Optical polarimetric study of open clusters: distribution of interstellar matter towards NGC 654

Medhi, Biman J.; Maheswar, G.; Pandey, J. C.; Kumar, T. S.; Sagar, Ram

doi:10.1111/j.1365-2966.2008.13405.x

Cited by 40 publications

(37 citation statements)

References 32 publications

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“…The instrumental polarization of AIMPOL on the 1.04-m ST has been monitored since 2004 for different projects and is 0.1% in different bands (e.g., Rautela et al 2004;Medhi et al 2007Medhi et al , 2008Medhi et al , 2010Eswaraiah et al 2011Eswaraiah et al , 2012. No correction for the instrumental polarization was applied to the data obtained with IFOSC since the instrumental polarization of the instrument on the 2-m telescope is <0.05 per cent.…”

Section: Polarimetrymentioning

confidence: 99%

A study of the starless dark cloud LDN 1570: Distance, dust properties, and magnetic field geometry

Eswaraiah

Maheswar

Pandey

et al. 2013

A&A

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Aims. We aim to map the magnetic field geometry and to study the dust properties of the starless cloud, L1570, using multi-wavelength optical polarimetry and photometry of the stars projected on the cloud. Methods. The direction of the magnetic field component parallel to the plane of the sky of a cloud can be obtained using polarimetry of the stars projected on and located behind the cloud. It is believed that the unpolarized light from the stars background to the cloud undergoes selective extinction while passing through non-spherical dust grains that are aligned with their minor axes parallel to the cloud magnetic field. The emerging light becomes partially plane polarized. The observed polarization vectors trace the direction of the projected magnetic field of the cloud. We made R-band imaging polarimetry of the stars projected on a cloud, L1570, to trace the magnetic field orientation. We also made multi-wavelength polarimetric and photometric observations to constrain the properties of dust in L1570. Results. We estimated a distance of 394 ± 70 pc to the cloud using 2MASS JHK s colors. Using the values of the Serkowski parameters, σ 1 , , λ max , and the position of the stars on the near-infrared color-color diagram, we identified 13 stars that could possibly have intrinsic polarization and/or rotation in their polarization angles. One star, 2MASS J06075075+1934177, which is a B4Ve spectral type, shows diffuse interstellar bands in the spectrum in addition to the Hα line in emission. There is an indication for slightly bigger dust grains toward L1570 on the basis of the dust grain size-indicators such as λ max and R V values. The magnetic field lines are found to be parallel to the cloud structures seen in the 250 μm images (also in the 8 μm and 12 μm shadow images) of L1570. Based on the magnetic field geometry, the cloud structure, and the complex velocity structure, we conclude that L1570 is in the process of formation due to the converging flow material mediated by the magnetic field lines. A structure function analysis showed that in the L1570 cloud region the large-scale magnetic fields are stronger than the turbulent component of the magnetic fields. The estimated magnetic field strengths suggest that the L1570 cloud region is subcritical and hence could be strongly supported by the magnetic field lines.

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Section: Polarimetrymentioning

confidence: 99%

A study of the starless dark cloud LDN 1570: Distance, dust properties, and magnetic field geometry

Eswaraiah

Maheswar

Pandey

et al. 2013

A&A

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“…In fact, the instrumental polarization of ST has been monitored since 2004 within other projects as well (e.g. Medhi et al, 2007;Medhi et al, 2008;Pandey et al, 2009). These measurements demonstrated that it is invariable in all B, V and R pass bands.…”

Section: Optical Polarimetrymentioning

confidence: 98%

BVRI photometric and polarimetric studies of W UMa type eclipsing binary FO Hydra

Prasad¹,

Pandey²,

Patel³

et al. 2013

New Astronomy

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h i g h l i g h t s " We present analysis of optical photometric and polarimetric observations of contact binary system FO Hydra (FO Hya). " The computed period of the system is 0.469556 ± 0.000003 days. " An O-C curve analysis indicates an increase in its period by 5.77 Â 10 -8 day yr À1 . " The photometric light curves are analyzed using Wilson-Devinney code (WD). " In this analysis we have taken up, presumably for the first time, the polarimetric studies of FO Hya, and obtain the mean values of degree of polarization and polarization position angle. a b s t r a c tWe present analysis of optical photometric and polarimetric observations of contact binary system FO Hydra (FO Hya). The computed period of the system is 0.469556 ± 0.000003 days. An O-C curve analysis indicates an increase in its period by 5.77 Â 10 À8 day yr À1 . The photometric light curves are analyzed using Wilson-Devinney code (WD). The present analysis shows that FO Hya is a B-subtype of W UMa type contact binary. The radii and mass of primary and secondary components are found, respectively, to be R 1 = 1.62 ± 0.03 R and R 2 = 0.91 ± 0.02 R , and M 1 = 1.31 ± 0.07 M and M 2 = 0.31 ± 0.11 M . The light curve shape shows small asymmetries around the primary and secondary maxima. This may be due to the presence of dark spots on the components. The polarimetric observations yield average values of its polarization to be 0.18 ± 0.03, 0.15 ± 0.03, 0.17 ± 0.02 and 0.15 ± 0.02% in B, V, R and I bands, respectively. These values are appreciably lower than the typical polarization of W UMa type binaries. We have discussed the possible sources of the observed polarization but in order to arrive at definitive answer to this more phase locked observations are needed.

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“…The focal plane instrument used was the ARIES Imaging Polarimeter (AIMPOL) (Medhi et al (2008), Pandey et al (2009)) which consists of a Wollaston prism used to split the incident unpolarized beam into two orthogonally polarized ordinary and extraordinary components and a rotatable half-wave plate (HWP) used to alter the polarization state of the light wave. The observations of Comet C/2012 L2 (LINEAR)…”

Section: Observation and Data Reductionmentioning

confidence: 99%

“…The gain and the read-out noise of the CCD are 11.98 e − /ADU and 7.0 e − , respectively. Four sets of exposures of each 60 s were made on both the nights of observation.The detailed description of the instrument is given in Rautela et al (2004) and Medhi et al (2008Medhi et al ( , 2010.…”

Section: Observation and Data Reductionmentioning

confidence: 99%

Imaging polarimetry of Comet C/2012 L2 (LINEAR)

Roy

Das

Medhi

2015

Icarus

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Optical polarimetric study of open clusters: distribution of interstellar matter towards NGC 654

Cited by 40 publications

References 32 publications

A study of the starless dark cloud LDN 1570: Distance, dust properties, and magnetic field geometry

A study of the starless dark cloud LDN 1570: Distance, dust properties, and magnetic field geometry

BVRI photometric and polarimetric studies of W UMa type eclipsing binary FO Hydra

Imaging polarimetry of Comet C/2012 L2 (LINEAR)

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