177
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of gamma-ray pulsations from the nearby isolated millisecond pulsar (MSP) PSR J0030+0451 with the Large Area Telescope on the Fermi Gamma-ray Space Telescope (formerly GLAST). This discovery makes PSR J0030+0451 the second MSP to be detected in gamma rays after PSR J0218+4232, observed by the EGRET instrument on the Compton Gamma-Ray Observatory. The spin-down power (E) over dot = 3.5 x 10(33) erg s(-1) is an order of magnitude lower than the empirical lower bound of previously known gamma-ray pulsars. The emission profile is characterized by two narrow peaks, 0.07 +/- 0.01 and 0.08 +/- 0.02 wide, respectively, separated by 0.44 +/- 0.02 in phase. The first gamma-ray peak falls 0.15 +/- 0.01 after the main radio peak. The pulse shape is similar to that of the "normal" gamma-ray pulsars. An exponentially cutoff power-law fit of the emission spectrum leads to an integral photon flux above 100 MeV of (6.76 +/- 1.05 +/- 1.35) x 10(-8) cm(-2) s(-1) with cutoff energy (1.7 +/- 0.4 +/- 0.5) GeV. Based on its parallax distance of (300 +/- 90) pc, we obtain a gamma-ray efficiency L-gamma/E similar or equal to 15% for the conversion of spin-down energy rate into gamma-ray radiation, assuming isotropic emission.
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| 5. |
- Aharonian, F., et al.
(författare)
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SIMULTANEOUS OBSERVATIONS OF PKS 2155-304 WITH HESS, FERMI, RXTE, AND ATOM : SPECTRAL ENERGY DISTRIBUTIONS AND VARIABILITY IN A LOW STATE
- 2009
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 0004-637X .- 1538-4357. ; 696:2, s. L150-L155
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first simultaneous observations that cover the optical, X-ray, and high-energy gamma-ray bands of the BL Lac object PKS 2155-304. The gamma-ray bands were observed for 11 days, between 2008 August 25 and 2008 September 6 (MJD 54704-54715), jointly with the Fermi Gamma-ray Space Telescope and the HESS atmospheric Cherenkov array, providing the first simultaneous MeV-TeV spectral energy distribution (SED) with the new generation of gamma-ray telescopes. The ATOM telescope and the RXTE and Swift observatories provided optical and X-ray coverage of the low-energy component over the same time period. The object was close to the lowest archival X-ray and very high energy (VHE; > 100 GeV) state, whereas the optical flux was much higher. The light curves show relatively little (similar to 30%) variability overall when compared to past flaring episodes, but we find a clear optical/VHE correlation and evidence for a correlation of the X-rays with the high-energy spectral index. Contrary to previous observations in the flaring state, we do not find any correlation between the X-ray and VHE components. Although synchrotron self-Compton models are often invoked to explain the SEDs of BL Lac objects, the most common versions of these models are at odds with the correlated variability we find in the various bands for PKS 2155-304.
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| 6. |
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| 7. |
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| 8. |
- Burström, Kristina, et al.
(författare)
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A comparison of individual and social time trade-off values for health states in the general population
- 2006
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Ingår i: Health policy (Amsterdam). - : Elsevier Ireland Ltd. - 1872-6054 .- 0168-8510. ; 76:3, s. 359-370
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to compare directly elicited individual time trade-off (TTO) values in a general population sample with the social values derived using the UK EQ-5D index tariff. In the Stockholm County 1998 postal Public Health Survey (n =4950, 20–88 years), the EQ-5D self-classifier, a TTO and a rating scale (RS) question were included (n = 2549 for all three questions). The mean TTO (EQ-5D) value was 0.943 (0.890) in the youngest age-group and 0.699 (0.733) in the oldest age-group. The difference between TTO and EQ-5D values was greater in more severe health status groups was. The same equation as for the UK EQ-5D index tariff was estimated for TTO and RS and resulted in significant and consistent coefficients for nearly all dimensions. The coefficients for moderate problems were closer to the EQ-5D index tariff than the coefficients for severe problems. Age was also significant after controlling for the EQ-5D dimensions (p < 0.05). The results suggest that individual and social TTO values differ systematically and that the difference is greater the more severe the health status is. The social EQ-5D index tariff may also underestimate the severity in health status at older ages; age appears to correlate with additional health problems not captured by the EQ-5D classification.
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| 9. |
- Burström, Kristina, et al.
(författare)
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Increasing socio-economic inequalities in life expectancy and QALYs in Sweden 1980-1997
- 2005
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Ingår i: Health Economics. - : Wiley-Blackwell. - 1099-1050 .- 1057-9230. ; 14:8, s. 831-850
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to estimate the change in socio-economic differences in life expectancy and in quality-adjusted life years (QALYs), for men and women at different ages, in Sweden 1980 to 1997. We used data from the Swedish Survey of Living Conditions (the ULF survey), which is linked to mortality data, to estimate the life expectancy in different socio-economic groups in 1980 and 1997 (n=100 868). Health state scores were obtained by mapping responses to selected ULF survey interview questions into the generic health-related quality of life measure EQ-5D, using the UK EQ-5D index tariff (n=34 447). For 20-year-old men the difference in life expectancy between the highest (higher non-manual) and the lowest socio-economic group (unskilled manual) was 2.11 years in 1980 and 3.79 years in 1997. The corresponding figures for 20-year-old women were 1.56 in 1980 and 2.15 in 1997. The difference in QALYs between the highest and the lowest socio-economic group increased from 5.76 QALYs in 1980 to 7.06 QALYs in 1997 for 20-year-old men, and from 4.14 QALYs in 1980 to 5.66 QALYs in 1997 for 20-year-old women. The widening socio-economic inequalities over time were more stable for men than for women. We conclude that our results suggest that the socio-economic inequality in health has increased between 1980 and 1997 in Sweden.
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| 10. |
- Cesarini, David, et al.
(författare)
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Confidence interval estimation tasks and the economics of overconfidence
- 2006
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Ingår i: Journal of economic behavior & organization. - : Elsevier B.V. - 1879-1751 .- 0167-2681. ; 61:3, s. 453-470
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the robustness of results from confidence interval estimation tasks with respect to a number of manipulations: frequency assessments, peer frequency assessments, iteration, and monetary incentives. Our results suggest that a large share of the overconfidence in interval estimation tasks is an artifact of the response format. Using frequencies and monetary incentives reduces the measured overconfidence in the confidence interval method by about 65 percent. The results are consistent with the notion that subjects have a deep aversion to setting broad confidence intervals, a reluctance that we attribute to a socially rational trade-off between informativeness and accuracy.
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