A5013677579- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Geophysics and Gravity Measurements
- Geomagnetism and Paleomagnetism Studies
- History and Developments in Astronomy
- Adaptive optics and wavefront sensing
- Gamma-ray bursts and supernovae
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Spacecraft and Cryogenic Technologies
- Scientific Research and Discoveries
- Astrophysical Phenomena and Observations
- CCD and CMOS Imaging Sensors
- Cryospheric studies and observations
- Pulsars and Gravitational Waves Research
- Nuclear Physics and Applications
- Inertial Sensor and Navigation
- Bacteriophages and microbial interactions
- Atomic and Subatomic Physics Research
- Astrophysics and Cosmic Phenomena
- Radiation Detection and Scintillator Technologies
Université de Moncton
2014-2024
Main Astronomical Observatory
1995-2017
Royal Military College of Canada
2007
National Academy of Sciences of Ukraine
2002-2004
Isaac Newton Institute
2002-2003
ABSTRACT Numerous magnetic hot stars exhibit gyrosynchrotron radio emission. The source electrons were previously thought to be accelerated relativistic velocities in the current sheet formed middle magnetosphere by wind opening field lines. However, a lack of dependence luminosity on power, and strong rotation, has recently challenged this paradigm. We have collected all measurements early-type available literature. When constraints and/or rotational period are not available, we determined...
Subluminous Type Ia supernovae, such as the Iax class prototype SN 2002cx, are described by a variety of models failed detonation and partial deflagration an accreting carbon-oxygen white dwarf star, or explosion accreting, hybrid carbon-oxygen-neon core. These predict that bound remnants survive events with, according to some simulations, high kick velocity. We report discovery proper motion, low-mass (LP 40-365) travels at velocity greater than Galactic escape whose peculiar atmosphere is...
Recently, high-precision optical 2~min cadence light curves obtained with \emph{TESS} for targets located in the mission's defined first four sectors have been released. The majority of these high-cadence and measurements currently span $\sim28\,{\rm d}$, thereby allowing periodic variability occurring on timescales $\lesssim14\,{\rm d}$ to potentially be detected. Magnetic chemically peculiar (mCP) A-type stars are well known exhibit rotationally modulated photometric that is produced by...
In this paper we introduce the MOBSTER collaboration and lay out its scientific goals. We present first results based on analysis of nineteen previously known magnetic O, B A stars observed in 2-minute cadence sectors 1 2 Transiting Exoplanet Survey Satellite (TESS) mission. derive precise rotational periods from newly obtained light curves compare them to published values. also discuss overall photometric phenomenology massive intermediate-mass propose an observational strategy augment...
Mercury-manganese (HgMn) stars are late-B upper main sequence chemically peculiar distinguished by large overabundances of heavy elements, slow rotation, and frequent membership in close binary systems. These lack strong magnetic fields typical Bp but occasionally exhibit non-uniform surface distributions chemical elements. The physical origin the extent this spot formation phenomenon remains unknown. Here we use 2-min cadence light curves 64 HgMn observed TESS satellite during first two...
ABSTRACT We present the results of a systematic search Transiting Exoplanet Survey Satellite (TESS) 2-min cadence data for new rapidly oscillating Ap (roAp) stars observed during Cycle 2 phase its mission. find seven roAp previously unreported as such and analysis further 25 that are already known. Three show multiperiodic pulsations, while all members rotationally variable stars, leading to almost 70 per cent (22) presented being α2 CVn-type stars. targeted observations known chemically...
More than 200 A- and F-type stars observed with Kepler exhibit a distinctive 'hump & spike' feature in their Fourier spectra. The hump is commonly interpreted as unresolved Rossby modes, while the spike has been linked to rotational modulation. Two competing interpretations exist for spike: magnetic phenomena, such stellar spots, or Overstable Convective (OsC) modes resonantly exciting low-frequency g within envelope. We analysed photometric data from TESS HR 7495, brightest star (V=5.06),...
More than 200 A- and F-type stars observed with Kepler exhibit a distinctive hump spike feature in their Fourier spectra. The is commonly interpreted as unresolved Rossby modes, while the has been linked to rotational modulation. This led these be referred `hump spike' stars. However, two competing interpretations exist for spike. study aims determine whether caused by magnetic phenomena, such spots on stellar surface, or overstable convective (OsC) modes resonantly exciting low-frequency g...
We present the results of a systematic search for new rapidly oscillating Ap (roAp) stars using 2-min cadence data collected by Transiting Exoplanet Survey Satellite (TESS) during its Cycle 1 observations. identify 12 roAp stars. Amongst these we discover star with longest pulsation period, another shortest rotation and six multiperiodic variability. In addition to stars, an analysis 44 known observed TESS 1, providing first high-precision homogeneous sample significant fraction The...
Context.It is commonly believed that the observed overabundances of many chemical species relative to expected cluster metallicity in blue horizontal branch (BHB) stars appear as a result atomic diffusion photosphere. The slow rotation BHB (with K), typically km s-1, consistent with this idea.
We present results for the estimation of gravity, effective temperature, and radial velocity poorly studied chemically peculiar stars recently observed with spectropolarimeter Echelle SpectroPolarimetric Device Observations Stars at Canada–France–Hawaii Telescope in frame Vertical Stratification Element Abundances project. The temperature surface gravity values are determined very first time four from our sample (HD 23878, HD 83373, 95608, 164584). Grids stellar atmosphere models...
The surface magnetic field configuration of the Ap star HD 118022 (78 Vir) has been reconstructed in framework charge distribution (MCD) method from analysis Stokes $IQUV$ spectra obtained using MuSiCoS spectropolarimeter at Pic du Midi Observatory. Magnetically-sensitive Fe~{\sc ii} lines were primarily employed analysis, supposing that iron is evenly distributed over stellar surface. We show profile shapes and variations 78 Vir can be approximately fit assuming a global described by...
Context.The observed abundance peculiarities of many chemical species relative to the expected cluster metallicity in blue horizontal-branch (BHB) stars presumably appear as a result atomic diffusion photosphere. The slow rotation (typically < 10 km s-1) BHB with effective temperatures Teff > 11 500 K supports this idea since mechanism is only stable stellar atmosphere.
Blue horizontal-branch (BHB) stars with $T_{\rm eff}$ approximately larger than 11500 K show several observational anomalies. In globular clusters, they exhibit low rotational velocities, abundance anomalies (as compared to cluster abundances), photometric jumps and gaps spectroscopic gravities lower predicted by canonical models. It is commonly believed that the velocities of these permit atomic diffusion be efficient in their atmosphere thereby causing observed Recent detections vertical...
The aim of this study is to search for observational evidence vertical iron stratification in the atmosphere 14 blue horizontal-branch (BHB) stars. We have found from our numerical simulations that five BHB stars: B22, B186 globular cluster NGC 288, WF 2−820, 2−2692 M13 and B203 M15 show clear signatures whose abundance increases toward lower atmosphere. Two other stars (B334 B176 M92) also possible their A dependence slope on effective temperature was discovered. It strongest with Teff...
Using high resolution, high-S/N archival UVES spectra, we have performed a detailed spectroscopic analysis of 4 chemically peculiar HgMn stars (HD 71066, HD 175640, 178065 and 221507). spectrum synthesis, mean photospheric chemical abundances are derived for 22 ions 16 elements. We find good agreement between our those published previously by other authors. For the 5 elements that present sufficient number suitable lines, attempted to detect vertical stratification analyzing dependence...
NGC288 is a globular cluster with well-developed blue horizontal branch covering the u-jump that indicates onset of diffusion. It therefore well suited to study effects diffusion in (HB) stars. We compare observed abundances predictions from stellar evolution models calculated and stratified atmospheric models. verify effect using model spectra derive parameters. In addition, we investigate nature overluminous HB stars around u-jump. defined new photometric index sz uvby measurements...
The magnetic star HD 21699 possesses a unique field structure where the dipole is displaced from centre by 0.4 +/- 0.1 of stellar radius (perpendicularly to axis), as result, poles are situated close one another on surface with an angular separation 55$^o$ and not 180$^o$ seen in case centred dipole. Respectively, two form large "magnetic spot". High-resolution spectra were obtained allowing He I Si II abundance variations be studied function rotational phase. results show that helium...
A portion of main-sequence stars, called chemically peculiar (CP) show important abundance anomalies mainly due to atomic diffusion the species within these stars. Certain CP stars have hydrodynamically stable atmospheres where may dominate and lead vertical stratification there. Recently, Project VeSElkA (a word meaning rainbow in Ukrainian standing for ‘Vertical Stratification Element Abundances’) was initiated with goal detect chemical abundances selected using high-resolution spectra...
How magnetic fields contribute to the differentiation of rotation rates Ap stars and affect occurrence non-radial pulsation in some them are important open questions. Valuable insight can be gained into these questions by studying most extreme examples processes at play. The super-slowly rotating rapidly oscillating (roAp) star HD 166473 is such an example. We performed first accurate determination its period, P rot = (3836 ± 30) d, from analysis 56 measurements mean field modulus ⟨ B ⟩...
We report about HD 213258, an Ap star that we recently identified as presenting a unique combination of rare, remarkable properties. Our study this is based on ESPaDOnS Stokes I and V data obtained at 7 epochs spanning time interval slightly shorter than 2 years, TESS data, radial velocity measurements from the CORAVEL base. confirm 213258 definitely star. found that, in its spectrum, Fe II {\lambda}6149.2 {\AA} line resolved into two magnetically split components. The mean magnetic field...
As a further step in our Lithium project we present results of abundance determination some elements the roAp star HD 60435. Possible NLTE effects were considered. Equivalent widths spectral lines vary with rotational phase which suggests nonuniform distribution chemical over stars' surface. Large differences derived from various ions rare earth indicate their possible vertical stratification. Two spots enhanced lithium distinguished at magnetic poles on 60435 and parameters derived. The...
Project VeSElkA (Vertical Stratification of Element Abundances) has been initiated with the aim to detect and study vertical stratification element abundances in atmosphere chemically peculiar stars. Abundance occurs hydrodynamically stable stellar atmospheres due migration elements caused by atomic diffusion. Two HgMn stars, HD53929 HD63975 were selected from sample analysed some abundance peculiarities employing ZEEMAN2 code. We present results analysis observed recently spectropolarimeter...
Modelling of the spectra magnetic A and B main sequence stars is generally done assuming that all lines are split by field according to Zeeman effect. However, a number prominent spectral produced closely spaced doublets or triplets. Such should be treated using theory partial Paschen-Back (PPB) Depending on strength orientation field, PPB effect can result in Stokes IV profiles line differ significantly from those predicted theory. It important understand size types errors introduced into...
High resolution spectropolarimetric observations of the strongly magnetic, super-slowly rotating rapidly oscillating Ap star HD166473 are used to investigate implications presence a variable strong magnetic field on vertical and surface horizontal distribution various chemical elements. The analysis calculated LSD Stokes $I$ $V$ profiles confirms previously reported detection non-uniform several To test abundance stratification iron peak rare earth elements, measurements were carried out...