New Evidence of Proton-Cyclotron Resonance in a Magnetar Strength Field from SGR 1806−20

Ibrahim, Alaa; Swank, J. H.; Parke, William C.

doi:10.1086/345774

Cited by 99 publications

(108 citation statements)

References 32 publications

(34 reference statements)

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“…Therefore, we consider it to be only marginal evidence of an absorption line. Note that the absorption features previously reported in some bursts from this source were at a slightly different energy of $5 keV (Ibrahim et al 2003).…”

Section: Analysis Of the Burstsmentioning

confidence: 50%

“…Interestingly, this scenario may provide an explanation for the transient appearance of a cyclotron line as that tentatively detected at 4 keV during the bursts seen with XMM-Newton and at 5 keV with RXTE (Ibrahim et al 2002(Ibrahim et al , 2003, at times when the source has a particularly large luminosity and hard spectrum. In fact, when the luminosity at !…”

Section: Discussionmentioning

confidence: 69%

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AnXMM‐NewtonView of the Soft Gamma Repeater SGR 1806−20: Long‐Term Variability in the Pre–Giant Flare Epoch

Mereghetti

Tiengo

Esposito

et al. 2005

ApJ

102

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The low-energy (<10 keV) X-ray emission of the soft gamma repeater SGR 1806À20 has been studied by means of four XMM-Newton observations carried out in the last two years, the latest performed in response to a strong sequence of hard X-ray bursts observed on 2004 October 5. The source was caught in different states of activity; over the [2003][2004] period, the 2-10 keV flux doubled with respect to the historical level observed previously. The long-term rise in luminosity was accompanied by a gradual hardening of the spectrum, with the power-law photon index decreasing from 2.2 to 1.5, and by a growth of the bursting activity. The pulse period measurements obtained in the four observations are consistent with an average spin-down rate of 5:5 ; 10 À10 s s À1 , higher than the values observed in the previous years. The long-term behavior of SGR 1806À20 exhibits the correlation between spectral hardness and spin-down rate previously found only by comparing the properties of different sources (both SGRs and anomalous X-ray pulsars

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Section: Analysis Of the Burstsmentioning

confidence: 50%

Section: Discussionmentioning

confidence: 69%

AnXMM‐NewtonView of the Soft Gamma Repeater SGR 1806−20: Long‐Term Variability in the Pre–Giant Flare Epoch

Mereghetti

Tiengo

Esposito

et al. 2005

ApJ

102

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“…Possible spectral features have been reported in a burst from the AXP 1E 1048.1À5937 and from bursts from two SGRs (Strohmayer & Ibrahim 2000;Ibrahim et al 2002Ibrahim et al , 2003. In no spectrum of any burst for 1E 2259+586 did we detect a significant feature.…”

Section: Absence Of Spectral Lines and The Average Burst Spectrummentioning

confidence: 51%

A Comprehensive Study of the X‐Ray Bursts from the Magnetar Candidate 1E 2259+586

Gavriil

Kaspi

Woods

2004

ApJ

118

164

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We present a statistical analysis of the X-ray bursts observed from the 2002 June 18 outburst of the anomalous X-ray pulsar (AXP) 1E 2259+586, observed with the Proportional Counter Array (PCA) aboard the Rossi X-Ray Timing Explorer. We show that the properties of these bursts are similar to those of soft gamma repeaters (SGRs). We find the following similarities: the burst durations follow a lognormal distribution that peaks at 99 ms, the differential burst fluence distribution is well described by a power law of index À1.7, the burst fluences are positively correlated with the burst durations, the distribution of waiting times is well described by a log normal distribution of mean 47 s, and the bursts are generally asymmetric, with shorter rise than fall times. However, we find several quantitative differences between the AXP and SGR bursts. Specifically, the AXP bursts we observed exhibit a wider range of durations, the correlation between burst fluence and duration is flatter than for SGRs, the observed AXP bursts are on average less energetic than observed SGR bursts, and the more energetic AXP bursts have the hardest spectra-the opposite of what is seen for SGRs. Unlike the case of SGRs, we find a correlation of burst phase with pulsed intensity. We conclude that the bursts are sufficiently similar that AXPs and SGRs can be considered united as a source class, yet there are some interesting differences that may help determine what physically differentiates the two closely related manifestations of neutron stars.

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“…Obviously the rotational energy loss cannot power either the observed X-ray emission or the hard X-ray (20−200 keV) emission. The RXTE/PCA has detected a relatively strong narrow line at 5 keV during some bright bursts, interpreted as cyclotron absorbtion (Ibrahim et al 2002(Ibrahim et al , 2003. The high quality 1−10 keV XMM spectrum of SGR 1806-20 allows us to put constraints on the possible presence of such a feature in the persistent spectrum of the source during this observation.…”

Section: Sgr 1806-20mentioning

confidence: 85%

The broad-band spectrum of the persistent emission from SGR 1806-20

Molkov

Hurley

Sunyaev

et al. 2005

A&A

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Abstract. We present the results of an analysis of the quiescent X-ray emission from the Soft Gamma-Ray Repeater SGR 1806-20, taken during an INTEGRAL ultra-deep survey of the Galactic center region in Aug.−Sep. 2003. The total effective exposure time spent on the source by the IBIS telescope during these observations was 1.6 million seconds. Combining the INTEGRAL results with results from the XMM-Newton observatory, we present the broad band (1−200 keV) spectrum of the quiescent emission from this source. This is the first spectrum of the persistent emission from an SGR in the broad energy range up to 200 keV. The spectrum of the source is very hard and has a power law shape (Γ = 1.6 ± 0.1) without any trace of a high energy cutoff up to ∼160 keV. No strong cyclotron line was detected in the persistent spectrum. The luminosity of SGR 1806-20 in this range (1−200 keV) was ∼3.6 × 10 36 erg s −1 for an assumed distance of 15 kpc. We show that weak undetected bursts should not contribute significantly to the quiescent emission. During our next observations in August 2004 the source went into an active phase and its average flux between powerful bursts was 2−3 times higher than in 2003. During Aug.−Sep. 2003, two other SGR candidates, SGR 1801-23 and SGR 1808-20, were in the field of view. Neither persistent hard X-ray emission nor bursts were detected from them. The upper limit on the persistent flux from each of them in the energy band 18−100 keV is about 4 × 10 −11 erg s −1 cm −2 .

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New Evidence of Proton-Cyclotron Resonance in a Magnetar Strength Field from SGR 1806−20

Cited by 99 publications

References 32 publications

AnXMM‐NewtonView of the Soft Gamma Repeater SGR 1806−20: Long‐Term Variability in the Pre–Giant Flare Epoch

AnXMM‐NewtonView of the Soft Gamma Repeater SGR 1806−20: Long‐Term Variability in the Pre–Giant Flare Epoch

A Comprehensive Study of the X‐Ray Bursts from the Magnetar Candidate 1E 2259+586

The broad-band spectrum of the persistent emission from SGR 1806-20

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