R-Mode Oscillations and Spindown of Young Rotating Magnetic Neutron Stars

Recent work has shown that a young, rapidly rotating neutron star loses angular momentum to gravitational waves generated by unstable r-mode oscillations. We study the spin evolution of a young, magnetic neutron star including both the effects of gravitational radiation and magnetic braking (modeled as magnetic dipole radiation). Our phenomenological description of nonlinear r-modes is similar to, but distinct from, that of Owen et al. (1998) in that our treatment is consistent with the principle of adiabatic invariance in the limit when direct driving and damping of the mode are absent. We show that, while magnetic braking tends to increase the r-mode amplitude by spinning down the neutron star, it nevertheless reduces the efficiency of gravitational wave emission from the star. For B >= 10^14 (\nus/300 Hz)^2 G, where \nus is the spin frequency, the spindown rate and the gravitational waveforms are significantly modified by the effect of magnetic braking. We also estimate the growth rate of the r-mode due to electromagnetic (fast magnetosonic) wave emission and due to Alfven wave emission in the neutron star magnetosphere. The Alfven wave driving of the r-mode becomes more important than the gravitational radiation driving when B >= 10^13 (\nus/150 Hz)^3 G; the electromagnetic wave driving of the r-mode is much weaker. Finally, we study the properties of local Rossby-Alfven waves inside the neutron star and show that the fractional change of the r-mode frequency due to the magnetic field is of order 0.5 (B/10^16 G)^2 (\nus/100 Hz)^-2.Comment: 18 pages, 4 figures; ApJ, accepted (v544: Nov 20, 2000); added two footnotes and more discussion of mode driving by Alfven wave

Equilibrium spin pulsars unite neutron star populations

Many pulsars are formed with a binary companion from which they can accrete matter. Torque exerted by accreting matter can cause the pulsar spin to increase or decrease, and over long times, an equilibrium spin rate is achieved. Application of accretion theory to these systems provides a probe of the pulsar magnetic field. We compare the large number of recent torque measurements of accreting pulsars with a high-mass companion to the standard model for how accretion affects the pulsar spin period. We find that many long spin period (P > 100 s) pulsars must possess either extremely weak (B < 10^10 G) or extremely strong (B > 10^14 G) magnetic fields. We argue that the strong-field solution is more compelling, in which case these pulsars are near spin equilibrium. Our results provide evidence for a fundamental link between pulsars with the slowest spin periods and strong magnetic fields around high-mass companions and pulsars with the fastest spin periods and weak fields around low-mass companions. The strong magnetic fields also connect our pulsars to magnetars and strong-field isolated radio/X-ray pulsars. The strong field and old age of our sources suggests their magnetic field penetrates into the superconducting core of the neutron star.Comment: 6 pages, 4 figures; to appear in MNRA

Seawater capacitance &ndash; a promising proxy for mapping and characterizing drifting hydrocarbon plumes in the deep ocean

Hydrocarbons released into the deep ocean are an inevitable consequence of natural seep, seafloor drilling, and leaking wellhead-to-collection-point pipelines. The Macondo 252 (Deepwater Horizon) well blowout of 2010 was even larger than the Ixtoc event in the Gulf of Campeche in 1979. History suggests it will not be the last accidental release, as deepwater drilling expands to meet an ever-growing demand. For those who must respond to this kind of disaster, the first line of action should be to know what is going on. This includes knowing where an oil plume is at any given time, where and how fast it is moving, and how it is evolving or degrading. We have experimented in the laboratory with induced polarization as a method to track hydrocarbons in the seawater column and find that finely dispersed oil in seawater gives rise to a large distributed capacitance. From previous sea trials, we infer this could potentially be used to both map and characterize oil plumes, down to a ratio of less than 0.001 oil-to-seawater, drifting and evolving in the deep ocean. A side benefit demonstrated in some earlier sea trials is that this same approach in modified form can also map certain heavy placer minerals, as well as communication cables, pipelines, and wrecks buried beneath the seafloor

Malic enzyme : Its purification and characterization from Mucor circinelloides and occurrence in other oleaginous fungi

Malic enzyme was purified 43-fold from Mucor circinelloides. The enzyme was dependent on Mg2+ or Mn2+ for activity, was not active with Dmalate and had a pH optimum at 7.8. The apparent Km values for malate and NADP+ were 488 ΜM and 41 Μm respectively. The Mr of the native enzyme was 160 kDa. Five metabolic analogues of malate: oxaloacetate, tartronic acid, 1-methylenecyclopropane trans-2,3-dicarboxyIic acid, malonic acid and glutaric acid, were found to inhibit malic enzyme activity at 10 mM. Four oleaginous fungi, Mucor circinelloides, Mortierella alpina, Mortierella elongata and Pythium ultimum, were also examined, all possessed a soluble malic enzyme, two also possessed a microsomal malic enzyme

The Glitch That Stole Christmas From The Pac-10

The Bowl Championship Series (BCS) employs a multi-criteria decision model (MCDM) to determine eligibility to play in the most elite college football bowls at the end of the season.&nbsp; MCDM&rsquo;s are widely used in business and government to make important decisions, including those with tremendous financial impacts.&nbsp; The BCS college bowls have the biggest payouts involving several million dollars.&nbsp; This year, the PAC-10 could have been the first football conference to place two teams in the BCS bowl.&nbsp; What a Merry Christmas that would have been!&nbsp; The payout would have been $2.75 million or$275 thousand per team.&nbsp; Unfortunately, due to the use of a faulty MCDM that distorts the relationship between those football programs considered, a glitch in the BCS formula stole the Rose Bowl prestige and the money from the PAC-10 during the Christmas holidays.&nbsp; Using appropriate multipliers, the economic impact in PAC-10 communities could have been very significant.&nbsp;&nbsp; The implication for future competition through enhanced athletic facilities, for example, could have a sustained economic impact for several years in those communities.&nbsp; It will be demonstrated in this paper that had the BCS employed a valid and consistent algorithm for determining a final score, even with the BCS&rsquo;s own data, the University of California would have a higher score than the University of Texas and the PAC-10 would have benefited by $2.75 Million, and they would have a much merrier Christmas than they had from playing in the Holiday Bowl

Cooling of the Cassiopeia A neutron star and the effect of diffusive nuclear burning

The study of how neutron stars cool over time can provide invaluable insights into fundamental physics such as the nuclear equation of state and superconductivity and superfluidity. A critical relation in neutron star cooling is the one between observed surface temperature and interior temperature. This relation is determined by the composition of the neutron star envelope and can be influenced by the process of diffusive nuclear burning (DNB). We calculate models of envelopes that include DNB and find that DNB can lead to a rapidly changing envelope composition which can be relevant for understanding the long-term cooling behavior of neutron stars. We also report on analysis of the latest temperature measurements of the young neutron star in the Cassiopeia A supernova remnant. The 13 Chandra observations over 18 years show that the neutron star's temperature is decreasing at a rate of 2-3 percent per decade, and this rapid cooling can be explained by the presence of a proton superconductor and neutron superfluid in the core of the star.Comment: 7 pages, 7 figures; to appear in the AIP Conference Proceedings of the Xiamen-CUSTIPEN Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave Astronomy (January 3-7, 2019, Xiamen, China

Does slow and steady win the race? Investigating feedback processes in giant molecular clouds

We investigate the effects of gradual heating on the evolution of turbulent molecular clouds of mass $2\times 10^6$ M$_\odot$ and virial parameters ranging between $0.7-1.2$. This gradual heating represents the energy output from processes such as winds from massive stars or feedback from High Mass X-ray binaries (HMXBs), contrasting the impulsive energy injection from supernovae (SNe). For stars with a mass high enough that their lifetime is shorter than the life of the cloud, we include a SN feedback prescription. Including both effects, we investigate the interplay between slow and fast forms of feedback and their effectiveness at triggering/suppressing star formation. We find that SN feedback can carve low density chimneys in the gas, offering a path of least resistance for the energy to escape. Once this occurs the more stable, but less energetic, gradual feedback is able to keep the chimneys open. By funneling the hot destructive gas away from the centre of the cloud, chimneys can have a positive effect on both the efficiency and duration of star formation. Moreover, the critical factor is the number of high mass stars and SNe (and any subsequent HMXBs) active within the free-fall time of each cloud. This can vary from cloud to cloud due to the stochasticity of SN delay times and in HMXB formation. However, the defining factor in our simulations is the efficiency of the cooling, which can alter the Jeans mass required for sink particle formation, along with the number of massive stars in the cloud.Comment: 35 pages, 46 figures, accepted for publication in MNRA

Infrared and radio observations of W51: Another Orion-KL at a distance of 7kpc

The bright infrared sources W51-IRS2 has at least three components with different physical and evolutionary properties. The spatial distribution and the near infrared spectra of the components in IRS2 are remarkably similar to, but more luminous than those found in Orion, where an H2 region of comparable linear size is also located close to a cluster of compact infrared sources. The characteristics of the nearby W51-NORTH H2O maser source, and the detection of 2 micro m H2 quadrupole emission in IRS2 indicate that the mass loss phenomena found in Orion-KL also exist in W51

Spitzer Space Telescope Observations of the Magnetic Cataclysmic Variable AE Aqr

The magnetic cataclysmic variable AE Aquarii hosts a rapidly rotating white dwarf which is thought to expel most of the material streaming onto it. Observations of AE Aqr have been obtained in the wavelength range of 5 - 70 microns with the IRS, IRAC, and MIPS instruments on board the Spitzer Space Telescope. The spectral energy distribution reveals a significant excess above the K4V spectrum of the donor star with the flux increasing with wavelength above 12.5 microns. Superposed on the energy distribution are several hydrogen emission lines, identified as Pf alpha and Hu alpha, beta, gamma. The infrared spectrum above 12.5 microns can be interpreted as synchrotron emission from electrons accelerated to a power-law distribution dN=E^{-2.4}dE in expanding clouds with an initial evolution timescale in seconds. However, too many components must then be superposed to explain satisfactorily both the mid-infrared continuum and the observed radio variability. Thermal emission from cold circumbinary material can contribute, but it requires a disk temperature profile intermediate between that produced by local viscous dissipation in the disk and that characteristic of a passively irradiated disk. Future high-time resolution observations spanning the optical to radio regime could shed light on the acceleration process and the subsequent particle evolution.Comment: 15 pages, 3 figures, accepted for publication in Ap