K. M. G. Silva

Stokes imaging of AM Her systems using 3D inhomogeneous models – II. Modelling X-ray and optical data of CP Tucanae

The viewing geometry of the polar CP Tuc that better explains its optical and X-ray light curves is controversial. Previous modelling of white-light polarimetric data considered the partial self-eclipse of an extended inhomogeneous emitting region. Alternatively, phase-dependent absorption has been used to reproduce the X-ray data. This paper presents new optical polarimetric data of CP Tuc and a model that consistently explains its optical and X-ray data. The model was based on an extension of the CYCLOPS code that added X-ray bremsstrahlung emission and pre-shock region absorption to the original version, which only accounted for cyclotron emission. The new code creates the possibility of simultaneous optical and X-ray fitting. We show that self-eclipse and absorption data have distinct signatures on the X-ray spectra. Although we were able to reasonably fit the CP Tuc optical data to cases of absorption and self-eclipse, we were only able to reproduce the X-ray orbital modulation after considering the absorption in the pre-shock region. Specifically, we were unable to reproduce the X-ray observations in the self-eclipse case. We found that the primary emitting region in CP Tuc is located near the rotation pole that approximately points to the observer.

Concept of SPARC4:a simultaneous polarimeter and rapid camera in 4 bands

We present a summary of the concept design report of a new astronomical instrument: SPARC4, Simultaneous Polarimeter and Rapid Camera in 4 bands. SPARC4 will provide photometry and polarimetry in four optical broad bands (griz SDSS) simultaneously. This is achieved by the use of dichroic beam splitters. The square eld of view is around 5.6 arcmin on a side. SPARC4 time resolution is sub-second for photometry and somewhat longer for polarimetry. This is provided by the use of fast EMCCDs. The main motivation for building SPARC4 is to explore astrophysical objects which exhibit fast temporal variability in ux and polarization. The instrument will be installed at the 1.6-m telescope of the Observatorio do Pico dos Dias (Brazil).

SPARC4 A simultaneous polarimeter and rapid camera in 4 bands

We present the basic concept of a new astronomical instrument: SPARC4 - Simultaneous Polarimeter and Rapid Camera in 4 bands. SPARC4 combines in one instrument: (i) photometric and polarimetric modes; (ii) sub-second time-resolution in photometric mode and excellent timeresolution in polarimetric mode; (iii) simultaneous imaging in four broad-bands for both modes. This combination will make SPARC4 a unique facility for ground-based optical observatories. Presently, the project is in its conceptual design phase.