Blind Search Methods for Binary Gamma-ray Pulsars

AbstractGamma-ray observations by the Fermi Large Area Telescope (LAT) have been used very successfully in the last 9 years to detect more than 200 gamma-ray pulsars. Sixty of these have been found by directly searching for pulsations in the gamma-ray data, but only one binary MSP has been found this way. Pulsars in binaries are often difficult to detect in radio data because of large eclipses, and some binary MSPs may even be radio quiet. For those, a gamma-ray blind search might be the only possibility for detection. While searches for isolated pulsars up to kilohertz frequencies are already computationally very challenging, blind searches for binary gamma-ray pulsars are simply infeasible without further knowledge of their orbital parameters. Here we present methods with which we can conduct searches for candidate binary gamma-ray pulsars for which orbital constraints are known from optical observations of a likely companion star. We also highlight some example sources where these methods have been used.

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The Einstein@Home Survey for Gamma-ray Pulsars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317009231 ◽

2017 ◽

Vol 13 (S337) ◽

pp. 21-24

Author(s):

Colin J. Clark ◽

Jason Wu ◽

Holger J. Pletsch ◽

Lucas Guillemot

Keyword(s):

Large Scale ◽

Gamma Ray ◽

Large Fraction ◽

Computing System ◽

Data Reconstruction ◽

Volunteer Computing ◽

Radio Observations ◽

Large Area ◽

Space Telescope ◽

Blind Search

AbstractSince the launch of the Fermi Gamma-ray Space Telescope in 2008, the onboard Large Area Telescope (LAT) has detected gamma-ray pulsations from more than 200 pulsars. A large fraction of these remain undetected in radio observations, and could only be found by directly searching the LAT data for pulsations. However, the sensitivity of such “blind” searches is limited by the sparse photon data and vast computational requirements. In this contribution we present the latest large-scale blind-search survey for gamma-ray pulsars, which ran on the distributed volunteer computing system, Einstein@Home, and discovered 19 new gamma-ray pulsars. We explain how recent improvements to search techniques and LAT data reconstruction have boosted the sensitivity of blind searches, and present highlights from the survey’s discoveries. These include: two glitching pulsars; the youngest known radio-quiet gamma-ray pulsar; and two isolated millisecond pulsars (MSPs), one of which is the only known radio-quiet rotationally powered MSP.

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Einstein@Home Discovery of the Gamma-ray Millisecond Pulsar PSR J2039−5617 Confirms Its Predicted Redback Nature

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3484 ◽

2020 ◽

Author(s):

C J Clark ◽

L Nieder ◽

G Voisin ◽

B Allen ◽

C Aulbert ◽

...

Keyword(s):

Orbital Period ◽

Gamma Ray ◽

High Energy ◽

Orbital Parameter ◽

Directed Search ◽

Millisecond Pulsar ◽

Large Area ◽

Companion Star ◽

Parameter Constraints

Abstract The Fermi Large Area Telescope gamma-ray source 3FGL J2039.6−5618 contains a periodic optical and X-ray source that was predicted to be a “redback” millisecond pulsar (MSP) binary system. However, the conclusive identification required the detection of pulsations from the putative MSP. To better constrain the orbital parameters for a directed search for gamma-ray pulsations, we obtained new optical light curves in 2017 and 2018, which revealed long-term variability from the companion star. The resulting orbital parameter constraints were used to perform a targeted gamma-ray pulsation search using the Einstein@Home distributed volunteer computing system. This search discovered pulsations with a period of 2.65 ms, confirming the source as a binary MSP now known as PSR J2039−5617. Optical light curve modelling is complicated, and likely biased, by asymmetric heating on the companion star and long-term variability, but we find an inclination i ≳ 60 ○, for a low pulsar mass between 1.1 M⊙ < Mpsr < 1.6 M⊙, and a companion mass of 0.15–0.22 M⊙, confirming the redback classification. Timing the gamma-ray pulsations also revealed significant variability in the orbital period, which we find to be consistent with quadrupole moment variations in the companion star, suggestive of convective activity. We also find that the pulsed flux is modulated at the orbital period, potentially due to inverse Compton scattering between high-energy leptons in the pulsar wind and the companion star’s optical photon field.

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Blind Search Methods for Binary Gamma-ray Pulsars

10.22323/1.312.0014 ◽

2017 ◽

Author(s):

Lars Nieder ◽

Colin Clark ◽

Keyword(s):

Gamma Ray ◽

Search Methods ◽

Blind Search

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Distinguishing Photons from Muons using the Time-Over-Threshold in the Tracker from the Gamma Ray Large Area Space Telescope

10.2172/815654 ◽

2003 ◽

Author(s):

Renata A Rawlings

Keyword(s):

Gamma Ray ◽

Large Area ◽

Space Telescope

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On a Possible Origin of the Gamma-ray Excess around the Galactic Center

Symmetry ◽

10.3390/sym13081432 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1432

Author(s):

Dmitry O. Chernyshov ◽

Andrei E. Egorov ◽

Vladimir A. Dogiel ◽

Alexei V. Ivlev

Keyword(s):

Dark Matter ◽

Gamma Rays ◽

Molecular Clouds ◽

Alternative Explanation ◽

Gamma Ray ◽

Galactic Center ◽

The Self ◽

Large Area ◽

Mhd Turbulence ◽

The Standard Model

Recent observations of gamma rays with the Fermi Large Area Telescope (LAT) in the direction of the inner galaxy revealed a mysterious excess of GeV. Its intensity is significantly above predictions of the standard model of cosmic rays (CRs) generation and propagation with a peak in the spectrum around a few GeV. Popular interpretations of this excess are that it is due to either spherically distributed annihilating dark matter (DM) or an abnormal population of millisecond pulsars. We suggest an alternative explanation of the excess through the CR interactions with molecular clouds in the Galactic Center (GC) region. We assumed that the excess could be imitated by the emission of molecular clouds with depleted density of CRs with energies below ∼10 GeV inside. A novelty of our work is in detailed elaboration of the depletion mechanism of CRs with the mentioned energies through the “barrier” near the cloud edge formed by the self-excited MHD turbulence. This depletion of CRs inside the clouds may be a reason for the deficit of gamma rays from the Central Molecular Zone (CMZ) at energies below a few GeV. This in turn changes the ratio between various emission components at those energies and may potentially absorb the GeV excess by a simple renormalization of key components.

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Discovery of recombining plasma inside the extended gamma-ray supernova remnant HB9

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2461 ◽

2019 ◽

Vol 489 (3) ◽

pp. 4300-4310 ◽

Cited By ~ 5

Author(s):

A Sezer ◽

T Ergin ◽

R Yamazaki ◽

H Sano ◽

Y Fukui

Keyword(s):

Supernova Remnant ◽

Gamma Ray ◽

Radio Continuum ◽

Continuum Emission ◽

Large Area ◽

Imaging Spectrometer ◽

X Ray ◽

East Region ◽

X Ray Imaging ◽

Collisional Ionization

ABSTRACT We present the results from the Suzaku X-ray Imaging Spectrometer observation of the mixed-morphology supernova remnant (SNR) HB9 (G160.9+2.6). We discovered recombining plasma (RP) in the western Suzaku observation region and the spectra here are well described by a model having collisional ionization equilibrium (CIE) and RP components. On the other hand, the X-ray spectra from the eastern Suzaku observation region are best reproduced by the CIE and non-equilibrium ionization model. We discuss possible scenarios to explain the origin of the RP emission based on the observational properties and concluded that the rarefaction scenario is a possible explanation for the existence of RP. In addition, the gamma-ray emission morphology and spectrum within the energy range of 0.2–300 GeV are investigated using 10 yr of data from the Fermi Large Area Telescope (LAT). The gamma-ray morphology of HB9 is best described by the spatial template of radio continuum emission. The spectrum is well fit to a log-parabola function and its detection significance was found to be 25σ. Moreover, a new gamma-ray point source located just outside the south-east region of the SNR’s shell was detected with a significance of 6σ. We also investigated the archival H i and CO data and detected an expanding shell structure in the velocity range of $-10.5$ and $+1.8$ km s−1 that is coinciding with a region of gamma-ray enhancement at the southern rim of the HB9 shell.

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