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Danezis, E.; Nikolaidis, D.; Lyratzi, V.; Stathopoulou, M.; Theodossiou, E.; Kosionidis, A.; Drakopoulos, C.; Christou, George; Koutsouris, P.

doi:10.1023/a:1023668422608

Cited by 13 publications

(8 citation statements)

References 16 publications

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“…Discrete absorption components are observed as peculiar line profiles in hot OB, Oe, and Be-type stars. These components have been interpreted as absorption lines created at different density regions moving radially at distinct velocities (Danezis et al 2003). Mennickent et al (2012b) have interpreted DACs observed in the DPV system V393 Sco as signatures of a clumpy wind emerging from the disc in the direction of the binary motion.…”

Section: The O I 7773 Line and Dacsmentioning

confidence: 99%

Exploring the long-term variability and evolutionary stage of the interacting binary DQ Velorum

Barría

Mennickent

Graczyk

et al. 2014

A&A

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Aims. In order to better understand the double periodic variable (DPV) phenomenon, we analyse a series of optical spectra of the DPV system DQ Velorum during much of its long-term cycle. In addition, we investigate the evolutionary history of DQ Vel using theoretical evolutionary models to obtain the best representation for the current observed stellar and orbital parameters of the binary. We investigate the evolution of DQ Vel through theoretical evolutionary models to estimate the age and the mass transfer rate which are then compared with those of its twin V393 Scorpii. Methods. We subtracted the donor star contribution from the composite spectra of DQ Vel using a synthetic spectrum as a donor template. Donor-subtracted spectra covering around 60% of the long-term cycle allowed us to investigate time-modulated spectral variations of the gainer star plus the disc. We used Gaussian fits to measure the equivalent widths (EWs) of Balmer and helium lines in the separated spectra during the long-term cycle and thus analyse EW variabilities. We compared the observed stellar parameters of the system with a grid of theoretical evolutionary tracks computed under a conservative and a non-conservative evolution regime. Results. We have found that the EW of Balmer and helium lines in the donor-subtracted spectra are modulated with the long-term cycle. We observe a strengthening in the EWs in all analysed spectral features at the minimum of the long-term cycle which might be related to an extra line emission during the maximum of the long-term variability. Difference spectra obtained at the secondary eclipse support this scenario. We have found that a non-conservative evolutionary model where DQ Vel has lost mass at some stage of its binary history, is a better representation of the current observed properties of the system. The best evolutionary model suggests that DQ Vel has an age of 7.40 × 10 7 yr and is currently in a low mass transfer rate (−9.8 × 10 −9 M /yr) stage, after a mass transfer burst episode. Comparing the evolutionary stages of DQ Vel and V393 Sco we observed that the former is an older system with a lower mass transfer rate. This might explain the differences observed in the physical parameters of their accretion discs.

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Section: The O I 7773 Line and Dacsmentioning

confidence: 99%

Exploring the long-term variability and evolutionary stage of the interacting binary DQ Velorum

Barría

Mennickent

Graczyk

et al. 2014

A&A

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“…They are used in astrophysical plasma diagnostics and modeling (Danezis et al 2003;Eracleous & Halpern 2003;Bohm-Vitense et al 2001;Arav et al 2001;Lobel & Dupree 2000;Charlton et al 2000;Wood & Karovska 2000;Luttermoser 2000;Popović et al 2001;Uitenbroek & Briand 1995, and in many other studies). Therefore, knowledge of the Mg II spectral line characteristics (the widths and the shifts) are of interest.…”

Section: Introductionmentioning

confidence: 99%

Mg II spectral line broadening in helium, oxygen and argon-helium plasmas

Djeniže

Bukvić

Srećković

et al. 2004

A&A

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Abstract. Stark widths (W) and shifts (d) of the astrophysically very important six (279.0777, 279.5528, 279.7998, 280.2705, 292.8633 and 293.6510 nm) singly ionized magnesium (Mg II) spectral lines in helium, oxygen and argon-helium plasmas have been measured at electron temperatures between 30 000 and 52 300 K and electron densities between 1.2 × 10 23 and 1.65 × 10 23 m −3 . They are the first experimental results obtained at electron temperatures higher than 20 000 K. A linear, low-pressure, pulsed arc has been used as an optically thin plasma source. The magnesium atoms, as impurities in the driving gases, have been introduced by erosion from the pure magnesium bands fixed on the discharge electrodes. Our measured Stark width and shift values have been compared to the existing experimental and theoretical data. We have found a good agreement with W and d values calculated by the semiclassical perturbation formalism (SCPF).

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“…OpenId to allow for certi cate-bound identities and distributed authentication across multiple social networks [15]; (e) a contact list private to the user's individual, such as a phone book, Outlook contacts or a private FOAF le; (f ) means for encrypting messages and for concealing messaging interaction, using remailers such as Mixminion [3].…”

Section: Hidden Friendship Relations Protocolmentioning

confidence: 99%

Establishing Distributed Hidden Friendship Relations

Preibusch

2013

Security Protocols XVII

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The social Web is going mobile and needs support for friendship management in a distributed manner, while privacy concerns mandate con guring the public visibility of one's friends. In this paper we leverage existing Web standards to describe a simple P2P protocol for establishing, enforcing, and revoking hidden friendship relations and report on an implementation for a mobile platform. We examine the suitability of hidden friendship links for bilateral and delegated access control and discuss how the social connotation of friendship can be preserved when concealing the friend's identity.

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Cited by 13 publications

References 16 publications

Exploring the long-term variability and evolutionary stage of the interacting binary DQ Velorum

Exploring the long-term variability and evolutionary stage of the interacting binary DQ Velorum

Mg II spectral line broadening in helium, oxygen and argon-helium plasmas

Establishing Distributed Hidden Friendship Relations

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