Correlations between Spectral Properties and Spin-down Rate in Soft Gamma-Ray Repeaters and Anomalous X-Ray Pulsars

AbstractSoft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are peculiar X-ray sources which are believed to be magnetars: ultra-magnetized neutron stars which emission is dominated by surface fields (often in excess of 1E14 G, i.e. well above the QED threshold).Spectral analysis is an important tool in magnetar astrophysics since it can provide key information on the emission mechanisms. The first attempts at modelling the persistent (i.e. outside bursts) soft X-ray (¡10 keV) spectra of AXPs proved that a model consisting of a blackbody (kT 0.3-0.6 keV) plus a power-law (photon index 2-4) could successfully reproduce the observed emission. Moreover, INTEGRAL observations have shown that, while in quiescence, magnetars emit substantial persistent radiation also at higher energies, up to a few hundreds of keV. However, a convincing physical interpretation of the various spectral components is still missing.In this talk I will focus on the interpretation of magnetar spectral properties during quiescence. I will summarise the present status of the art and the currents attempts to model the broadband persistent emission of magnetars (from IR to hard Xrays) within a self consistent, physical scenario.

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THE INTERPLAY OF PROMPT AND AFTERGLOW EMISSION IN GRB 060418

International Journal of Modern Physics D ◽

10.1142/s0218271808012899 ◽

2008 ◽

Vol 17 (09) ◽

pp. 1343-1349 ◽

Cited By ~ 2

Author(s):

S. D. VERGANI ◽

D. MALESANI ◽

E. MOLINARI

Keyword(s):

Gamma Rays ◽

Spectral Properties ◽

Gamma Ray ◽

Early Time ◽

Lorentz Factor ◽

X Ray ◽

Central Engine ◽

Low Energies ◽

Prompt Emission

We present observations of the early afterglow emission of GRB 060418. Thanks to the simultaneous coverage at optical, X-ray and gamma-ray wavelengths, we can detect and separate the external shock emission (visible in the optical and late X-ray data) and the central engine activity (early X and gamma rays). The two components are clearly distinguished based on temporal and spectral properties. The detection of the afterglow onset (in the optical) allows the determination of the fundamental fireball properties, namely its bulk Lorentz factor and total energy. The early time X-ray flare closely resembles the prompt emission gamma-ray pulses in its temporal profile, being wider at low energies and showing lags between the hard and soft bands. This provides a strong suggestion that X-ray flares are a continuation of the prompt emission.

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Spectral Properties of the Prompt X-ray Emission and Afterglow from the Gamma-Ray Burst of 1997 February 28

The Astrophysical Journal ◽

10.1086/311132 ◽

1998 ◽

Vol 493 (2) ◽

pp. L67-L70 ◽

Cited By ~ 44

Author(s):

F. Frontera ◽

E. Costa ◽

L. Piro ◽

J. M. Muller ◽

L. Amati ◽

...

Keyword(s):

Spectral Properties ◽

Gamma Ray ◽

Gamma Ray Burst ◽

X Ray

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A Review of Gamma-Ray Burst Observations

Symposium - International Astronomical Union ◽

10.1017/s007418090016125x ◽

1987 ◽

Vol 125 ◽

pp. 477-487

Author(s):

W. Doyle Evans ◽

John G. Laros

Keyword(s):

Neutron Stars ◽

Spectral Properties ◽

Gamma Ray ◽

Gamma Ray Bursts ◽

Gamma Ray Burst ◽

X Ray

Gamma-ray bursts are generally believed to originate in the vicinity of neutron stars, but the phenomenology is still not understood. In this paper we review the known characteristics of gamma bursts and give new observational results on temporal and spectral properties. We suggest that a class of repeating bursters exists that are spectrally harder than x-ray bursters but significantly softer than “classical” gamma bursts. The March 5, 1979, burst may be the prototype of this class of bursters.

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The First Survey of X‐Ray Flares from Gamma‐Ray Bursts Observed bySwift: Spectral Properties and Energetics

The Astrophysical Journal ◽

10.1086/523296 ◽

2007 ◽

Vol 671 (2) ◽

pp. 1921-1938 ◽

Cited By ~ 126

Author(s):

A. D. Falcone ◽

D. Morris ◽

J. Racusin ◽

G. Chincarini ◽

A. Moretti ◽

...

Keyword(s):

Spectral Properties ◽

Gamma Ray ◽

Gamma Ray Bursts ◽

X Ray

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A new hard X-ray-selected sample of extreme high-energy peaked BL Lac objects and their TeV gamma-ray properties

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz812 ◽

2019 ◽

Vol 486 (2) ◽

pp. 1741-1762 ◽

Cited By ~ 12

Author(s):

L Foffano ◽

E Prandini ◽

A Franceschini ◽

S Paiano

Keyword(s):

Spectral Properties ◽

Gamma Ray ◽

Spectral Energy Distribution ◽

Broad Band ◽

High Energy ◽

Spectral Energy ◽

X Rays ◽

Bl Lac Objects ◽

X Ray ◽

Bl Lac

ABSTRACT Extreme high-energy peaked BL Lac objects (EHBLs) are an emerging class of blazars with exceptional spectral properties. The non-thermal emission of the relativistic jet peaks in the spectral energy distribution (SED) plot with the synchrotron emission in X-rays and with the gamma-ray emission in the TeV range or above. These high photon energies may represent a challenge for the standard modelling of these sources. They are important for the implications on the indirect measurements of the extragalactic background light, the intergalactic magnetic field estimate, and the possible origin of extragalactic high-energy neutrinos. In this paper, we perform a comparative study of the multiwavelength spectra of 32 EHBL objects detected by the Swift-BAT telescope in the hard X-ray band and by the Fermi-LAT telescope in the high-energy gamma-ray band. The source sample presents uniform spectral properties in the broad-band SEDs, except for the TeV gamma-ray band where an interesting bimodality seems to emerge. This suggests that the EHBL class is not homogeneous, and a possible subclassification of the EHBLs may be unveiled. Furthermore, in order to increase the number of EHBLs and settle their statistics, we discuss the potential detectability of the 14 currently TeV gamma-ray undetected sources in our sample by the Cherenkov telescopes.

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From the earliest pulses to the latest flares in long gamma-ray bursts

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732270 ◽

2018 ◽

Vol 615 ◽

pp. A80

Author(s):

A. Pescalli ◽

M. Ronchi ◽

G. Ghirlanda ◽

G. Ghisellini

Keyword(s):

Spectral Properties ◽

Gamma Ray ◽

Gamma Ray Bursts ◽

Peak Time ◽

Emission Pulse ◽

X Ray ◽

Temporal Properties ◽

Central Engine ◽

Prompt Emission ◽

Different Origin

The prompt emission of gamma-ray bursts extends from the early pulses observed in γ-rays (>15 keV) to very late flares of X-ray photons (0.3–10 keV). The duration of prompt γ-ray pulses is rather constant, while the width of X-ray flares correlates with their peak time, suggesting a possibly different origin. However, pulses and flares have similar spectral properties. Considering internal and external shock scenarios, we derive how the energy and duration of pulses scale with their time of occurrence, and we compare this with observations. The absence of an observed correlation between the prompt emission pulse duration and its time of occurrence favours an “internal” origin and confirms earlier results. We show that the energetic and temporal properties of X-ray flares are also consistent with being produced by internal shocks between slow fireballs with a small contrast between their bulk Lorentz factors. These results relax the requirement of a long-lasting central engine to explain the latest X-ray flares.

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