We have investigated a sample of 28 well-known spectroscopically-identified magnetic Ap/Bp stars, with weak, poorly-determined or previously undetected magnetic fields. The aim of this study is to explore the weak part of the magnetic field distribution of Ap/Bp stars. Using the MuSiCoS and NARVAL spectropolarimeters at Telescope Bernard Lyot (Observatoire du Pic du Midi, France) and the cross-correlation technique Least Squares Deconvolution (LSD), we have obtained 282 LSD Stokes $V$ signatures of our 28 sample stars, in order to detect the magnetic field and to infer its longitudinal component with high precision (median sigma=40G).
A large number of magnetic white dwarfs discovered in the SDSS have so far only been analyzed by visual comparison of the observations with relatively simple models of the radiation transport in a magnetised stellar atmosphere. We model the structure of the surface magnetic fields of the hydrogen-rich white dwarfs in the SDSS.
Spectropolarimetric observations of 96 chemically peculiar (CP) main-sequence stars have been carried out at the 6-m telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) with the aim of searching for the presence of stellar magnetic fields. The stars selected for investigation were CP stars known to have strong anomalies in the wavelength region of the continuum flux depression around {lambda} 5200{AA}. This selection was conducted with the aid of low-resolution spectral observations, made with the SAO RAS 1-m telescope, and of published differential photometric data. Magnetic fields have been successfully detected in 72 stars of which only three stars were previously known to have magnetic fields. For two stars, the longitudinal component of the magnetic field B_e_exceeds 5kG: HD178892 - 7.4kG, and HD258686 - 6.7kG. We failed to reliably detect the magnetic field in the other 24 CP stars. These stars are mostly fast rotators, a feature which hampers accurate measurements of B_e_. It is demonstrated in this paper that selecting candidate magnetic stars by considering their photometric indices Z or {Delta}alpha}, or alternatively, by inspecting low-resolution spectra around the {lambda}5200{AA} flux depression, considerably increases the detection rate.
We present the results of measuring longitudinal magnetic fields (B_e_), rotation velocities (v_e_sini), and radial velocities (V_r_) of 92 stars observed with the Main Stellar Spectrograph (MSS) of the 6-m BTA telescope of the Special Astrophysical Observatory in 2010. Observations of standard stars without magnetic fields confirm the absence of systematic errors capable of introducing distortions into the longitudinal-field measurement results.
We present the results of measuring longitudinal magnetic fields (Be), rotation velocities (v_esini), and radial velocities (VR) of 163 stars observed with the Main Stellar Spectrograph (MSS) of the 6-m BTA telescope of the Special Astrophysical Observatory in 2012. Observations of standard stars without magnetic fields confirm the absence of systematic errors capable of introducing distortions into the longitudinal-field measurement results.
We carried out optical polarimetry of five dense cores, (IRAM 04191, L1521F, L328, L673-7, and L1014) which are found to harbour very low luminosity objects (VeLLOs; Lint<~0.1L_{sun}_). This study was conducted mainly to understand the role played by the magnetic field in the formation of very low and substellar mass range objects. Light from the stars, while passing through the dust grains that are aligned with their short axis parallel to an external magnetic field, becomes linearly polarised. The polarisation position angles measured for the stars can provide the plane-of-the sky magnetic field orientation. Because the light in the optical wavelength range is most efficiently polarised by the dust grains typically found at the outer layers of the molecular clouds, optical polarimetry mostly traces the magnetic field orientation of the core envelope.
We present 850{mu}m imaging polarimetry of the W51A massive star forming region performed with SCUBA on the James Clerk Maxwell Telescope (JCMT) situated close to the summit of Mauna Kea, Hawaii, on the night 6 October 2000. Positions, fluxes and polarimetry of the data points shown in Fig. 1 of the paper are reported in the file table2.dat. The positional offsets are given relative to W51d (19:23:39.0, +14:31:08, J2000). All fluxes (including the Stokes Q and U parameters) are given in units of Jy/beam. The position angles give the direction of the E-vector.
One hundred and twenty-five new high-precision spectropolarimetric observations have been obtained with ESPaDOnS (Eschelle Spectro-Polarimetric Device for the Observation of Stars) at the Canada-France-Hawaii Telescope and Narval at Telescope Bernard Lyot to investigate the magnetic properties of the classical Be star omega Ori. No Stokes V signatures are detected in our polarimetric data. Measurements of the longitudinal magnetic field, with a median error bar of 30G, and direct modelling of the mean least-squares deconvolved Stokes V profiles yield no evidence for a dipole magnetic field with polar surface strength greater than ~80G.
Fifty-two magnetic white dwarfs have been identified in spectroscopic observations from the Sloan Digital Sky Survey (SDSS) obtained between mid-2002 and the end of 2004, including Data Releases 2 and 3. Although not as numerous or diverse as the discoveries from the first data release, the collection exhibits polar field strengths ranging from 1.5 to ~1000MG and includes two new unusual atomic DQA examples, a molecular DQ, and five stars that show hydrogen in fields above 500MG. The highest field example, SDSS J2346+3853, may be the most strongly magnetic white dwarf yet discovered. Analysis of the photometric data indicates that the magnetic sample spans the same temperature range as for non-magnetic white dwarfs from the SDSS, and support is found for previous claims that magnetic white dwarfs tend to have larger masses than their non-magnetic counterparts. A glaring exception to this trend is the apparently low-gravity object SDSS J0933+1022, which may have a history involving a close binary companion.
