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How to calibrate the RINGO3 polarimeter as well as polarimetric statistical studies of DA and DC spectral types white dwarfs.

Data: 
poniedziałek, luty 15, 2016 - 08:30

IA seminar on Wednesday, February 17th at 11:15 a.m., building A-2, room number 34.

Speaker: Dr Agnieszka Słowikowska (IA, UZ)

Title: "How to calibrate the RINGO3 polarimeter as well as polarimetric statistical studies of DA and DC spectral types white dwarfs."

Abstract:
In my talk I am going to present an analysis of polarimetric observations of standard stars performed over the period of more than three years with the RINGO3 polarimeter mounted on the Liverpool Telescope. The main objective was to determine the instrumental polarization of the RINGO3 polarimeter in three spectral energy ranges between 350 nm and 1000 nm. Our results should be applied to calibrate all polarimetric observations performed with the RINGO3 polarimeter. In the second part of my talk I will present polarimetric observations of selected white dwarfs (WDs). Our sample consists of DA and DC spectral types WDs in the R magnitude range from 13 to 17. We performed polarimetric observations with the RoboPol polarimeter attached to the 1.3-m telescope at the Skinakas Observatory. Together we have 76 WDs in our sample. There is a strong evidence that on average the isolated WDs of DC type have higher polarization degree (PD) than the isolated DA type WDs. On the other hand the median of the PD of isolated DA type WDs is almost the same as the median PD of DA type WD in binary systems. This shows, as expected, that there is no contribution to the PD from the companion that in most cases of WDs binary systems is a red dwarf. Reaching fainter objects by using infrastructure with larger mirror introduced a serious problem, namely, the lack of faint polarization standards of both types, the zero-polarized and polarized ones. Our list of WDs address this need with respect to zero-polarized standard stars and is complementary to the existing list where most of WDs are in the magnitude range from 6 to 13.

My best regards,

Agnieszka Słowikowska