Detectability of micro-variables in the ASAS database

David, M.; Hensberge, H.; Nitschelm, Christian

doi:10.1051/0004-6361/201321178

Cited by 7 publications

(13 citation statements)

References 15 publications

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“…In agreement with the findings of David et al (2014) and Pigulski (2014), we conclude that ASAS-3 data are well suited to investigating variable stars with rather low photometric amplitudes. 1.85811(4) Vogt & Faundez (1979)…”

Section: Discussionsupporting

confidence: 92%

“…However, because of the long time baseline of almost ten years, the detection limit of the ASAS-3 data for periodic signals is much lower than this value. David et al (2014) have detected periodic variables with amplitudes of variability of 0.01−0.02 mag in the magnitude range of 7 < ∼ V < ∼ 10. Pigulski (2014) estimated that periodic signals with amplitudes as low as 4−5 mmag can still be detected well.…”

Section: Characteristics Of the Asas-3 Datamentioning

confidence: 96%

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A search for photometric variability in magnetic chemically peculiar stars using ASAS-3 data

Bernhard

Hümmerich

Otero

et al. 2015

A&A

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Context. The (magnetic) chemically peculiar (CP) stars of the upper main sequence are well-suited laboratories for investigating the influence of magnetic fields on the stellar surface because they produce abundance inhomogeneities (spots), which results in photometric variability that is explained in terms of the oblique rotator model. CP stars exhibiting this phenomenon are normally classified as α 2 Canum Venaticorum (ACV) variables. It is important to increase the sample of known rotational periods among CP stars by discovering new ACV variables. An increased sample size will contribute to the understanding of the CP stars' evolution in time. Aims. We aim at discovering new ACV variables in the public data of the third phase of the All Sky Automated Survey (ASAS-3). Furthermore, by analysis of the available photometric data, we intend to derive rotational periods of the stars. Methods. The ASAS-3 data were cross-correlated with the Catalogue of Ap, HgMn, and Am stars in order to analyse the light curves of bona fide CP and related stars. The light curves were downloaded and cleaned of outliers and data points with a flag indicating bad quality. Promising candidates showing a larger scatter than observed for constant stars in the corresponding magnitude range were searched for periodic signals using a standard Fourier technique. Objects exhibiting periodic signals well above the noise level were considered and visually inspected, whereas borderline cases were rejected. Results. In total, we found 323 variables, from which 246 are reported here for the first time, and 77 were probably wrongly classified before. The observed variability pattern of most stars is in accordance with an ACV classification. For some cases, it is difficult to distinguish between the light curves of double-waved ACVs and the variability induced by orbital motion (ellipsoidal variables/eclipsing variables), especially for objects exhibiting very small amplitudes and/or significant scatter in their light curves. Thus, some eclipsing or rotating ellipsoidal variables might be present. However, we are confident that the given periods are the correct ones. There seems to be a possible weak correlation between the rotational period and colour, in the sense that cooler magnetic CP stars rotate more slowly. However, this correlation seems to disappear when correcting for the interstellar reddening. Conclusions. The next steps have to include a compilation of all available rotational periods from the literature and a detailed investigation of the astrophysical parameters of these stars. This includes a determination of the individual masses, luminosities, ages, and inclination angles. However, this information cannot be straightforwardly determined from photometric data alone.

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Section: Discussionsupporting

confidence: 92%

Section: Characteristics Of the Asas-3 Datamentioning

confidence: 96%

A search for photometric variability in magnetic chemically peculiar stars using ASAS-3 data

Bernhard

Hümmerich

Otero

et al. 2015

A&A

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“…ASAS monitored about 10 7 sources in the magnitude range between the saturation limit 5 V = 7 (up to V ≈ 8.5 for few frames; cf. David et al 2014) and the detection threshold at V =14. During the third project phase, observations were acquired in the Johnson V passband.…”

Section: The Asas-3 Photometric Archivementioning

confidence: 99%

An investigation of the photometric variability of confirmed and candidate Galactic Be stars using ASAS-3 data

Bernhard

Otero

Hümmerich

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We present an investigation of a large sample of confirmed (N=233) and candidate (N=54) Galactic classical Be stars (mean V magnitude range of 6.4 to 12.6 mag), with the main aim of characterizing their photometric variability. Our sample stars were preselected among early-type variables using light curve morphology criteria. Spectroscopic information was gleaned from the literature, and archival and newly-acquired spectra. Photometric variability was analyzed using archival ASAS-3 time series data. To enable a comparison of results, we have largely adopted the methodology of Labadie-Bartz et al. (2017), who carried out a similar investigation based on KELT data. Complex photometric variations were established in most stars: outbursts on different time-scales (in 73±5 % of stars), long-term variations (36±6 %), periodic variations on intermediate time-scales (1±1 %) and short-term periodic variations (6±3 %). 24±6 % of the outbursting stars exhibit (semi)periodic outbursts. We close the apparent void of rare outbursters reported by Labadie-Bartz et al. (2017) and show that Be stars with infrequent outbursts are not rare. While we do not find a significant difference in the percentage of stars showing outbursts among early-type, mid-type and late-type Be stars, we show that early-type Be stars exhibit much more frequent outbursts. We have measured rising and falling times for well-covered and well-defined outbursts. Nearly all outburst events are characterized by falling times that exceed the rising times. No differences were found between early-, mid-and late-type stars; a single non-linear function adequately describes the ratio of falling time to rising time across all spectral subtypes, with the ratio being larger for short events.

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“…However, many more variables, especially with small amplitudes could be found using the ASAS data (see, e.g., Sect. 4.4 or David et al 2013). Given the limited information used for the automatic classification of variable stars in the ASAS catalogs, no-one can expect that the result will be unambiguous.…”

Section: Pulsating Stars In the Asas Datamentioning

confidence: 99%