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151. Polarimetry of stars in NGC 5617
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.
152. Polarimetry of V838 Mon and stars around
ID:
ivo://CDS.VizieR/J/ApJ/598/L43
Title:
Polarimetry of V838 Mon and stars around
Short Name:
J/ApJ/598/L43
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present imaging polarimetry observations of the eruptive variable V838 Monocerotis and its neighboring field obtained in 2002 October. The polarization of field stars confirms the previously determined interstellar polarization along the line of sight to V838 Mon. While V838 Mon showed intrinsic polarization shortly after its second outburst on 2002 February 8, all subsequent observations only showed a quiescent interstellar polarization component. We find that V838 Mon once again showed significant intrinsic polarization in 2002 October, suggesting the presence of an asymmetrical geometry of scattering material close to the star. Furthermore, an observed 90{deg} position angle flip in the intrinsic polarization from 2002 February to October suggests that the distribution of nearby circumstellar material has experienced significant changes. We discuss the opacity changes in the evolving circumstellar cloud around V838 Mon that may explain these observations.
153. Polarimetry & photometry of GRB with RINGO2
ID:
ivo://CDS.VizieR/J/ApJ/843/143
Title:
Polarimetry & photometry of GRB with RINGO2
Short Name:
J/ApJ/843/143
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of early-time (~10^2^-10^4^s) photometry and polarimetry of all gamma-ray burst (GRB) optical afterglows observed with the RINGO2 imaging polarimeter on the Liverpool Telescope. Of the 19 optical afterglows observed, the following nine were bright enough to perform photometry and attempt polarimetry: GRB100805A, GRB101112A, GRB110205A, GRB110726A, GRB120119A, GRB120308A, GRB120311A, GRB120326A, and GRB120327A. We present multiwavelength light curves for these 9 GRBs, together with estimates of their optical polarization degrees and/or limits. We carry out a thorough investigation of detection probabilities, instrumental properties, and systematics. Using two independent methods, we confirm previous reports of significant polarization in GRB 110205A and 120308A, and report the new detection of P=6_-2_^+3^% in GRB101112A. We discuss the results for the sample in the context of the reverse- and forward-shock afterglow scenario, and show that GRBs with detectable optical polarization at early time have clearly identifiable signatures of reverse-shock emission in their optical light curves. This supports the idea that GRB ejecta contain large-scale magnetic fields, and it highlights the importance of rapid-response polarimetry.
154. Polarimetry toward Musca dark cloud
ID:
ivo://CDS.VizieR/J/ApJ/603/584
Title:
Polarimetry toward Musca dark cloud
Short Name:
J/ApJ/603/584
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used CCD imaging polarimetry to obtain linear polarization measurements of background stars toward the filamentary Musca dark cloud. We present a catalog of 2497 objects with polarization signal-to-noise ratio larger than 5. This allows us to build polarization maps to infer the detailed geometry of the local magnetic field. We show composite polarization maps along the cloud and explore general correlations of the polarimetric data with the morphology of the region. We find the overall field to be strikingly aligned with the projected small axis of the filamentary cloud. We detect a lower limit for the polarization across the cloud of ~2%, with an enhanced polarization of 6%-7% in the central region. We find evidence that the polarization pattern is altered in the inner regions, those associated with higher extinction.
155. Polarimetry toward sightlines through ChaI
ID:
ivo://CDS.VizieR/J/ApJ/720/1045
Title:
Polarimetry toward sightlines through ChaI
Short Name:
J/ApJ/720/1045
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained optical multi-band polarimetry toward sightlines through the Chamaeleon I cloud, particularly in the vicinity of the young B9/A0 star HD 97300. We show, in agreement with earlier studies, that the radiation field impinging on the cloud in the projected vicinity of the star is dominated by the flux from the star, as evidenced by a local enhancement in the grain heating. By comparing the differential grain heating with the differential change in the location of the peak of the polarization curve, we show that the grain alignment is enhanced by the increase in the radiation field. We also find a weak, but measurable, variation in the grain alignment with the relative angle between the radiation field anisotropy and the magnetic field direction. Such an anisotropy in the grain alignment is consistent with a unique prediction of modern radiative alignment torque theory and provides direct support for radiatively driven grain alignment.
156. Polarisation and magnetic fields in Ap stars
ID:
ivo://CDS.VizieR/J/MNRAS/426/1003
Title:
Polarisation and magnetic fields in Ap stars
Short Name:
J/MNRAS/426/1003
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper we describe and evaluate new spectral line polarization observations obtained with the goal of mapping the surfaces of magnetic Ap stars in great detail. One hundred complete or partial Stokes IQUV sequences, corresponding to 297 individual polarized spectra, have been obtained for seven bright Ap stars using the Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) and NARVAL high-resolution spectropolarimeters. The targets span a range of masses from approximately 1.8 to 3.4M_{sun}_, a range of rotation periods from 2.56 to 6.80d and a range of maximum longitudinal magnetic field strengths from 0.3 to over 4kG. For three of the seven stars, we have obtained dense phase coverage sampling the entire rotational cycle.
157. Polarisation around filamentary dark cloud GF 9
ID:
ivo://CDS.VizieR/J/ApJ/650/945
Title:
Polarisation around filamentary dark cloud GF 9
Short Name:
J/ApJ/650/945
Date:
21 Oct 2021
Publisher:
CDS
Description:
New visible polarization data combined with existing IR and FIR polarization data are used to study how the magnetic field threading the filamentary molecular cloud GF 9 connects to larger structures in its general environment. When visible and NIR polarization data are combined, no evidence is found for a plateau in the polarization above extinction A_V_~1.3, as seen in dark clouds in Taurus. This lack of saturation effect suggests that even in the denser parts of GF 9 magnetic fields can be probed. The visible polarization is smooth and has a well-defined orientation. In the core region, the IR and FIR data are also well defined, but each with a different direction. A multiscale analysis of the magnetic field shows that on the scale of a few times the mean radial dimension of the molecular cloud, it is as if the magnetic field were blind to the spatial distribution of the filaments, while on smaller scales in the core region, multiwavelength polarimetry shows a rotation of the magnetic field lines in these denser phases. Finally, the Chandrasekhar and Fermi method is used to evaluate the magnetic field strength, indicating that the core region is approximately magnetically critical. A global interpretation suggests that in the core region an original poloidal field could have been twisted by a rotating elongated (core+envelope) structure. There is no evidence for turbulence, and ambipolar diffusion does not seem to be effective at the present time.
158. Polarisation at 850mu{m} in OMC-2 and OMC-3
ID:
ivo://CDS.VizieR/J/ApJ/716/893
Title:
Polarisation at 850mu{m} in OMC-2 and OMC-3
Short Name:
J/ApJ/716/893
Date:
21 Oct 2021
Publisher:
CDS
Description:
The SCUBA polarized 850um thermal emission data of the OMC-2 region in Orion A are added to and homogeneously reduced with data already available in the OMC-3 region. The data set shows that OMC-2 is a region generally less polarized than OMC-3. Where coincident, most of the 850um polarization pattern is similar to that measured in 350um polarization data. Only 850um polarimetry data have been obtained in and around MMS7, FIR1 and FIR2, and in the region south of FIR6. A realignment of the polarization vectors with the filament can be seen near FIR1 in the region south of OMC-3. An analysis shows that the energy injected by CO outflows and H2 jets associated with OMC-2 and OMC-3 does not appear to alter the polarization patterns at a scale of the 14" resolution beam. A second-order structure function analysis of the polarization position angles shows that OMC-2 is a more turbulent region than OMC-3. OMC-3 appears to be a clear case of a magnetically dominated region with respect to the turbulence. However, for OMC-2 it is not clear that this is the case. A more in-depth analysis of five regions displayed along OMC-2/3 indicates a decrease of the mean polarization degree and an increase of the turbulent angular dispersion from north to south. A statistical analysis suggests the presence of two depolarization regimes in our maps: one regime including the effects of the cores, the other one excluding it.
159. Polarisation of Be stars
ID:
ivo://CDS.VizieR/II/220
Title:
Polarisation of Be stars
Short Name:
II/220
Date:
20 Dec 2021 15:54:35
Publisher:
CDS
Description:
The catalogue contains observations of the linear polarization in the UBVRI photometric system of 8 Northern Be stars; the observations are part of a long-term monitoring program begun in 1984.
160. Polarisation of candidates Be stars
ID:
ivo://CDS.VizieR/J/ApJ/671/2040
Title:
Polarisation of candidates Be stars
Short Name:
J/ApJ/671/2040
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first detailed imaging polarization observations of six SMC and six LMC clusters, known to have large populations of B-type stars that exhibit excess H{alpha} emission from 2-CD photometric studies, to constrain the evolutionary status of these stars and hence better establish links between the onset of disk formation in classical Be stars and cluster age and/or metallicity. We parameterize and remove the interstellar polarization (ISP) associated with each line of sight, thereby isolating the presence of any intrinsic polarization. We use the wavelength dependence of this intrinsic polarization to discriminate pure gas disk systems, i.e., classical Be stars, from composite gas-plus-dust disk systems, i.e., Herbig Ae/Be or B[e] stars.