摘要:

A pair of spectroscopically nearly identical M supergiant stars were proposed [1] as possible counterparts toSGR&hthinsp;1900+14based on positional coincidences with gamma-ray and x-ray localizations. Whether these stars or the nearby fading radio source [9] are associated withSGR&hthinsp;1900+14is not yet clear. We obtained I- and J-band photometric observations of the M stars with 10 to 120 second time resolution obtained on 16 nights before and during the active phase ofSGR&hthinsp;1900+14beginning in June 1998. Despite more than 54,000 seconds of integration time, no observations were obtained within an hour of a gamma-ray burst event. No short term variability was found for any object within the ROSAT error circle toI⩽24.5,although an unrelated eclipsing binary was discovered just outside the ROSAT circle. PSF subtraction of the bright M stars reveals a previously hidden compact star cluster. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361646

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Infrared observations of the environment of the two Soft Gamma-ray Repeaters (SGRs) with the best known locations on the sky show that they are associated with clusters of massive stars. Observations with ISO revealed thatSGR&hthinsp;1806−20is in a cluster of giant massive stars, still enshrouded in a dense cloud of gas and dust [1].SGR&hthinsp;1900+14is at the edge of a similar cluster that was recently found hidden in the glare of a pair of M5 supergiant stars [2]. Since none of the stars of these clusters has shown in the last years significant flux variations in the infrared, these two SGRs do not form bound binary systems with massive stars.SGR&hthinsp;1806−20is at only ∼0.4 pc, andSGR&hthinsp;1900+14at ∼0.8 pc from the centers of their parental star clusters. If these SGRs were born with typical neutron star runaway velocities of ∼300 km&hthinsp;s−1, they are not older than a few103years. We propose thatSGR&hthinsp;1806−20andSGR&hthinsp;1900+14are ideal laboratories to study the evolution of supernovae explosions inside interstellar bubbles produced by the strong winds that prevail in clusters of massive stars. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361647

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We present the result of a target of opportunity observation performed by the ESA’s Infrared Space Observatory (ISO) following the detection of the possible newSGR&hthinsp;1801−23in June and September 1997. Four 60 &mgr;m sources are detected in a10′×10′region, but the association of any toSGR&hthinsp;1801−23remains open due to the small fraction of the revised IPN error observed byISO. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361648

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We present the results of optical/IR observations obtained in the period June–October 1998. Images in the Gunn-z band were serendipitously taken just 3 days after the giant burst that took place on 27 Aug 1998. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361649

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We report on medium-resolution near-infrared spectroscopic observations of the M5 super-giant binary that may be related to the Soft Gamma RepeaterSGR&hthinsp;1900+14.The observations were performed with CGS4 at UKIRT and cover the wavelength range from 1.9 to 2.5 &mgr;m. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361650

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

In magnetic fields stronger thanBQ≡me2c3/ℏe=4.4×1013Gauss, an electron’s Landau excitation energy exceeds its rest energy. I review the physics of this strange regime and some of its implications for the crusts and magnetospheres of neutron stars. In particular, I describe how ultra-strong fields • render the vacuumbirefringentand capable of distorting and magnifying images (“magnetic lensing”); • change the self-energy of electrons: asBincreases they are first slightly lighter thanme,then slightly heavier; • cause photons to rapidly split and merge with each other; • distort atoms into long, thin cylinders and molecules into strong, polymer-like chains; • enhance the pair density in thermal pair-photon gases; • strongly suppress photon-electron scattering, and • drive the vacuum itself unstable, at extremely largeB. In a concluding section, I discuss the spindown of ultra-magnetized neutron stars and recent soft gamma repeater observations. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361651

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We measure the period and spin-down rate forSGR&hthinsp;1900+14during the quiescent period two years before the recent interval of renewed burst activity. We find that the spin-down rate doubled during the burst activity, which is inconsistent with both magnetic dipole driven spin-down and a magnetic field energy source for the bursts. We also show thatSGRs&hthinsp;1900+14and1806−20have braking indices of ∼1, which indicates that the spin-down is due to wind torques and not magnetic dipole radiation. We further show that a combination of dipole radiation and wind luminosity, coupled with estimated ages and present spin parameters, imply that the magnetic fields ofSGRs&hthinsp;1900+14and1806−20are less than the critical field of4×1013&hthinsp;Gand that the efficiency for conversion of wind luminosity to x-ray luminosity is <2&percent;. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361652

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Soft gamma-ray repeaters (SGRs) and anomalous x-ray pulsars (AXPs) are young (<100 kyr), radio-quiet, x-ray pulsars which have been rapidly spun-down to slow spin periods clustered at 5–12 s. Nearly all of these unusual pulsars also appear to be associated with supernova shell remnants (SNRs) with typical ages <20 kyr. If the unusual properties of SGRs and AXPs are due to an innate feature, such as a super-strong magnetic field, then the pre-supernova environments of SGRs and AXPs should be typical of neutron star progenitors. This isnotthe case, however, as we demonstrate that the interstellar media which surrounded the SGR and AXP progenitors and their SNRs were unusually dense compared to the environments around most young radio pulsars and SNRs. Thus, if these SNR associations are real, the SGRs and AXPs can not be “magnetars,” and we suggest instead that the environments surrounding SGRs and AXPs play a controlling role in their development. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361653

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Recent observations of soft gamma-ray repeaters and anomalous X-ray pulsars are furnishing greater evidence for the existence of a class of neutron stars with surface magnetic fields exceeding the critical field of4.4×1013&hthinsp;Gauss.The main effort of this study is to understand the role of relativistic Compton scattering as it operates with other QED processes, to develop approximate expressions of the exact rate and to incorporate them in a full acceleration-cascade model. Previous modeling of Compton scattering in magnetic fields has assumed that the scattering cross section can be adequately described by the nonrelativistic Compton scattering cross section (Thomson limit) below resonance and at the resonance, and the Klein-Nishina cross section above the resonance. Consequently, these studies have not included the effects of the strong fields of pulsars and magnetars. The study of the strong field effects on the inverse Compton scattering process will provide insight into the particle-photon interactions associated with a variety of pulsar phenomena, burst spectra of soft gamma-ray repeaters and the transport of thermal radiation through neutron star atmospheres. This paper will summarize the role of inverse Compton scattering and the effects of strong magnetic fields upon the integrated cross section for Compton scattering. An analytical approximation to the exact QED cross section will be discussed. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361654

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Recently, neutron stars with very strong surface magnetic fields have been suggested as the site for the origin of observed soft gamma repeaters (SGRs). We investigate the influence of a strong magnetic field on the properties and internal structure of such strongly magnetized neutron stars (magnetars). The presence of a sufficiently strong magnetic field changes the ratio of protons to neutrons as well as the neutron appearance density. We also study the pion production and pion condensation in a strong magnetic field. We discuss the pion condensation in the interior of magnetars as a possible source of SGRs. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1361655

出版商:AIP    

年代:1900

数据来源: AIP