- ID:
- ivo://CDS.VizieR/J/other/PASA/34.13
- Title:
- S-PASS catalog at 2.3GHz
- Short Name:
- J/other/PASA/34.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The S-band Polarisation All-Sky Survey (S-PASS) has observed the entire southern sky using the 64-metre Parkes radio telescope at 2.3GHz with an effective bandwidth of 184MHz. The surveyed sky area covers all declinations DE<0{deg}. To analyse compact sources the survey data have been re-processed to produce a set of 107 Stokes I maps with 10.75-arcmin resolution and the large scale emission contribution filtered out. In this paper we use these Stokes I images to create a total intensity southern-sky extragalactic source catalogue at 2.3GHz. The source catalogue contains 23389 sources and covers a sky area of 16600deg^2^, excluding the Galactic plane for latitudes |b|<10{deg}. Approximately 8% of catalogued sources are resolved. S-PASS source positions are typically accurate to within 35-arcsec. At a flux density of 225mJy the S-PASS source catalogue is more than 95% complete, and ~94% of S-PASS sources brighter than 500mJy/beam have a counterpart at lower frequencies.
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- ID:
- ivo://CDS.VizieR/J/ApJ/829/5
- Title:
- S-PASS & NVSS bright extragalactic radio sources
- Short Name:
- J/ApJ/829/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a polarization catalog of 533 extragalactic radio sources that have a 2.3GHz total intensity above 420mJy from the S-band Polarization All Sky Survey, S-PASS, with corresponding 1.4GHz polarization information from the NRAO VLA Sky Survey, NVSS. We studied the selection effects and found that fractional polarization, {pi}, of radio objects at both wavelengths depends on the spectral index, the source magnetic field disorder, the source size, and depolarization. The relationship between depolarization, spectrum, and size shows that depolarization occurs primarily in the source vicinity. The median {pi}_2.3_ of resolved objects in NVSS is approximately two times larger than that of unresolved sources. Sources with little depolarization are ~2 times more polarized than both highly depolarized and re-polarized sources. This indicates that intrinsic magnetic field disorder is the dominant mechanism responsible for the observed low fractional polarization of radio sources at high frequencies. We predict that number counts from polarization surveys will be similar at 1.4GHz and at 2.3GHz, for fixed sensitivity, although ~10% of all sources may currently be missing because of strong depolarization. Objects with {pi}_1.4_~{pi}_2.3_>=4% typically have simple Faraday structures, so they are most useful for background samples. Almost half of flat-spectrum ({alpha}>=-0.5) and ~25% of steep-spectrum objects are re-polarized. Steep-spectrum, depolarized sources show a weak negative correlation of depolarization with redshift in the range 0<z<2.3. Previous non-detections of redshift evolution are likely due the inclusion of re-polarized sources as well.
- ID:
- ivo://CDS.VizieR/J/A+A/482/989
- Title:
- Spectropolarimetric model for Earth-like planets
- Short Name:
- J/A+A/482/989
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of numerical simulations of flux F and degree of polarization P of light that is reflected by Earth-like extrasolar planets orbiting solar type stars. Our results are presented as functions of the wavelength (from 0.3 to 1.0{mu}m, with 0.001{mu}m spectral resolution) and as functions of the planetary phase angle. We use different surface coverages for our model planets, including vegetation and a Fresnel reflecting ocean, and clear and cloudy atmospheres.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/120
- Title:
- Spectropolarimetric survey of classical Be stars
- Short Name:
- J/ApJ/786/120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent observational and theoretical studies of classical Be stars have established the utility of polarization color diagrams (PCDs) in helping to constrain the time-dependent mass decretion rates of these systems. We expand on our pilot observational study of this phenomenon, and report the detailed analysis of a long-term (1989-2004) spectropolarimetric survey of nine additional classical Be stars, including systems exhibiting evidence of partial disk-loss/disk-growth episodes as well as systems exhibiting long-term stable disks. After carefully characterizing and removing the interstellar polarization along the line of sight to each of these targets, we analyze their intrinsic polarization behavior. We find that many steady-state Be disks pause at the top of the PCD, as predicted by theory. We also observe sharp declines in the Balmer jump polarization for later spectral type, near edge-on steady-state disks, again as recently predicted by theory, likely caused when the base density of the disk is very high, and the outer region of the edge-on disk starts to self absorb a significant number of Balmer jump photons. The intrinsic V-band polarization and polarization position angle of {gamma} Cas exhibits variations that seem to phase with the orbital period of a known one-armed density structure in this disk, similar to the theoretical predictions of Halonen & Jones. We also observe stochastic jumps in the intrinsic polarization across the Balmer jump of several known Be+sdO systems, and speculate that the thermal inflation of part of the outer region of these disks could be responsible for producing this observational phenomenon. Finally, we estimate the base densities of this sample of stars to be between ~8x10^-11^ and ~4x10^-12^ g/cm^3^ during quasi steady state periods given there maximum observed polarization.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/2879
- Title:
- Spectropolarimetry of active galaxy 3C 390.3
- Short Name:
- J/MNRAS/448/2879
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Here we present the spectropolarimetric observations of the radio-loud active galaxy 3C 390.3 in the period 2009-2014 (24 epochs). The galaxy has been observed with the 6-m telescope of Special Astrophysical Observatory of the Russian Academy of Science (SAO RAS) using the Spectral Camera with Optical Reducer for Photometric and Interferometric Observations (SCORPIO) spectropolarimeter. We explore the variability and lags in the polarized light of the continuum and broad H{alpha} line. We give the Stokes parameters Q, U, degree of linear polarization P and the position angle of the polarization plane, {phi}, for 24 epochs. We find a small lag (10-40 d) between the unpolarized and polarized continuum that is significantly smaller than the estimated lags for the unpolarized broad emission lines (lag(H{alpha}) ~138-186 and lag(H{beta}) ~60-79 d). This shows that the region of the variable polarized continuum is significantly smaller than the broad line region, indicating that a part of the polarized continuum is coming from the jet. The lag of the polarized light in the H{alpha} line (89-156 d) indicates an additional component to the disc one that has an outflowing velocity of ~-1200 km/s. This region seems to depolarize the polarized broad H{alpha} line emitted from the disc and scattered in the inner part of the torus.
- ID:
- ivo://CDS.VizieR/J/ApJ/709/1306
- Title:
- Spectropolarimetry of 60 Cyg and {pi} Aqr
- Short Name:
- J/ApJ/709/1306
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Classical Be stars are known to occasionally transition from having a gaseous circumstellar disk ("Be phase") to a state in which all observational evidence for the presence of these disks disappears ("normal B-star phase"). We present one of the most comprehensive spectropolarimetric views to date of such a transition for two Be stars, {pi} Aquarii and 60 Cygni. The disk-loss episode of 60 Cyg was characterized by a generally monotonic decrease in emission strength over a timescale of ~1000 days from the maximum V-band polarization to the minimum H{alpha} equivalent width, consistent with the viscous timescale of the disk, assuming {alpha}~0.14. {pi} Aqr's disk loss was episodic in nature and occurred over a timescale of ~2440 days.
- ID:
- ivo://CDS.VizieR/J/AJ/134/1877
- Title:
- Spectropolarimetry of R CrB in 1998-2003
- Short Name:
- J/AJ/134/1877
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an extended optical spectropolarimetry of R CrB from 1998 January to 2003 September. The polarization was almost constant in the phase of maximum brightness, being consistent with past observations. We detected, however, temporary changes of the polarization (~0.5%) in 2001 March and August, which were the first detections of large polarization variability in R CrB near maximum brightness. The amplitude and the position angle of the "transient polarization" were almost constant with wavelength in both events. There was a difference of about 20{deg} in the position angle between the two events. Each event could be explained by light scattering due to a short-lived dust puff occasionally ejected off the line of sight.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A85
- Title:
- SPHERE images of HD 32297
- Short Name:
- J/A+A/630/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectro-photometry of debris disks in total intensity and polarimetry can provide new insight into the properties of the dust grains therein (size distribution and optical properties). We aim to constrain the morphology of the highly inclined debris disk HD32297. We also intend to obtain spectroscopic and polarimetric measurements to retrieve information on the particle size distribution within the disk for certain grain compositions. We observed HD32297 with SPHERE in Y, J, and H bands in total intensity and in J band in polarimetry. The observations are compared to synthetic models of debris disks and we developed methods to extract the photometry in total intensity overcoming the data-reduction artifacts, namely the self-subtraction. The spectro-photometric measurements averaged along the disk mid-plane are then compared to model spectra of various grain compositions. These new images reveal the very inner part of the system as close as 0.15". The disk image is mostly dominated by the forward scattering making one side (half-ellipse) of the disk more visible, but observations in total intensity are deep enough to also detect the back side for the very first time. The images as well as the surface brightness profiles of the disk rule out the presence of a gap as previously proposed. We do not detect any significant asymmetry between the northeast and southwest sides of the disk. The spectral reflectance features a "gray to blue" color which is interpreted as the presence of grains far below the blowout size. The presence of sub-micron grains in the disk is suspected to be the result of gas drag and/or "avalanche mechanisms". The blue color of the disk could be further investigated with additional total intensity and polarimetric observations in K and H bands respectively to confirm the spectral slope and the fraction of polarization.
- ID:
- ivo://CDS.VizieR/J/PAZh/43/407
- Title:
- S5 0716+714 polarization & brightness 1991-2004
- Short Name:
- J/PAZh/43/407
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the photometric and polarimetric behavior of the blazar S5 0716+714 based on the observations carried out in 1991-2004 at the 125-cm Crimean Astrophysical Observatory telescope (AZT11) with a photopolarimeter that allows simultaneous polarization and brightness measurements to be made in the UBV RI bands. We also provide the UBV photometry for the blazar obtained in 2000-2009 with a 60-cm telescope at the Crimean Station of the Sternberg Astronomical Institute. The pattern of flux variability and the correlation between the brightness, color, and polarization variations have been investigated. In this time interval the blazar showed a significant brightness and polarization variability similar to noise processes.
- ID:
- ivo://CDS.VizieR/J/A+A/624/L8
- Title:
- Starlight polarization
- Short Name:
- J/A+A/624/L8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galactic dust emission is polarized at unexpectedly high levels, as revealed by Planck. The origin of the observed 20% polarization fractions can be identified by characterizing the properties of optical starlight polarization in a region with maximally polarized dust emission. We measure the R-band linear polarization of 22 stars in a region with a submillimeter polarization fraction of 20%. A subset of 6 stars is also measured in the B, V, and I bands to investigate the wavelength dependence of polarization. We find that starlight is polarized at correspondingly high levels. Through multiband polarimetry we find that the high polarization fractions are unlikely to arise from unusual dust properties, such as enhanced grain alignment. Instead, a favorable magnetic field geometry is the most likely explanation, and is supported by observational probes of the magnetic field morphology. The observed starlight polarization exceeds the classical upper limit of [pV/E(B-V]_{max}_=9%/mag and is at least as high as 13%/mag, as inferred from a joint analysis of Planck data, starlight polarization and reddening measurements. Thus, we confirm that the intrinsic polarizing ability of dust grains at optical wavelengths has long been underestimated.
