scholarly journals Spectroscopic and photometric time series of the bright RRc star T Sex

2020 ◽  
Vol 500 (2) ◽  
pp. 2554-2563
Author(s):  
József M Benkő ◽  
Ádám Sódor ◽  
András Pál
Keyword(s):  
Time Series ◽  
Weak Shock ◽  
Characteristic Line ◽  
Interstellar Space ◽  
Data Sets ◽  
Pulsation Frequency ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars ◽  
Different Sources

ABSTRACT We present spectroscopic time series observations on one of the brightest northern RRc stars, namely T Sex. Additionally, we also analysed extended photometric data sets, particularly the recent observations of the TESS space telescope. The main findings of our studies are as follows: T Sex, unlike all RRc stars whose space photometry has been analysed, shows only the 0.5fx frequency as an additional pulsation frequency. With this, T Sex may be the first represent of such rare RRc stars found from space photometry. The spectroscopic data show a periodic distortion of the H α line with the pulsation phase. This phenomenon has not been reported for any RR Lyrae stars. The characteristic line distortion is probably caused by the turbulent convection, which resulted in higher macroturbulent velocity for T Sex than that for typical RRab stars. Line doubling of the Na D line was observed between the 0.37 and 0.80 pulsation phases. The explanation of this phenomenon is that the two absorption components originate from different sources. The redder component comes from the pulsating atmosphere of the star, while the bluer one comes from the interstellar space. At phase 0.438, we detected emission on the Na D line, which may indicate a weak shock wave.

STRucture and Evolution of the GAlaxy (STREGA): The case of Pal 3

2019 ◽  
Vol 14 (S351) ◽  
pp. 478-481
Author(s):  
M. I. Moretti ◽  
I. Musella ◽  
M. Marconi ◽  
V. Ripepi ◽  
R. Molinaro
Keyword(s):  
Time Series ◽  
Globular Cluster ◽  
Variable Stars ◽  
Rr Lyrae Stars ◽  
North East ◽  
The North ◽  
Rr Lyrae ◽  
The Galaxy ◽  
Lyrae Stars ◽  
Candidate Variable

AbstractIn the context of the STRucture and Evolution of the GAlaxy survey, we describe the preliminary results obtained for the fields around the globular cluster Pal 3 (about 2.75 square degrees), by exploiting the obtained g, r, i time series photometry. The final aim is to use variable stars as tools to verify and study the presence of streams around Pal 3. We found 20 candidate variable stars of which 7 RR Lyrae stars possibly belonging to Pal 3, also at large distance from the center. The distribution of the candidate RR Lyrae seems to confirm a preferential distribution in the north-east direction, confirming previous results in literature.

scholarly journals A DECam view of the diffuse dwarf galaxy Crater II – Variable stars

2019 ◽  
Vol 492 (1) ◽  
pp. 1061-1077 ◽  
Author(s):  
A Katherina Vivas ◽  
Alistair R Walker ◽  
Clara E Martínez-Vázquez ◽  
Matteo Monelli ◽  
Giuseppe Bono ◽  
...  
Keyword(s):  
Time Series ◽  
Dwarf Galaxy ◽  
Position Angle ◽  
Variable Stars ◽  
Distance Modulus ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
The Galaxy ◽  
Binary Evolution ◽  
Lyrae Stars

ABSTRACT Time series observations of a single dithered field centred on the diffuse dwarf satellite galaxy Crater II were obtained with the Dark Energy Camera (DECam) at the 4m Blanco Telescope at Cerro Tololo Inter-American Observatory, Chile, uniformly covering up to two half-light radii. Analysis of the g and i time series results in the identification and characterization of 130 periodic variable stars, including 98 RR Lyrae stars, 7 anomalous Cepheids, and 1 SX Phoenicis star belonging to the Crater II population, and 24 foreground variables of different types. Using the large number of ab-type RR Lyrae stars present in the galaxy, we obtained a distance modulus to Crater II of (m − M)0 = 20.333 ± 0.004 (stat) ±0.07 (sys). The distribution of the RR Lyrae stars suggests an elliptical shape for Crater II, with an ellipticity of 0.24 and a position angle of 153°. From the RR Lyrae stars, we infer a small metallicity dispersion for the old population of Crater II of only 0.17 dex. There are hints that the most metal-poor stars in that narrow distribution have a wider distribution across the galaxy, while the slightly more metal-rich part of the population is more centrally concentrated. Given the features in the colour–magnitude diagram of Crater II, the anomalous Cepheids in this galaxy must have formed through a binary evolution channel of an old population.

scholarly journals A Full-Amplitude Nonlinear Model for RR Lyr: Pulsations, Shock Waves and Hα Peculiarities

1993 ◽  
Vol 139 ◽  
pp. 265-265
Author(s):  
Andrew Fokin
Keyword(s):  
Transfer Problem ◽  
Weak Shock ◽  
Rr Lyrae Stars ◽  
Strong Emission ◽  
Rr Lyrae ◽  
Metallic Line ◽  
Line Transfer ◽  
Lyrae Stars ◽  
Strong Scattering ◽  
Very High

AbstractThe shock phenomena and Hα formation in the atmosphere of RR Lyrae are investigated by means of numerical simulations. The full-amplitude hydrodynamical model is generated, adopting M = 0.578M⊙, L = 62L⊙, Teff = 7175K and Population II composition. The Hα profiles are obtained by solution of the non-LTE line transfer problem for the multilevel hydrogen atom. In the course of pulsations an extended (about 16 static scales) low-density atmosphere is produced with nearly exponential density decrease. Two shocks, propagating outwards, are successively generated during one period. The shock amplitude reaches 140 km/s. No mass loss has been found. These results confirm the earlier results of S. Hill (1972). The main shock develops very high, at mass depths near 0.001 g per area, whereas computations for W Vir yield 100. An analysis of the Fe I and Ti II lines shows that this difference is sufficient to explain the lack of metallic line-doubling in RR Lyrae stars. The bump on the light curve is due to a weak shock, propagating below the photosphere, which is generated with the early shock at the stage of expansion at the H-recombination front. The central intensities, Dopplerian shifts, amplitudes and phases of splitting of the computed Hα profiles agree well with the observed values (Gillet & Crowe 1988). The lack of strong emission also fits the observations, resulting from strong scattering processes near the shock. The predicted Lyman lines show strong emission, reaching maximum at the maximum light.

scholarly journals Gaia Data Release 2

2019 ◽  
Vol 625 ◽  
pp. A97 ◽  
Author(s):  
L. Rimoldini ◽  
B. Holl ◽  
M. Audard ◽  
N. Mowlavi ◽  
K. Nienartowicz ◽  
...  
Keyword(s):  
Time Series ◽  
High Amplitude ◽  
Rr Lyrae Stars ◽  
Long Period ◽  
Rr Lyrae ◽  
Multi Stage ◽  
Long Period Variables ◽  
Data Release ◽  
Lyrae Stars

Context. More than half a million of the 1.69 billion sources in Gaia Data Release 2 (DR2) are published with photometric time series that exhibit light variations during the 22 months of observation. Aims. An all-sky classification of common high-amplitude pulsators (Cepheids, long-period variables, δ Scuti/SX Phoenicis, and RR Lyrae stars) is provided for stars with brightness variations greater than 0.1 mag in G band. Methods. A semi-supervised classification approach was employed, firstly training multi-stage random forest classifiers with sources of known types in the literature, followed by a preliminary classification of the Gaia data and a second training phase that included a selection of the first classification results to improve the representation of some classes, before the improved classifiers were applied to the Gaia data. Dedicated validation classifiers were used to reduce the level of contamination in the published results. A relevant fraction of objects were not yet sufficiently sampled for reliable Fourier series decomposition, consequently classifiers were based on features derived from statistics of photometric time series in the G, GBP, and GRP bands, as well as from some astrometric parameters. Results. The published classification results include 195 780 RR Lyrae stars, 150 757 long-period variables, 8550 Cepheids, and 8882 δ Scuti/SX Phoenicis stars. All of these results represent candidates whose completeness and contamination are described as a function of variability type and classification reliability. Results are expressed in terms of class labels and classification scores, which are available in the vari_classifier_result table of the Gaia archive.

scholarly journals NGC 1261: A TIME-SERIES VI STUDY OF ITS VARIABLE STARS

2019 ◽  
Vol 55 (2) ◽  
pp. 337-350 ◽  
Author(s):  
A. Arellano Ferro ◽  
I. H. Bustos Fierro ◽  
J. H. Calderón ◽  
J. A. Ahumada
Keyword(s):  
Time Series ◽  
Variable Stars ◽  
Individual Values ◽  
Ccd Photometry ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Cluster Distance ◽  
The Mean ◽  
Lyrae Stars ◽  
Gaia Dr2

Time-series VI CCD photometry of the globular cluster NGC 1261 is employed to study its variable star population. A membership analysis of most variables based on Gaia DR2 proper motions and colours was performed prior to the estimation of the mean cluster distance and metallicity. The light curves of the member RR Lyrae were Fourier decomposed to calculate their individual values of distance, [Fe/H], radius and mass. The I band P-L for RR Lyrae stars was also employed. Our best estimates of the metallicity and distance of this Oo I cluster are [Fe/H]ZW =−1.42 ± 0.05 dex and d = 17.2 ± 0.4 kpc. No mixture of fundamental and first overtone RR Lyrae stars in the either-or or bimodal region is seen in this cluster, as it seems to be the rule for Oo I clusters with a red horizontal branch. A multi-approach search in a region of about 10' × 10' around the cluster revealed no new variable stars within the limitations of our CCD photometry.

scholarly journals Erratum: Photometric and radial-velocity time-series of RR Lyrae stars in M3: analysis of single-mode variables

2018 ◽  
Vol 481 (2) ◽  
pp. 2778-2778
Author(s):  
J Jurcsik ◽  
P Smitola ◽  
G Hajdu ◽  
Á Sódor ◽  
J Nuspl ◽  
...  
Keyword(s):  
Time Series ◽  
Radial Velocity ◽  
Single Mode ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars

scholarly journals Gaia Data Release 2

2018 ◽  
Vol 618 ◽  
pp. A30 ◽  
Author(s):  
B. Holl ◽  
M. Audard ◽  
K. Nienartowicz ◽  
G. Jevardat de Fombelle ◽  
O. Marchal ◽  
...  
Keyword(s):  
Time Series ◽  
Variable Stars ◽  
Great Promise ◽  
Published Data ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Short Timescale ◽  
Classical Statistics ◽  
Data Release ◽  
Lyrae Stars

Context. The Gaia Data Release 2 (DR2) contains more than half a million sources that are identified as variable stars. Aims. We summarise the processing and results of the identification of variable source candidates of RR Lyrae stars, Cepheids, long-period variables (LPVs), rotation modulation (BY Dra-type) stars, δ Scuti and SX Phoenicis stars, and short-timescale variables. In this release we aim to provide useful but not necessarily complete samples of candidates. Methods. The processed Gaia data consist of the G, GBP, and GRP photometry during the first 22 months of operations as well as positions and parallaxes. Various methods from classical statistics, data mining, and time-series analysis were applied and tailored to the specific properties of Gaia data, as were various visualisation tools to interpret the data. Results. The DR2 variability release contains 228 904 RR Lyrae stars, 11 438 Cepheids, 151 761 LPVs, 147 535 stars with rotation modulation, 8882 δ Scuti and SX Phoenicis stars, and 3018 short-timescale variables. These results are distributed over a classification and various Specific Object Studies tables in the Gaia archive, along with the three-band time series and associated statistics for the underlying 550 737 unique sources. We estimate that about half of them are newly identified variables. The variability type completeness varies strongly as a function of sky position as a result of the non-uniform sky coverage and intermediate calibration level of these data. The probabilistic and automated nature of this work implies certain completeness and contamination rates that are quantified so that users can anticipate their effects. Thismeans that even well-known variable sources can be missed or misidentified in the published data. Conclusions. The DR2 variability release only represents a small subset of the processed data. Future releases will include more variable sources and data products; however, DR2 shows the (already) very high quality of the data and great promise for variability studies.

scholarly journals Photometric and radial-velocity time series of RR Lyrae stars in M3: analysis of single-mode variables

2017 ◽  
Vol 468 (2) ◽  
pp. 1317-1337 ◽  
Author(s):  
J. Jurcsik ◽  
P. Smitola ◽  
G. Hajdu ◽  
Á. Sódor ◽  
J. Nuspl ◽  
...  
Keyword(s):  
Time Series ◽  
Radial Velocity ◽  
Single Mode ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars

scholarly journals Frequency Analysis of δ Scuti and RR Lyrae Stars in the OGLE-1 Database

2002 ◽  
Vol 185 ◽  
pp. 392-395 ◽  
Author(s):  
P. Moskalik ◽  
E. Poretti
Keyword(s):  
Frequency Analysis ◽  
Systematic Search ◽  
Pulsation Frequency ◽  
Galactic Bulge ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars

AbstractWe discuss the results of a systematic search for multi-periodic pulsations in Galactic Bulge δ Scuti and RR Lyrae stars. Six “normal” double-mode variables pulsating in two radial modes have been identified (5 δ Scuti-type and 1 RR Lyrae-type). In 37 RR Lyrae stars secondary periodicities very close to the primary pulsation frequency have been detected. These periodicities correspond to nonradial modes of oscillation. They are found in ∼ 23% of RRab and in ∼ 3% of RRc variables of our sample.

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