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Marcin P. Gawronski

Publications and source records attributed to Marcin P. Gawronski.

10 recordsLinked to original sources
arXiv2016

Physical properties and astrometry of radio-emitting brown dwarf TVLM513-46546 revisited

We present multi-epoch astrometric observations of the M9 ultra-cool dwarf TVLM513-46546 that is placed at the brown dwarf boundary. The new observations have been performed with the European VLBI Network (EVN) at 6cm band. The target has been detected at 7~epochs spanning three years, with measured quiescent emission flux in the range 180-300 muJy. We identified four short-duration flaring events (0.5-2 mJy) with very high circular polarization (~75%-100%). Properties of the observed radio flares support the physical model of the source that is characterized by the electron cyclotron maser instability responsible for outbursts of radio emission. Combined with Very Long Baseline Array (VLBA) earlier data, our detections make it possible to refine the absolute parallax pi=93.27(+0.18,-0.17) mas. Our measurements rule out TVLM513-46546 companions more massive than Jupiter in orbits with periods longer than ~1 yr.

astro-ph.SR↗
arXiv2014

A multi-wavelength view on the dusty Wolf-Rayet star WR 48a

We present results from the first attempts to derive various physical characteristics of the dusty Wolf-Rayet star WR 48a based on a multi-wavelength view of its observational properties. This is done on the basis of new optical and near-infrared spectral observations and on data from various archives in the optical, radio and X-rays. The optical spectrum of WR 48a is acceptably well represented by a sum of two spectra: of a WR star of the WC8 type and of a WR star of the WN8h type. The strength of the interstellar absorption features in the optical spectra of WR 48a and the near-by stars D2-3 and D2-7 (both members of the open cluster Danks 2) indicates that WR 48a is located at a distance of ~4 kpc from us. WR 48a is very likely a thermal radio source and for such a case and smooth (no clumps) wind its radio emission suggests a relatively high mass-loss rate of this dusty WR star (dM/dt = a few x 10^(-4) solar masses per year). Long timescale (years) variability of WR 48a is established in the optical, radio and X-rays. Colliding stellar winds likely play a very important role in the physics of this object. However, some LBV-like (luminous blue variable) activity could not be excluded as well.

astro-ph.SR↗
arXiv2013

Project RISARD

Red Dwarfs (RDs) are the most common, low-mass stars (<=0.5 M_sun) in the Solar neighbourhood, and probably in the Universe as well. Most (likely all) young RDs are magnetically active, and therefore it is impossible to measure their radial velocities (RVs) with the accuracy required by contemporary planetary searches (5-50 m/s). Some of RDs are known as a source of variable radio emission at centimetre wavelengths. This radiation is relatively weak (~0.2 to 1 mJy). However, recent development of the EVN and e-VLBI systems in terms of sensitivity gives a new possibility to investigate such stars. Here, we present first results from our ongoing RISARD project (Radio Interferometric Survey of Active Red Dwarfs). The main goal of this project is to detect an exoplanet by direct, precise measurements of a RD position and possible changes to this position caused by the planet.

astro-ph.SR↗
arXiv2011

High resolution studies of Broad Absorption Line radio-loud quasars

Broad absorption lines (BALs), seen in a small fraction of both the radio-quiet and radio-loud quasar populations, are probably caused by the outflow of gas with high velocities and are part of the accretion process. The presence of BALs is the geometrical effect and/or it is connected with the quasar evolution. Using the final release of FIRST survey combined with a A Catalog of BAL QSOs (SDSS/DR3), we have constructed a new sample of compact radio-loud BAL QSOs, which makes the majority of radio-loud BAL QSOs. The main goal of this project is to study the origin of BALs by analysis the BAL QSOs radio morphology, their orientation and jets evolution, using EVN at 1.6 GHz and VLBA at 5 and 8.4 GHz. We will discuss also the first multi-frequency radio observations of very compact BAL quasar 1045+352 made using the VLBA, EVN, MERLIN and CHANDRA. We speculate that the most probable interpretation of the observed radio structure of 1045+352 is the ongoing process of the jet precession due to internal instabilities within the flow.

astro-ph.CO↗
arXiv2011

Sunyaev Zel'dovich observations of a statistically complete sample of galaxy clusters with OCRA-p

We present 30 GHz Sunyaev Zel'dovich observations of a statistically complete sample of galaxy clusters with OCRA-p. The clusters are the 18 most X-ray luminous clusters at z > 0.2 in the ROSAT Brightest Cluster Sample. We correct for contaminant radio sources via supplementary observations with the Green Bank Telescope, also at 30 GHz, and remove a cluster that is contaminated by an unresolved X-ray source. All 17 remaining clusters have central SZ effects with Comptonisation parameter y_0 exceeding 1.9x10^-4, and 13 are detected at significance > 3 sigma. We use our data to examine scalings between y_0 and X-ray temperature, X-ray luminosity, and the X-ray mass proxy Y_X, and find good agreement with predictions from self-similar models of cluster formation, with an intrinsic scatter in y_0 of about 25%. We also comment on the success of the observations in the face of the contaminant source population, and the implications for upcoming cm-wave surveys.

astro-ph.CO↗
arXiv2010

Origin of the complex radio structure in BAL QSO 1045+352

We present new more sensitive high-resolution radio observations of a compact broad absorption line (BAL) quasar, 1045+352, made with the EVN+MERLIN at 5 GHz. They allowed us to trace the connection between the arcsecond structure and the radio core of the quasar. The radio morphology of 1045+352 is dominated by a knotty jet showing several bends. We discuss possible scenarios that could explain such a complex morphology: galaxy merger, accretion disk instability, precession of the jet and jet-cloud interactions. It is possible that we are witnessing an ongoing jet precession in this source due to internal instabilities within the jet flow, however, a dense environment detected in the submillimeter band and an outflowing material suggested by the X-ray absorption could strongly interact with the jet. It is difficult to establish the orientation between the jet axis and the observer in 1045+352 because of the complex structure. Nevertheless taking into account the most recent inner radio structure we conclude that the radio jet is oriented close to the line of sight which can mean that the opening angle of the accretion disk wind can be large in this source. We also suggest that there is no direct correlation between the jet-observer orientation and the possibility of observing BALs.

astro-ph.CO↗
arXiv2009

Inner radio structure of compact BAL quasar 1045+352

The first multifrequency radio observations of the very compact BAL quasar, 1045+352, were made using MERLIN and the VLBA in a snapshot mode. However, its unusual radio structure was still very difficult to interpret, indicating a scenario of intermittent activity or a jet precession. Here, we present some of a new full-track radio observations of 1045+352 made with the EVN+MERLIN at 5 GHz. The new more sensitive high-resolution observations made possible to trace the connection between the arcsecond structure and the radio core, and showed the presence of strong interactions between the jet and the medium of the host galaxy.

astro-ph.CO↗
arXiv2007

Preliminary Sunyaev Zel'dovich Observations of Galaxy Clusters with OCRA-p

We present 30 GHz Sunyaev Zel'dovich (SZ) observations of a sample of four galaxy clusters with a prototype of the One Centimetre Receiver Array (OCRA-p) which is mounted on the Torun 32-m telescope. The clusters (Cl0016+16, MS0451.6-0305, MS1054.4-0321 and Abell 2218) are popular SZ targets and serve as commissioning observations. All four are detected with clear significance (4-6 sigma) and values for the central temperature decrements are in good agreement with measurements reported in the literature. We believe that systematic effects are successfully suppressed by our observing strategy. The relatively short integration times required to obtain these results demonstrate the power of OCRA-p and its successors for future SZ studies.

astro-ph↗
arXiv2006

Multi-frequency VSOP and VLBI observations of the quasar 3C309.1

We present multi-frequency observational results for the Compact Steep-Spectrum (CSS) quasar 3C309.1. The observations were carried out with the VSOP at 1.6 and 4.8GHz and the VLBA at 15.4GHz. The source has a distorted, one-sided radio jet. Relativistics effects and physical properties are discussed. Comparing the predicted and observed X-ray fluxes in the framework of the synchrotron self-Compton model we derive the beaming factor for 3C309.1. The complex structure of the jet may be explained by a relativistic helical flow in a heterogeneous, clumpy ISM.

astro-ph↗