The kinematics and structure of N49

Shull, Peter

doi:10.1086/161559

Cited by 22 publications

(13 citation statements)

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“…This is truly a magnetar-like Ðeld ! The actual case is most likely between the two curves on Figure 3, with a more gentle peak giving a more relaxed energy requirement, but one that still implies G. B Z 1015 Such large Ðelds may not be consistent with the association of the SGR with N49, which has an age in the range 5È16 kyr (Vancura et al 1992 ;Shull 1983). Calculations for AXPs (Colpi et al 2000) indicate that a magnetar with an initial dipolar Ðeld of B [ 1015 G would spin down to the present-day SGR spin period in only D1000 yr, and increasing the Ðeld only makes the situation worse.…”

Section: A Magnetarmentioning

confidence: 97%

Hubble Space TelescopeObservations of SGR 0526−66: New Constraints on Accretion and Magnetar Models

Kaplan

Kulkarni

Kerkwijk

et al. 2001

ApJ

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Soft c-ray repeaters (SGRs) are among the most enigmatic sources known today. Exhibiting huge X-ray and c-ray bursts and Ñares, as well as soft quiescent X-ray emission, their energy source remains a mystery. Just as mysterious are the anomalous X-ray pulsars (AXPs), which share many of the same characteristics. Thanks to recent Chandra X-Ray Observatory observations, SGR 0526[66, the Ðrst SGR, now appears to be a transition object bridging the two classes, and therefore observations of it have implications for both SGRs and AXPs. The two most popular current models for their persistent emission are accretion of a fossil disk and decay of an enormous (D1015 G) magnetic Ðeld in a magnetar. We show how deep optical observations of SGR 0526[66, the only SGR with small enough optical extinction for meaningful observations, show no evidence of an optical counterpart. These observation place strong new constraints on both accretion disk and magnetar models and suggest that the spectral energy distribution may peak in the hard UV. Almost all accretion disks are excluded by the optical data, and a magnetar would require a D1015È1016 G Ðeld.

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Section: A Magnetarmentioning

confidence: 97%

Hubble Space TelescopeObservations of SGR 0526−66: New Constraints on Accretion and Magnetar Models

Kaplan

Kulkarni

Kerkwijk

et al. 2001

ApJ

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“…Obviously for model 2 and 3 the value of τ e would be larger for an earlier start of reionization. Free electrons left after recombination may also increase τ e somewhat (see Shull & Venkatesan 2007, for a recent detailed discussion of these issues).…”

Section: The Igm Neutral Hydrogen Fraction and Electron Scattering Opmentioning

confidence: 99%

The observed ionization rate of the intergalactic medium and the ionizing emissivity at z >= 5: evidence for a photon-starved and extended epoch of reionization

Bolton

Haehnelt

2007

Monthly Notices of the Royal Astronomical Society

361

429

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Galaxies and quasars are thought to provide the bulk of the photons responsible for ionizing the hydrogen in the intergalactic medium (IGM). We use a large set of hydrodynamical simulations, combined with measurements of the Lyα opacity of the IGM taken from the literature, to obtain robust estimates of the photoionization rate per hydrogen atom at z= 5 and 6. We find the photoionization rate drops by a factor of 2 and 4, respectively, compared to our recent measurements at z= 2–4. The number of ionizing photons emitted by known sources at z= 5 and 6, based on an extrapolation of source numbers below the detection limit and standard assumptions for the relationship between the ionizing emissivity and observed luminosity density at 1500 Å, are in reasonable agreement with the photoionization rates inferred from the Lyα forest if the escape fraction of ionizing photons from galaxies is large (≳20 per cent). The expected number of ionizing photons from observed sources at these redshifts therefore appears sufficient to maintain the IGM in its highly ionized state. Claims to the contrary may be attributed to the adoption of an unduly high value for the clumping factor of ionized hydrogen. Using physically motivated assumptions for the mean free path of ionizing photons our measurements of the photoionization rate can be turned into an estimate of the ionizing emissivity. In comoving units the inferred ionizing emissivity is nearly constant over the redshift range 2–6 and corresponds to 1.5–3 photons emitted per hydrogen atom over a time interval corresponding to the age of the Universe at z= 6. This strongly suggests that the epoch of reionization was photon‐starved and extended. Completion of reionization at or before z= 6 requires either an emissivity which rises towards higher redshifts or one which remains constant but is dominated by sources with a rather hard spectral index. For standard assumptions, the ionizing emissivity required for completion of reionization at or before z= 6 lies at the upper end of recently reported values from searches for high‐redshift galaxies at z= 8–10.

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“…upper limits) into data analysis. We first convert the age and SNR radii values of Tables 1 and 3 to ambient ISM densities n using the standard formulae in Shull (1983) and using values for each age and SNR radius midway between the range of values listed in the tables. A total supernova kinetic energy of 10 51 ergs was assumed for both the SGR/AXPs and radio pulsars.…”

Section: The Significance Of the Environmental Evidencementioning

confidence: 99%

Nature versus Nurture: The Origin of Soft Gamma‐Ray Repeaters and Anomalous X‐Ray Pulsars

Marsden¹,

Lingenfelter²,

Rothschild³

et al. 2001

ApJ

100

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Soft gamma-ray repeaters (SGRs) and anomalous x-ray pulsars (AXPs) are young and radio-quiet x-ray pulsars which have been rapidly spun-down to slow spin periods clustered in the range 5 − 12 s. Most of these unusual pulsars also appear to be associated with supernova shell remnants (SNRs) with typical ages < 30 kyr. By examining the sizes of these remnants versus their ages, 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. We explore the implications of this evidence on magnetar and propeller-based models for the rapid spin-down of SGRs and AXPs. We find that evidence of dense environments is not consistent with the magnetar model unless a causal link can be shown between the development of magnetars and the external ISM. Propeller-driven spin-down by fossil accretion disks for SGRs and AXPs appears to be consistent with dense environments since the environment can facilitate the formation of such a disk. This may occur in two ways: 1) formation of a "pushback" disks from the innermost ejecta pushed back by prompt reverse shocks from supernova remnant interactions with massive progenitor wind material stalled in dense surrounding gas, or 2) acquisition of disks by a high velocity neutron stars, which may be able to capture a sufficient amounts of co-moving outflowing ejecta slowed by the prompt reverse shocks in dense environments.

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The kinematics and structure of N49

Cited by 22 publications

References 0 publications

Hubble Space TelescopeObservations of SGR 0526−66: New Constraints on Accretion and Magnetar Models

Hubble Space TelescopeObservations of SGR 0526−66: New Constraints on Accretion and Magnetar Models

The observed ionization rate of the intergalactic medium and the ionizing emissivity at z >= 5: evidence for a photon-starved and extended epoch of reionization

Nature versus Nurture: The Origin of Soft Gamma‐Ray Repeaters and Anomalous X‐Ray Pulsars

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