arXiv subjects

John Middleditch

Publications and source records attributed to John Middleditch.

14 recordsLinked to original sources

arXiv2019

Disruption of Supernovae and would-be "Direct Collapsars"

The speed of an intensity pattern of polarization currents on a circle, induced within a star by its rotating, magnetized core, will exceed the speed of light for a sufficiently large star, and/or rapid rotation, and will, in turn, generate focused electromagnetic beams which disrupt them. Upon core collapse within such a star, the emergence of these beams will concentrate near the two rotational poles, driving jets of matter into material previously ejected via the same excitation mechanism acting through the pre-core-collapse rotation of its magnetized stellar core(s). This interpenetration of material, light-days in extent from the progenitor, produces a significant fraction of the total supernova luminosity, and the magnitude and time of maximum of this contribution both vary with the progenitor's rotational orientation. The net effect is to render supernovae unusable as standard candles without further detailed understanding, leaving no firm basis, at this time, to favor any cosmology, including those involving "Dark Energy." Thus we are not now, nor have we ever been, in an era of precision cosmology, nor are we likely to be anytime soon. Mass loss induced through the same mechanism also keeps aggregates of gas and plasma in the early Universe, or at any other epoch, from forming the ~billion solar mass stars which have been suggested to produce ~billion solar mass black holes via "direct collapse," but can also provide a signature to predict core collapse some months in advance.

astro-ph.HE↗

arXiv2019

Predicting the next local supernova

Core collapse within blue supergiant stars, as occurred within Sk -69$^{\circ}$202/Supernova 1987A, is generally attributed to a merger of two electron-degenerate cores within a common envelope, with a merged mass in excess of 1.4 solar. Supernova 1987A also had two associated bright sources, one with about 8% of the H-alpha flux, and 74 milli-arc seconds distant by day 50, and another, four times fainter and 160 milli-arc seconds away in the opposite direction on day 38. Using recent advances in our understanding of pulsars, we can show that the second source was the result of the core-merger process, which can drive a relativistic jet of particles prior to the completion of the merger process, whether this proceeds to core collapse, or not. As with those resulting from core-collapse, such beams and jets are likely to produce an obvious spectral signature (e.g., even in un-red/blue-shifted H-alpha), which can be detected in nearby galaxies. There is very likely a time interval of a few months, during which such supergiant stars, a high fraction of which will eventually undergo core collapse, can be identified. These can be carefully followed observationally to maximize the chance of observing core collapses as they happen. Such studies may eventually help in using such objects as standard candles.

astro-ph.HE↗

arXiv2013

Pulsar-driven Jets in Supernovae, Gamma-Ray Bursts, and the Universe

The bipolarity of Supernova 1987A can be understood through its very early light curve observed from the CTIO 0.4-m telescope and IUE FES, and following speckle observations of the `Mystery Spot' by two groups. These indicate a highly directional beam/jet of light/particles, with initial collimation factors in excess of 10,000 and velocities in excess of 0.95 c, as an impulsive event of up to 1e-5 solar masses interacting with circumstellar material. These can be produced by a model proposed in 1972, by Bolotovskii and Ginzburg, which employs pulsar emission from polarization currents induced/(modulated faster than c) beyond the pulsar light cylinder by the periodic electromagnetic field (supraluminally induced polarization currents -- SLIP). SLIP accounts for the disruption of progenitors in supernova explosions and their anomalous dimming at cosmological distances, jets from Sco X-1 and SS 433, the lack/presence of intermittent pulsations from the high/low luminosity low mass X-ray binaries, long/short gamma-ray bursts and predicts that their afterglows are the pulsed optical/near infrared emission associated with these pulsars. SLIP may also account for the TeV e+/e- results from PAMELA and ATIC, the WMAP `Haze'/Fermi `Bubbles', and the r-process. SLIP jets from SNe of the first stars may allow galaxies to form without dark matter, and explain the peculiar, non-gravitational motions observed from pairs of distant galaxies by GALEX.

astro-ph.HE↗

arXiv2009

A Maximum-Likelihood Analysis of Observational Data on Fluxes and Distances of Radio Pulsars: Evidence for Violation of the Inverse-Square Law

We analyze pulsar fluxes at 1400 MHz ($S_{1400}$) and distances ($d$) extracted from the Parkes Multibeam Survey. Under the assumption that distribution of pulsar luminosities is distance-independent, we find that either (a) pulsar fluxes diminish with distance according to a non-standard power law, due, we suggest, to the presence of a component with $S_{1400} \propto 1/d$, or (b) that there are very significant (i.e. order of magnitude) errors in the dispersion-measure method for estimating pulsar distances. The former conclusion (a) supports a model for pulsar emission that has also successfully explained the frequency spectrum of the Crab and 8 other pulsars over 16 orders of magnitude of frequency, whilst alternative (b) would necessitate a radical re-evaluation of both the dispersion-measure method and current ideas about the distribution of free electrons within our Galaxy.

astro-ph.GA↗

arXiv2009

Pulsed Gamma-Ray-Burst Afterglows

The bipolarity of Supernova 1987A can be understood in terms of its very early light curve as observed from the CTIO 0.4-m telescope, as well as the IUE FES, and the slightly later speckle observations of the "Mystery Spot" by two groups. These observations imply a highly directional beam of light and jet of particles, with initial collimation factors in excess of 10,000, velocities in excess of 0.95 c, as an impulsive event involving up to 0.00001 solar masses, which interacts with circumstellar material. The jet and beam coincide with the 194 degree angle of the bipolarity on the sky, and are oriented at 75 degrees to the line of sight to the Earth. By day 30 the collimation of the jet decreases, and its velocity declines to ~0.5 c. These observations and the resulting kinematic solution can be understood in terms of pulsar emission from polarization currents, induced by the periodically modulated electromagnetic field beyond the pulsar light cylinder, which are thus modulated at up to many times the speed of light. With plasma available at many times the light cylinder radius, as would be the case for a spinning neutron star formed at the center of its progenitor, pulsed emission is directed close to the rotation axis, eviscerating this progenitor, and continuing for months to years, until very little circumpulsar material remains. This model provides a candidate for the central engine of the gamma-ray burst (GRB) mechanism, both long and short, and predicts that GRB afterglows are the_pulsed_ optical/near infrared emission associated with these newly-born neutron stars.

astro-ph.HE↗

arXiv2009

A new mechanism for generating broadband pulsar-like polarization

Observational data imply the presence of superluminal electric currents in pulsar magnetospheres. Such sources are not inconsistent with special relativity; they have already been created in the laboratory. Here we describe the distinctive features of the radiation beam that is generated by a rotating superluminal source and show that (i) it consists of subbeams that are narrower the farther the observer is from the source: subbeams whose intensities decay as 1/R instead of 1/R^2 with distance (R), (ii) the fields of its subbeams are characterized by three concurrent polarization modes: two modes that are 'orthogonal' and a third mode whose position angle swings across the subbeam bridging those of the other two, (iii) its overall beam consists of an incoherent superposition of such coherent subbeams and has an intensity profile that reflects the azimuthal distribution of the contributing part of the source (the part of the source that approaches the observer with the speed of light and zero acceleration), (iv) its spectrum (the superluminal counterpart of synchrotron spectrum) is broader than that of any other known emission and entails oscillations whose spacings and amplitudes respectively increase and decrease algebraically with increasing frequency, and (v) the degree of its mean polarization and the fraction of its linear polarization both increase with frequency beyond the frequency for which the observer falls within the Fresnel zone. We also compare these features with those of the radiation received from the Crab pulsar.

astro-ph.SR↗

arXiv2008

The SN 1987A Link to Others and Gamma-Ray Bursts

Early measurements of SN 1987A can be interpreted in light of a beam/jet (BJ), with a collimation factor >10,000, which impacted polar ejecta (PE) to produce the "Mystery Spot" (MS), ~24 lt-d away. Other details of SN 1987A suggest that it came from a merger of 2 stellar cores of a common envelope (CE) binary, i.e. a "double degenerate" (DD) SN. Even having to penetrate the CE, the BJ may have caused a long-soft (l)GRB upon hitting the PE, thus DD can produce lGRBs. Because DD must be the dominant merger/SN mechanism in elliptical galaxies (EGs), where only short, hard GRBs (sGRBs) have been observed, DD without CE or PE must also produce sGRBs, and thus NS-NS mergers may not make GRBs as we know them, and/or be as common as previously thought. Millisecond pulsars (MSPs) in the non-core-collapsed globular clusters are also 99% DD-formed from WD-WD merger, consistent with their 2.10 ms minimum spin period, the 2.14 ms signal seen from SN 1987A, and sGRBs offset from the centers of EGs. The details of Ia's suggest that these are also DD, and the total thermonuclear disruption paradigm is now in serious doubt as well, a cause for concern in Ia Cosmology, because Ia's will appear to be Ic's when viewed from their DD merger poles, given sufficient matter above that lost to core-collapse. As a DD SN, 1987A appears to be the Rosetta Stone for 99% of SNe, GRBs and MSPs, including all recent nearby SNe except SN 1986J, and the more distant SN 2006gy. There is no need to invent exotica, such as "collapsars," to account for GRBs.

astro-ph↗

arXiv2007

Core-collapse, GRBs, Type Ia Supernovae, and Cosmology

Type Ia Supernovae (SNe) have been used by many to argue for an accelerated expansion of the universe. However, high velocity and polarized features in many nearby SNe Ia, and their inverse relation to luminosity, particularly for polarization, are consistent with an extreme version of the axisymmetry seen in SN 1987A, which could be the result of double degenerate merger-induced core-collapse. This could be the correct paradigm for many SNe Ia and Ic, where Ia's are both thermonuclear and core-collapsed objects, which leave weakly-magnetized, rapidly spinning (~2 ms) pulsars. In this paradigm Ia/c is produced from the merger of two degenerate cores of common envelope WR stars, or of two CO white dwarfs. Its polar blowouts produce the observed high velocity and polarized spectral features in Ia's, and its equatorial bulge is much brighter in Ia's, due to the greater fraction of 56Ni contained within it. These become classified as Ia's when viewed from the merger equator, and Ic's when viewed from the poles, where a hypernova signature and a gamma-ray burst (GRB) will be observed for lines of sight close to the merger axis. Thus cosmology determined strictly from Ia's alone may be flawed because the local sample is selectively biased. Finally, all GRBs start as the short-duration, hard-spectrum variety (sGRBs), after which some are modified to the long-duration, soft-spectrum variety (lGRBs) by interaction with the merger common envelope and previous polar ejection. Thus the initial photon spectrum of all GRBs is known.

astro-ph↗

arXiv2007

The SN 1987A Link to Gamma-Ray Bursts

Early measurements of SN 1987A indicate a beam/jet (BJ) which hit polar ejecta (PE) to produce the "Mystery Spot" (MS). The SN flash takes an extra 8 d to hit the MS, and this was confirmed at 2e39 ergs/s in the optical at day 8. A ramp in luminosity starting near day 10 indicates particles from the BJ hitting the PE, with the fastest particles traveling at 0.8 c, and an upper limit for the optical luminosity of the MS of 5e40 ergs/s at day 20. The details of SN 1987A strongly suggest that it resulted from a merger of 2 stellar cores of a common envelope (CE) binary, i.e. a "double-degenerate" (DD)-initiated SN, and is thus the Rosetta Stone for 99% of MSPs in the non-core-collapsed globular clusters, GRBs, and SNe, including all recent nearby SNe except SN 1986J and the more distant SN 2006gy. Without having to blast through the CE of Sk -69 202, it is likely that the BJ would have caused a full, long-soft gamma-ray burst (lGRB) upon hitting the PE, thus DD can produce lGRBs. The typical 0.5 deg collimation of a GRB, over the 22 lt-d from SN 1987A to its PE, produces ~100 s of delay, MATCHING the observed delay of the non-prompt parts of lGRBs. Because DD must be the dominant SN mechanism in elliptical galaxies, where only short, hard GRBs (sGRBs) have been observed, DD without CE or PE must also make sGRBs, thus the initial photon spectrum of 99% of ALL GRBs is KNOWN, & neutron star (NS)-NS mergers may not make GRBs as we know them. Observations of Ia's strongly suggest that these are also DD, implying another systematic effect in Ia Cosmology, as Ia's will appear to be Ic's when viewed from their DD merger poles, given sufficient matter above that lost to core- collapse (otherwise it would just beg the question of what ELSE they could possibly be). There is no need to invent exotica, such as collapsars or hypernovae, to account for GRBs.

astro-ph↗

arXiv2006

Predicting the Starquakes in PSR J0537-6910

We report on more than 7 years of monitoring of PSR J0537-6910, the 16 ms pulsar in the Large Magellanic Cloud, using data acquired with the RXTE. During this campaign the pulsar experienced 23 sudden increases in frequency (``glitches'') amounting to a total gain of over six ppm of rotation frequency superposed on its gradual spindown of d(nu)/d(t) = -2e-10 Hz/s. The time interval from one glitch to the next obeys a strong linear correlation to the amplitude of the first glitch, with a mean slope of about 400 days ppm (6.5 days per uHz), such that these intervals can be predicted to within a few days, an accuracy which has never before been seen in any other pulsar. There appears to be an upper limit of ~40 uHz for the size of glitches in_all_ pulsars, with the 1999 April glitch of J0537 as the largest so far. The change in the spindown of J0537 across the glitches, Delta(d(nu)/d(t)), appears to have the same hard lower limit of -1.5e-13 Hz/s, as, again, that observed in all other pulsars. The spindown continues to increase in the long term, d(d(nu)/d(t))/d(t) = -1e-21 Hz/s/s, and thus the timing age of J0537 (-0.5 nu d(nu)/d(t)) continues to decrease at a rate of nearly one year every year, consistent with movement of its magnetic moment away from its rotational axis by one radian every 10,000 years, or about one meter per year. J0537 was likely to have been born as a nearly-aligned rotator spinning at 75-80 Hz, with a |d(nu)/d(t)| considerably smaller than its current value of 2e-10 Hz/s. The pulse profile of J0537 consists of a single pulse which is found to be flat at its peak for at least 0.02 cycles.

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arXiv2004

Millisecond Pulsar Searches and Double Neutron Star Binaries

A unified strategy is developed that can be used to search for millisecond pulsars (MSPs) with ~solar mass companions (including neutron star companions in double neutron star binaries [DNSBs]) belonging to both very short period binaries, and those with periods so long that they could be appropriate targets for acceleration searches, and to bridge the gap between these two extremes. In all cases, the orbits are assumed to be circular. Applications to searches for binary pulsars similar to PSR J0737-3039 are discussed. The most likely candidates for more DNSBs consist of weakly magnetized neutron stars, spinning only moderately fast, like J0737-3039A, with periods generally longer than 15 ms, though this issue is not yet settled. Because of the similarity between the MSP components of DNSBs, and the longer period MSP population specific to massive condensed or core collapsed globular clusters, as well as the uncertainties about accretion-driven spinup, doubts linger about the standard models of DNSB formation.

astro-ph↗

arXiv2003

A White Dwarf Merger Paradigm for Supernovae and Gamma-Ray Bursts

Gamma-ray bursts can appear to be a hundred times as luminous as supernovae, but their underlying energy source(s) have remained a mystery. However, there has been evidence for some time now of an association of gamma-ray bursts with supernovae of Type Ib and Ic, a fact which has been exploited by a number of models, to explain the gamma-ray burst phenomenon. Here we interpret the results of basic observations of SN 1987A and of pulsars in globular clusters, to propose the energy source, which powers at least some long-duration gamma-ray bursts, as core-collapse following the merger of two white dwarfs, either as stars or stellar cores. The beaming and intrinsic differences among gamma-ray bursts arise, at least in part, from differing amounts and composition of the gas in the merged stellar common envelopes, with the more energetic bursts resulting from mergers within less massive envelopes. In order for the beams/jets associated with gamma-ray bursts to form in mergers within massive common envelopes (as with SN 1987A), much of the intervening stellar material in the polar directions must be cleared out by the time of core-collapse, or the beams/jets themselves must clear their own path. The core-collapse produces supernovae of Type Ib, Ic, or II (as with SN 1987A, a SNa IIp), leaving a weakly magnetized neutron star remnant with a spin period near 2 milliseconds. There is no compelling reason to invoke any other model to account for gamma-ray bursts. Far from being an unusual event, SN 1987A is typical, having the same merger source of initiation as 95% of all supernovae, the rare exceptions being Ia's induced via gradual accretion from a binary companion, and Fe catastrophe II's.

astro-ph↗

arXiv2003

Does merger-induced core-collapse produce gamma-ray bursts in type Ib & Ic supernovae?

Gamma-ray bursts, discovered over three decades ago, can appear to be a hundred times as luminous as the brightest supernovae. However, there has been evidence for some time now of an association of gamma-ray bursts with supernovae of type Ib and Ic. Here we interpret the overabundance of millisecond pulsars in globular clusters and the details of supernova 1987A to reveal the energy source, which powers at least some long-duration gamma-ray bursts, as core-collapse following the merger of two white dwarfs, either as stars or stellar cores. In order for the beams/jets associated with gamma-ray bursts to form in mergers within massive common envelopes (as with SN1987A), much of the intervening stellar material in the polar directions must be cleared out by the time of core-collapse, or the beams/jets themselves must clear their own path. The core-collapse produces supernovae of type Ib, Ic, or II (as with SN1987A, a SNa IIp), leaving a weakly magnetized neutron star remnant with a spin period near 2 milliseconds. There is no compelling reason to invoke any other model for gamma-ray bursts.

astro-ph↗

arXiv2002

Fourier Techniques for Very Long Astrophysical Time Series Analysis

In this paper, we present an assortment of both standard and advanced Fourier techniques that are useful in the analysis of astrophysical time series of very long duration -- where the observation time is much greater than the time resolution of the individual data points. We begin by reviewing the operational characteristics of Fourier transforms (FTs) of time series data, including power spectral statistics, discussing some of the differences between analyses of binned data, sampled data, and event data, and briefly discuss algorithms for calculating discrete Fourier transforms (DFTs) of very long time series. We then discuss the response of DFTs to periodic signals, and present techniques to recover Fourier amplitude "lost" during simple traditional analyses if the periodicities change frequency during the observation. These techniques include Fourier interpolation which allows us to correct the response for signals that occur between Fourier frequency bins. We then present techniques for estimating additional signal properties such as the signal's centroid and duration in time, the first and second derivatives of the frequency, the pulsed fraction, and an overall estimate of the significance of a detection. Finally, we present a recipe for a basic but thorough Fourier analysis of a time series for well-behaved pulsations.

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