- 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.
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Search Results
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/376/371
- Title:
- Polarisation of flat-spectrum radio sources
- Short Name:
- J/MNRAS/376/371
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the very large JVAS/CLASS 8.4GHz surveys of flat-spectrum radio sources to obtain a large, uniformly observed and calibrated, sample of radio source polarizations. These are useful for many investigations of the properties of radio sources and the interstellar medium. We discuss comparisons with polarization measurements from this survey and from other large-scale surveys of polarization in flat-spectrum sources.
- ID:
- ivo://CDS.VizieR/J/AJ/87/859
- Title:
- Polarisation of 404 radio sources at 6 and 20cm
- Short Name:
- J/AJ/87/859
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate positions of 404 compact radio sources used as calibrators by the VLA are presented. In addition, the structure and polarization of each source at both 4885 and 1465MHz are given. Eighty-five percent of the sources have spectral indices flatter than 0.5; all of these are dominated by an unresolved core. Half of these flat-spectrum sources contain nearby, associated diffuse structure at a level exceeding approximately 0.4% of the core brightness at 20cm.
