The vast majority of binaries containing a compact object and a regular star spend most of their time in a quiescent state where no strong interactions occur between components. Detection of these binaries is extremely challenging and only few candidates have been detected through optical spectroscopy. Self-lensing represents a new means of detecting compact objects in binaries, where gravitational lensing of the light from the visible component by the compact object produces periodic optical flares. Here we show that current and planned large-area optical surveys can detect a significant number (∼100–10,000s) of these self-lensing binaries and provide insights into the properties of the compact lenses. We show that many of the predicted population of observable self-lensing binaries will be observed with multiple self-lensing flares; this both improves the chances of detection and also immediately distinguishes them from chance-alignment micro-lensing events. Through self-lensing we can investigate long – but previously hidden – stages of binary evolution and consequently provide new constraints on evolutionary models which impact on the number and nature of double compact object mergers.
The discovery of neutron stars powering several ultraluminous X-ray sources (ULXs) raises important questions about the nature of the underlying population. In this paper we build on previous work studying simulated populations by incorporating a model where the emission originates from a precessing, geometrically beamed wind-cone, created by a super-critical inflow. We obtain estimates – independent of the prescription for the precession period of the wind – for the relative number of ULXs that are potentially visible (persistent or transient) for a range of underlying factors such as the relative abundance of black holes or neutron stars within the population, maximum precessional angle, and LMXB duty cycle. We make initial comparisons to existing data using a catalogue compiled from XMM-Newton. Finally, based on estimates for the precession period, we determine how the eROSITA all-sky survey (eRASS) will be able to constrain the underlying demographic.
The advancement of RFID technology has been viewed by many as one of the most beneficial developments in the business world. Furthermore, the progress in this technology has motivated software and hardware manufacturers to leverage RFID capability and drive the adoption of RFID in the data center market. RFID technology holds promise in transforming supply chain management by providing real time intelligence for tracking enterprise assets. As it stands, the objective of RFID is to manage the entire life cycle of an asset by determining the time of initial asset acquisition, the asset's physical location, the asset's movement within a data center and the time of the asset's ultimate decommission. In addition, RFID is also capable of managing the motion of devices in and between data centers thus enhancing the ability to forecast data center capacity. Although data centers has been readily adopted and implemented in commercial sectors such as the retail environment, its introduction and implementation in the financial market sector has not occurred with similar speed and enthusiasm, suggesting presence of some reluctance. However, financial institutions are being under pressure from clients in order to provide real-time financial data and are looking at data centers integrated with RFID based supply chain systems for this purpose. The motivation for the present study arises from the growing body of literature which has examined the contribution of RFID supply chain systems in data centers and the motivation of financial institutions to use these data centers in order to become more competitive in the market. The paper asks the questions whether the RFID based supply chain systems in data centers can help to improve the performance of financial institutions.
The presence of radiatively driven outflows is well established in ultraluminous X-ray sources (ULXs). These outflows are optically thick and can reprocess a significant fraction of the accretion luminosity. Assuming isotropic emission, escaping radiation from the outflow’s photosphere has the potential to irradiate the outer disc. Here, we explore how the atmosphere of the outer disc would respond to such irradiation, and specifically whether unstable heating may lead to significant mass loss via thermally-driven winds. We find that, for a range of physically relevant system parameters, this mass loss may actually switch off the inflow entirely and potentially drive limit-cycle behaviour (likely modulated on the timescale of the outer disc). In ULXs harbouring neutron stars, magnetic fields tend to have a slight destabilizing effect; for the strongest magnetic fields and highest accretion rates, this can push otherwise stable systems into the unstable regime. We explore the prevalence of the instability in a simulated sample of ULXs obtained from a binary population synthesis calculation. We find that almost all neutron star and black hole ULXs with Eddington-scaled accretion rates of $\dot{m}_0 < 100$ should be able to drive powerful outflows from their outer discs. Several known ULXs are expected to lie in this regime; the persistence of accretion in these sources implies the irradiation may be anisotropic which can be reconciled with the inferred reprocessed (optical) emission if some of this originates in the wind photosphere or irradiation of the secondary star.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.