scholarly journals A blazar as the likely counterpart to 4FGL J0647.7−4418 instead of a gamma-ray binary

2020 ◽  
Vol 492 (3) ◽  
pp. 4291-4297
Author(s):  
Josep Martí ◽  
Estrella Sánchez-Ayaso ◽  
Pedro L Luque-Escamilla ◽  
Josep M Paredes ◽  
Valentí Bosch-Ramon ◽  
...  
Keyword(s):  
White Dwarf ◽  
Active Galactic Nucleus ◽  
Gamma Ray ◽  
Confidence Ellipse ◽  
Stellar Association ◽  
X Ray ◽  
Alternative Identification

ABSTRACT The persistent gamma-ray source 4FGL J0647.7−4418 is tentatively associated in the latest Fermi catalogue with the subdwarf O-type X-ray binary HD 49798. However, an active galactic nucleus (AGN) candidate is also mentioned as an alternative identification in updated versions of the catalogue accompanying paper. If the first association were correct, this would add HD 49798 to the handful of currently known gamma-ray binaries, and therefore represent a significant breakthrough not only because of a new member addition, but also because of the apparent white dwarf companion in this system. Despite these perspectives, here, we show that the stellar association is likely wrong and that the proposed AGN object, well inside the Fermi 95 per cent confidence ellipse, is a more conceivable counterpart candidate to the Fermi source due to its strong blazar similarities.

scholarly journals Relativistic and Newtonian Shock Breakouts

2011 ◽  
Vol 7 (S279) ◽  
pp. 282-284
Author(s):  
Ehud Nakar
Keyword(s):  
White Dwarf ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Core Collapse ◽  
Theoretical Expectation ◽  
X Ray ◽  
Type Ia ◽  
Luminous Signal

AbstractObservations of the first light from a stellar explosion can open a window to a wealth of information on the progenitor system and the explosion itself. Here I briefly discuss the theoretical expectation of that emission, comparing Newtonian and relativistic breakouts. The former takes place in regular core-collapse supernovae (SNe) while the latter is expected in SNe that are associated with gamma-ray bursts (GRBs), extremely energetic SNe (e.g., SN2007bi) and white dwarf explosions (e.g., type Ia and .Ia SNe, accretion induced collapse). I present the characteristic observable signatures of both types of breakouts, when spherical. Finally, I discuss Newtonian shock breakouts through wind, which produce a very luminous signal, with an X-ray component that is weak around the breakout, and becomes brighter afterwards.

scholarly journals Magnetars and white dwarf pulsars

2016 ◽  
Vol 25 (09) ◽  
pp. 1641025 ◽  
Author(s):  
Ronaldo V. Lobato ◽  
Manuel Malheiro ◽  
Jaziel G. Coelho
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
White Dwarf ◽  
Alternative Model ◽  
Gamma Ray ◽  
X Ray ◽  
Surface Magnetic Field ◽  
Rotation Periods ◽  
Strong Surface

The anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are a class of pulsars understood as neutron stars (NSs) with super strong surface magnetic fields, namely [Formula: see text][Formula: see text]G, and for that reason are known as magnetars. However, in the last years, some SGRs/AXPs with low surface magnetic fields [Formula: see text]–[Formula: see text][Formula: see text]G have been detected, challenging the magnetar description. Moreover, some fast and very magnetic white dwarfs (WDs) have also been observed, and at least one showed X-ray energy emission as an ordinary pulsar. Following this fact, an alternative model based on WDs pulsars has been proposed to explain this special class of pulsars. In this model, AXPs and SGRs as dense and magnetized WDs can have surface magnetic field [Formula: see text]–[Formula: see text] G and rotate very fast with frequencies [Formula: see text][Formula: see text]rad/s, consistent with the observed rotation periods [Formula: see text]–12)[Formula: see text]s.

scholarly journals Soft gamma-ray selected giant radio galaxies: an update

2020 ◽  
Vol 500 (3) ◽  
pp. 3111-3122
Author(s):  
L Bassani ◽  
F Ursini ◽  
A Malizia ◽  
G Bruni ◽  
F Panessa ◽  
...  
Keyword(s):  
Active Galactic Nucleus ◽  
Gamma Ray ◽  
Radio Galaxies ◽  
X Ray ◽  
The Past ◽  
First Time ◽  
Candidate Object

ABSTRACT We present an update on the sample of soft gamma-ray selected giant radio galaxies (GRGs) extracted from INTEGRAL/IBIS and Swift/BAT surveys; it includes eight new sources and one candidate object. In the new sample, all but one source display FR II radio morphologies; the only exception is B21144+35B, which is an FR I. The objects belong to both type 1 and type 2 active galactic nucleus (AGN) optical classes and have redshifts in the range 0.06–0.35, while the radio sizes span from 0.7 to 1 Mpc. In this study, we present for the first time two objects that were never discussed as GRGs before and propose a new candidate GRG. We confirm the correlation between the X-ray luminosity and the radio core luminosity found for other soft gamma-ray selected GRGs and expected for AGNs powered by efficient accretion. We also corroborate previous results that indicate that the luminosity of the radio lobes is relatively low compared with the nuclear X-ray emission. This supports the idea that the nucleus of these GRGs is now more powerful than in the past, consistent with a restarting activity scenario.

scholarly journals SIMILARITIES OF SGRs WITH LOW MAGNETIC FIELD AND WHITE DWARF PULSARS

2012 ◽  
Vol 18 ◽  
pp. 96-100 ◽  
Author(s):  
J. G. COELHO ◽  
M. MALHEIRO
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
White Dwarf ◽  
Alternative Explanation ◽  
Gamma Ray ◽  
Strong Magnetic Fields ◽  
X Ray ◽  
Surface Magnetic Field ◽  
Astrophysical Objects ◽  
Low Magnetic Field

Some of the most interesting types of astrophysical objects that have been intensively studied in the recent years are the Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) seen usually as neutron stars pulsars with super strong magnetic fields. However, in the last two years two SGRs with low magnetic fields have been detected. Moreover, fast and very magnetic white dwarf pulsars have also been observed in the last years. Based on these new pulsar discoveries, white dwarf pulsars have been proposed as an alternative explanation to the observational features of SGRs and AXPs. Here we present several properties of these SGRs/AXPs as WD pulsar, in particular the surface magnetic field and the magnetic dipole momentum.

scholarly journals X-RAY EMISSION FROM AN ASYMMETRIC BLAST WAVE AND A MASSIVE WHITE DWARF IN THE GAMMA-RAY EMITTING NOVA V407 Cyg

2012 ◽  
Vol 748 (1) ◽  
pp. 43 ◽  
Author(s):  
Thomas Nelson ◽  
Davide Donato ◽  
Koji Mukai ◽  
Jennifer Sokoloski ◽  
Laura Chomiuk
Keyword(s):  
Blast Wave ◽  
White Dwarf ◽  
Gamma Ray ◽  
X Ray

FLASH X-RAY DEVICES FOR PUMPING NUCLEAR MATERIALS DEVELOPED IN THE GAMMA-RAY LASER PROGRAM AT TEXAS

1987 ◽  
Vol 48 (C9) ◽  
pp. C9-367-C9-370
Author(s):  
C. B. COLLINS ◽  
F. DAVANLOO ◽  
T. S. BOWEN ◽  
J. J. COOGAN
Keyword(s):  
Gamma Ray ◽  
Nuclear Materials ◽  
X Ray

Digital pulse processor for spectrometry of charged particles, neutrons, x-ray, and gamma-ray

2003 ◽  
Vol 8 (5-6) ◽  
pp. 60-64
Author(s):  
A.I. Arkhangelsky ◽  
◽  
Yu.D. Kotov ◽  
P.Yu. Chistiakov ◽  
◽  
...  
Keyword(s):  
Gamma Ray ◽  
Charged Particles ◽  
X Ray ◽  
Digital Pulse

A Combined Model for the X‐Ray to Gamma‐Ray Emission of Cygnus X‐1

1998 ◽  
Vol 502 (1) ◽  
pp. 428-436 ◽  
Author(s):  
Igor V. Moskalenko ◽  
Werner Collmar ◽  
Volker Schonfelder
Keyword(s):  
Gamma Ray ◽  
Combined Model ◽  
X Ray ◽  
Gamma Ray Emission

scholarly journals Aperiodic Flux Variability in A 0535+262

1996 ◽  
Vol 165 ◽  
pp. 313-319
Author(s):  
Mark H. Finger ◽  
Robert B. Wilson ◽  
B. Alan Harmon ◽  
William S. Paciesas
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Beat Frequency ◽  
Power Spectra ◽  
Center Frequency ◽  
X Ray ◽  
Binary Pulsar ◽  
Transient Source ◽  
Flux Variability ◽  
Burst And Transient Source

A “giant” outburst of A 0535+262, a transient X-ray binary pulsar, was observed in 1994 February and March with the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma-Ray Observatory. During the outburst power spectra of the hard X-ray flux contained a QPO-like component with a FWHM of approximately 50% of its center frequency. Over the course of the outburst the center frequency rose smoothly from 35 mHz to 70 mHz and then fell to below 40 mHz. We compare this QPO frequency with the neutron star spin-up rate, and discuss the observed correlation in terms of the beat frequency and Keplerian frequency QPO models in conjunction with the Ghosh-Lamb accretion torque model.

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