- ID:
- ivo://CDS.VizieR/J/MNRAS/267/755
- Title:
- Polarimetry in the Chamaeleon I Dark Cloud
- Short Name:
- J/MNRAS/267/755
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Position angles and magnitudes of linear polarization in the H band have been measured for 66 stars embedded in or behind the Chamaeleon I dark cloud. These data are used to demonstrate that the magnetic field permeating the cloud has an ordered structure over the full extent of the dark cloud (~4pc), with the magnetic field direction changing smoothly from a position angle of ~100 degrees in the vicinity of HD 97300 in the north to ~140 degrees in the vicinity of HD 97048 in the south and west. The elongation of the dark cloud is consistent with collapse preferentially along magnetic field lines. The polarizing efficiency of the cloud decreases with increasing line-of-sight extinction. Cloud members show a larger range in degree of polarization and position angle, which is interpreted as due to anisotropic scattering local to these stars. The IRAS 11054-7706C bipolar CO outflow is unusual in that it is oriented at >60 degrees to the cloud magnetic field direction. The Chamaeleon Infrared Nebula is polarized at ~30 per cent in the H band and also is oriented at ~50 degrees to the local magnetic field. We suggest that gravitational forces may have overwhelmed magnetic support locally to form these relatively massive stars.
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- ID:
- ivo://CDS.VizieR/J/ApJ/849/157
- Title:
- Polarimetry obs. toward IC5146 background stars
- Short Name:
- J/ApJ/849/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical and near-infrared stellar polarization observations toward the dark filamentary clouds associated with IC5146. The data allow us to investigate the dust properties (this paper) and the magnetic field structure (Paper II). A total of 2022 background stars were detected in the Rc, i', H, and/or K bands to A_V_<~25mag. The ratio of the polarization percentage at different wavelengths provides an estimate of {lambda}_max_, the wavelength of the peak polarization, which is an indicator of the small-size cutoff of the grain size distribution. The grain size distribution seems to significantly change at A_V_~3mag, where both the average and dispersion of P_Rc_/P_H_ decrease. In addition, we found {lambda}_max_~0.6-0.9{mu}m for A_V_>2.5mag, which is larger than the ~0.55{mu}m in the general interstellar medium (ISM), suggesting that grain growth has already started in low-AV regions. Our data also reveal that polarization efficiency (PE=P_{lambda}_/A_V_) decreases with A_V_ as a power law in the Rc, i', and K bands with indices of -0.71+/-0.10, -1.23+/-0.10, and -0.53+/-0.09. However, H-band data show a power index change; the PE varies with A_V_ steeply (index of -0.95+/-0.30) when A_V_<2.88+/-0.67mag, but softly (index of -0.25+/-0.06) for greater AV values. The soft decay of PE in high-AV regions is consistent with the radiative alignment torque model, suggesting that our data trace the magnetic field to A_V_~20mag. Furthermore, the breakpoint found in the H band is similar to that for A_V_, where we found the P_Rc_/P_H_ dispersion significantly decreased. Therefore, the flat PE-A_V_ in high-A_V_ regions implies that the power-index changes result from additional grain growth.
- ID:
- ivo://CDS.VizieR/J/A+AS/114/79
- Title:
- Polarimetry of Ap stars: general catalogue
- Short Name:
- J/A+AS/114/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A systematic program of broadband linear polarimetry, bearing on 55 Ap stars, has been developed during the 4 last years, at the Pic du Midi Observatory. While separate data have been already published, we present in this paper a complete catalogue of our observational material, including more than 400 measurements. We complement these data with another 100 measurements, obtained previously by other authors, so as to get a synthetic view of the phenomenon. Most of the observations have been dedicated to a small number (15) of stars, which show conspicuous changes of the linear polarization, so that it is possible to know accurately the time variation of the Stokes parameters: we expect that these new data will really improve our knowledge of the magnetic configuration, after a proper analysis which is currently being developed. For the other 40 stars, the polarization is either too small, or strongly contaminated by the interstellar polarization, so that broadband polarimetry is not very effective. Anyway, this first systematic investigation on the linear polarization of Ap stars will be a useful starting point for future measurements which should be made with higher spectral resolution. Finally, our measurements have provided new determinations of the rotation period for several stars.
- ID:
- ivo://CDS.VizieR/J/A+A/412/405
- Title:
- Polarimetry of evolved stars. III.
- Short Name:
- J/A+A/412/405
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present broadband optical polarimetry, and broadband optical and infrared photometry, of eight RV Tau-type and five R CrB-type stars; much of the photometry and polarimetry was obtained simultaneously. For nine of the objects polarimetric data is reported for the first time. ************************************************************************** * * * Sorry, but the author(s) never supplied the tabular material * * announced in the paper * * * **************************************************************************
- ID:
- ivo://CDS.VizieR/J/ApJ/698/2031
- Title:
- Polarimetry of HAeBe stars
- Short Name:
- J/ApJ/698/2031
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the correlation between the direction of the symmetry axis of the circumstellar material around intermediate mass young stellar objects and that of the interstellar magnetic field. We use CCD polarimetric data on 100 Herbig Ae/Be stars. A large number of them show intrinsic polarization, which indicates that their circumstellar envelopes are not spherical. The interstellar magnetic field direction is estimated from the polarization of field stars. There is an alignment between the position angle of the Herbig Ae/Be star polarization and that of the field stars for the most polarized objects. This may be an evidence that the ambient interstellar magnetic field plays a role in shaping the circumstellar material around young stars of intermediate mass and/or in defining their angular momentum axis.
- ID:
- ivo://CDS.VizieR/J/ApJ/708/758
- Title:
- Polarimetry of HH1-2 region
- Short Name:
- J/ApJ/708/758
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HH 1-2 region in the L1641 molecular cloud was observed in the near-infrared (IR) J, H, and Ks bands, and imaging polarimetry was performed. Seventy-six point-like sources were detected in all three bands. The near-IR polarizations of these sources seem to be caused mostly by the dichroic extinction. Using a color-color diagram, reddened sources with little IR excess were selected to trace the magnetic field structure of the molecular cloud. The mean polarization position angle of these sources is about 111{deg}, which is interpreted as the projected direction of the magnetic field in the observed region of the cloud. The distribution of the polarization angle has a dispersion of about 11{deg}, which is smaller than what was measured in previous studies. This small dispersion gives a rough estimate of the strength of the magnetic field to be about 130uG and suggests that the global magnetic field in this region is quite regular and straight. In contrast, the outflows driven by young stellar objects in this region seem to have no preferred orientation. This discrepancy suggests that the magnetic field in the L1641 molecular cloud does not dictate the orientation of the protostars forming inside.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A42
- Title:
- Polarimetry of Main-Belt Asteroids
- Short Name:
- J/A+A/626/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a polarimetric survey of main-belt asteroids at Complejo Astronomico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry and to estimate the diversity in the polarimetric properties of asteroids. The survey began in 1995 and a second period began in 2013 using the CASPOL polarimeter with a more sensitive detector to study small asteroids, families, and special taxonomic groups. The data were obtained using this instrument at the 2.15 m telescope of CASLEO. We present 128 observations for 82 asteroids of different taxonomic types. These results revealed phase-polarization curves and polarimetric parameters for 20 asteroids, amounting to a total of 135 objects with sufficient good data in the Catalogue of Asteroid Polarization Curves. Using the values obtained for the objects with a taxonomic classification, we obtained the mean polarimetric parameters for 19 taxonomic types and the Barbarians. The asteroids with large mean scatter separation distances have a minimum of the phase-polarization curve greater than -1%, slopes at the inversion angle of less than 0.12-0.15% per degree, and perihelion distances 1.8<q<2.5 au; these measurements indicate the asteroids could have high or moderate albedos and that they are objects with perihelia in the inner asteroid belt. These large mean scatter separation distance values could be the result of an electrostatic mechanism acting on the small grains of the regolith, a manifestation of a coherent backscattering mechanism, or the result of a surface formed by a mixture of dark and bright particles.
- ID:
- ivo://CDS.VizieR/J/MNRAS/466/2948
- Title:
- Polarimetry of 53 post-AGB stars
- Short Name:
- J/MNRAS/466/2948
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new optical broad-band (UBVRI) aperture polarimetric observations of 53 post-asymptotic giant branch (AGB) stars selected to exhibit a large near-infrared excess. 24 out of the 53 stars (45% of our sample) are presented for the first time. A statistical analysis shows four distinctive groups of polarized post-AGB stars: unpolarized or very lowly polarized (degree of polarization or DoP<1%), lowly polarized (1%<DoP<4%), moderately polarized (4%<DoP<8%) and highly polarized (DoP>8%). 23 out of the 53 (66%) belong to the first group, 10 (19%) to the second, five ( %) to the third and only three (6%) to the last group. Approximately 34%of our sample was found to be unpolarized objects, which is close to the percentage of round planetary nebulae. On average, the low and moderate groups show a wavelength-dependent polarization that increases towards shorter wavelengths, implying an intrinsic origin of the polarization, which signifies a Rayleigh-like scattering spectrum typical for non-symmetrical envelopes composed principally of small dust grains. The moderately polarized stars exhibit higher K-W3 and W1-W3 colour indices compared with the group of lowly polarized stars, suggesting a possible relation between DoP and mass-loss rate. Moreover, they are found to be systematically colder (redder in B-V), which may be associated with the condensation process close to these stars that results in a higher degree of polarization. We also provide evidence that multiple scattering in optically thin polar outflows is the mechanism that gives high DoP in post-AGB stars with bipolar or multi-polar envelopes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/474/4629
- Title:
- Polarimetry of 600 pulsars from 1.4GHz obs.
- Short Name:
- J/MNRAS/474/4629
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Over the past 13yr, the Parkes radio telescope has observed a large number of pulsars using digital filter bank backends with high time and frequency resolution and the capability for Stokes recording. Here, we use archival data to present polarimetry data at an observing frequency of 1.4GHz for 600 pulsars with spin-periods ranging from 0.036 to 8.5s. We comment briefly on some of the statistical implications from the data and highlight the differences between pulsars with high and low spin-down energy. The data set, images and table of properties for all 600 pulsars are made available in a public data archive maintained by the CSIRO.
- ID:
- ivo://CDS.VizieR/J/A+A/513/A75
- Title:
- Polarimetry of stars in NGC 5617
- Short Name:
- J/A+A/513/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present polarimetric observations in the UBVRI bands of 72 stars located in the direction of the medium age open cluster NGC 5617. Our intention is to use polarimetry as a tool in membership identification, by building on previous investigations intended mainly to determine the cluster's general characteristics rather than provide membership suitable for studies such as stellar content and metallicity, as well as study the characteristics of the dust lying between the Sun and the cluster.
