Blue and yellow long-period variables in the direction of the Small Magellanic Cloud

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

doi:10.1051/0004-6361:20065361

Cited by 12 publications

(20 citation statements)

References 31 publications

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“…These stars also show relatively large reddening. These stars are possibly a mix of various types of stars such as interacting binaries and DPVs, supporting the suggestion by Mennickent et al (2002, 2006). Type 2 stars in the LMC and the SMC show similar spectral and NIR properties. Their NIR properties are similar to the Galactic CBe stars, suggesting that they are likely to be CBe stars.…”

Section: Discussionsupporting

confidence: 82%

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Study of candidate Be stars in the Magellanic Clouds using near-infrared photometry and optical spectroscopy

Paul

Subramaniam

Mathew

et al. 2012

Monthly Notices of the Royal Astronomical Society

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Mennickent et al. and Sabogal et al. identified a large number of classical Be (CBe) candidates (∼3500) in the Large and Small Magellanic Clouds (LMC and SMC) based on their photometric variability using the OGLE II data base. They classified these stars into four different groups based on the appearance of their variability. In order to refine and understand the nature of this large number of stars, we studied the infrared properties of the sample and the spectroscopic properties of a subsample. We cross‐correlated the optical sample with the IRSF‐MCPS catalogue to obtain the J, H, Ks magnitudes of all the four types of stars (∼2500) in the LMC and SMC. Spectra of 120 stars belonging to the types 1, 2 and 3 were analysed to study their spectral properties. Among the four types, the type 4 stars are the dominant group, with ∼60 and ∼65 per cent of the total sample in the LMC and SMC, respectively. The near‐infrared (NIR) colour–colour diagrams suggest that the type 4 stars in the LMC have a subclass, which is not found in our Galaxy or in the SMC. This subclass is ∼18 per cent of the type 4 sample. The main type 4 sample which is ∼49 per cent of the total sample has NIR properties similar to the Galactic CBe stars and the SMC type 4 stars. Though the new subclass of type 4 stars have high E(B−V) ∼ 0.75, they are not located close to regions with high reddening. The type 3 stars (∼6 per cent and 7.3 per cent in the LMC and SMC) are found to have large Hα equivalent width (EW) in the SMC and some are found to have large NIR excess. This small fraction of stars are unlikely to be CBe stars. Three stars among the type 3 stars in the LMC are found to be double periodic variables. The type 2 stars are found in larger fraction in the SMC (∼14.5 per cent), when compared to the LMC (∼6 per cent). The spectroscopic and the NIR properties suggest that these could be CBe stars. The type 1 stars are relatively more in the LMC (∼24 per cent) when compared to the SMC (∼13 per cent). The SMC type 1 stars have relatively large Hα EW and this class has properties similar to CBe stars. The spectroscopic sample of type 1 stars which show Hα in emission and are confirmed as CBe stars are more abundant in the SMC by a factor of 2.6. If the effect of metallicity is to cause more CBe stars in the SMC, when compared to the LMC, then type 1, type 2 and type 4 stars follow this rule, with an enhancement of 2.6, 2.4 and 1.3, respectively.

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Section: Discussionsupporting

confidence: 82%

“…Sabogal et al (2005) found that type 3 stars have bimodal period distribution and that double periodic variables (DPVs) are a small subgroup of type 3 stars. Mennickent et al (2006) studied some long period variables in the SMC and some of these are type 3 stars. They suggested that the type 3 stars are a mix of different kinds of stars.…”

Section: Resultsmentioning

confidence: 99%

Study of candidate Be stars in the Magellanic Clouds using near-infrared photometry and optical spectroscopy

Paul

Subramaniam

Mathew

et al. 2012

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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“…Our improved XMM-Newton position confirms the identification with this star and its optical magnitudes and colours are listed in Table 4. The spectral type was determined to B0IIIe by Mennickent et al (2006).…”

Section: Discovery Of 291 S Pulsations From Rx J00582-7231mentioning

confidence: 99%

XMM-Newton observations of the Small Magellanic Cloud: Be/X-ray binary pulsars active between October 2006 and June 2007

Haberl¹,

Eger²,

Pietsch³

2008

A&A

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Aims. We analysed eight XMM-Newton observations toward the Small Magellanic Cloud (SMC), performed between October 2006 and June 2007, to investigate high mass X-ray binary systems. Methods. We produced images from the European Photon Imaging Cameras (EPIC) and extracted X-ray spectra and light curves in different energy bands from sources which yielded a sufficiently high number of counts for a detailed temporal and spectral analysis. To search for periodicity we applied Fourier transformations and folding techniques and determined pulse periods using a Bayesian approach. To identify optical counterparts we produced X-ray source lists for each observation using maximum likelihood source detection techniques and correlated them with optical catalogues. The correlations were also used for astrometric boresight corrections of the X-ray source positions. Results. We found new X-ray binary pulsars with periods of 202 s (XMMU J005929.0-723703), 342 s (XMMU J005403.8-722632), 645 s (XMMU J005535.2-722906) and 325 s (XMMU J005252.1-721715), in the latter case confirming the independent discovery in Chandra data. In addition we detected sixteen known Be/X-ray binary pulsars and six ROSAT-classified candidate high mass Xray binaries. From one of the candidates, RX J0058.2-7231, we discovered X-ray pulsations with a period of 291 s which makes it the likely counterpart of XTE J0051-727. From the known pulsars, we revise the pulse period of CXOU J010206.6-714115 to 967 s, and we detected the 18.37 s pulsar XTE J0055-727 (= XMM J004911.4-724939) in outburst, which allowed us to localise the source. The pulse profiles of the X-ray pulsars show a large variety of shapes from smooth to highly structured patterns and differing energy dependence. For all the candidate high mass X-ray binaries optical counterparts can be identified with magnitudes and colours consistent with Be stars. Twenty of the Be/X-ray binaries were detected with X-ray luminosities in the range 1.5×10 35 erg s −1 -5.5×10 36 erg s −1 . The majority of the spectra is well represented by an absorbed power-law with an average power-law index of 0.93. The absorption (in addition to the Galactic foreground value) varies over a wide range between a few 10 20 cm −2 and several 10 22 cm −2 . An overall correlation of the absorption with the total SMC H I column density suggests that the absorption seen in the X-ray spectra is often largely caused by interstellar gas.

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Blue and yellow long-period variables in the direction of the Small Magellanic Cloud

Cited by 12 publications

References 31 publications

Study of candidate Be stars in the Magellanic Clouds using near-infrared photometry and optical spectroscopy

Study of candidate Be stars in the Magellanic Clouds using near-infrared photometry and optical spectroscopy

The optically bright post-AGB population of the LMC

XMM-Newton observations of the Small Magellanic Cloud: Be/X-ray binary pulsars active between October 2006 and June 2007

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