Binarity as the Origin of Long Secondary Periods in Red Giant Stars

Soszyński, I.; Olechowska, A.; Ratajczak, M.; Iwanek, P.; Skowron, D. M.; Mróz, P.; Pietrukowicz, P.; Udalski, A.; Szymański, M. K.; Skowron, J.; Gromadzki, M.; Poleski, R.; Kozłowski, S.; Wrona, Marcin; Ulaczyk, K.; Rybicki, K.

doi:10.3847/2041-8213/abf3c9

Cited by 37 publications

(22 citation statements)

References 40 publications

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“…We ensured this was not an alias of the shorter period by checking that the secondary peak remains after we removed the primary pulsation from the data. Furthermore, the 41-year pulsation period is consistent with long sec-ondary periods detected in several AGB stars (Wood et al 1999;Soszyński et al 2021). Henceforth, we refer to the "pulsation" as the first 372-day period and "variability" as the long-term variability of 41 years.…”

Section: Stellar Pulsationsupporting

confidence: 82%

Locating dust and molecules in the inner circumstellar environment of R Sculptoris with MATISSE

Drevon

Millour

Cruzalèbes

et al. 2022

A&A

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Context. Asymptotic giant branch (AGB) stars are one of the main sources of dust production in the Galaxy. However, it is not yet clear what this process looks like and where the dust happens to be condensing in the circumstellar environment. Aims. By characterizing the location of the dust and the molecules in the close environment of an AGB star, we aim to achieve a better understanding the history of the dust formation process. Methods. We observed the carbon star R Scl with the thermal-infrared VLTI/MATISSE instrument in L-and N-bands. The high angular resolution of the VLTI observations (as small as 4.4 mas in the L-band and 15 mas in the N-band with ATs), combined with a large uv-plane coverage allowed us to use image reconstruction methods. To constrain the dust and molecules' location, we used two different methods: one using MIRA image reconstruction algorithm and the second using the 1D code RHAPSODY. Results. We found evidence of C 2 H 2 and HCN molecules between 1 and 3.4 R ⋆ which is much closer to the star than the location of the dust (between 3.8 and 17.0 R ⋆ ). We also estimated a mass-loss rate of 1.2 ± 0.4 × 10 −6 M ⊙ yr −1 . In the meantime, we confirmed the previously published characteristics of a thin dust shell, composed of amorphous carbon (amC) and silicon carbide (SiC). However, no clear SiC feature has been detected in the MATISSE visibilities. This might be caused by molecular absorption that can affect the shape of the SiC band at 11.3 µm. Conclusions. The appearance of the molecular shells is in good agreement with predictions from dynamical atmosphere models. For the first time, we co-located dust and molecules in the environment of an AGB star. We confirm that the molecules are located closer to the star than the dust. The MIRA images unveil the presence of a clumpy environment in the fuzzy emission region beyond 4.0 R ⋆ . Furthermore, with the available dynamic range and angular resolution, we did not detect the presence of a binary companion. To solve this problem, additional observations combining MATISSE and SAM-VISIR instrument should enable this detection in future studies.

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Section: Stellar Pulsationsupporting

confidence: 82%

Locating dust and molecules in the inner circumstellar environment of R Sculptoris with MATISSE

Drevon

Millour

Cruzalèbes

et al. 2022

A&A

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“…The variability of LPVs is not only associated with stellar oscillations. In particular, LPVs often display so-called long secondary periods (LSPs) that form sequence D in the PLD and whose origin is still a matter of debate (e.g., Wood 2000;Olivier & Wood 2003;Wood et al 2004;Derekas et al 2006;Soszyński 2007;Nicholls et al 2009;Stothers 2010;Takayama et al 2015;Saio et al 2015;Takayama & Ita 2020;Pawlak 2021;Soszyński et al 2021). As it is generally accepted that these periods are not due to pulsation, we aim to exclude them from the data set.…”

Section: Pulsation Mode Identificationmentioning

confidence: 99%

Semi-regular red giants as distance indicators

Trabucchi

Mowlavï

Lebzelter

2021

A&A

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Context. Semi-regular variables (SRVs) are similar to Miras in brightness, and they also follow one or more period–luminosity relations (PLRs), though not necessarily the same one as Miras. As potential standard candles they are more challenging than Miras because of their smaller variability amplitudes and less regular light curves, but they are substantially more numerous and especially promising for probing old stellar populations. Aims. We aim to characterise the variability of SRVs, specifically focusing on their connection with Miras, in order to prepare the ground for investigating their potential as distance indicators. Methods. We examine SRVs and Miras in the Magellanic Clouds from OGLE-III observations, with data from Gaia and 2MASS. After cleaning the sample of variability periods unrelated to pulsation, we classify each source by chemical type and combination of pulsation modes. We examine the results in terms of global photometric and pulsation properties. Results. We identify four SRV groups that fit the general evolutionary scenario predicted by theory. SRVs dominated by fundamental-mode pulsation are very similar to Miras, especially if mono-periodic. They further split into two subgroups, one of which follows the same sequence as Miras in the period–luminosity and period–amplitude diagrams, without discontinuity. Conclusions. The similarities between Miras and SRVs suggest that the latter can be adopted as distance indicators in a way that is complementary to the use of the former, thereby at least doubling the available number of long-period variables (LPVs) suitable for use as distance indicators. The traditional amplitude-based separation between Miras and SRVs is not necessarily appropriate, and a more physically sound criterion should also involve pulsation periods. While this would require comparatively longer time-series, they are expected to become accessible in the coming years even for weak sources thanks to current and future large-scale surveys. The table of reclassified LPVs is made public.

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“…Here we show that those remarks are genuine for a larger sample of HBSs in the LMC as well as for HBSs located toward the GB. Recently, Soszyński et al (2021) showed that LSP variables (sequence D) are systems that contain an RG and a stellar or sub-stellar companion. In combination with eclipsing and ellipsoidal stars (sequence E), they form a group with a wide range of periods (from a few days to about three years), for which the brightness changes are driven mainly by the interactions between the components of the binary system.…”

Section: Period-amplitude Diagramsmentioning

confidence: 99%

Photometric Analysis of the OGLE Heartbeat Stars

Wrona,

Kołaczek-Szymański,

Ratajczak

et al. 2021

Preprint

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We present an analysis of 991 heartbeat stars (HBSs) from the OGLE Collection of Variable Stars (OCVS). The sample consists of 512 objects located toward the Galactic bulge (GB), 439 in the Large Magellanic Cloud (LMC) and 40 in the Small Magellanic Cloud (SMC). We model the I-band OGLE light curves using an analytical model of flux variations, reflecting tidal deformations between stars. We present distributions of the model parameters that include the eccentricity, orbital inclination, and argument of the periastron, but also the period-amplitude diagrams. On the Hertzsprung-Russell (HR) diagram, our HBS sample forms two separate groups of different evolutionary status. The first group of about 90 systems, with short orbital periods (P 50 days), consists of an early-type primary star lying on (or close to) the main sequence (MS). The second group of about 900 systems, with long orbital periods (P 100 days), contains a red giant (RG). The position of RG HBSs on the periodluminosity diagram strongly indicates their binary nature. They appear to be a natural extension of confirmed binary systems that include the OGLE ellipsoidal and Long Secondary Period (LSP) variables. We also present a time-series analysis leading to detection of tidally-excited oscillations (TEOs). We identify such pulsations in about 5% of stars in the sample with a total number of 78 different modes. This first relatively large homogeneous sample of TEOs allowed us to construct a diagram revealing the correlation between the TEO's orbital harmonic number and the eccentricity of the host binary system.

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Binarity as the Origin of Long Secondary Periods in Red Giant Stars

Cited by 37 publications

References 40 publications

Locating dust and molecules in the inner circumstellar environment of R Sculptoris with MATISSE

Locating dust and molecules in the inner circumstellar environment of R Sculptoris with MATISSE

Semi-regular red giants as distance indicators

Photometric Analysis of the OGLE Heartbeat Stars

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