Ultra-Low Amplitude Variables in the Large Magellanic Cloud—classical Cepheids, Pop. Ii Cepheids, Rv Tau Stars, and Binary Variables

Buchler, J. R.; Wood, P. R.; Soszyński, I.

doi:10.1088/0004-637x/698/1/944

Cited by 8 publications

(2 citation statements)

References 10 publications

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“…We note here Buchler et al (2005) and Buchler et al (2009), who used data from the MACHO and OGLE databases to find ∼30 objects near the Cepheid instability strip of the LMC with amplitudes 0.01 mag. At least ∼20 of these objects are members of the LMC.…”

Section: Discussionmentioning

confidence: 94%

Ultralow-amplitude RR Lyrae Stars in M4

Wallace

Hartman

Bakos

et al. 2019

ApJL

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We report evidence for a new class of variable star, which we dub millimagnitude RR Lyrae (mmRR). From K2 observations of the globular cluster M4, we find that out of 24 horizontal branch stars not previously known to be RR Lyrae variables, two show photometric variability with periods and shapes consistent with those of first overtone RR Lyrae variables. The variability of these two stars, however, have amplitudes of only one part in a thousand, which is ∼200 times smaller than for any RR Lyrae variable in the cluster, and much smaller than any known RR Lyrae variable generally. The periods and amplitudes are: 0.33190704 d with 1.0 mmag amplitude and 0.31673414 d with 0.3 mmag amplitude. The stars lie just outside the instability strip, one blueward and one redward. The star redward of the instability strip also exhibits significant multi-periodic variability at lower frequencies. We examine potential blend scenarios and argue that they are all either physically implausible or highly improbable. Stars such as these are likely to shed valuable light on many aspects of stellar physics, including the mechanism(s) that set amplitudes of RR Lyrae variables.

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Section: Discussionmentioning

confidence: 94%

Ultralow-amplitude RR Lyrae Stars in M4

Wallace

Hartman

Bakos

et al. 2019

ApJL

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“…RV Tauri stars are population II Cepheid variables with spectral types typically between F and K. There are 126 RV Tauri stars known in the Galaxy (see GCVS Samus et al (2009)) and many of them have been discovered in the Small Magellanic Cloud (SMC) and Large Magellanic Cloud (LMC) (Alcock et al 1998;Soszyński et al 2008;Buchler et al 2009;Soszyñski et al 2010). They owe their name to the prototype RV Tau.…”

Section: Introductionmentioning

confidence: 99%

GK Car and GZ Nor: two low-luminous, depleted RV Tauri stars

Gezer

Winckel

Manick

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We performed a photometric and spectroscopic analysis of two RV Tauri stars GK Car and GZ Nor. Both objects are surrounded by hot circumstellar dust. Their pulsation periods, derived from ASAS photometric time series, have been used to derive their luminosities and distances via the PLC relation. In addition, for both objects, GAIA distances are available. The Gaia distances and luminosities are consistent with the values obtained from the PLC relationship. GK Car is at distance of 4.5±1.3 kpc and has a luminosity of 1520±840 L , while GZ Nor is at distance of 8.4±2.3 kpc and has a luminosity of 1240 ±690 L . Our abundance analysis reveals that both stars show depletion of refractory elements with [Fe/H]=−1.3 and [Zn/Ti]=+1.2 for GK Car and [Fe/H]=−2.0 and [Zn/Ti]=+0.8 for GZ Nor. In the WISE colour-colour diagram, GK Car is located in the RV Tauri box as originally defined by Lloyd Evans (1985) and updated by Gezer et al. (2015), while GZ Nor is not. Despite this, we argue that both objects are surrounded by a gravitationally bound disc. As depletion is observed in binaries, we postulate that both stars are binaries as well. RV Tauri stars are generally acknowledged to be post−AGB stars. Recent studies show that they might be either indeed post−AGB or post−RGB objects depending on their luminosity. For both objects, the derived luminosities are relatively low for post-AGB objects, however, the uncertainties are quite large. We conclude that they could be either post-RGB or post-AGB objects.

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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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Ultra-Low Amplitude Variables in the Large Magellanic Cloud—classical Cepheids, Pop. Ii Cepheids, Rv Tau Stars, and Binary Variables

Cited by 8 publications

References 10 publications

Ultralow-amplitude RR Lyrae Stars in M4

Ultralow-amplitude RR Lyrae Stars in M4

GK Car and GZ Nor: two low-luminous, depleted RV Tauri stars

The optically bright post-AGB population of the LMC

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