The anomalous x-ray pulsar 4U 0142+61: a neutron star with a gaseous fallback disk

The recent detection of the anomalous X-ray pulsar (AXP) 4U 0142+61 in the mid infrared with the Spitzer Observatory (Wang, Chakrabarty & Kaplan 2006) constitutes the first instance for a disk around an AXP. We show, by analyzing earlier optical and near IR data together with the recent data, that the overall broad band data can be reproduced by a single irradiated and viscously heated disk model

Ultra-luminous X-ray sources as super-critical propellers

We study the evolution of newborn neutron stars in high-mass X-ray binaries interacting with a wind-fed super-Eddington disk. The inner disk is regularized to a radiation-dominated quasi-spherical configuration for which we calculate the inner radius of the disk, the total luminosity of the system and the torque acting on the neutron star accordingly, following the evolution of the system through the ejector and early propeller stages. We find that the systems with $B \gtrsim 10^{13}$ G pass through a short ($\sim 20\,{\rm yr}$) ejector stage appearing as supernova impostors followed by a propeller stage lasting $\sim 10^3\,{\rm yr}$. In the super-critical propeller stage the system is still bright ($L\sim 10^{40}\,{\rm erg\, s^{-1}}$) due to the spindown power and therefore appears as an ultra-luminous X-ray source (ULX). The system evolves into pulsating ULX (PULX) when the neutron star spins down to a period ($P\sim 1$ s) allowing for accretion onto its surface to commence. Systems with lower magnetic fields, $B \sim 10^{11}$ G, pass through a long ($10^5\,{\rm yr}$) super-critical propeller stage with luminosities similar to those of the ultra-luminous super-soft sources (ULS), $L \lesssim 10^{40}\,{\rm erg\, s^{-1}}$. The equilibrium periods of these systems in the accretion stage is about $10\,{\rm ms}$, which is much smaller than the typical period range of PULX observed to date. Such systems could have a larger population, but their pulsations would be elusive due to the smaller size of the magnetosphere. Our results suggest that the ULS and some nonpulsating ULX are rapidly spinning and highly magnetized young neutron stars at the super-critical propeller stage.Comment: ApJ in press. 9 pages, 4 figure

On fallback disks and magnetars

The discovery of a disk around the anomalous X-ray pulsar 4U 0142+61, has rekindled the interest in fallback disks around magnetars. We briefly review the assumptions of fallback disk models and magnetar models. Earlier data in optical and near IR bands combined with new Spitzer data in the mid-IR range are compatible with a gas disk. Higher multipole fields with magnetar strengths together with a dipole field of 1012-1013 G on the neutron star surface are compatible with the presence of a disk around the neutron star. The possible presence and properties of a fallback disk after the supernova explosion is a likely initial condition to complement the initial rotation period and initial dipole field in determining the evolutionary paths and different types of isolated neutron stars

Global Imbalances, Current Account Rebalancing and Exchange Rate Adjustments

We analyze the global imbalances and the required adjustments for rebalancing in current accounts and real exchange rates. We set up a two-country two-sector model for the US- China with two asymmetries. First, we assume that the size of China initially is one third of the US but its size becomes half of the US in the next ten years consistent with the fast growth expectations in China. Secondly, we assume that China initially runs a net export surplus against the US. Then we quantitatively study two adjustment scenarios. First scenario,called Slow Adjustment, assumes that in the process of growth, Chinese demand composition moves more towards domestic non-tradable sector. In this case, Chinese real exchange rate appreciates gradually and net export surplus also decreases slowly. Second scenario, called Quick Adjustment, assumes that in addition to the higher non-tradable share in output, net export surplus against US goes to zero quickly in fi�ve years. In this case, net export adjustment happens quickly and real exchange rates in China also appreciate faster and at a higher rate than Slow Adjustment case. Even though, global imbalances are eliminated faste in the Quick Adjustment case, high real appreciation in China hurts importers in the US. A comparison in terms of output shows that Slow Adjustments is preferred for both countries.Global imbalances, Current accounts, Exchange rate adjustments

A natural limit on the observable periods of anomalous x-ray pulsars and soft gamma-ray repeaters

We investigate the dependence of the evolution of neutron stars with fallback disks on the strength of the magnetic dipole field of the star. Using the same model as employed by Ertan et al. (2009), we obtain model curves for different dipole fields showing that the neutron stars with magnetic dipole fields greater than ∼ 1013 G on the surface of the star are not likely to become anomalous X‐ray pulsars (AXPs) and soft gamma‐ray repeaters (SGRs). Other sources with conventional dipole fields evolve into the AXP phase if their disk can penetrate the light cylinder. The upper limits to the observed periods of AXP and SGRs could be understood if the disk becomes inactive below a low temperature around 100 K. We summarize our present and earlier results indicated by the evolutionary model curves of these sources with an emphasis on the importance of the minimum disk temperature and the X‐ray irradiation in the long‐term evolution of AXPs and SGRs with fallback disks

‘Delightfully depressing’: Death/doom metal music world and the emotional responses of the fan

Death/doom metal music, from both sides of the name, usually occupies itself with the darker spectrum of human emotion. Depression, melancholy, and death are common themes in the music and in the reception of this music from an outsider point of view. In line with symbolic interactionism, these emotional responses differ significantly when they originate from a well-socialized member of this music world. This suggests that one may think of emotional responses as conventions of a music world. Common responses provide an emotional repertoire for members, and furthermore they become an adhesive for the community. In this article, I discuss my research of the fans of death/doom metal, and explore the ways in which the fan responds to the music while contemplating on how death/doom function in the lives of these fans