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Parthasarathy, N.; Karthikeyan, R.

doi:10.1023/a:1018328016810

Cited by 77 publications

(12 citation statements)

References 27 publications

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“…A general trend which obeys theoretical predictions with nitrogen over-abundance and carbon depletion relative to solar abundance of these species has been detected in pioneering studies (Plavec 1983;Parthasarathy et al 1983;Dobias & Plavec 1983;Cugier 1989;Tomkin et al 1993). In addition, the equivalent widths (EWs) of the prominent resonant C ii λ4267Å line were measured for the mass-gaining stars in a large sample (18) of Algols and compared to normal B-type stars that have the same effective temperature (T eff ) and luminosity class (İbanoǧlu et al 2012).…”

Section: Introductionsupporting

confidence: 69%

“…Such fitting gives v sin i = 72.5 ± 3.2 km s −1 . Two previous results for star A's v sin i were published: Cugier (1989) determined v sin i = 75 km s −1 (with no uncertainty), whilst Parthasarathy et al (1983) found a slightly lower value of v sin i = 69 ± 4 km s −1 . Our determination is within 1σ of both values.…”

Section: Atmospheric Parameters For the Componentsmentioning

confidence: 87%

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Evidence for conservative mass transfer in the classical Algol system δ Librae from its surface carbon-to-nitrogen abundance ratio

Dervişoğlu

Pavlovski

Lehmann

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Algol-type binary systems are the product of rapid mass transfer between the initially more massive component to its companion. It is still unknown whether the process is conservative, or whether substantial mass is lost from the system. The history of a system prior to mass exchange is imprinted in the photospheric chemical composition, in particular in the carbon-to-nitrogen (C/N) ratio. We use this to trace the efficiency of mass-transfer processes in the components of a classical Algol-type system, δ Librae. The present analysis is based on new spectroscopic data (groundbased high-resolutionéchelle spectra) and extracted archival photometric observations (space-based measurements from the STEREO satellites). In the orbital solution, non-Keplerian effects on the radial-velocity variations were taken into account. This reduces the primary's mass by 1.1 M ⊙ (∼23%) significantly in comparison to previous studies, and removes a long-standing discrepancy between the radius and effective temperature. A spectral disentangling technique is applied to theéchelle observations and the spectra of the individual components are separated. Atmospheric and abundance analyses are performed for the mass-gaining component and we found C/N = 1.55 ± 0.40 for this star. An extensive set of evolutionary models (3.5 × 10 6 ) for both components are calculated from which the best-fitting model is derived. It is found that β, the parameter which quantifies the efficiency of mass-loss from a binary system, is close to zero. This means that the mass-transfer in δ Lib is mostly conservative with little mass loss from the system.

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Section: Introductionsupporting

confidence: 69%

Section: Atmospheric Parameters For the Componentsmentioning

confidence: 87%

Evidence for conservative mass transfer in the classical Algol system δ Librae from its surface carbon-to-nitrogen abundance ratio

Dervişoğlu

Pavlovski

Lehmann

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…The implication of this result is that, even though KNP got its legal status as a PA, its floral diversity degraded over time as a result of anthropogenic disturbances. The disturbance is possibly attributed to the exclusion of the local people from exercising their traditional rights (Nath et al, 2000) Bangladesh* 2.60 (Gopalakrishna, Kaonga, Somashekar, Suresh, & Suresh, 2015) India 1.99 (Panda, Mahapatra, Acharya, & Debata, 2013) India 2.94 (Thakur & Khare, 2006) India 2.28 (Parthasarathy & Sethi, 1997) India 3.58 (Tripathi et al, 2004) India 3.50 (Velho & Krishnadas, 2011) India 2.50 (Parthasarathy & Karthikeyan, 1997) India 4.27 (Kumar, Marcot, & Saxena, 2006) India 2.02 (Bhuyan, Khan, & Tripathi, 2003) India 2.41 (Aye, Pampasit, Umponstira, Thanacharoenchanaphas, & Sasaki, 2014) Myanmar 1.34 (Mishra & Garkoti, 2016) Nepal 5.61 (Hayat, Kudus, Faridah-Hanum, Noor, & Nazre, 2010) Malaysia 3.87 (Ndah, Andrew, & Bechem, 2013) Cameroon 2.91 (Nangendo, Stein, Gelens, De Gier, & Albricht, 2002) Uganda Evenness index 0.75-0.83 0.88 (Tripathi et al, 2004) India 0.60 (Gopalakrishna et al, 2015) India 0.99 (Panda et al, 2013) India 0.87 (Velho & Krishnadas, 2011) India 0.46 (Bhuyan et al, 2003) India 0.22 (Hayat et al, 2010) Malaysia 0.90 (Ndah et al, 2013) Cameroon Simpson index 0.10-0.20 0.06 (Tripathi et al, 2004) India 0.90 (Gopalakrishna et al, 2015) India 0.02 (Panda et al, 2013) India 0.06 (Bhuyan et al, 2003) India 0.84 (Aye et al, 2014) Myanmar 0.52 (Mishra & Garkoti, 2016) Nepal 0.15 (Hayat et al, 2010) Malaysia 0.03 (Ndah et al, 2013) Cameroon…”

Section: Importance Value Index (Ivi)mentioning

confidence: 99%

The competitiveness of the phytosociological attributes of the protected areas in Bangladesh with that in the other tropical countries

Rahman

Mahmud

Shahidullah

et al. 2016

Journal of Sustainable Forestry

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Many forest reserves in Bangladesh have been converted to protected areas (PAs) to conserve the forests resources from further depletion. This study has investigated if such initiatives have improved the state of biodiversity of these PAs amid tremendous anthropogenic pressure on forest resources. We have assessed the phytosociological attributes of the PAs in the country through a case study at Kaptai National Park (KNP) and compared the attributes with those of the adjacent areas and of the tropical forests across the world. We have identified 52 species belonging to 45 genera and 28 families. The most dominant species in KNP was Dipterocarpus spp. and the adjacent area was dominated by Tectona grandis. Unexpectedly, the Shannon-Wiener index of KNP has dropped down from 2.98 in 2000 to 0.90 in 2014. However, in terms of relative density, relative dominance, and relative frequency, KNP was better than the adjacent areas. In contrast, the mean Shannon-Wiener index in KNP (0.90) was smaller than that in the tropical countries (2.99). We recommend strengthening effective comanagement of PAs and enabling nonforestry income generation activities for the forestdependent people so that the biodiversity of the PAs can be enriched while people's livelihoods are ensured.

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“…For abundance determinations of C and N, there are several lines from different regions of the spectrum. Chemical analysis of Algoltype stars has been performed several times in the past making use of the following lines: the ultraviolet (UV) multiplets from 1 to 11 of the 1330-A Ê C II lines (Cugier 1989); the C II 4267-A Ê line (Tomkin, Lambert & Lemke 1993) and the CH, CN bands (Parthasarathy, Lambert & Tomkin 1983). The numerous CH lines in the 4290± 4328 A Ê interval can be used to determine C abundances.…”

Section: Calculating Abundancesmentioning

confidence: 99%

The chemical evolution of the secondary stars in close binaries, arising from common-envelope evolution and nova outbursts

Marks

Sarna

1998

Monthly Notices RAS

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A B S T R A C TUsing a Paczyn Âski-type stellar evolution code, we have modelled the evolution of secondary stars through the common-envelope and semidetached phases of close binary evolution. Our calculations are aimed at determining the effects of the accretion of red giant envelope material during the common-envelope phase, and the accretion of novae ejecta during the semidetached phase, on the surface composition of the secondary. For the second case, we make use of the results of the calculations of Prialnik & Kovetz, Kovetz & Prialnik and Prialnik, which concern the effects of accretion on to carbon±oxygen white dwarfs with varying white dwarf mass, white dwarf central temperature and mass transfer rate (the de®ning characteristics of nova outburst behaviour).In this paper we present the results of our calculations of a large grid of models designed to test the effects of these two polluting processes, both individually and together. We ®nd that both processes may signi®cantly affect the surface composition of the secondary, and that in the case of the accretion of novae ejecta, thermohaline mixing is extremely important and cannot be neglected. Our results indicate four phases in the evolution of the surface composition of the secondary during semidetached evolution: (i) the material accreted during the common-envelope phase and that accreted from the novae ejecta are mixed by convection and thermohaline mixing and dominate the surface composition of the secondary; (ii) the material accreted during common-envelope evolution is lost through mass transfer and the surface composition of the secondary is dominated by material accreted from the novae ejecta, which is mixed with the underlying layers of the secondary by convection and thermohaline mixing; (iii) the surface convection zone of the secondary penetrates to deeper layers so that these deeper layers dominate the surface composition of the secondary and thermohaline mixing no longer operates; and (iv) for evolved Population I systems, when the secondary has lost most of its mass, its surface composition is again dominated by material accreted from novae ejecta.We make predictions concerning the abundances of carbon, nitrogen and oxygen and the values of the isotopic ratios 12 C/ 13 C, 14 N/ 15 N and 16 O/ 17 O on the surface of the secondary throughout its evolution. With observationally determined abundances and isotopic ratios, we can in principle determine whether or not these two polluting processes operate, and can further differentiate between them.

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Untitled

Cited by 77 publications

References 27 publications

Evidence for conservative mass transfer in the classical Algol system δ Librae from its surface carbon-to-nitrogen abundance ratio

Evidence for conservative mass transfer in the classical Algol system δ Librae from its surface carbon-to-nitrogen abundance ratio

The competitiveness of the phytosociological attributes of the protected areas in Bangladesh with that in the other tropical countries

The chemical evolution of the secondary stars in close binaries, arising from common-envelope evolution and nova outbursts

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