- ID:
- ivo://CDS.VizieR/J/ApJ/672/40
- Title:
- AO 0235+164 outburst in 2006 December
- Short Name:
- J/ApJ/672/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of polarimetric (R-band) and multicolor photometric (BVRIJHK) observations of the blazar AO 0235+16 during an outburst in 2006 December. The data reveal a short timescale of variability (several hours), which increases from optical to near-IR wavelengths; even shorter variations are detected in polarization. The flux density correlates with the degree of polarization, and at the maximum degree of polarization the electric vector tends to align with the parsec-scale jet direction. We find that a variable component with a steady power-law spectral energy distribution and very high optical polarization (30%-50%) is responsible for the variability. We interpret these properties of the blazar within a model of a transverse shock propagating down the jet. In this case a small change in the viewing angle of the jet, by ~<1{deg}, and a decrease in the shocked plasma compression by a factor of ~1.5 are sufficient to account for the variability.
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- ID:
- ivo://CDS.VizieR/J/A+A/658/A158
- Title:
- A polarimetric study of ACOs
- Short Name:
- J/A+A/658/A158
- Date:
- 22 Feb 2022 15:07:47
- Publisher:
- CDS
- Description:
- Asteroids in comet-like orbits (ACOs) consist of asteroids and dormant comets. Due to their similar appearance, it is challenging to distinguish dormant comets from ACOs via general telescopic observations. Surveys for discriminating dormant comets from the ACO population have been conducted via spectroscopy or optical and mid-infrared photometry. However, they have not been conducted through polarimetry. We conducted the first polarimetric research of ACOs. We conducted a linear polarimetric pilot survey for three ACOs: (944) Hidalgo, (3552) Don Quixote, and (331471) 1984 QY1. These objects are unambiguously classified into ACOs in terms of their orbital elements (i.e., the Tisserand parameters with respect to Jupiter TJ significantly less than 3). Three ACOs were observed by the 1.6-m Pirka Telescope from UT 2016 May 25 to UT 2019 July 22 (13 nights). We found that two ACOs, Don Quixote and Hidalgo, have polarimetric properties similar to comet nuclei and D-type asteroids (optical analogs of comet nuclei. However, 1984 QY1 exhibited a polarimetric property consistent with S-type asteroids. We conducted a backward orbital integration to determine the origin of 1984 QY1 and found that this object was transported from the main belt into the current comet-like orbit via the 3:1 mean motion resonance with Jupiter. We conclude that the origins of ACOs can be more reliably identified by adding polarimetric data to the color and spectral information. This study would be valuable for investigating how the ice-bearing small bodies distribute in the inner solar system.
- ID:
- ivo://CDS.VizieR/J/ApJS/121/171
- Title:
- Arecibo polarimetry of 98 pulsars
- Short Name:
- J/ApJS/121/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured full Stokes parameter profiles of 98 pulsars at 21 cm from Arecibo observatory. Average profiles are presented with integration times as long as 1/3 day. We have studied the resulting profiles and other published data on each pulsar and classified them according to the Rankin morphological scheme.
- ID:
- ivo://CDS.VizieR/J/A+A/611/A66
- Title:
- AR Sco VLA radio observations
- Short Name:
- J/A+A/611/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AR Scorpii is unique amongst known white dwarf binaries in showing powerful pulsations extending to radio frequencies. Here we aim to investigate the multi-frequency radio emission of AR Sco in detail, in order to constrain its origin and emission mechanisms. We present interferometric radio frequency imaging of AR Sco at 1.5, 5 and 9GHz, analysing the total flux and polarization behaviour of this source at high time resolution (10, 3 and 3s), across a full 3.6h orbital period in each band. We find strong modulation of the radio flux on the orbital period and the orbital sideband of the white dwarf's spin period (also known as the "beat" period). This indicates that, like the optical flux, the radio flux arises predominantly from on or near the inner surface of the M-dwarf companion star. The beat-phase pulsations of AR Sco decrease in strength with decreasing frequency. They are strongest at 9GHz and at an orbital phase ~0.5. Unlike the optical emission from this source, radio emission from AR Sco shows weak linear polarization but very strong circular polarization, reaching ~30% at an orbital phase ~0.8. We infer the probable existence of a non-relativistic cyclotron emission component, which dominates at low radio frequencies. Given the required magnetic fields, this also likely arises from on or near the M-dwarf.
- ID:
- ivo://CDS.VizieR/J/A+A/338/340
- Title:
- Asteroids as IR Standards for ISOPHOT
- Short Name:
- J/A+A/338/340
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Asteroids are used as far-IR calibrators for the imaging photopolarimeter ISOPHOT on board the Infrared Space Observatory ISO. For the 10 selected objects we compiled a large uniform database of 678 individual observations, ranging from 7-2000{mu}m. Applying a new thermophysical model to the observations we derived thermal properties of the selected asteroids, based on spin-vector solutions, direct size measurements and the HG-magnitude system. Our investigations indicate very rough surfaces, reflected in the beaming effect, and very low levels of heat conduction, expressed in thermal inertias between 5 and 25J/m^2^/s^0.5^/K. Due to scattering processes in the porous regolith, the emissivity varies significantly with wavelength. In case of Vesta we find emissivities as low as 0.6 in the far-IR/submillimetre region. By entering the combined results into the thermophysical model we defined new photometric standards for the far-IR. The absolute accuracy for thermal flux or lightcurve predictions is 5-10% for the first category objects and 10-20% for the secondaries. The methods and procedures discussed here are included in the first update of the ISOPHOT calibration in 1998.
- ID:
- ivo://CDS.VizieR/J/MNRAS/325/1411
- Title:
- ATCA Intraday Variability Survey
- Short Name:
- J/MNRAS/325/1411
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an Australia Telescope Compact Array (ATCA) survey for intraday variability (IDV) of the total and polarized flux densities of 118 compact, flat-spectrum, extragalactic radio sources from the Parkes 2.7-GHz Survey. A total of 22 total flux density IDV sources were discovered and 15 sources were found to show IDV of their polarized flux density. We discuss the statistical properties of the IDV sources, including the distribution of source modulation indices, and the dependence of the variability amplitude on source spectral index and on Galactic position. We suggest interstellar scintillation (ISS) in the Galactic interstellar medium as the most likely mechanism for IDV. Even so, the inferred high brightness temperatures cannot be easily explained.
- ID:
- ivo://CDS.VizieR/J/PASJ/55/351
- Title:
- ATCA observations of 202 compact radio sources
- Short Name:
- J/PASJ/55/351
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Australia Telescope Compact Array (ATCA) has been used in support of the VLBI Space Observatory Programme (VSOP) space VLBI mission, to monitor the total and polarised flux densities of 202 objects that make up 83% of the VSOP all-sky Survey of compact extragalactic radio sources south of DE=+10{deg}. The primary goal of the ATCA observations is to provide information on the total and polarised emission from the compact components in these sources, for correlation with parameters obtained from VSOP imaging observations. These data represent the first high resolution, long timescale flux density monitoring observations of a large number of southern compact radio sources. In the future, comparison of the ATCA and VSOP data will be used to investigate relativistic beaming models and identify similarities or differences between the major classes of extragalactic radio sources. As an illustration of the scientific value of the ATCA data we undertake a comparison of the properties of the gamma-ray loud and gamma-ray quiet AGN in the southern component of the VSOP Survey sample, finding that in a flat-spectrum sub-sample the gamma-ray loud AGN are more variable than the gamma-ray quiet AGN.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A94
- Title:
- A universal pattern in halo magnetic fields
- Short Name:
- J/A+A/649/A94
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Magnetic fields in galaxy halos are in general very difficult to observe. Most recently, the Continuum HAlos in Nearby Galaxies - an EVLA Survey (CHANG-ES) collaboration investigated the radio halos of 35 nearby edge-on spiral galaxies in detail and detected large-scale magnetic fields in 16 of them. We used the CHANG-ES radio polarization data to create rotation measure (RM) maps for all galaxies in the sample and stack them with the aim of amplifying any underlying universal toroidal magnetic field pattern in the halo above and below the disk of the galaxy. We discovered a large-scale magnetic field in the central region of the stacked galaxy profile, which is attributable to an axial electric current that universally outflows from the center, both above and below the plane of the disk. A similar symmetry-breaking has also been observed in astrophysical jets, but never before in galaxy halos. This is an indication that galaxy halo magnetic fields are probably not generated by pure magnetohydrodynamic (MHD) processes in the central regions of galaxies. One such promising physical mechanism is the Cosmic Battery operating in the innermost accretion disk around the central supermassive black hole. We anticipate that our discovery will stimulate a more general discussion on the origin of astrophysical magnetic fields.
- ID:
- ivo://CDS.VizieR/J/MNRAS/402/2403
- Title:
- Australia Telescope 20GHz Survey Catalog, AT20G
- Short Name:
- J/MNRAS/402/2403
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Australia Telescope 20GHz Survey (AT20G) is a blind radio survey carried out at 20GHz with the Australia Telescope Compact Array (ATCA) from 2004 to 2008, and covers the whole sky south of declination 0{deg}. The AT20G source catalogue presented here is an order of magnitude larger than any previous catalogue of high-frequency radio sources, and includes 5890 sources above a 20GHz flux-density limit of 40mJy. All AT20G sources have total intensity and polarisation measured at 20GHz, and most sources south of declination -15{deg} also have near-simultaneous flux-density measurements at 5 and 8GHz. A total of 1559 sources were detected in polarised total intensity at one or more of the three frequencies.
- ID:
- ivo://CDS.VizieR/J/AJ/154/252
- Title:
- A VLA survey of magnetic CVs. I. The data
- Short Name:
- J/AJ/154/252
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Jansky Very Large Array was used to observe 121 magnetic cataclysmic variables (MCVs). We report radio detections of 18 stars. Thirteen are new radio sources, increasing the number of MCVs that are radio sources by more than twofold, from 8 to 21. Most detections are at 8.7 GHz (X-band) with a lesser number at 5.4 and 21.1 GHz (C- and K-bands). With the exception of AE Aqr, whose flux density is typically >5 mJy, the flux densities are in the range of 24-780 {mu}Jy. Thirteen of the detections show highly circularly polarized emission, which is characteristic of electron-cyclotron maser emission. The data suggest that MCVs could possibly be divided into two classes of radio emitters: those dominated by weakly polarized gyrosynchrotron emission and those by highly polarized electron-cyclotron maser emission.
