Revealing the nature of double-periodic blue variables in the Magellanic Clouds

Mennickent, R. E.; Cidale, L. S.; Diaz, Marcos P.; Pietrzyński, G.; Gieren, W.; Sabogal, B. E.

doi:10.1111/j.1365-2966.2005.08718.x

Cited by 23 publications

(24 citation statements)

References 26 publications

(33 reference statements)

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“…Double periodic blue variables (DPVs) are a small subgroup of Type‐3 stars recently discovered in the Magellanic Clouds by Mennickent et al (2003b). They apparently are close binary systems consisting of two B‐type stars where the primary, more luminous component shows ellipsoidal variations (Mennickent et al 2005). These authors pointed out that many of the Type‐3 stars could be double periodic variables not well resolved photometrically.…”

Section: Resultsmentioning

confidence: 99%

Be star candidates in the Large Magellanic Cloud: the catalogue and comparison with the Small Magellanic Cloud sample

Sabogal

Mennickent

Pietrzyński

et al. 2005

Monthly Notices of the Royal Astronomical Society

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We present a catalogue with coordinates and photometric data of 2446 Be star candidates in the Large Magellanic Cloud (LMC), based on a search of the OGLE II data base. The I‐band light curves of these stars show outbursts in 24 per cent of the sample (Type‐1 stars), high and low states in 10 per cent, periodic variations in 6 per cent (Type‐3 stars), and stochastic variations in 60 per cent of the cases. We report on the result of the statistical study of light curves of Type‐1 and Type‐3 stars in the LMC, and the comparison with the previously reported results of the Small Magellanic Cloud (SMC) sample. We find a statistically significant difference between amplitude, duration and asymmetry distributions of outbursts in both galaxies. Outbursts of SMC Type‐1 stars are usually brighter, longer and with a slower decline. We find a bimodal distribution of periods of Type‐3 stars in both galaxies, probably related to the recently discovered double periodic blue variables. We find also period and amplitude distributions of Type‐3 LMC stars statistically different from those of the SMC stars. Our findings above suggest that the mechanisms causing the observed photometric variability of Type‐1 and Type‐3 stars could depend on metallicity. Moreover, they suggest that the outbursts are not primarily caused by stellar winds.

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Section: Resultsmentioning

confidence: 99%

Be star candidates in the Large Magellanic Cloud: the catalogue and comparison with the Small Magellanic Cloud sample

Sabogal

Mennickent

Pietrzyński

et al. 2005

Monthly Notices of the Royal Astronomical Society

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“…Most of the Ae and Be stars show evidence for short period oscillations, as well as longer-term trends. This behaviour is common in Ae and Be systems and the variability is thought to be caused by binarity along with possible nonradial pulsation (Mennickent et al 2005(Mennickent et al , 2006(Mennickent et al , 2010.…”

Section: Variabilitymentioning

confidence: 96%

The optically bright post-AGB population of the LMC

Aarle

Winckel

Evans

et al. 2011

A&A

109

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Context. The detected variety in chemistry and circumstellar shell morphology of the limited sample of Galactic post-asymptotic giant branch (AGB) stars is so large that there is no consensus yet on how the different objects are linked by evolutionary channels. The evaluation is complicated by the fact that their distances and hence luminosities remain largely unknown. Aims. We construct a catalogue of the optically bright post-AGB stars in the Large Magellanic Cloud (LMC). The sample forms an ideal testbed for stellar evolution theory predictions of the final phase of low-and intermediate-mass stars, because the distance and hence luminosity and also the current and initial mass of these objects is well constrained. Methods. Via cross-correlation of the Spitzer SAGE catalogue with optical catalogues we selected a sample of LMC post-AGB candidates based on their [8] − [24] colour index and estimated luminosity. We determined the fundamental properties of the central stars of 105 of these objects using low-resolution, optical spectra that we obtained at Siding Spring Observatory and SAAO. Results. We constructed a catalogue of 70 high probability and 1337 candidate post-AGB stars that is available at the CDS. About half of the objects in our sample of post-AGB candidates show a spectral energy distribution (SED) that is indicative of a disc rather than an expanding and cooling AGB remnant. Like in the Galaxy, the disc sources are likely associated with binary evolution. Important side products of this research are catalogues of candidate young stellar objects, candidate supergiants with circumstellar dust, and discarded objects for which a spectrum was obtained. These too are available at the CDS.

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“…The first spectroscopic data for a sample of DPVs in the Magellanic Clouds has been obtained by Mennickent et al (2005), finding that the optical spectrum was dominated by Balmer and helium absorption lines and a continuum with a blue or sometimes flat slope. One object in the sample showed a characteristic shortening of the long cycle by about 20% in some of the cycles, suggesting that the periodicity is not strict.…”

Section: Long Cycles In Interacting Semi-detached Binariesmentioning

confidence: 99%

A dynamo mechanism as the potential origin of the long cycle in double periodic variables

Schleicher¹,

Mennickent²

2017

A&A

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The class of Double Period Variables (DPVs) consists of close interacting binaries, with a characteristic long period that is an order of magnitude longer than the corresponding orbital period, many of them with a characteristic ratio of about 3.5 × 10 1 . We consider here the possibility that the accretion flow is modulated as a result of a magnetic dynamo cycle. Due to the short binary separations, we expect the rotation of the donor star to be synchronized with the rotation of the binary due to tidal locking. We here present a model to estimate the dynamo number and the resulting relation between the activity cycle length and the orbital period, as well as an estimate for the modulation of the mass transfer rate. The latter is based on Applegate's scenario, implying cyclic changes in the radius of the donor star and thus in the mass transfer rate as a result of magnetic activity. Our model is applied to a sample of 17 systems with known physical parameters, 10 also with known orbital periods. In spite of the uncertainties of our simplified framework, the results show a reasonable agreement, indicating that a dynamo interpretation is potentially feasible. At the same time, we note that the orbital period variations resulting from Applegate's model are sufficiently small to be consistent with the data. We conclude that both larger samples with known physical parameters as well as potential direct probes of the magnetism of the donor star, including cold spots as well as polarization, will be valuable to further constrain the nature of these systems.

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Revealing the nature of double-periodic blue variables in the Magellanic Clouds

Cited by 23 publications

References 26 publications

Be star candidates in the Large Magellanic Cloud: the catalogue and comparison with the Small Magellanic Cloud sample

Be star candidates in the Large Magellanic Cloud: the catalogue and comparison with the Small Magellanic Cloud sample

The optically bright post-AGB population of the LMC

A dynamo mechanism as the potential origin of the long cycle in double periodic variables

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