Polarimetric and spectropolarimetric observations with FoReRo2: Instrument overview and standard star monitoring

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Main Authors: Nikolov, Yanko, Borisov, Galin, Bagnulo, Stefano, Nikolov, Plamen, Bogdanovski, Rumen, Bonev, Tanyu
Format: Preprint
Published: 2025
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author Nikolov, Yanko
Borisov, Galin
Bagnulo, Stefano
Nikolov, Plamen
Bogdanovski, Rumen
Bonev, Tanyu
author_facet Nikolov, Yanko
Borisov, Galin
Bagnulo, Stefano
Nikolov, Plamen
Bogdanovski, Rumen
Bonev, Tanyu
contents In this paper, we present a description and characterisation of the 2-Channel Focal Reducer Rozhen (FoReRo2), with an emphasis on its polarimetric and spectropolarimetric observation modes. FoReRo2 is a multimode instrument mounted at the Ritchey-Chretien (RC) focus of the 2-meter Ritchey-Chretien-Coude (RCC) telescope at the Bulgarian National Astronomical Observatory (BNAO) - Rozhen. The primary targets of this instrument include novae, Be/X-ray binaries, symbiotic stars, asteroids, and comets. Standard stars with a high degree of polarisation are an essential part of the polarimetric observations. In our sample, HD 204827 shows short-term variability in the position angle (PA), making it unsuitable for calibration. HD 183143 displays intrinsic polarisation variability, but remains stable in terms of the PA. For the first time, we present a statistical study of the K and lambda_max parameters of Serkowski's law, including the mean value, standard deviation, and distribution. To demonstrate FoReRo2's polarimetric capabilities, we present several examples. The recurrent nova RS Oph shows the variability of Serkowski's K parameter, which is due to dust formation within the first few days after the 2021 outburst. These examples also include the imaging polarimetry of comet C/2019 Y4 (ATLAS) and spectropolarimetric observations of the symbiotic star Z And.
format Preprint
id arxiv_https___arxiv_org_abs_2512_05670
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Polarimetric and spectropolarimetric observations with FoReRo2: Instrument overview and standard star monitoring
Nikolov, Yanko
Borisov, Galin
Bagnulo, Stefano
Nikolov, Plamen
Bogdanovski, Rumen
Bonev, Tanyu
Solar and Stellar Astrophysics
Earth and Planetary Astrophysics
Instrumentation and Methods for Astrophysics
In this paper, we present a description and characterisation of the 2-Channel Focal Reducer Rozhen (FoReRo2), with an emphasis on its polarimetric and spectropolarimetric observation modes. FoReRo2 is a multimode instrument mounted at the Ritchey-Chretien (RC) focus of the 2-meter Ritchey-Chretien-Coude (RCC) telescope at the Bulgarian National Astronomical Observatory (BNAO) - Rozhen. The primary targets of this instrument include novae, Be/X-ray binaries, symbiotic stars, asteroids, and comets. Standard stars with a high degree of polarisation are an essential part of the polarimetric observations. In our sample, HD 204827 shows short-term variability in the position angle (PA), making it unsuitable for calibration. HD 183143 displays intrinsic polarisation variability, but remains stable in terms of the PA. For the first time, we present a statistical study of the K and lambda_max parameters of Serkowski's law, including the mean value, standard deviation, and distribution. To demonstrate FoReRo2's polarimetric capabilities, we present several examples. The recurrent nova RS Oph shows the variability of Serkowski's K parameter, which is due to dust formation within the first few days after the 2021 outburst. These examples also include the imaging polarimetry of comet C/2019 Y4 (ATLAS) and spectropolarimetric observations of the symbiotic star Z And.
title Polarimetric and spectropolarimetric observations with FoReRo2: Instrument overview and standard star monitoring
topic Solar and Stellar Astrophysics
Earth and Planetary Astrophysics
Instrumentation and Methods for Astrophysics
url https://arxiv.org/abs/2512.05670