A5071768599- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Astro and Planetary Science
- Astrophysics and Cosmic Phenomena
- Solar and Space Plasma Dynamics
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- Pulsars and Gravitational Waves Research
- Space Exploration and Technology
- Spacecraft Design and Technology
- History and Developments in Astronomy
- Cosmology and Gravitation Theories
- CCD and CMOS Imaging Sensors
- Molecular Spectroscopy and Structure
- Spacecraft and Cryogenic Technologies
- Spectroscopy and Laser Applications
- Calibration and Measurement Techniques
- Adaptive optics and wavefront sensing
- GNSS positioning and interference
- Superconducting and THz Device Technology
Atacama Large Millimeter Submillimeter Array
2018-2024
National Radio Astronomy Observatory
2024
Netherlands Institute for Radio Astronomy
2015-2017
Osservatorio Astrofisico di Catania
2007-2017
Centro de Astrobiología
2012-2015
Consejo Superior de Investigaciones Científicas
2013
Max Planck Society
2011
Max Planck Institute for Radio Astronomy
2009-2011
University of Catania
2004-2008
Center for Astrophysics Harvard & Smithsonian
2006-2008
We present an overview of the LOFAR Tied-Array All-Sky Survey (LOTAAS) for radio pulsars and fast transients. The survey uses high-band antennas Superterp, dense inner part core, to northern sky (dec > 0 deg) at a central observing frequency 135 MHz. A total 219 tied-array beams (coherent summation station signals, covering 12 square degrees), as well three incoherent (covering 67 degrees) are formed in each pointing. For ofthe 222 beams, intensity is recorded 491.52 us time resolution. Each...
(abridged). We outline LBCS (the LOFAR Long-Baseline Calibrator Survey), whose aim is to identify sources suitable for calibrating the highest-resolution observations made with International Telescope, which include baselines >1000 km. Suitable must contain significant correlated flux density (50-100mJy) at frequencies around 110--190~MHz on scales of a few hundred mas. At least 200--300-km international baselines, we find 1 calibrator source per square degree over large part northern...
In this paper, we present the analysis of incoherent non-thermal radio emission from a sample hot magnetic stars, ranging early-B to early-A spectral type. Spanning wide range stellar parameters and wind properties, these stars display commonality in their which presents new challenges scenario as originally conceived. It was thought that relativistic electrons, responsible for emission, originate current sheets formed where opens field lines. However, true mass-loss rates cooler are too...
The low-frequency radio spectra of the hotspots within powerful galaxies can provide valuable information about physical processes operating at site jet termination. These are responsible for dissipation kinetic energy, particle acceleration, and magnetic-field generation. Here, we report new observations galaxy Cygnus A using Low Frequency Array (LOFAR) between 109 183 MHz, an angular resolution ∼3.5 arcsec. emission lobes is found to have a complex spectral index distribution, with...
CONTEXT: Asymptotic giant branch (AGB) stars are in one of the latest evolutionary stages low to intermediate-mass stars. Their vigorous mass loss has a significant effect on stellar evolution, and is source heavy elements dust grains for interstellar medium. The mass-loss rate can be well traced by carbon monoxide (CO) line emission. AIMS: We present new Herschel HIFI IRAM 30m telescope CO data sample 53 galactic AGB lines cover fairly large range excitation energy from $J=1\to0$ $J=9\to8$...
We have observed a small sample of hot post-AGB stars with the InfraRed Array Camera (IRAC) and Spectrograph (IRS) on-board Spitzer Space Telescope. The were selected from literature on basis their far-Infrared excess (i.e., candidates) B spectral type close to ionization envelope). combination our IRAC observations 2MASS IRAS catalog data, along previous radio in cm range (where available) allowed us model SEDs targets find that almost all them at least two shells dust different...
The electron cyclotron maser is the coherent emission process that gives rise to radio lighthouse effect observed in hot magnetic chemically peculiar star CU Virginis. It has also been proposed explain highly circularly polarized pulses some ultracool dwarfs with spectral type earlier than M7. Coherent events of this kind resemble auroral from magnetized planets Solar system. In article, we present a three-dimensional model able simulate timing and profile emitted by those stars...
We present new ATCA multi-wavelength radio measurements (range 2.1-21.2 GHz) of the early-type magnetic star rho Oph A, performed in March 2019 during 3 different observing sessions. These observations evidence a clear rotational modulation stellar emission and detection coherent auroral from A at 2.1 GHz. collected high-resolution optical spectra acquired by several instruments over time span about ten years. also report field that, together with light curves temporal variation equivalent...
We present new radio/millimeter measurements of the hot magnetic star HR 5907 obtained with VLA and ALMA interferometers. find that is most radio luminous early type in cm–mm band among those presently known. Its multi-wavelength light curves are strongly variable an amplitude increases frequency. The emission can be explained by populations non-thermal electrons accelerated current sheets on outer border magnetosphere this fast-rotating star. classify as another member growing class stars...
Among its great findings, the IRAS mission showed existence of an unidentified mid-IR feature around 21 um. Since discovery, this has been detected in all C-rich proto-PNe intermediate spectral type (A-G) and - weakly a few PNe AGB stars, but nature carriers remains unknown. In paper, we show detection spectra three new stars transiting from to PN stage obtained with Spitzer Space Telescope. Following recent suggestion, try model SEDs our targets amorphous carbon FeO, which might be...
Radio emission has been detected in a broad variety of stellar objects from all stages evolution. However, most our knowledge originates targeted observations small samples, which are strongly biased to sources peculiar at other wavelengths. In order tackle this problem we have conducted deep 1.4 GHz survey by using the Australian Telescope Compact Array, with net bandwidth 1.7 (1.4–3.1 GHz) , following same observing setup as that used for Australia Large Area Survey project, time choosing...
We report the detection of auroral radio emission from early-type magnetic star HD142301. New VLA observations HD142301 detected highly polarized amplified occurring at fixed stellar orientations. The coherent mechanism responsible for amplifies radiation within a narrow beam, making where this phenomenon occurs similar to lighthouse. elementary process mainly one two magneto-ionic modes electromagnetic wave. This explains why pulses are circularly polarized. is characterized by reversal...
Late stages of stellar evolution are characterized by copious mass-loss events whose signature is the formation circumstellar envelopes (CSE). Planck multi-frequency measurements have provided relevant information on a sample Galactic planetary nebulae (PNe) in important and relatively unexplored observational band between 30 857GHz. enables assembly comprehensive PNe spectral energy distributions (SEDs) from radio {\bf to} far-infrared frequencies. Modelling derived SEDs provides us with...
The non-thermal radio emission of main-sequence early-type stars is a signature stellar magnetism. We present multi-wavelength (1.6-16.7 GHz) ATCA measurements the magnetic star rho OphC, which flat-spectrum source. OphC partially circularly polarized with steep spectral dependence: fraction about 60% at lowest frequency sub-band (1.6 while undetected 16.7 GHz. This clear evidence coherent Auroral Radio Emission (ARE) from magnetosphere. Interestingly, detection OphC's ARE not related to...
We present new Karl G. Jansky Very Large Array multifrequency measurements of a set stars in transition from the post-AGB to planetary nebula phase monitored radio range over several years. Clear variability is found for five sources. Their light curves show increasing and decreasing patterns. New observations at high angular resolution are also presented two Among these IRAS 18062 + 2410, whose structure compared near-infrared images available literature. With maps, we can estimate inner...
We have selected a small sample of post-AGB stars in transition towards the planetary nebula and present new Very Large Array multi-frequency high-angular resolution radio observations them. The data are used to create model targets' continuum spectra, proving that these started their evolution as very young nebulae. In optically thin range, slopes compatible with expected spectral index (-0.1). Two targets (IRAS 18062+2410 17423-1755) seem be thick even at high frequency, observed handful...
<i>Aims. <i/>Ultra compact HII (UCHII) regions are indicators of high-mass star formation sites and distributed mainly in the Galactic plane. They exhibit a broad band spectrum with significant emission between near-IR radio wavelengths. We intend to investigate possible contribution forthcoming ESA Planck mission science UCHII by evaluating possibility detecting UCHIIs that bright regime.<i>Methods. <i/>We performed new 7 mm observations sample regions. The were designed acquire...
Searching for variability, we have observed a sample of hot post-AGB stars and young Planetary Nebulae candidates with the Very Large Array at 4.8, 8.4, 22.4 GHz. The sources had been previously detected in radio continuum, which is proof that central started ionising their circumstellar envelopes an increase flux time can be expected as result progression ionisation front. Such behaviour has found IRAS 18062+2410, whose modelling allowed us to determine its ionised mass increased from...
In this paper we simulate the cyclic circularly-polarised pulses of ultra-cool dwarf TVLM513-46546, observed with VLA at 4.88 and 8.44 GHz on May 2006, by using a 3D model auroral radio emission from stellar magnetosphere. During epoch, light curves are characterised two left-hand polarised GHz, one doubly-peaked (of opposite polarisations) pulse GHz. To take into account possible deviation dipolar symmetry magnetic field topology, described in is also able to magnetosphere shaped like an...
We present a multi-wavelength study of the Galactic Luminous Blue Variable HR Carinae, based on new high resolution mid-infrared (IR) and radio images obtained with Very Large Telescope (VLT) Australia Compact Array (ATCA), which have been complemented by far-infrared Herschel-PACS observations ATCA archive data. The Herschel reveal large-scale distribution dusty emitting nebula, extends mainly to North-East direction, up 70 arcsec from central star, is oriented along direction space motion...
We present radio observations of 18 MIPSGAL bubbles performed at 5 GHz (6 cm) with the Karl G. Jansky Very Large Array in configuration B and BnA. The were aimed understanding what kind information high-resolution high-sensitivity maps can supply on circumstellar envelopes different kinds evolved stars their comparison infrared images similar resolution tell us. found that be grouped into five categories according to morphology. three presenting a central point source all correspond luminous...
Abstract We present ALMA band 6 observations of the luminous blue variable η Car obtained within ALMAGAL program. report SiO J = 5 → 4, SiS 12 11, and SiN N 4 emission in equatorial region Homunculus nebula, constituting first detection silicon- sulfur-bearing molecules outskirts a highly evolved, early-type massive star. The SiO, SiS, trace clumpy ring that surrounds central binary at projected distance ∼2″, delineating inner rims butterfly-shaped dusty region. formation silicon-bearing...
Context. The Sun is an active star that produces large-scale energetic events such as solar flares and coronal mass ejections numerous smaller-scale jets. These are often associated with accelerated particles can cause emission at radio wavelengths. reconfiguration of the magnetic field in corona believed to be majority particles. Aims. Here, we investigate a bright J-burst was jet possible mechanism causing these two phenomena. Methods. We used data from Solar Dynamics Observatory (SDO)...
Aims. We present 43 GHz (7 mm) observations of a sample radio-bright Planetary nebulae aimed to obtain, together with far-IR measurements (IRAS), reliable estimates the fluxes emitted in millimetre and sub-millimetre band, and, therefore, test their detectability by forthcoming ESA PLANCK mission. This spectral range, even though very important constrain physics circumstellar environments, is still far from being completely exploited.
Despite numerous efforts, the transition from Asymptotic Giant Branch (AGB) stars to Planetary Nebulae (PN) is a poorly understood phase of stellar evolution. We have therefore carried out interferometric (VLA) radio observations sample hot post-AGB stars, selected on basis their optical and infrared properties. Ten sources 16 observed were detected. This indicates that most our targets are surrounded by nebula where ionization has already started. definitively determines evolutionary status...