Explore the vast range of titles available.

A mid-sized black hole There should be some intermediate-mass black holes out there, in the gap between the stellar mass and super-massive populations. Too large to have formed by the collapse of a massive star, but too small to be found at the centre of galaxies, they are thought to form in dense stellar clusters or globular clusters. Until now there was no strong observational evidence for their existence. But the 'missing link' of the black hole world may have now been found with the discovery of a variable ultraluminous X-ray source, in the edge-on spiral galaxy ESO 243–49. The extreme luminosity of the source — HLX-1 for short — is consistent with the presence of an intermediate-mass black hole of over 500 solar masses. Ultraluminous X-ray sources are extragalactic objects located outside the nucleus of the host galaxy with bolometric luminosities exceeding 10 39 erg s −1 . These extreme luminosities imply the presence of an accreting black hole with a mass of ∼10 2 –10 5 solar masses, but the existence of such intermediate mass black holes is in dispute. A variable X-ray source with an implied mass of ∼500 solar masses is now reported in the galaxy ESO 243–49. Ultraluminous X-ray sources are extragalactic objects located outside the nucleus of the host galaxy with bolometric luminosities 1 exceeding 10 39  erg s -1 . These extreme luminosities—if the emission is isotropic and below the theoretical (Eddington) limit, where the radiation pressure is balanced by the gravitational pressure—imply the presence of an accreting black hole with a mass of ∼10 2 –10 5 solar masses ( ). The existence of such intermediate-mass black holes is in dispute, and though many candidates have been proposed, none are widely accepted as definitive. Here we report the detection of a variable X-ray source with a maximum 0.2–10 keV luminosity of up to 1.1 × 10 42  erg s -1 in the edge-on spiral galaxy ESO 243-49, with an implied conservative lower limit for the mass of the black hole of ∼500 .

Ultraluminous X-ray sources are extragalactic objects located outside the nucleus of the host galaxy with bolometric luminosities exceeding 10 super(39)ergs super(-1). These extreme luminosities-if the emission is isotropic and below the theoretical (Eddington) limit, where the radiation pressure is balanced by the gravitational pressure-imply the presence of an accreting black hole with a mass of 610 super(2)-10 super(5) solar masses (). The existence of such intermediate-mass black holes is in dispute, and though many candidates have been proposed, none are widely accepted as definitive. Here we report the detection of a variable X-ray source with a maximum 0.2-10keV luminosity of up to 1.110 super(42)e rgs super(-1) in the edge-on spiral galaxy ESO243-49, with an implied conservative lower limit for the mass of the black hole of 6500.

Relativistic jets are streams of plasma moving at appreciable fractions of the speed of light. They have been observed from stellar-mass black holes (∼3 to 20 solar masses, M ⊙ ) as well as supermassive black holes (∼10 6 to 10 9 M⊙) found in the centers of most galaxies. Jets should also be produced by intermediate-mass black holes (∼10 2 to 10 5 M ⊙ ), although evidence for this third class of black hole has, until recently, been weak. We report the detection of transient radio emission at the location of the intermediate-mass black hole candidate ESO 243-49 HLX-1, which is consistent with a discrete jet ejection event. These observations also allow us to refine the mass estimate of the black hole to be between ∼9 × 10 3 M ⊙ and ∼9 × 10 4 M ⊙ .

A unique signature for the presence of massive black holes in very dense stellar regions is occasional giant-amplitude outbursts of multi-wavelength radiation from tidal disruption and subsequent accretion of stars that make a close approach to the black holes 1 . Previous strong tidal disruption event (TDE) candidates were all associated with the centres of largely isolated galaxies 2 – 6 . Here, we report the discovery of a luminous X-ray outburst from a massive star cluster at a projected distance of 12.5 kpc from the centre of a large lenticular galaxy. The luminosity peaked at ~10 43  erg s −1 and decayed systematically over 10 years, approximately following a trend that supports the identification of the event as a TDE. The X-ray spectra were all very soft, with emission confined to be ≲3.0 keV, and could be described with a standard thermal disk. The disk cooled significantly as the luminosity decreased—a key thermal-state signature often observed in accreting stellar-mass black holes. This thermal-state signature, coupled with very high luminosities, ultrasoft X-ray spectra and the characteristic power-law evolution of the light curve, provides strong evidence that the source contains an intermediate-mass black hole with a mass tens of thousand times that of the solar mass. This event demonstrates that one of the most effective means of detecting intermediate-mass black holes is through X-ray flares from TDEs in star clusters. A bright X-ray outburst from a massive star cluster 12.5 kpc from a galactic centre fits the profile of a tidal disruption event (TDE), indicating the likely presence of an intermediate-mass black hole (IMBH). TDEs could be the most effective way of identifying IMBHs.

Multiwavelength flares from tidal disruption and accretion of stars can be used to find and study otherwise dormant massive black holes in galactic nuclei. Previous well-monitored candidate flares were short-lived, with most emission confined to within ∼1 year. Here we report the discovery of a well-observed super-long (>11 years) luminous X-ray flare from the nuclear region of a dwarf starburst galaxy. After an apparently fast rise within ∼4 months a decade ago, the X-ray luminosity, though showing a weak trend of decay, has been persistently high at around the Eddington limit (when the radiation pressure balances the gravitational force). The X-ray spectra are soft — steeply declining towards higher energies — and can be described with Comptonized emission from an optically thick low-temperature corona, a super-Eddington accretion signature often observed in accreting stellar-mass black holes. Dramatic spectral softening was also caught in one recent observation, implying either a temporary transition from the super-Eddington accretion state to the standard thermal state, or the presence of a transient highly blueshifted (∼0.36c) warm absorber. All these properties in concert suggest a tidal disruption event with an unusually long super-Eddington accretion phase that has never before been observed.

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory. Athena is a versatile observatory designed to address the Hot and Energetic Universe science theme, as selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), X-IFU aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over a hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR (i.e. in the course of its preliminary definition phase, so-called B1), browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters, such as the instrument efficiency, spectral resolution, energy scale knowledge, count rate capability, non X-ray background and target of opportunity efficiency. Finally, we briefly discuss the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, touch on communication and outreach activities, the consortium organisation and the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. The X-IFU will be provided by an international consortium led by France, The Netherlands and Italy, with ESA member state contributions from Belgium, Czech Republic, Finland, Germany, Poland, Spain, Switzerland, with additional contributions from the United States and Japan.

Charity watchdogs and the media level serious allegations of mismanagement of funds at charities serving former and current members of the U.S. armed services, affecting service recipients, families, donors, grantors, foundations, and taxpayers. To examine these allegations, we use two approaches from the literature to assess nonprofit financial effectiveness: the organization’s ability to gain resources and to sustain activities. We mirror the approach of charity raters, whose measures are widely available to the public. Using GuideStar/Internal Revenue Service data, we compare fund-raising expenditures, assets, and financial sustainability of large national military and veterans nonprofits to a random sample of national nonprofits. We apply propensity score matching and compare organizations similar in size, age, and other factors. We find little difference between military and veterans charities and other nonprofits and provide an improved method for evaluating the financial health of nonprofits across academic discipline, nonprofit field of service, and within or among countries.

The Athena mission entered a redefinition phase in July 2022, driven by the imperative to reduce the mission cost at completion for the European Space Agency below an acceptable target, while maintaining the flagship nature of its science return. This notably called for a complete redesign of the X-ray Integral Field Unit (X-IFU) cryogenic architecture towards a simpler active cooling chain. Passive cooling via successive radiative panels at spacecraft level is now used to provide a 50 K thermal environment to an X-IFU owned cryostat. 4.5 K cooling is achieved via a single remote active cryocooler unit, while a multi-stage Adiabatic Demagnetization Refrigerator ensures heat lift down to the 50 mK required by the detectors. Amidst these changes, the core concept of the readout chain remains robust, employing Transition Edge Sensor microcalorimeters and a SQUID-based Time-Division Multiplexing scheme. Noteworthy is the introduction of a slower pixel. This enables an increase in the multiplexing factor (from 34 to 48) without compromising the instrument energy resolution, hence keeping significant system margins to the new 4 eV resolution requirement. This allows reducing the number of channels by more than a factor two, and thus the resource demands on the system, while keeping a 4’ field of view (compared to 5’ before). In this article, we will give an overview of this new architecture, before detailing its anticipated performances. Finally, we will present the new X-IFU schedule, with its short term focus on demonstration activities towards a mission adoption in early 2027

Charity watchdogs and the media level serious allegations of mismanagement of funds at charities serving former and current members of the U.S. armed services, affecting service recipients, families, donors, grantors, foundations, and taxpayers. To examine these allegations, we use two approaches from the literature to assess nonprofit financial effectiveness: the organization's ability to gain resources and to sustain activities. We mirror the approach of charity raters, whose measures are widely available to the public. Using GuideStar/Internal Revenue Service data, we compare fund-raising expenditures, assets, and financial sustainability of large national military and veterans nonprofits to a random sample of national nonprofits. We apply propensity score matching and compare organizations similar in size, age, and other factors. We find little difference between military and veterans charities and other nonprofits and provide an improved method for evaluating the financial health of nonprofits across academic discipline, nonprofit field of service, and within or among countries.

The X-ray Integral Field Unit (X-IFU) is the high-resolution X-ray spectrometer to fly on board the Athena Space Observatory of the European Space Agency (ESA). It is being developed by an international Consortium led by France, involving twelve ESA member states, plus the United States. It is a cryogenic instrument, involving state of the art technology, such as micro-calorimeters, to be read out by low noise electronics. As the instrument was undergoing its system requirement review (in 2022), a life cycle assessment (LCA) was performed to estimate the environmental impacts associated with the development of the sub-systems that were under the responsibility of the X-IFU Consortium. The assessment included the supply, manufacturing and testing of sub systems, as well as involved logistics and manpower. We find that the most significant environmental impacts arise from testing activities, which is related to energy consumption in clean rooms, office work, which is related to energy consumption in office buildings, and instrument manufacturing, which is related to the use of mineral and metal resources. Furthermore, business travels is another area of concern, despite the policy to reduced flying adopted by the Consortium. As the instrument is now being redesigned to fit within the new boundaries set by ESA, the LCA will be updated, with a focus on the hot spots identified in the first iteration. The new configuration, consolidated in 2023, is significantly different from the previously studied version and is marked by an increase of the perimeter of responsibility for the Consortium. This will need to be folded in the updated LCA, keeping the ambition to reduce the environmental footprint of X-IFU, while complying with its stringent requirements in terms of performance and risk management.