-
M Ackermann,
M Ajello,
A Allafort,
L Baldini,
J Ballet,
G Barbiellini,
M G Baring,
D Bastieri,
K Bechtol,
R Bellazzini, [......],
G Vianello,
V Vitale,
A P Waite,
M Werner,
B L Winer,
K S Wood,
M Wood,
R Yamazaki,
Z Yang,
S Zimmer
[show abstract]
[hide abstract]
ABSTRACT: Cosmic rays are particles (mostly protons) accelerated to relativistic speeds. Despite wide agreement that supernova remnants (SNRs) are the sources of galactic cosmic rays, unequivocal evidence for the acceleration of protons in these objects is still lacking. When accelerated protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma rays. This offers a compelling way to detect the acceleration sites of protons. The identification of pion-decay gamma rays has been difficult because high-energy electrons also produce gamma rays via bremsstrahlung and inverse Compton scattering. We detected the characteristic pion-decay feature in the gamma-ray spectra of two SNRs, IC 443 and W44, with the Fermi Large Area Telescope. This detection provides direct evidence that cosmic-ray protons are accelerated in SNRs.
Science 02/2013; 339(6121):807-11. · 31.20 Impact Factor
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C. M. Espinoza,
L. Guillemot,
O. Celik,
P. Weltevrede,
B. W. Stappers, D. A. Smith,
M. Kerr,
V. E. Zavlin,
I. Cognard,
R. P. Eatough, [......],
S. Johnston,
M. Keith,
M. Kramer,
A. Lyne,
R. N. Manchester,
S. M. Ransom,
P. S. Ray,
R. Shannon,
G. Theureau,
N. Webb
[show abstract]
[hide abstract]
ABSTRACT: 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
2051-0827. 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 the latter is firmly detected, we an only give
upper limits for the X-ray flux of the former. There are no dedicated X-ray
observations available for the other 3 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 which 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. As well, we also observe a trend
towards very low, or undetectable, radio linear polarisation 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.
12/2012;
-
H J Pletsch,
L Guillemot,
H Fehrmann,
B Allen,
M Kramer,
C Aulbert,
M Ackermann,
M Ajello,
A de Angelis,
W B Atwood, [......],
J Vandenbroucke,
V Vasileiou,
G Vianello,
V Vitale,
A P Waite,
B L Winer,
K S Wood,
M Wood,
Z Yang,
S Zimmer
[show abstract]
[hide abstract]
ABSTRACT: Millisecond pulsars, old neutron stars spun-up by accreting matter from a companion star, can reach high rotation rates of hundreds of revolutions per second. Until now, all such "recycled" rotation-powered pulsars have been detected by their spin-modulated radio emission. In a computing-intensive blind search of gamma-ray data from the Fermi Large Area Telescope (with partial constraints from optical data), we detected a 2.5-millisecond pulsar, PSR J1311-3430. This unambiguously explains a formerly unidentified gamma-ray source that had been a decade-long enigma, confirming previous conjectures. The pulsar is in a circular orbit with an orbital period of only 93 minutes, the shortest of any spin-powered pulsar binary ever found.
Science 10/2012; · 31.20 Impact Factor
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R. Rousseau,
M. -H. Grondin,
A. Van Etten,
M. Lemoine-Goumard,
S. Bogdanov,
J. W. T. Hessels,
V. M. Kaspi,
Z. Arzoumanian,
F. Camilo,
J. M. Casandjian,
C. M. Espinoza,
S. Johnston,
A. G. Lyne, D. A. Smith,
B. W. Stappers,
G. A. Caliandro
[show abstract]
[hide abstract]
ABSTRACT: Since its launch, the Fermi satellite has firmly identified 5 pulsar wind
nebulae plus a large number of candidates, all powered by young and energetic
pulsars. HESS J1857+026 is a spatially extended gamma-ray source detected by
H.E.S.S. and classified as a possible pulsar wind nebula candidate powered by
PSR J1856+0245. We search for gamma-ray pulsations from PSR J1856+0245 and
explore the characteristics of its associated pulsar wind nebula. Using a
rotational ephemeris obtained from the Lovell telescope at Jodrell Bank
Observatory at 1.5 GHz, we phase-fold 36 months of gamma-ray data acquired by
the Large Area Telescope (LAT) aboard Fermi. We also perform a complete
gamma-ray spectral and morphological analysis. No gamma-ray pulsations were
detected from PSR J1856+0245. However, significant emission is detected at a
position coincident with the TeV source HESS J1857+026. The gamma-ray spectrum
is well described by a simple power-law with a spectral index of 1.53 \pm
0.11_{\rm stat} \pm 0.55_{\rm syst}$ and an energy flux of $G(0.1$--100
GeV$)=(2.71 \pm 0.52_{\rm stat} \pm 1.51_{\rm syst}) \times 10^{-11}$ ergs
cm$^{-2}$ s$^{-1}$. The $\gamma$-ray luminosity is $L_{PWN}^{\gamma} (0.1$--100
GeV$)=(2.5 \pm 0.5_{stat} \pm 1.5_{syst}) \times 10^{35} (\frac{d}{9 kpc})^2$
ergs s$^{-1}$, assuming a distance of 9 kpc. This implies a $\gamma-$ray
efficiency of $\sim$ 5% for $\dot{E}=4.6 \times 10^{36}$ erg $s^{-1}$, in the
range expected for pulsar wind nebulae. Detailed multi-wavelength modeling
provides new constraints on its pulsar wind nebula nature.
06/2012;
-
P. S. Ray,
A. A. Abdo,
D. Parent,
D. Bhattacharya,
B. Bhattacharyya,
F. Camilo,
I. Cognard,
G. Theureau,
E. C. Ferrara,
A. K. Harding, [......],
M. Kramer,
M. A. McLaughlin,
S. M. Ransom,
M. S. E. Roberts,
P. M. Saz Parkinson,
M. Ziegler, D. A. Smith,
B. W. Stappers,
P. Weltevrede,
K. S. Wood
[show abstract]
[hide abstract]
ABSTRACT: We present a summary of the Fermi Pulsar Search Consortium (PSC), an
international collaboration of radio astronomers and members of the Large Area
Telescope (LAT) collaboration, whose goal is to organize radio follow-up
observations of Fermi pulsars and pulsar candidates among the LAT gamma-ray
source population. The PSC includes pulsar observers with expertise using the
world's largest radio telescopes that together cover the full sky. We have
performed very deep observations of all 35 pulsars discovered in blind
frequency searches of the LAT data, resulting in the discovery of radio
pulsations from four of them. We have also searched over 300 LAT gamma-ray
sources that do not have strong associations with known gamma-ray emitting
source classes and have pulsar-like spectra and variability characteristics.
These searches have led to the discovery of a total of 43 new radio millisecond
pulsars (MSPs) and four normal pulsars. These discoveries greatly increase the
known population of MSPs in the Galactic disk, more than double the known
population of so-called `black widow' pulsars, and contain many promising
candidates for inclusion in pulsar timing arrays.
05/2012;
-
P. L. Nolan,
A. A. Abdo,
M. Ackermann,
M. Ajello,
A. Allafort,
E. Antolini,
W. B. Atwood,
M. Axelsson,
L. Baldini,
J. Ballet, [......],
A. P. Waite,
E. Wallace,
P. Wang,
M. Werner,
B. L. Winer,
D. L. Wood,
K. S. Wood,
M. Wood,
Z. Yang,
and S. Zimmer
[show abstract]
[hide abstract]
ABSTRACT: We present the second catalog of high-energy γ-ray sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi), derived from data taken during the first 24 months of the science phase of the mission, which began on 2008 August 4. Source detection is based on the average flux over the 24 month period. The second Fermi-LAT catalog (2FGL) includes source location regions, defined in terms of elliptical fits to the 95% confidence regions and spectral fits in terms of power-law, exponentially cutoff power-law, or log-normal forms. Also included are flux measurements in five energy bands and light curves on monthly intervals for each source. Twelve sources in the catalog are modeled as spatially extended. We provide a detailed comparison of the results from this catalog with those from the first Fermi-LAT catalog (1FGL). Although the diffuse Galactic and isotropic models used in the 2FGL analysis are improved compared to the 1FGL catalog, we attach caution flags to 162 of the sources to indicate possible confusion with residual imperfections in the diffuse model. The 2FGL catalog contains 1873 sources detected and characterized in the 100 MeV to 100 GeV range of which we consider 127 as being firmly identified and 1171 as being reliably associated with counterparts of known or likely γ-ray-producing source classes.
The Astrophysical Journal Supplement Series 03/2012; 199(2):31. · 13.46 Impact Factor
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L. Guillemot,
P. C. C. Freire,
I. Cognard,
T. J. Johnson,
Y. Takahashi,
J. Kataoka,
G. Desvignes,
F. Camilo,
E. C. Ferrara,
A. K. Harding, [......],
M. Keith,
M. Kerr,
M. Kramer,
D. Parent,
S. M. Ransom,
P. S. Ray,
P. M. Saz Parkinson, D. A. Smith,
B. W. Stappers,
G. Theureau
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of the millisecond pulsar PSR J2043+1711 in a search
of a Fermi Large Area Telescope (LAT) source with no known associations, with
the Nancay Radio Telescope. The new pulsar, confirmed with the Green Bank
Telescope, has a spin period of 2.38 ms, is relatively nearby (d <~ 2 kpc), and
is in a 1.48 day orbit around a low mass companion, probably a He-type white
dwarf. Pulsed gamma-ray emission was detected in the data recorded by the Fermi
LAT. The gamma-ray light curve and spectral properties are typical of other
gamma-ray millisecond pulsars seen with Fermi. X-ray observations of the pulsar
with Suzaku and the Swift/XRT yielded no detection. At 1.4 GHz we observe
strong flux density variations because of interstellar diffractive
scintillation, however a sharp peak can be observed at this frequency during
bright scintillation states. At 327 MHz the pulsar is detected with a much
higher signal-to-noise ratio and its flux density is far more steady. However,
at that frequency the Arecibo instrumentation cannot yet fully resolve the
pulse profile. Despite that, our pulse time-of-arrival measurements have a
post-fit residual rms of 2 \mus. This and the expected stability of this system
has made PSR J2043+1711 one of the first new Fermi-selected millisecond pulsars
to be added to pulsar gravitational wave timing arrays. It has also allowed a
significant measurement of relativistic delays in the times of arrival of the
pulses due to the curvature of space-time near the companion, but not yet with
enough precision to derive useful masses for the pulsar and the companion. A
mass for the pulsar between 1.7 and 2.0 solar masses can be derived if a
standard millisecond pulsar formation model is assumed. In this article we also
present a comprehensive summary of pulsar searches in Fermi LAT sources with
the Nancay Radio Telescope to date.
02/2012;
-
L. Guillemot,
T. J. Johnson,
C. Venter,
M. Kerr,
B. Pancrazi,
M. Livingstone,
G. H. Janssen,
P. Jaroenjittichai,
M. Kramer,
I. Cognard, [......],
P. F. Michelson,
A. Noutsos,
D. Parent,
S. M. Ransom,
P. S. Ray,
R. Shannon, D. A. Smith,
G. Theureau,
S. E. Thorsett,
and N. Webb
[show abstract]
[hide abstract]
ABSTRACT: We report the detection of pulsed gamma-ray emission from the fast millisecond pulsars (MSPs) B1937+21 (also known as J1939+2134) and B1957+20 (J1959+2048) using 18 months of survey data recorded by the Fermi Large Area Telescope and timing solutions based on radio observations conducted at the Westerbork and Nançay radio telescopes. In addition, we analyzed archival Rossi X-ray Timing Explorer and XMM-Newton X-ray data for the two MSPs, confirming the X-ray emission properties of PSR B1937+21 and finding evidence (~4σ) for pulsed emission from PSR B1957+20 for the first time. In both cases the gamma-ray emission profile is characterized by two peaks separated by half a rotation and are in close alignment with components observed in radio and X-rays. These two pulsars join PSRs J0034–0534 and J2214+3000 to form an emerging class of gamma-ray MSPs with phase-aligned peaks in different energy bands. The modeling of the radio and gamma-ray emission profiles suggests co-located emission regions in the outer magnetosphere.
The Astrophysical Journal 12/2011; 744(1):33. · 6.02 Impact Factor
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P. C. C. Freire,
A. A. Abdo,
M. Ajello,
A. Allafort,
J. Ballet,
G. Barbiellini,
D. Bastieri,
K. Bechtol,
R. Bellazzini,
R. D. Blandford, [......],
C. Venter,
G. Vianello,
N. Vilchez,
V. Vitale,
A. P. Waite,
P. Wang,
K. S. Wood,
Z. Yang,
M. Ziegler,
S. Zimmer
[show abstract]
[hide abstract]
ABSTRACT: We report on the Fermi Large Area Telescope’s detection of γ-ray (>100 mega–electron volts) pulsations from pulsar J1823–3021A
in the globular cluster NGC 6624 with high significance (∼7 σ). Its γ-ray luminosity, Lγ = (8.4 ± 1.6) × 1034 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 γ-ray MSPs, not ∼100 as previously
estimated. The γ-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.
Science 11/2011; 334(6059):1107-1110. · 31.20 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Forty six gamma-ray pulsars were reported in the First Fermi Large Area
Telescope (LAT) Catalog of Gamma-ray Pulsars. Over forty more have been seen
since then. A simple but effective figure-of-merit for gamma-detectability is
sqrt(Edot)/d^2, where Edot is the pulsar spindown power and d the distance. We
are tracking down the best gamma-ray candidates not yet seen. We present the
timing and spectral analysis results of some new high spindown power, nearby
gamma-ray pulsars. We also update some population distribution plots in
preparation for the 2nd Fermi LAT gamma-ray Pulsar Catalog.
10/2011;
-
M. Lemoine-Goumard,
V. E. Zavlin,
M.-H. Grondin,
R. Shannon, D A Smith,
M. Burgay,
F. Camilo,
J Cohen-Tanugi,
P. C. C. Freire,
J. E. Grove, [......],
M Kramer,
R. N. Manchester,
P. F. Michelson,
D. Parent,
A. Possenti,
P. S. Ray,
M. Renaud,
S. E. Thorsett,
P. Weltevrede,
M. T. Wolff
[show abstract]
[hide abstract]
ABSTRACT: Since the launch of the Fermi satellite, the number of known gamma-ray
pulsars has increased tenfold. Most gamma-ray detected pulsars are young and
energetic, and many are associated with TeV sources. PSR J1357-6429 is a high
spin-down power pulsar (Edot = 3.1 * 10^36 erg/s), discovered during the Parkes
multibeam survey of the Galactic plane, with significant timing noise typical
of very young pulsars. In the very-high-energy domain, H.E.S.S. has reported
the detection of the extended source HESS J1356-645 (intrinsic Gaussian width
of 12') whose centroid lies 7' from PSR J1357-6429. Using a rotational
ephemeris obtained with 74 observations made with the Parkes telescope at 1.4
GHz, we phase-fold more than two years of gamma-ray data acquired by Fermi-LAT
as well as those collected with XMM-Newton, and perform gamma-ray spectral
modeling. Significant gamma and X-ray pulsations are detected from PSR
J1357-6429. The light curve in both bands shows one broad peak. Gamma-ray
spectral analysis of the pulsed emission suggests that it is well described by
a simple power-law of index 1.5 +/- 0.3stat +/- 0.3syst with an exponential
cut-off at 0.8 +/- 0.3stat +/- 0.3syst GeV and an integral photon flux above
100 MeV of (6.5 +/- 1.6stat +/- 2.3syst) * 10^-8 cm^-2 s^-1. The X-ray spectra
obtained from the new data provide results consistent with those reported by
Zavlin (2007). Upper limits on the gamma-ray emission from its potential pulsar
wind nebula (PWN) are also reported. Assuming a distance of 2.4 kpc, the Fermi
LAT energy flux yields a gamma-ray luminosity for PSR J1357-6429 of L_gamma =
(2.13 +/- 0.25stat +/- 0.83syst) * 10^34 erg/s, consistent with an L_gamma
\propto sqrt(Edot) relationship. The Fermi non-detection of the pulsar wind
nebula associated with HESS J1356-645 provides new constraints on the electron
population responsible for the extended TeV emission.
07/2011;
-
[show abstract]
[hide abstract]
ABSTRACT: Most pulsars observed by the Fermi LAT have gamma-ray luminosities scaling
with spindown power Edot as L_gamma (Edot x 10^33 erg/s)^{1/2}. However, there
exist one detection and several upper limits an order of magnitude or more
fainter than this trend. We describe these `sub-luminous' gamma-ray pulsars,
and discuss the case for this being an orientation effect. Of the 12 known
young radio pulsars with Edot>10^34 erg/s and d<2kpc several are substantially
sub-luminous. The limited available geometrical constraints favor aligned
geometries for these pulsars, although no one case for alignment is compelling.
In this scenario GeV emission detected from such sub-luminous pulsars can be
due to a lower altitude, lower-power accelerator gap.
06/2011;
-
M. J. Keith,
S. Johnston,
P. S. Ray,
E. C. Ferrara,
P. M. Saz Parkinson,
Ö. Çelik,
A. Belfiore,
D. Donato,
C. C. Cheung,
A. A. Abdo, [......],
L. Guillemot,
A. K. Harding,
M. Kramer,
P. F. Michelson,
S. M. Ransom,
R. W. Romani, D. A. Smith,
D. J. Thompson,
P. Weltevrede,
K. S. Wood
[show abstract]
[hide abstract]
ABSTRACT: 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.
Monthly Notices of the Royal Astronomical Society 06/2011; 414(2):1292 - 1300. · 4.90 Impact Factor
-
I. Cognard,
L. Guillemot,
T. J. Johnson, D A Smith,
C. Venter,
A. K. Harding,
M. T. Wolff,
C. C. Cheung,
D. Donato,
A. A. Abdo, [......],
D. Parent,
S. M. Ransom,
P. S. Ray,
R. W. Romani,
P. M. Saz Parkinson,
B. W. Stappers,
G. Theureau,
D. J. Thompson,
P. Weltevrede,
K. S. Wood
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery of two millisecond pulsars in a search for radio
pulsations at the positions of \emph{Fermi Large Area Telescope} sources with
no previously known counterparts, using the Nan\c{c}ay radio telescope. The two
millisecond pulsars, PSRs J2017+0603 and J2302+4442, have rotational periods of
2.896 and 5.192 ms and are both in binary systems with low-eccentricity orbits
and orbital periods of 2.2 and 125.9 days respectively, suggesting long
recycling processes. Gamma-ray pulsations were subsequently detected for both
objects, indicating that they power the associated \emph{Fermi} sources in
which they were found. The gamma-ray light curves and spectral properties are
similar to those of previously-detected gamma-ray millisecond pulsars. Detailed
modeling of the observed radio and gamma-ray light curves shows that the
gamma-ray emission seems to originate at high altitudes in their
magnetospheres. Additionally, X-ray observations revealed the presence of an
X-ray source at the position of PSR J2302+4442, consistent with thermal
emission from a neutron star. These discoveries along with the numerous
detections of radio-loud millisecond pulsars in gamma rays suggest that many
\emph{Fermi} sources with no known counterpart could be unknown millisecond
pulsars.
02/2011;
-
M. J. Keith,
S. Johnston,
P. S. Ray,
E. C. Ferrara,
P. M. Saz Parkinson,
O. Celik,
A. Belfiore,
D. Donato,
C. C. Cheung,
A. A. Abdo, [......],
L. Guillemot,
A. K. Harding,
M Kramer,
P. F. Michelson,
S. M. Ransom,
R. W. Romani, D A Smith,
D. J. Thompson,
P. Weltevrede,
K. S. Wood
[show abstract]
[hide abstract]
ABSTRACT: Using the Parkes radio telescope we have carried out deep observations of
eleven 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 gammaray pulsars discovered by the Fermi satellite to a
level of - 0.04 mJy (for pulsars with a 10% duty cycle). Timing of the
millisecond pulsar PSR J1103-5403 has shown that its position is 9' 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 hour orbital period. The
relatively high flux density and low dispersion measure of PSR J2241-5236 makes
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
exponential cutoff, and phasebinning with the radio ephemeris results in a
multi-peaked gamma-ray pulse profile. Observations with Chandra have identified
a coincident X-ray source within 0.1" of the position of the pulsar obtained by
radio timing
02/2011;
-
A. Noutsos,
A. A. Abdo,
M. Ackermann,
M. Ajello,
J. Ballet,
G. Barbiellini,
M. G. Baring,
D. Bastieri,
K. Bechtol,
R. Bellazzini, [......],
M. Villata,
V Vitale,
A. von Kienlin,
A P Waite,
P Wang,
K. Watters,
P. Weltevrede,
B. L. Winer,
K. S. Wood,
M Ziegler
[show abstract]
[hide abstract]
ABSTRACT: We report on the first year of Fermi gamma-ray observations of pulsed high-energy emission from the old PSR J2043+2740. The study of the gamma-ray efficiency of such old pulsars gives us an insight into the evolution of pulsars' ability to emit in gammma rays as they age. The gamma-ray lightcurve of this pulsar above 0.1 GeV is clearly defined by two sharp peaks, 0.353+/-0.035 periods apart. We have combined the gamma-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 and an Outer Gap model. The ranges of magnetic inclination and viewing angle were determined to be {alpha,zeta}~{52-57,61-68} for the Two Pole Caustic model, and {alpha,zeta}~{62-73,74-81} and {alpha,zeta}~{72-83,60-75} for the Outer Gap 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, gamma-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 5 and 10 times less energetic, respectively. Comment: 17 pages, 6 figures, Accepted for publication in ApJ
12/2010;
-
G. Theureau,
D. Parent,
I. Cognard,
G. Desvignes, D A Smith,
J. M. Casandjian,
C. C. Cheung,
H. A. Craig,
D. Donato,
R. Foster,
L. Guillemot,
A. K. Harding,
J. -F. Lestrade,
P. S. Ray,
R. W. Romani,
D. J. Thompson,
W. W. Tian,
K. Watters
[show abstract]
[hide abstract]
ABSTRACT: Pulsars PSR J0248+6021 (rotation period P=217 ms and spin-down power Edot = 2.13E35 erg/s) and PSR J2240+5832 (P=140 ms, Edot = 2.12E35 erg/s) were discovered in 1997 with the Nancay radio telescope during a northern Galactic plane survey, using the Navy-Berkeley Pulsar Processor (NBPP) filter bank. GeV gamma-ray pulsations from both were discovered using the Fermi Large Area Telescope. Twelve years of radio and polarization data allow detailed investigations. The two pulsars resemble each other both in radio and in gamma-ray data. Both are rare in having a single gamma-ray pulse offset far from the radio peak. The high dispersion measure for PSR J0248+6021 (DM = 370 pc cm^-3) is most likely due to its being within the dense, giant HII region W5 in the Perseus arm at a distance of 2 kpc, not beyond the edge of the Galaxy as obtained from models of average electron distributions. Its high transverse velocity and the low magnetic field along the line-of-sight favor this small distance. Neither gamma-ray, X-ray, nor optical data yield evidence for a pulsar wind nebula surrounding PSR J0248+6021. The gamma-ray luminosity for PSR J0248+6021 is L_ gamma = (1.4 \pm 0.3)\times 10^34 erg/s. For PSR J2240+5832, we find either L_gamma = (7.9 \pm 5.2) \times 10^34 erg/s if the pulsar is in the Outer arm, or L_gamma = (2.2 \pm 1.7) \times 10^34 erg/s for the Perseus arm. These luminosities are consistent with an L_gamma ~ sqrt(Edot) rule. Comparison of the gamma-ray pulse profiles with model predictions, including the constraints obtained from radio polarization data, favor emission in the far magnetosphere. These two pulsars differ mainly in their inclination angles and acceleration gap widths, which in turn explains the observed differences in the gamma-ray peak widths. Comment: 13 pages, Accepted to Astronomy & Astrophysics
10/2010;
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A A Abdo,
M Ackermann,
M Ajello,
W B Atwood,
L Baldini,
J Ballet,
G Barbiellini,
D Bastieri,
K Bechtol,
R Bellazzini, [......],
M Sasada,
V I Shenavrin,
S N Shore,
G K Skinner,
J Sokoloski,
M Stroh,
A M Tatarnikov,
M Uemura,
G M Wahlgren,
M Yamanaka
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ABSTRACT: Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from a companion star. Current physical models posit that shocked expanding gas from the nova shell can produce x-ray emission, but emission at higher energies has not been widely expected. Here, we report the Fermi Large Area Telescope detection of variable gamma-ray emission (0.1 to 10 billion electron volts) from the recently detected optical nova of the symbiotic star V407 Cygni. We propose that the material of the nova shell interacts with the dense ambient medium of the red giant primary and that particles can be accelerated effectively to produce pi(0) decay gamma-rays from proton-proton interactions. Emission involving inverse Compton scattering of the red giant radiation is also considered and is not ruled out.
Science 08/2010; 329(5993):817-21. · 31.20 Impact Factor
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P. M. Saz Parkinson,
M. Dormody,
M Ziegler,
P. S. Ray,
A. A. Abdo,
J. Ballet,
M. G. Baring,
A. Belfiore,
T H Burnett,
G. A. Caliandro, [......],
D. Parent,
S. M. Ransom,
O. Reimer,
R. W. Romani, D A Smith,
D. J. Thompson,
K. Watters,
P. Weltevrede,
M. T. Wolff,
K. S. Wood
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ABSTRACT: We report the discovery of eight gamma-ray pulsars in blind frequency searches using the LAT, onboard the Fermi Gamma-ray Space Telescope. Five of the eight pulsars are young (tau_c<100 kyr), energetic (Edot>10^36 erg/s), and located within the Galactic plane (|b|<3 deg). The remaining three are older, less energetic, and located off the plane. Five pulsars are associated with sources included in the LAT bright gamma-ray source list, but only one, PSR J1413-6205, is clearly associated with an EGRET source. PSR J1023-5746 has the smallest characteristic age (tau_c=4.6 kyr) and is the most energetic (Edot=1.1E37 erg/s) of all gamma-ray pulsars discovered so far in blind searches. PSRs J1957+5033 and J2055+25 have the largest characteristic ages (tau_c~1 Myr) and are the least energetic (Edot~5E33 erg/s) of the newly-discovered pulsars. We present the timing models, light curves, and detailed spectral parameters of the new pulsars. We used recent XMM observations to identify the counterpart of PSR J2055+25 as XMMU J205549.4+253959. In addition, publicly available archival Chandra X-ray data allowed us to identify the likely counterpart of PSR J1023-5746 as a faint, highly absorbed source, CXOU J102302.8-574606. The large X-ray absorption indicates that this could be among the most distant gamma-ray pulsars detected so far. PSR J1023-5746 is positionally coincident with the TeV source HESS J1023-575, located near the young stellar cluster Westerlund 2, while PSR J1954+2836 is coincident with a 4.3 sigma excess reported by Milagro at a median energy of 35 TeV. Deep radio follow-up observations of the eight pulsars resulted in no detections of pulsations and upper limits comparable to the faintest known radio pulsars, indicating that these can be included among the growing population of radio-quiet pulsars in our Galaxy being uncovered by the LAT, and currently numbering more than 20. Comment: Submitted to ApJ
06/2010;
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A A Abdo,
M Ackermann,
M Ajello,
A Allafort,
E Antolini,
W B Atwood,
M Axelsson,
L Baldini,
J Ballet,
G Barbiellini, [......],
V Vitale,
A P Waite,
E Wallace,
P Wang,
K Watters,
B L Winer,
K S Wood,
Z Yang,
T Ylinen,
M Ziegler
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ABSTRACT: We present a catalog of high-energy gamma-ray sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi), during the first 11 months of the science phase of the mission, which began on 2008 August 4. The First Fermi-LAT catalog (1FGL) contains 1451 sources detected and characterized in the 100 MeV to 100 GeV range. Source detection was based on the average flux over the 11 month period, and the threshold likelihood Test Statistic is 25, corresponding to a significance of just over 4 sigma. The 1FGL catalog includes source location regions, defined in terms of elliptical fits to the 95% confidence regions and power-law spectral fits as well as flux measurements in five energy bands for each source. In addition, monthly light curves are provided. Using a protocol defined before launch we have tested for several populations of gamma-ray sources among the sources in the catalog. For individual LAT-detected sources we provide firm identifications or plausible associations with sources in other astronomical catalogs. Identifications are based on correlated variability with counterparts at other wavelengths, or on spin or orbital periodicity. For the catalogs and association criteria that we have selected, 630 of the sources are unassociated. Care was taken to characterize the sensitivity of the results to the model of interstellar diffuse gamma-ray emission used to model the bright foreground, with the result that 161 sources at low Galactic latitudes and toward bright local interstellar clouds are flagged as having properties that are strongly dependent on the model or as potentially being due to incorrectly modeled structure in the Galactic diffuse emission.
The Astrophysical Journal Supplement Series 06/2010; 188(2):405-436. · 13.46 Impact Factor
