A multi-spectral band stellar photo-polarimeter

Srinivasulu, G. Naga; Raveendran, A. V.; Muneer, S.; Mekkaden, M. V.; Jayavel, N.; Somashekar, M. R.; Sagayanathan, K.; Ramamoorthy, Sripriya; Rosario, M. J.; Jayakumar, K.

doi:10.48550/arxiv.1505.04244

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“…For polarimetric observations, two telescopes were used, one the 104 cm telescope, located at VBO and the other the 104 cm Sampurnand telescope located at the Aryabhatta Research Institute for Observational Sciences (ARIES), Nainital. At the telescope in VBO, a three-band, double beam photo-polarimeter was used, the details of which can be found in Srinivasulu et al (2015). We used diaphragm of 20 diameter for the observations.…”

Section: Polarimetrymentioning

confidence: 99%

Flux and Polarization Variability of OJ 287 during the Early 2016 Outburst

Rakshit

Stalin

Muneer

et al. 2017

ApJ

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The gamma-ray blazar OJ 287 was in a high activity state during December 2015 -February 2016 Coinciding with this high brightness state, we observed this source for photometry on 40 nights in R-band and for polarimetry on 9 epochs in U BV RI bands. During the period of our observations, the source brightness varied between 13.20 ± 0.04 to 14.98 ± 0.04 mag and the degree of polarization (P ) fluctuated between 6.0 ± 0.3% and 28.3 ± 0.8% in R-band. Focusing on intra-night optical variability (INOV), we find a duty cycle of about 71% using χ 2 -statistics, similar to that known for blazars. From INOV data, the shortest variability time scale is estimated to be 142 ± 38 min yielding a lower limit of the observed Doppler factor δ 0 = 1.17, the magnetic field strength B ≤ 3.8 G and the size of the emitting region R s < 2.28 × 10 14 cm. On inter-night timescales, a significant anti-correlation between R-band flux and P is found. The observed P at U -band is generally larger than that observed at longer wavelength bands suggesting a wavelength dependent polarization. Using V -band photometric and polarimetric data from Steward Observatory obtained during our monitoring period we find a varied correlation between P and V -band brightness. While an anticorrelation is seen between P and V -band mag at sometimes, no correlation is seen at other times, thereby, suggesting the presence of more than one short-lived shock components in the jet of OJ 287.

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Section: Polarimetrymentioning

confidence: 99%