A5070619859- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Space exploration and regulation
- Solar and Space Plasma Dynamics
- Atomic and Molecular Physics
- Astrophysics and Star Formation Studies
- Mechanics and Biomechanics Studies
- Photocathodes and Microchannel Plates
- Spacecraft Design and Technology
- Astronomy and Astrophysical Research
- Adaptive optics and wavefront sensing
- Arctic and Russian Policy Studies
Leibniz Institute for Astrophysics Potsdam
2022-2024
Royal Observatory
2020-2022
University of Edinburgh
2020-2022
Scottish Universities Physics Alliance
2022
Johnson Space Center
1994
The eROSITA telescope array aboard the Spektrum Roentgen Gamma (SRG) satellite began surveying sky in December 2019, with aim of producing all-sky X-ray source lists and maps an unprecedented depth. Here we present catalogues both point-like extended sources using data acquired first six months survey operations (eRASS1; completed June 2020) over half whose proprietary rights lie German Consortium. We describe observation process, analysis pipelines, characteristics sources. With nearly 930...
Context . The soft X-ray instrument eROSITA on board the Spectrum-Roentgen-Gamma (SRG) observatory has successfully completed four of eight planned all-sky surveys, detecting almost one million sources during first survey (eRASS1). catalog this will be released as part data release (DR1). Aims Based aperture photometry, we provide flux upper limits for eRASS1 in several energy bands. We cover galactic longitudes between 180° ≲ l 360° (eROSITA-DE). These are crucial studying properties...
Context. During its all-sky survey, the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) on board Spectrum-Roentgen-Gamma (SRG) observatory has uncovered a growing number of X-ray transients associated nuclei quiescent galaxies. Benefitting from large field view and excellent sensitivity, eROSITA window into time-domain astrophysics yields valuable sample selected nuclear transients. Multi-wavelength follow-up enables us to gain new insights understanding nature emission...
The ROSAT-selected tidal disruption event (TDE) candidate RX J133157.6-324319.7 (J1331), was detected in 1993 as a bright (0.2-2 keV flux of $(1.0 \pm 0.1) \times 10^{-12}$ erg s$^{-1}$ cm$^{-2}$), ultra-soft ($kT=0.11 0.03$ keV) X-ray flare from quiescent galaxy ($z=0.05189$). During its fifth All-Sky survey (eRASS5) 2022, SRG/eROSITA the repeated flaring J1331, where it had rebrightened to an observed 0.2-2 $(6.0 0.7) 10^{-13}$ cm$^{-2}$, with spectral properties ($kT=0.115 0.007$...
In this letter, we present the results from subsequent X-ray and UV observations of nuclear transient eRASSt J045650.3−203750 (hereafter, J0456−20). We detected five repeating flares J0456−20, marking it as one most promising partial tidal disruption event ( p TDE) candidates. More importantly, also found rapid changes in recurrence time, T recur , by modelling long-term light curve J0456−20. that first decreased rapidly about 300 days to around 230 days. It continued decrease 190 with an...
We report on multi-wavelength observations of the tidal disruption event (TDE) candidate eRASSt J074426.3+291606 (J0744), located in nucleus a previously quiescent galaxy at $z=0.0396$. J0744 was first detected as new, ultra-soft X-ray source (photon index $\sim 4$) during second SRG/eROSITA All-Sky Survey (eRASS2), where it had brightened 0.3--2~keV band by factor more than $\sim$160 relative to an archival 3$\sigma$ upper limit inferred from serendipitous Chandra pointing 2011. The...
ABSTRACT We present an extensive radio monitoring campaign of the nuclear transient eRASSt J234402.9−352640 with Australia Telescope Compact Array, one most X-ray luminous TDE candidates discovered by SRG/eROSITA all-sky survey. The observations reveal a flare lasting >1000 d, coincident X-ray, UV, optical, and infrared this event. Through modelling 10 epochs spectral obtained, we find that emission is well-described expanding synchrotron emitting region, consisting single ejection...
Context. Recent years have seen broad observational support for the presence of a clumpy component within circumnuclear gas around supermassive black holes (SMBHs). In X-ray band, individual clouds can manifest themselves when they transit line sight to corona, temporarily obscuring continuum and thereby indicating characteristics location these clouds. Aims. flux monitoring with Spectrum Roentgen Gamma extended ROentgen Survey an Imaging Telescope Array ( SRG /eROSITA) has revealed that in...
ABSTRACT We investigate the responsiveness of 2798 Å Mg ii broad emission line in active galactic nuclei (AGNs) on time-scales several years. Our study is based a sample extremely variable AGNs as well population sample. The observed response previous studies has been mixed. By focusing extreme variability (|Δg| > 1), we find that clearly does respond to continuum. However, degree varies strikingly from one object another: see cases changing by much continuum, more than or very little...
We examine the long-term history of optical spectrum extremely variable Active Galactic Nucleus (AGN) MKN 110. By combining various archival data with new data, we cover an unprecedented long period $\sim$30 years (1987 - 2019). find that He II $\lambda 4686$ emission line changes by a factor forty and varies more strongly than continuum. Following Ferland et al. (2020), take as proxy for FUV continuum compare flux several other species against it. This comparison reveals clear pattern,...
Recent years have seen broad observational support for the presence of a clumpy component within circumnuclear gas around SMBHs. In X-ray band, individual clouds can manifest themselves when they transit line sight to corona, temporarily obscuring continuum and thereby indicating characteristics location these clouds. flux monitoring with SRG/eROSITA has revealed that in Seyfert 1 AGN EC 04570-5206, soft dipped abruptly about 10-18 months over 2020-2021, only recover then drop second time by...
In this letter, we present the results from further X-ray and UV observations of nuclear transient eRASSt J045650.3-203750 (hereafter J0456-20). We detected five repeating flares J0456-20, making it one most promising partial tidal disruption event (pTDE) candidates. More importantly, also found rapid changes in recurrence time $T_\text{recur}$ by modelling long-term light curve J0456-20. first decreased rapidly about 300 days to around 230 days. It continued decrease 190 with an indication...
Extreme continuum variability in extragalactic nuclear sources can indicate extreme changes accretion flows onto supermassive black holes. We explore the multiwavelength nature of a flare Seyfert LCRS B040659.9$-$385922. The all-sky X-ray surveys conducted by Spectrum Roentgen Gamma (SRG)/extended ROentgen Survey with an Imaging Telescope Array (eROSITA) showed that its flux increased factor roughly five over six months, and concurrent optical photometric monitoring Asteroid...
Aims . The eROSITA telescope aboard the Spectrum Roentgen Gamma (SRG) satellite provides an unprecedented opportunity to explore transient and variable extragalactic X-ray sky due sensitivity, coverage, cadence of all-sky survey. While previous studies showed dominance regular active galactic nuclei (AGN) variability, a small fraction sources expected in such survey arise from more exotic phenomena as tidal disruption events (TDEs), quasi-periodic eruptions, or other short-lived associated...
The soft X-ray instrument eROSITA on board the Spectrum-Roentgen-Gamma (SRG) observatory has successfully completed four of eight planned all-sky surveys, detecting almost one million sources during first survey (eRASS1). catalog this will be released as part data release (DR1). Based aperture photometry, we provide flux upper limits for eRASS1 in several energy bands. We cover galactic longitudes between $180^{\circ}\lesssim l \lesssim 360^{\circ}$ (eROSITA-DE). These are crucial studying...
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This behaviour, coupled with host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼10 6 M ⊙ black hole (BH) is currently process of “turning on”. Aims. We present multi-wavelength photometric...
ABSTRACT The discovery of radio‐quiet, x‐ray thermally emitting isolated neutron stars (XINSs) in the ROSAT All‐Sky Survey revealed a previously overlooked component star population. Advancements instrumentation and availability deep, wide‐area optical surveys now enable us to explore XINSs at fainter fluxes greater distances. In this study, we investigated candidates selected from 4XMM‐DR9 catalogue using XMM‐Newton, focusing on long‐term flux stability, spectral characterisation,...
Context. Multiwavelength studies of transients in actively accreting supermassive black holes have revealed that large-amplitude variability is frequently linked to significant changes the optical spectra -- a phenomenon referred as changing-look AGN (CLAGN). Aim. In 2020, Zwicky Transient Facility detected transient flaring event type-1.9 6dFGS~gJ042838.8-000040, wherein sharp increase magnitude $\sim$0.55 and $\sim$0.3 $g$- $r$-bands, respectively, occurred over $\sim$40 days. Spectrum...