A5059928158- Stellar, planetary, and galactic studies
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Astrophysics and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Geophysics and Sensor Technology
- Galaxies: Formation, Evolution, Phenomena
- High-pressure geophysics and materials
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Geological and Geophysical Studies
- Historical Astronomy and Related Studies
- Relativity and Gravitational Theory
- Advanced Statistical Methods and Models
- Advanced Scientific Techniques and Applications
- Material Science and Thermodynamics
- Thin-Film Transistor Technologies
- Particle Accelerators and Free-Electron Lasers
- Scientific Measurement and Uncertainty Evaluation
Friedrich Schiller University Jena
2014-2025
Yerevan State University
2025
Byurakan Astrophysical Observatory
1997-2024
National Academy of Sciences of Armenia
1996-2021
Leibniz Institute for Astrophysics Potsdam
2002-2008
Russian-Armenian University
1999
Aims. Pointed observations with XMM-Newton provide the basis for creating catalogues of X-ray sources detected serendipitously in each field. This paper describes creation and characteristics 2XMM catalogue.
In the last 3000 yr, one significant and rapid increase in concentration of 14C tree rings was observed; it corresponds to a γ-ray energy input 7 × 1024 erg at Earth within up year AD 774/5. A normal supernova solar or stellar flare are unlikely as cause, so that source remained unknown. Here, we show short gamma-ray burst (GRB) our Galaxy is consistent with all observables: such an event sufficiently provides necessary relevant spectral range γ-rays. Its hardness differential production...
X-ray spectra of the isolated neutron star RBS1223 obtained with instruments on board XMM-Newton in December 2001 and January 2003 show deviations from a Planckian energy distribution at energies below 500 eV. The are well fit when broad, Gaussian-shaped absorption line eV centered an 300 is added to absorbed blackbody model. resulting equivalent width -150 However, spectral resolution these low EPIC detectors lower statistical quality restricted band RGS not sufficient exclude even broader...
We present the Young Exoplanet Transit Initiative (YETI), in which we use several 0.2 to 2.6m telescopes around world monitor continuously young (< 100 Myr), nearby 1 kpc) stellar clusters mainly detect transiting planets (and study other variability phenomena on time-scales from minutes years). The telescope network enables us observe targets for days order not miss any transit. runs are typically one two weeks long, about three per year cluster or subsequent years ten clusters. There...
The directly detected planetary mass companion candidate close to the young, nearby star Fomalhaut is a subject of intense discussion. While detection common proper motion led interpretation as Jovian-mass companion, later non-detections in infrared raised doubts. Recent astrometric measurements indicate belt crossing or highly eccentric orbit for object, if making potentially even more problematic. In this study we discuss possibility Fomalhaut\,b being background object with high motion....
ABSTRACT The detection of ∼1.5–3.2 Myr old 60Fe on Earth indicates recent nearby core-collapse supernovae. For supernovae in multiple stars, the primary stars may become neutron while former companions unbound and runaway stars. We wrote software for tracing back space motion to young associations massive apply it here Scorpius–Centaurus–Lupus groups, all known possibly coming from there, 400 with transverse velocity. find kinematic evidence that ζ Oph radio pulsar PSR B1706−16 were released...
Abstract Runaway stars are characterized by higher space velocities than typical field stars. They presumed to have been ejected from their birth places one or more energetic mechanisms, including supernova explosions. Accurate radial essential for investigating origin, tracing back Galactic orbits look close encounters in and time with neutron young associations. While most studies of runaways focused on OB stars, later-type also considered occasion. Here we report the results a long-term...
We present results from the high-resolution optical spectroscopy and spectropolarimetry of peculiar high-mass X-ray binary 4u. aim to estimate size circumstellar disc investigate interaction between compact object matter in disc. also study interstellar polarisation towards performed a periodogram analysis on spectral data identify periodicities. estimated radius distance components at periastron. used two methods determine 4u, both which yield similar results. that outer Hα-emitting varies...
We have redetermined the parallax and proper motion of nearby isolated neutron star RX J185635−3754. used eight observations with high-resolution camera HST/ACS taken from 2002 through 2004. performed astrometric fitting using five independent methods, all which yielded consistent results. The mean estimate parallax, 8.16+0.9−0.8 mas (1σ), corresponds to a distance 123+11−15 pc, in good agreement our earlier published determination.
The data from all observations of RBS 1223 (1RXS J130848.6+212708) conducted by XMM-Newton EPIC pn with the same instrumental setup in 2003-2007 were combined to form spin-phase resolved spectra. A number complex models neutron stars strongly magnetized ($B_{pole} 10^{13}-10^{14}$ G) surface, temperature and magnetic field distributions around poles, partially ionized hydrogen thin atmosphere above it have been implemented into X-ray spectral fitting package XSPEC for simultaneous...
The data from all observations of RX J0720.4-3125 conducted by XMM-Newton EPIC-pn with the same instrumental setup in 2000-2012 were reprocessed to form a homogenous set solar barycenter corrected photon arrival times registered J0720.4-3125. A Bayesian method for search, detection, and estimation parameters an unknown-shaped periodic signal was employed as developed Gregory & Loredo (1992). number complex models (single double peaked) light curves pulsating neutron stars statistically...
ABSTRACT Carina is a nearby young stellar association. So far, only small number of stars have been clearly identified as members this In paper, we reanalyse the membership association in light Gaia DR2 data, particular finding that HD 95086 potential member (probability 71 per cent). This star noteworthy one few hosts both detected debris disc and directly imaged planet. It has previously considered Lower Centaurus Crux (LCC) – part Scorpius–Centaurus We also age Using Bayesian inference...
The isolated neutron star candidate RBS 1223 was observed with the Advanced CCD Imaging Spectrometer aboard Chandra observatory on 2000 June 24. A timing analysis of data yielded a periodic modulation period s. Using ROSAT HRI archived observations we detected s and determined derivative . detection this indicates that has "characteristic" age 6000-12 000 years huge magnetic field at surface () typical for anomalous pulsars (AXPs).
In the X-ray spectra of most dim isolated neutron stars (XDINSs) absorption features with equivalent widths (EWs) 50 -- 200 eV are observed. We theoretically investigate different models to explain and compare their properties observations. consider various theoretical for magnetized star surface: naked condensed iron surfaces partially ionized hydrogen model atmospheres, including semi-infinite thin atmospheres above a surface. The (especially widths) angular distributions emergent...
By detecting high frequency quasi-periodic oscillations (QPOs) and estimating frequencies of them during the decaying tail giant flares from Soft Gamma-ray Repeaters (SGRs) useful constraints for equation state (EoS) superdense matter may be obtained via comparison with theoretical predictions eigenfrequencies. We used data collected by Rossi X-Ray Timing Explorer (RXTE/XTE) Proportional Counter Array (PCA) a flare SGR 1806-20 on 2004 Dec 27 applied Bayesian periodicity detection method...
We present an analysis of the X-ray light curves magnetic cataclysmic variable DP Leo using recently performed XMM-Newton EPIC and archival published unpublished ROSAT PSPC observations. combine timings eclipses with derived from HST-observations new optical observations photon counting OPTIMA camera. determine eclipse length at wavelengths to be s, slightly longer than ultra-violet wavelengths, where it lasts 225 s. A orbital ephemeris is which connects more 120 000 binary cycles covered...
We present a multi-epoch spectral and timing analysis of the isolated neutron star RBS1223. New XMM-Newton data obtained in January 2004 confirm spin period to be twice as long previously thought, P_spin = 10.31 s. The combined ROSAT, Chandra, (6 epochs) give, contrary earlier findings, no clear indication evolution star. X-ray light curves are double-humped with pronounced hardness ratio variations suggesting an inhomogeneous surface temperature two spots separated by about ~160 degr....
We report on our observational attempt to constrain the compactness of isolated neutron stars via X-ray spin phase-resolved spectroscopy. There are seven thermally emitting known from and optical observations, which young (up few Myrs), nearby (hundreds pc), radio-quiet with blackbody-like spectra. A model a condensed iron surface partially ionized hydrogen-thin atmosphere allows us fit simultaneously observed general spectral shape broad absorption feature (observed at 0.3 keV) in different...
We report on the discovery of a very low mass (VLM) star in solar neighborhood, originally identified as an optical counterpart flaring X-ray source detected ROSAT All-Sky survey. Optical spectroscopy and infrared photometry consistently reveal spectral type distance ≈ pc. The 1RXS J115928.5-524717 shows large proper motion /year. is fourth object among VLM stars displaying huge flare, reaching unprecedent value .
<i>Context. <i/>In the past, isolated, radio-quiet neutron star RX J0720.4-3125 showed variations in its spectral parameters (apparent radius, temperature of emitting area and equivalent width absorption feature) seen X-ray spectra, not only during spin period 8.39 s, but also over time scales years. New observations with XMM-Newton extend coverage to about 7.5 years latest pointing performed November 2007. Out a total fourteen available EPIC-pn datasets, eleven have been obtained an...
We present further considerations regarding the strong 14C variation in AD 774/5. For its cause, either a solar super-flare or short Gamma-Ray Burst were suggested. show that all kinds of stellar neutron star flares would be too weak for observed energy input at Earth Even though Maehara et al. (2012) two super-flares with 10e35 erg presumably solar-type stars, we like to caution: These stars are poorly studied and may well close binaries, and/or having M-type dwarf companion, much younger...
<i>Aims. <i/>By measuring the gravitational redshift of spectral features in spectrum thermal radiation emitted from neutron stars, useful constraints for equation state superdense matter can be obtained via an estimate mass-to-radius ratio. We searched line high-resolution X-ray isolated star RX J0720.4-3125.<i>Methods. <i/>Our target was observed by <i>XMM-Newton<i/> on many occasions. used <i>XMM-Newton SAS<i/> task <i>rgscombine<i/> order to create a co-added RGS J0720.4-3125. modeled...
With more adaptive optics images available, we aim at detecting orbital motion for the first time in system TWA 5 A+B. We measured separation and position angle between A B each high-resolution image available followed their change time, because should orbit around A. The astrometric measurement precision is about one milli arc sec. ten year difference epoch, can clearly detect of A, a decrease by ~ 0.0054 sec per 0.26 degrees year. brown dwarf with 25 Jupiter masses (Neuhäuser et al. 2000),...