Anton Pannekoek Institute for Astronomy
Relativistic macroscopic plasma dynamics can be described by general-relativistic magnetohydrodynamics. In many high-energy astrophysical settings, such as the interior dynamics of magnetized stars, the ideal GRMHD approximation, in which we assume infinite conductivity, provides an excellent description. However, ideal GRMHD neglects resistive effects that are essential for processes such as magnetic reconnection, dissipation, and magnetospheric dynamics. Incorporating resistivity into astrophysical plasma models accounts for the fact that plasmas in such environments are not perfect conductors. We present a resistive version of the GPU-accelerated GRMHD code GRaM-X, which evolves the full resistive GRMHD equations using the Z4c formalism for Einstein's equations. We implement a second-order implicit-explicit Runge-Kutta scheme to handle stiff source terms, obtain the primitive quantities from the conserved quantities using a one-dimensional recovery method, and employ the HLLE Riemann solver in combination with TVD and WENO reconstruction schemes. We validate the module using a range of standard tests, including 1D shocktubes, current sheets, Alfvén waves, 2D cylindrical explosions, and 3D TOV stars. The results of these tests demonstrate accurate recovery of the ideal MHD limit, correct resistive behavior, and stable evolution in dynamical spacetimes. Leveraging the GPU-accelerated resistive version of GRaM-X enables efficient large-scale simulations, paving the way for realistic studies of binary mergers, accretion flows, and relativistic jets within the framework of multi-messenger astrophysics.
Gravitational waves from black-hole merging events have revealed a population of extra-galactic BHs residing in short-period binaries with masses that are higher than expected based on most stellar evolution models - and also higher than known stellar-origin black holes in our Galaxy. It has been proposed that those high-mass BHs are the remnants of massive metal-poor stars. Gaia astrometry is expected to uncover many Galactic wide-binary systems containing dormant BHs, which may not have been detected before. The study of this population will provide new information on the BH-mass distribution in binaries and shed light on their formation mechanisms and progenitors. As part of the validation efforts in preparation for the fourth Gaia data release (DR4), we analysed the preliminary astrometric binary solutions, obtained by the Gaia Non-Single Star pipeline, to verify their significance and to minimise false-detection rates in high-mass-function orbital solutions. The astrometric binary solution of one source, Gaia BH3, implies the presence of a 32.70 \pm 0.82 M\odot BH in a binary system with a period of 11.6 yr. Gaia radial velocities independently validate the astrometric orbit. Broad-band photometric and spectroscopic data show that the visible component is an old, very metal-poor giant of the Galactic halo, at a distance of 590 pc. The BH in the Gaia BH3 system is more massive than any other Galactic stellar-origin BH known thus far. The low metallicity of the star companion supports the scenario that metal-poor massive stars are progenitors of the high-mass BHs detected by gravitational-wave telescopes. The Galactic orbit of the system and its metallicity indicate that it might belong to the Sequoia halo substructure. Alternatively, and more plausibly, it could belong to the ED-2 stream, which likely originated from a globular cluster that had been disrupted by the Milky Way.
Stellar-mass black holes are the final remnants of stars born with more than 15 solar masses. Billions are expected to reside in the Local Group, yet only few are known, mostly detected through X-rays emitted as they accrete material from a companion star. Here, we report on VFTS 243: a massive X-ray faint binary in the Large Magellanic Cloud. With an orbital period of 10.4-d, it comprises an O-type star of 25 solar masses and an unseen companion of at least nine solar masses. Our spectral analysis excludes a non-degenerate companion at a 5-sigma confidence level. The minimum companion mass implies that it is a black hole. No other X-ray quiet black hole is unambiguously known outside our Galaxy. The (near-)circular orbit and kinematics of VFTS 243 imply that the collapse of the progenitor into a black hole was associated with little or no ejected material or black-hole kick. Identifying such unique binaries substantially impacts the predicted rates of gravitational-wave detections and properties of core-collapse supernovae across the Cosmos.
Studying the escaping atmospheres of highly-irradiated exoplanets is critical for understanding the physical mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this planet's outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hours after egress until the target set, demonstrating the outflow extends at least 5.8×1055.8 \times 10^5 km or 7.5 planet radii. This detection is significantly longer than previous observations which report an outflow extending \sim2.2 planet radii just one year prior. The outflow is blue-shifted by -23 km s1^{-1} in the planetary rest frame. We estimate a current mass loss rate of 1 MM_{\oplus} Gyr1^{-1}. Our observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind. However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or differences in instrumental precision.
XRISM/Resolve observations of NGC 3516 provided the first intra-observation variability detection in highly ionized X-ray absorbers, constraining gas density to >10^6 cm^-3 and distance to <11.6 light days for one outflow. The study identified eight distinct photoionized gas components, including a transient ultra-fast inflow at ~14,800 km/s, and found a 40 ks oscillatory "rocking" motion in the Fe Kα emission correlated with continuum flux.
Radio observations at low frequencies are sensitive to the magnetic activity of stars and the plasma environment surrounding them. The accurate interpretation of the processes underlying the radio signatures requires a detailed characterisation of the stellar magnetism. We study two M dwarfs, StKM 1-1262 (M0 type, Prot=1.24_\mathrm{rot}=1.24 d) and V374 Peg (M4 type, Prot=0.4455_\mathrm{rot}=0.4455 d), which were detected with the LOw Frequency ARray (LOFAR). StKM 1-1262 exhibited a type-II radio burst, potentially resulting from a coronal mass ejection event. V374 Peg manifested low-frequency radio emission typical of an electron-cyclotron maser instability emission mechanism. We analysed spectropolarimetric observations of these M dwarfs collected with the SpectroPolarimètre InfraRouge (SPIRou). Firstly, we refined the stellar parameters such as effective temperature, surface gravity, and metallicity, and measured the average surface magnetic flux via modelling of Zeeman broadening in unpolarised spectra. We then applied Zeeman-Doppler imaging to least-squares deconvolution line profiles in circular polarisation to reconstruct their large-scale magnetic fields. StKM 1-1262 has a total, unsigned magnetic field of 3.53±0.063.53\pm0.06 kG on average and the large-scale magnetic field topology is dipolar and moderately axisymmetric, with an average strength of 300 G. V374 Peg has an unsigned magnetic field of 5.46±0.095.46\pm0.09 kG and the large-scale field is dipolar and axisymmetric, with an average strength of 800 G. For StKM 1-1262, we found a strong anti-correlation between the total magnetic field and the effective temperature which is reminiscent of the tight link between small-scale magnetic fields and surface inhomogeneities. For V374 Peg, we found a moderate anti-correlation, possibly due to a more even distribution of surface features. (Abridged)
ETH Zurich logoETH ZurichCNRS logoCNRSTohoku University logoTohoku UniversityUniversity of New South WalesUniversity of Amsterdam logoUniversity of AmsterdamUniversity of OsloINFN Sezione di NapoliMonash University logoMonash UniversityChinese Academy of Sciences logoChinese Academy of SciencesKyoto Sangyo UniversityTel Aviv University logoTel Aviv UniversityKEKUniversity College London logoUniversity College LondonUniversity of Oxford logoUniversity of OxfordOsaka University logoOsaka UniversityNagoya University logoNagoya UniversityTokyo University of ScienceRIKEN logoRIKENTata Institute of Fundamental ResearchCSICNASA Goddard Space Flight Center logoNASA Goddard Space Flight CenterColumbia University logoColumbia UniversityINFN Sezione di PisaCurtin UniversityUniversity of Tokyo logoUniversity of TokyoUniversité Paris-Saclay logoUniversité Paris-SaclayFriedrich-Alexander-Universität Erlangen-NürnbergSorbonne Université logoSorbonne UniversitéUniversity of TurkuDeutsches Elektronen-Synchrotron DESYCEA logoCEAUniversity of GenevaUniversidade Federal do ABCUniversity of HaifaUniversität WürzburgUniversidad Complutense de MadridUniversità di GenovaTechnische Universität BerlinThe University of ChicagoNicolaus Copernicus Astronomical Center, Polish Academy of SciencesObservatoire de ParisUniversity College DublinINAF - Osservatorio Astrofisico di TorinoUniversité Côte d’AzurDurham University logoDurham UniversityUniversità degli Studi di PaviaUniversidad Nacional Autónoma de MéxicoJagiellonian UniversitySaha Institute of Nuclear PhysicsInstituto de Astrofísica de CanariasGran Sasso Science Institute (GSSI)University of the WitwatersrandUniversidad de ChileUniversidade de São PauloUniversität HamburgUniversity of BergenRuhr-Universität BochumHarvard-Smithsonian Center for Astrophysics logoHarvard-Smithsonian Center for AstrophysicsINFN, Sezione di TorinoPontificia Universidad Católica de ChileDublin Institute for Advanced StudiesUniversidad de ValparaísoTechnische Universität DortmundPSL Research UniversityUniversidad de La LagunaJosip Juraj Strossmayer University of OsijekIndian Institute of AstrophysicsKonan UniversityInter-University Centre for Astronomy and AstrophysicsTaras Shevchenko National University of KyivINFN Sezione di PerugiaINAF-Istituto di RadioastronomiaUniversidad de JaénINAF – Osservatorio Astronomico di RomaInstitut de Física d’Altes Energies (IFAE)FZU - Institute of Physics of the Czech Academy of SciencesInstituto de Astrofísica de Andalucía (IAA)Max-Planck-Institut für KernphysikUniv. Savoie Mont BlancUniversitá degli Studi dell’InsubriaLaboratório de Instrumentação e Física Experimental de Partículas (LIP)University of NamibiaUniversidade Federal de ItajubáUniversidad de GuadalajaraCentro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT)Universidad Católica del NorteINFN Sezione di LecceInternational Centre for Radio Astronomy Research (ICRAR)Tuorla ObservatoryEuropean Space Agency (ESA)Anton Pannekoek Institute for AstronomyYerevan Physics InstituteRudjer Boskovic InstituteUniversidad Autónoma de San Luis PotosíCalifornia Polytechnic State University - San Luis ObispoFred Lawrence Whipple ObservatoryAgenzia Spaziale Italiana (ASI)Università di SienaUniversidad Metropolitana de Ciencias de la EducaciónAPCMullard Space Science LaboratoryTechnical University of KosiceUniversidade Federal de PelotasLeopold-Franzens-Universität InnsbruckInstitut de Recherche en Astrophysique et Planétologie (IRAP)Open University of IsraelThe Barcelona Institute of Science and Technology (BIST)Astronomical Institute, Czech Academy of SciencesNamibia University of Science and TechnologyGEPIInstituto de Física de São CarlosKoyama Astronomical ObservatoryErlangen Centre for Astroparticle Physics (ECAP)Istituto Nazionale di Geofisica e Vulcanologia (INGV)ISDCINFN (Sezione di Bari)Institut de Ciències de l’Espai (ICE)National University of LesothoInstitute of Theoretical and Experimental Physics ITEPINAF, Istituto di Astrofisica Spaziale e Fisica Cosmica (IASF) MilanoGRAPPAINAF – Istituto di Astrofisica Spaziale e Fisica Cosmica (IASF) BolognaInstituto Federal de Educação, Ciência e Tecnologia do Piauí (IFPI)Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG)INAF - Osservatorio Astronomico di Palermo “G.S. Vaiana”Universit PSL* North–West UniversityUniversit de ParisSorbonne Paris Cit",Universit Paris DiderotUniversit del SalentoINAF Osservatorio Astronomico di CapodimonteMax Planck Institut fr AstronomieUniversit degli Studi di PadovaUniversit de BordeauxSapienza Universit di RomaINAF Osservatorio Astrofisico di ArcetriUniversit de MontpellierUniversit degli Studi di TorinoUniversit degli Studi di PalermoUniversit e Politecnico di BariUniversit degli Studi di Napoli Federico IIUniversidad de AlcalNational Research Centre “Kurchatov Institute”
The dSphs around the Milky Way are commonly considered as systems that are supported by velocity dispersion against self-gravitation. They have been long accounted among the best targets to search for indirect DM signatures in the GeV-to-TeV gamma-rays due to absence of astrophysical gamma-ray foreground or background emission. We present forecasts on the sensitivity of the future CTAO for the search for annihilating or decaying DM in such targets. We perform an original selection of candidates out of the current catalog of known objects, including both classical and ultra-faint targets. For each of them, we calculate the expected amount of DM using the most updated and complete available samples of photometric and spectroscopic data of member stars, adopting a common framework of data treatment for both classes of objects. In this way, we are able to generate novel astrophysical factor profiles for general indirect DM searches that we compare with the current literature. Out of a starting sample of 64 dSphs, we highlight the 8 most promising targets - DraI, CBe, UMaII, UMi and Wil1 in the Northern hemisphere; RetII, Scl and SgrII in the Southern hemisphere - for which different DM density models (either cored or cuspy) lead to similar expectations, at variance with what happens for other DM targets - thus resulting in more robust predictions. We find that CTAO will provide the strongest limits above ~10 TeV, down to values of velocity-averaged annihilation cross section of ~5×1025 \times 10^{-25} cm3^3 s1^{-1} and up to decay lifetimes of ~1026^{26} s for combined limits on the best targets. We argue that the largest source of inaccuracy is due to the still imprecise determination of the DM content, especially for ultra-faint dSphs. We propose possible strategies of observation for CTAO, either optimized on a deep focus on the best known candidates, or on the diversification of targets.
The visibility of Lyman-α\alpha emission at z&gt;7 provides crucial insights into the reionization process and the role of galaxies in shaping the ionized intergalactic medium. Using JWST FRESCO data, we investigate the environments of Lyman-α\alpha emitters (LAEs) in the GOODS-N and GOODS-S fields by identifying [OIII] emitters and analyzing their large-scale distribution. Using the FRESCO redshifts, we recover eight new LAEs from archival Keck/MOSFIRE observations at z=7.07.7z=7.0-7.7, including a potential AGN candidate at z7.2z \sim 7.2. Complemented by six literature LAEs, our sample consists of 14 LAEs in total, all of which are [OIII] emitters except for one very faint source not detected by FRESCO. We define seven groups of [OIII] emitters centered around the brightest LAEs and find that these bright LAEs do not reside in more overdense environments than the average galaxy population. The overdensity parameters for LAEs and [OIII] emitters without Lyman-α\alpha, calculated for sources with \mathrm{M_{UV}&lt;-19.5} to ensure completeness, are similar, indicating that overdensities alone cannot fully explain Lyman-α\alpha visibility. While LAEs have slightly higher recent star formation (SFR10_{10}/SFR501.3×_{50} \approx 1.3\times) and [OIII] EW (1.5×\approx1.5\times), they show no significant differences from [OIII] emitters in UV slope (β\beta), UV magnitude (MUV\mathrm{M_{UV}}), or stellar mass (logM\log_{\mathrm{M}_{\star}}). Our results suggest that other factors may contribute to the observability of Lyman-α\alpha emission. Future spectroscopic surveys with broader wavelength coverage and more complete sampling will be crucial for refining our understanding of reionization.
The formation mechanisms of merging binary black holes (BBHs) observed by the LIGO-Virgo-KAGRA collaboration remain uncertain. Detectable eccentricity provides a powerful diagnostic for distinguishing between different formation channels, but resolving their eccentricity distributions requires the detection of a large number of eccentric mergers. Future gravitational wave detectors such as the Einstein Telescope and Cosmic Explorer will detect tens of thousands of BBH mergers out to redshifts z10z \ge 10, making it critical to understand the redshift-dependent evolution of eccentricity distributions. We simulate this evolution for two key channels: dynamical assembly in globular clusters (GCs), which leads to rapid, eccentric mergers; and hierarchical triples in the field, where three-body dynamics can induce eccentricity in the inner binary. When considering all BBH mergers, the GC channel dominates overall, consistent with previous studies. However, when focusing on mergers with detectable eccentricity in next-generation detectors, we find that hierarchical triples dominate the eccentric merger rate at 0z40\le z \le 4, with GC mergers becoming competitive at higher redshifts. Across all model variations, eccentric mergers in the local Universe (z1z\lesssim 1) have significant contributions from field triples, challenging the common view that such systems primarily form in dense environments. We show that, regardless of cluster and stellar evolution uncertainties, hierarchical triples contribute at least 30 per cent of eccentric mergers across a large range of redshifts.
SPHERE (Beuzit et al,. 2019) has now been in operation at the VLT for more than 5 years, demonstrating a high level of performance. SPHERE has produced outstanding results using a variety of operating modes, primarily in the field of direct imaging of exoplanetary systems, focusing on exoplanets as point sources and circumstellar disks as extended objects. The achievements obtained thus far with SPHERE (~200 refereed publications) in different areas (exoplanets, disks, solar system, stellar physics...) have motivated a large consortium to propose an even more ambitious set of science cases, and its corresponding technical implementation in the form of an upgrade. The SPHERE+ project capitalizes on the expertise and lessons learned from SPHERE to push high contrast imaging performance to its limits on the VLT 8m-telescope. The scientific program of SPHERE+ described in this document will open a new and compelling scientific window for the upcoming decade in strong synergy with ground-based facilities (VLT/I, ELT, ALMA, and SKA) and space missions (Gaia, JWST, PLATO and WFIRST). While SPHERE has sampled the outer parts of planetary systems beyond a few tens of AU, SPHERE+ will dig into the inner regions around stars to reveal and characterize by mean of spectroscopy the giant planet population down to the snow line. Building on SPHERE's scientific heritage and resounding success, SPHERE+ will be a dedicated survey instrument which will strengthen the leadership of ESO and the European community in the very competitive field of direct imaging of exoplanetary systems. With enhanced capabilities, it will enable an even broader diversity of science cases including the study of the solar system, the birth and death of stars and the exploration of the inner regions of active galactic nuclei.
The space mission LISA (Laser Interferometer Space Antenna), scheduled for launch in 2035, aims to detect gravitational wave (GW) signals in the milli-Hz band. In the context of ESA Voyage 2050 Call for new mission concepts, other frequency ranges are explored by the Gravitational-Wave Space 2050 Working Group to conceive new proposals for a post-LISA space-based detector. In this work, we give a preliminary estimate of the observational potential of three mission designs proposed in the literature, namely μ\muAres, AMIGO and the Decihertz Observatory. The analysis framework includes astrophysical GW sources such as massive black hole binaries, extreme mass-ratio inspirals and compact binaries such as stellar black holes and white dwarfs. For each detector, we first present a consistent computation of the unresolved gravitational wave background (GWB) produced by the sum of all anticipated astrophysical populations, using an iterative subtraction algorithm. We then investigate which types of systems are the most appealing, by measuring the number of GW signals detected and exploring the source properties.
Fast radio bursts (FRBs) are being detected with increasing regularity. However, their spontaneous and often once-off nature makes high-precision burst position and frequency-time structure measurements difficult without specialised real-time detection techniques and instrumentation. The Australian Square Kilometre Array Pathfinder (ASKAP) has been enabled by the Commensal Real-time ASKAP Fast Transients Collaboration (CRAFT) to detect FRBs in real-time and save raw antenna voltages containing FRB detections. We present the CRAFT Effortless Localisation and Enhanced Burst Inspection pipeline (CELEBI), an automated software pipeline that extends CRAFT's existing software to process ASKAP voltages in order to produce sub-arcsecond precision localisations and polarimetric data at time resolutions as fine as 3 ns of FRB events. We use Nextflow to link together Bash and Python code that performs software correlation, interferometric imaging, and beamforming, making use of common astronomical software packages.
We have searched for continuous gravitational wave (CGW) signals produced by individually resolvable, circular supermassive black hole binaries (SMBHBs) in the latest EPTA dataset, which consists of ultra-precise timing data on 41 millisecond pulsars. We develop frequentist and Bayesian detection algorithms to search both for monochromatic and frequency-evolving systems. None of the adopted algorithms show evidence for the presence of such a CGW signal, indicating that the data are best described by pulsar and radiometer noise only. Depending on the adopted detection algorithm, the 95\% upper limit on the sky-averaged strain amplitude lies in the range 6×10151096\times 10^{-15}10^9M_\odot out to a distance of about 25Mpc, and with \cal{M}_c&gt;10^{10}M_\odot out to a distance of about 1Gpc (z0.2z\approx0.2). We show that state-of-the-art SMBHB population models predict &lt;1\% probability of detecting a CGW with the current EPTA dataset, consistent with the reported non-detection. We stress, however, that PTA limits on individual CGW have improved by almost an order of magnitude in the last five years. The continuing advances in pulsar timing data acquisition and analysis techniques will allow for strong astrophysical constraints on the population of nearby SMBHBs in the coming years.
The Event Horizon Telescope (EHT) collaboration, an Earth-size sub-millimetre radio interferometer, recently captured the first images of the central supermassive black hole in M87. These images were interpreted as gravitationally-lensed synchrotron emission from hot plasma orbiting around the black hole. In the accretion flows around low-luminosity active galactic nuclei such as M87, electrons and ions are not in thermal equilibrium. Therefore, the electron temperature, which is important for the thermal synchrotron radiation at EHT frequencies of 230 GHz, is not independently determined. In this work, we investigate the commonly used parameterised ion-to-electron temperature ratio prescription, the so-called R-β\beta model, considering images at 230 GHz by comparing with electron-heating prescriptions obtained from general-relativistic magnetohydrodynamical (GRMHD) simulations of magnetised accretion flows in a Magnetically Arrested Disc (MAD) regime with different recipes for the electron thermodynamics. When comparing images at 230 GHz, we find a very good match between images produced with the R-β\beta prescription and those produced with the turbulent- and magnetic reconnection- heating prescriptions. Indeed, this match is on average even better than that obtained when comparing the set of images built with the R-β\beta prescription with either a randomly chosen image or with a time-averaged one. From this comparative study of different physical aspects, which include the image, visibilities, broadband spectra, and light curves, we conclude that, within the context of images at 230 GHz relative to MAD accretion flows around supermassive black holes, the commonly-used and simple R-β\beta model is able to reproduce well the various and more complex electron-heating prescriptions considered here.
On 2024 December 28, CHIME/FRB detected the thus-far non-repeating FRB 20241228A with a real-time signal-to-noise ratio of &gt;50. Approximately 112~s later, the X-ray Telescope onboard the Neil Gehrels Swift Observatory was on source, the fastest follow-up to-date of a non-repeating FRB (Tohuvavohu et al. in prep.). Using CHIME/FRB and two of the three CHIME/FRB Outriggers, we obtained a Very Long Baseline Interferometry localization for FRB 20241228A with a 1σ\sigma confidence ellipse of 11^{\prime\prime} by 0.2^{\prime\prime}. This represents the first published localization using both the CHIME-KKO and CHIME-GBO Outriggers. We associate FRB 20241228A with a star-forming galaxy at a redshift of z=0.1614±0.0002z = 0.1614\pm0.0002. The persistent X-ray luminosity limit at this source's location and distance is $<1.2 \times 10^{43}ergs erg s^{-1}inthe in the 0.3-10$ keV band, the most stringent limit of any non-repeating FRB to-date (Tohuvavohu et al. in prep.). The stellar mass ($\sim 2.6 \times 10^{10}\,M_{\odot})andstarformationrate() and star formation rate (\sim 2.9\,M_{\odot} yr~yr^{-1}$) of the host galaxy of FRB 20241228A are consistent with the broader FRB host galaxy population. We measure significant scattering (\sim1ms) and scintillation (\sim20 kHz at 600 MHz) along the line of sight to this source, and suggest the scintillation screen is Galactic while the scattering screen is extragalactic. FRB 20241228A represents an exciting example of a new era in which we can harness VLBI-localizations and rapid high-energy follow-up to probe FRB progenitors.
Rare, energetic (long) thermonuclear (Type I) X-ray bursts are classified either as intermediate-duration or superbursts, based on their duration. Intermediate-duration bursts lasting a few to tens of minutes are thought to arise from the thermonuclear runaway of a relatively thick (10^10 g/cm2) helium layer, while superbursts lasting hours are attributed to the detonation of an underlying carbon layer. We present a catalogue of 84 long thermonuclear bursts from 40 low-mass X-ray binaries, and defined from a new set of criteria distinguishing them from the more frequent short bursts. The three criteria are: (1) a total energy release larger than 10^40 erg, (2) a photospheric radius expansion phase longer than 10 s, and (3) a burst time-scale longer than 70 s. This work is based on a comprehensive systematic analysis of 70 bursts found with INTEGRAL, RXTE, Swift, BeppoSAX, MAXI, and NICER, as well as 14 long bursts from the literature that were detected with earlier generations of X-ray instruments. For each burst, we measure its peak flux and fluence, which eventually allows us to confirm the distinction between intermediate-duration bursts and superbursts. Additionally, we list 18 bursts that only partially meet the above inclusion criteria, possibly bridging the gap between normal and intermediate-duration bursts. With this catalogue, we significantly increase the number of long-duration bursts included in the MINBAR and thereby provide a substantial sample of these rare X-ray bursts for further study.
We present the detection of a bright radio burst at radio frequencies between 2.2--2.3 GHz with the NASA Deep Space Network (DSN) 70 m dish (DSS-63) in Madrid, Spain from FRB~20200120E. This repeating fast radio burst (FRB) was recently discovered by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) instrument and reported to be associated with the M81 spiral galaxy at a distance of 3.6 Mpc. The high time resolution capabilities of the recording system used in this observation, together with the small amount of scattering and intrinsic brightness of the burst, allow us to explore the burst structure in unprecedented detail. We find that the burst has a duration of roughly 30 μ\mus and is comprised of several narrow components with typical separations of 2--3 μ\mus. The narrowest component has a width of \lesssim 100 ns, which corresponds to a light travel time size as small as 30 m, the smallest associated with an FRB to date. The peak flux density of the narrowest burst component is 270 Jy. We estimate the total spectral luminosity of the narrowest component of the burst to be 4 ×\times 1030^{\text{30}} erg s-1^{\text{-1}} Hz-1^{\text{-1}}, which is a factor of \sim500 above the luminosities of the so-called "nanoshots" associated with giant pulses from the Crab pulsar. This spectral luminosity is also higher than that of the radio bursts detected from the Galactic magnetar SGR 1935+2154 during its outburst in April 2020, but it falls on the low-end of the currently measured luminosity distribution of extragalatic FRBs. These results provide further support for the presence of a continuum of FRB burst luminosities.
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We present the results from a full polarization study carried out with ALMA during the first VLBI campaign, which was conducted in Apr 2017 in the λ\lambda3mm and λ\lambda1.3mm bands, in concert with the Global mm-VLBI Array (GMVA) and the Event Horizon Telescope (EHT), respectively. We determine the polarization and Faraday properties of all VLBI targets, including Sgr A*, M87, and a dozen radio-loud AGN. We detect high linear polarization fractions (2-15%) and large rotation measures (RM >103.3105.5>10^{3.3}-10^{5.5} rad m2^{-2}). For Sgr A* we report a mean RM of (4.2±0.3)×105(-4.2\pm0.3) \times10^5 rad m2^{-2} at 1.3 mm, consistent with measurements over the past decade, and, for the first time, an RM of (2.1±0.1)×105(-2.1\pm0.1) \times10^5 rad m2^{-2} at 3 mm, suggesting that about half of the Faraday rotation at 1.3 mm may occur between the 3 mm photosphere and the 1.3 mm source. We also report the first unambiguous measurement of RM toward the M87 nucleus at mm wavelengths, which undergoes significant changes in magnitude and sign reversals on a one year time-scale, spanning the range from -1.2 to 0.3 ×105\times\,10^5 rad m2^{-2} at 3 mm and -4.1 to 1.5 ×105\times\,10^5 rad m2^{-2} at 1.3 mm. Given this time variability, we argue that, unlike the case of Sgr A*, the RM in M87 does not provide an accurate estimate of the mass accretion rate onto the black hole. We put forward a two-component model, comprised of a variable compact region and a static extended region, that can simultaneously explain the polarimetric properties observed by both the EHT and ALMA. These measurements provide critical constraints for the calibration, analysis, and interpretation of simultaneously obtained VLBI data with the EHT and GMVA.
Fast radio bursts (FRBs) are millisecond pulses of radio emission of seemingly extragalactic origin. More than 50 FRBs have now been detected, with only one seen to repeat. Here we present a new FRB discovery, FRB 110214, which was detected in the high latitude portion of the High Time Resolution Universe South survey at the Parkes telescope. FRB 110214 has one of the lowest dispersion measures of any known FRB (DM = 168.9±\pm0.5 pc cm3^{-3}), and was detected in two beams of the Parkes multi-beam receiver. A triangulation of the burst origin on the sky identified three possible regions in the beam pattern where it may have originated, all in sidelobes of the primary detection beam. Depending on the true location of the burst the intrinsic fluence is estimated to fall in the range of 50 -- 2000 Jy ms, making FRB 110214 one of the highest-fluence FRBs detected with the Parkes telescope. No repeating pulses were seen in almost 100 hours of follow-up observations with the Parkes telescope down to a limiting fluence of 0.3 Jy ms for a 2-ms pulse. Similar low-DM, ultra-bright FRBs may be detected in telescope sidelobes in the future, making careful modeling of multi-beam instrument beam patterns of utmost importance for upcoming FRB surveys.
Neutron stars and black holes in X-ray binaries are observed to host strong collimated jets in the hard spectral state. Numerical simulations can act as a valuable tool in understanding the mechanisms behind jet formation and its properties. Although there have been significant efforts in understanding black-hole jets from general-relativistic magnetohydrodynamic (GRMHD) simulations in the past years, neutron star jets, however, still remain poorly explored. We present the results from three-dimensional (3D) GRMHD simulations of accreting neutron stars with oblique magnetospheres for the very first time. The jets in our simulations are produced due to the anchored magnetic field of the rotating star in analogy with the Blandford-Znajek process. We find that for accreting stars, the star-disk magnetic field interaction plays a significant role and as a result, the jet power becomes directly proportional to Φ2jet{\Phi^2}_{\rm jet}, where Φjet\Phi_{\rm jet} is the open flux in the jet. The jet power decreases with increasing stellar magnetic inclination and finally for an orthogonal magnetosphere, it reduces by a factor of 2.95\simeq 2.95 compared to the aligned case. We also find that in the strong propeller regime, with a highly oblique magnetosphere, the disk-induced collimation of the open stellar flux preserves parts of the striped wind resulting in a striped jet.
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