A search for SX Phe stars among<i>Kepler</i>δ Scuti stars

Balona, L. A.; Nemec, J. M.

doi:10.1111/j.1365-2966.2012.21957.x

Cited by 33 publications

(36 citation statements)

References 21 publications

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“…It has the highest specific frequency of DC among the other extra-galactic systems and the globular clusters of the Milky Way; (ii) There seems to be a fundamental difference between the DC population in dSph galaxies and the galactic field. While high amplitude DC are extremely rare in the field (Balona & Nemec 2012), they are at least 100× more frequent in Carina. (iii) There are important differences observed among the properties of the DC population of Carina, Fornax and the LMC which may be a reflection of a metallicity spread, depth along the line of sight, and/or different evolutionary paths of the DC.…”

Section: Introductionmentioning

confidence: 99%

The Population of Pulsating Variable Stars in the Sextans Dwarf Spheroidal Galaxy

Vivas

Alonso-García

Mateo

et al. 2019

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A large extension of the Sextans dwarf spheroidal galaxy, 7 sq degrees, has been surveyed for variable stars using the Dark Energy Camera at the Blanco Telescope in Cerro Tololo Inter-American Observatory, Chile. We report 7 Anomalous Cepheids, 199 RR Lyrae stars and 16 dwarf Cepheids in the field. This is only the fifth extra-galactic systems in which dwarf Cepheids have been systematically searched. Henceforth, the new stars increase the census of stars coming from different environments that can be used to asses the advantages and limitations of using dwarf Cepheids as standard candles in populations for which the metallicity is not necessarily known. The dwarf Cepheids found in Sextans have a mean period of 0.066 days, and a mean g amplitude of 0.87 mags. They are located below the horizontal branch spanning a range of 0.8 mag, between 21.9 < g < 22.7. The number of dwarf Cepheids in Sextans is low compared with other galaxies such as Carina, which have a strong intermediate-age population. On the other hand, the number and ratio of RR Lyrae stars to dwarf Cepheids is quite similar to Sculptor, a galaxy which, as Sextans, is dominated by an old stellar population. The dwarf Cepheid stars found in Sextans follow a well constrained Period-Luminosity relationship with an rms=0.05 mag in the g band, which was set up by anchoring to the distance modulus given by the RR Lyrae stars. Although the majority of the variable stars in Sextans are located toward the center of the galaxy, we have found 2 RR Lyrae stars and 1 Anomalous Cepheid in the outskirts of the galaxy, which may be extra-tidal stars and suggest this galaxy may be undergoing tidal destruction. These possible extra-tidal variable stars share the same proper motions as Sextans, as seen by recent Gaia measurements. Two additional stars which we initially classified as foreground RR Lyrae stars may actually be other examples of Sextans extra-tidal Anomalous Cepheids, although radial velocities are needed to prove that scenario.

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Section: Introductionmentioning

confidence: 99%

The Population of Pulsating Variable Stars in the Sextans Dwarf Spheroidal Galaxy

Vivas

Alonso-García

Mateo

et al. 2019

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“…The most commonly observed variables in the A/F spectral classes are δ-Scuti and their cousins γ-Doradus and dwarf Cepheid variables. NASA's Kepler telescope observed over 1400 δ-Scuti stars out of the ∼150,000 stars in Kepler's field of view (Balona & Nemec 2012).…”

Section: Introductionmentioning

confidence: 99%

Dealing With δ-Scuti Variables: Transit Light Curve Analysis of Planets Orbiting Rapidly Rotating, Seismically Active A/F Stars

Ahlers

Barnes

Myers

2019

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We measure the bulk system parameters of the seismically active, rapidly-rotating δ-Scuti KOI-976 and constrain the orbit geometry of its transiting binary companion using a combined approach of asteroseismology and gravity-darkening light curve analysis. KOI-976 is a 1.62 ± 0.2 M star with a measured v sin(i) of 120 ± 2 km/s and seismically-induced variable signal that varies by ∼ 0.6% of the star's total photometric brightness. We take advantage of the star's oblate shape and seismic activity to perform three measurements of its obliquity angle relative to the plane of the sky. We first apply rotational splitting theory to the star's variable signal observed in short-cadence Kepler photometry to constrain KOI-976's obliquity angle, and then subtract off variability from that dataset using the linear algorithm for significance reduction software LASR. We perform gravitydarkened fits to Kepler variability-subtracted short-cadence photometry and to Kepler's phase-folded long-cadence photometry to obtain two more measurements of the star's obliquity. We find that the binary system transits in a grazing configuration with measured obliquity values of 36 • ± 17 • , 46 • ± 16 • , and 43 • ± 20 • respectively for the three measurements. We perform these analyses as a way to demonstrate overcoming the challenges high-mass stars can present to transit light curve fitting and to prepare for the large number of exoplanets TESS will discover orbiting A/F stars.

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“…Our study in Carina ( [17]) has raised several interesting points: (i) Carina is very rich in dwarf Cepheid stars; (ii) There seems to be a fundamental difference between the dwarf Cepheid population in dSph galaxies and the Galactic field. While high amplitude dwarf Cepheid stars are extremely rare in the field ( [19]), they are at least 100× more frequent in Carina. (iii) There are important differences observed among the properties of the dwarf Cepheid population of Carina, Fornax and the LMC which may be a reflection of a metallicity spread, depth along the line of sight, and/or different evolutionary paths of the dwarf Cepheid.…”

Section: Introductionmentioning

confidence: 99%

Faint (and bright) variable stars in the satellites of the Milky Way

Vivas

2017

EPJ Web Conf.

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Abstract. I describe two ongoing projects related with variable stars in the satellites of the Milky Way. In the first project, we are searching for dwarf Cepheid stars (a.k.a δ Scuti and/or SX Phe) in some of the classical dwarf spheroidal galaxies. Our goal is to characterize the population of these variable stars under different environments (age, metallicity) in order to study their use as standard candles in systems for which the metallicity is not necessarily known. In the second project we search for RR Lyrae stars in the new ultra-faint satellite galaxies that have been discovered around the Milky Way in recent years.

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A search for SX Phe stars amongKeplerδ Scuti stars

Cited by 33 publications

References 21 publications

The Population of Pulsating Variable Stars in the Sextans Dwarf Spheroidal Galaxy

The Population of Pulsating Variable Stars in the Sextans Dwarf Spheroidal Galaxy

Dealing With δ-Scuti Variables: Transit Light Curve Analysis of Planets Orbiting Rapidly Rotating, Seismically Active A/F Stars

Faint (and bright) variable stars in the satellites of the Milky Way

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