A5002636178- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Geophysics and Gravity Measurements
- Scientific Research and Discoveries
- Solar and Space Plasma Dynamics
- Advanced Power Generation Technologies
- Geomagnetism and Paleomagnetism Studies
- Atmospheric Ozone and Climate
- Earthquake Detection and Analysis
- Mechanics and Biomechanics Studies
- Advanced Research in Systems and Signal Processing
- Nuclear Physics and Applications
- Adaptive optics and wavefront sensing
- High-pressure geophysics and materials
- Time Series Analysis and Forecasting
- Cosmology and Gravitation Theories
- Big Data Technologies and Applications
European Southern Observatory
2020-2024
Space Telescope Science Institute
2016-2024
Roma Tre University
2024
Yale University
2024
University of Cambridge
2018-2022
Radboud University Nijmegen
2003-2020
SRON Netherlands Institute for Space Research
2016-2019
Max Planck Society
2018
Netherlands Institute for Radio Astronomy
2017-2018
Michigan State University
2016
Aims. We describe the photometric content of second data release Gaia project (Gaia DR2) and its validation along with quality data. Methods. The was mainly carried out using an internal analysis photometry. External comparisons were also made, but limited by precision systematics that may be present in external catalogues used. Results. In addition to assessment, we best estimates three passbands. Various colour-colour transformations are derived enable users convert between commonly used...
Stars that interact with supermassive black holes (SMBHs) can either be completely or partially destroyed by tides. In a partial tidal disruption event (TDE) the high-density core of star remains intact, and low-density, outer envelope is stripped feeds luminous accretion episode. The TDE AT2018fyk, an inferred hole mass $10^{7.7\pm0.4}$ M$_{\odot}$, experienced extreme dimming at X-ray (factor $>$6000) UV $\sim$15) wavelengths $\sim$500--600 days after discovery. Here we report on...
The tidal disruption of a star by supermassive black hole leads to short-lived thermal flare. Despite extensive searches, radio follow-up observations known stellar flares (TDFs) have not yet produced conclusive detection. We present detection variable emission from TDF, which we interpret as originating newly-launched jet. multi-wavelength properties the source natural analogy with accretion state changes mass holes, suggesting all TDFs could be accompanied In rest frame our are an order...
The mass of the central black hole in a galaxy that hosted tidal disruption event (TDE) is an important parameter understanding its energetics and dynamics.We present first homogeneously measured masses complete sample 12 optically/UV-selected TDE host galaxies (down to g ≤ 22 mag z = 0.37) Northern sky.The estimates are based on velocity dispersion measurements, performed late time optical spectroscopic observations.We find range 3 × 10 5 M BH 2 7 .The dominated by low-mass holes (∼ 6 ), as...
ABSTRACT We present optical spectroscopic and Swift UVOT/XRT observations of the X-ray UV/optical bright tidal disruption event (TDE) candidate AT 2018fyk/ASASSN–18ul discovered by ASAS–SN. The light curve is atypical for a TDE, entering plateau after ∼40 d decline from peak. After 80 breaks again to further, while emission becomes brighter harder. In addition broad H, He, potentially O/Fe lines, narrow lines emerge in spectra during phase. identify both high-ionization (O iii)...
We present light curves and spectra of the tidal disruption event (TDE) ASASSN-18pg / AT 2018dyb spanning a period one year. The shows plethora strong emission lines, including Balmer series, He II, I metal lines O III $\lambda$3760 N $\lambda\lambda$ 4100, 4640 (blended with II). latter are consistent originating from Bowen fluorescence mechanism. By analyzing literature past events, we conclude that these common in TDEs. spectral diversity optical TDEs is thus larger than previously...
At 66 Mpc, AT2019qiz is the closest optical tidal disruption event (TDE) to date, with a luminosity intermediate between bulk of population and iPTF16fnl. Its proximity allowed very early detection triggering multiwavelength spectroscopic follow-up well before maximum light. The velocity dispersion host galaxy fits TDE light curve indicate black hole mass $\approx 10^6$ M$_\odot$, disrupting star 1$ M$_\odot$. Comprehensive UV, X-ray data shows that emission dominated by an outflow,...
ABSTRACT We present new medium resolution, optical long-slit spectra of a sample six ultraviolet (UV)/optical and 17 X-ray-selected tidal disruption event candidate host galaxies. measure emission line ratios from the spectra, finding that large majority hosts are quiescent galaxies, while those displaying lines generally consistent with star formation dominated environments; only three sources show clear evidence nuclear activity. bulge velocity dispersions using absorption infer black hole...
Context. Since July 2014, the Gaia mission has been engaged in a high-spatial-resolution, time-resolved, precise, accurate astrometric, and photometric survey of entire sky. Aims. We present Science Alerts project, which operation since 1 June 2016. describe system developed to enable discovery publication transient events as seen by . Methods. outline data handling, timings, performances, we detection algorithms filtering procedures needed manage high false alarm rate. identify two classes...
Quasi-periodic X-ray eruptions (QPEs) are a recently discovered phenomenon, the nature of which remains unclear. Based on their discovery in active galactic nuclei (AGN), explanations related to an AGN accretion disk, or potentially stellar tidal disruption event (TDE), were put forward. Following report QPEs apparently passive galaxies, alternatives including highly unequal mass compact object binaries have been proposed explain properties. We perform systematic study five known QPE host...
Abstract A bright ( m F150W,AB = 24 mag), z 1.95 supernova (SN) candidate was discovered in JWST/NIRCam imaging acquired on 2023 November 17. The SN is quintuply imaged as a result of strong gravitational lensing by foreground galaxy cluster, detected three locations, and remarkably the second lensed found same host galaxy. previous called “Requiem,” therefore new named “Encore.” This makes MACS J0138.0−2155 cluster first known system to produce more than one multiply SN. Moreover, both...
Quasi-periodic eruptions (QPEs) are luminous bursts of soft X-rays from the nuclei galaxies, repeating on timescales hours to weeks
Abstract An accretion disk formed around a supermassive black hole after it disrupts star is expected to be initially misaligned with respect the equatorial plane of hole. This misalignment induces relativistic torques (the Lense–Thirring effect) on disk, causing precess at early times, whereas late times aligns and precession terminates 1,2 . Here we report, using high-cadence X-ray monitoring observations tidal disruption event (TDE), discovery strong, quasi-periodic flux temperature...
Quasi-periodic Eruptions (QPEs) represent a novel class of extragalactic X-ray transients that are known to repeat at roughly regular intervals few hours days. Their underlying physical mechanism is topic heated debate, with most models proposing they originate either from instabilities within the inner accretion flow or orbiting objects. At present, our knowledge how QPEs evolve over an extended timescale multiple years limited, except for unique QPE source GSN 069. In this study, we...
Binaries containing a compact object orbiting supermassive black hole are thought to be precursors of gravitational wave events, but their identification has been extremely challenging. Here, we report quasi-periodic variability in x-ray absorption, which interpret as outflows (QPOuts) from previously low-luminosity active galactic nucleus after an outburst, likely caused by stellar tidal disruption. We rule out several models based on observed properties and instead show using general...
The hard X-ray emission in active galactic nuclei (AGN) and black hole binaries is thought to be produced by a hot cloud of electrons referred as the corona. This emission, commonly described power law with high-energy cutoff, suggestive Comptonization thermal electrons. While several hypotheses have been proposed explain origin, geometry, composition corona, we still lack clear understanding this fundamental component. NuSTAR has playing key role improving our knowledge coronæ thanks its...
X-ray quasi-periodic eruptions (QPEs) are a novel mode of variability in nearby galactic nuclei whose origin remains unknown. Their multi-wavelength properties poorly constrained, as studies have focused almost entirely on the band. Here we report time-resolved, coordinated Hubble Space Telescope far ultraviolet and XMM-Newton observations shortest period QPE source currently known, eRO-QPE2. We detect bright UV point ($L_{\rm FUV} \approx {\rm few} \times 10^{41}$ erg s$^{-1}$) that does...
We present results from spectroscopic observations of AT 2018hyz, a transient discovered by the ASAS-SN survey at an absolute magnitude $M_V\sim -20.2$ mag, in nucleus quiescent galaxy with strong Balmer absorption lines. 2018hyz shows blue spectral continuum and broad emission lines, consistent previous TDE candidates. High cadence follow-up spectra show lines He I early spectra, II making appearance after $\sim70-100$ days. The evolve smooth profile, through boxy, asymmetric double-peaked...
Spectroscopically, TDEs are characterized by broad ( 10$^{4}$ km/s) emission lines and show large diversity as well different line profiles. After carefully consistently performing a series of data reduction tasks including host galaxy light subtraction, we present here the first detailed, spectroscopic population study 16 optical/UV TDEs. We report time lag between peaks optical light-curves peak luminosity H$\alpha$ spanning 7 - 45 days. If interpreted light-echoes, these lags correspond...
Following a tidal disruption event (TDE), the accretion rate can evolve from quiescent to near-Eddington levels and back over months - years timescales. This provides unique opportunity study formation evolution of flow around supermassive black holes (SMBHs). We present two multi-wavelength monitoring observations TDE AT2018fyk at X-ray, UV, optical radio wavelengths. identify three distinct states state transitions between them. These appear remarkably similar behaviour stellar-mass in...
ABSTRACT We present the results of a large multiwavelength follow-up campaign tidal disruption event (TDE) AT 2019dsg, focusing on low to high resolution optical spectroscopy, X-ray, and radio observations. The galaxy hosts super massive black hole mass $\rm (5.4\pm 3.2)\times 10^6\, M_\odot$ careful analysis finds no evidence for presence an active galactic nucleus, instead TDE host shows narrow emission lines that likely arise from star formation activity. transient is luminous in X-rays,...
Tidal disruption events (TDEs) occur when a star gets torn apart by supermassive black hole as it crosses its tidal radius. We present late-time optical and X-ray observations of the nuclear transient AT2019qiz, which showed typical signs an optical-UV class commonly believed to be TDEs. Optical spectra were obtained 428, 481 828 rest-frame days after lightcurve peak, UV/X-ray observation coincided with later spectrum. The show strong coronal emission lines, including [Fe VII], X], XI] XIV]....