scholarly journals The ASAS-SN catalogue of variable stars VI: an all-sky sample of δ Scuti stars

2020 ◽  
Vol 493 (3) ◽  
pp. 4186-4208 ◽  
Author(s):  
T Jayasinghe ◽  
K Z Stanek ◽  
C S Kochanek ◽  
P J Vallely ◽  
B J Shappee ◽  
...  
Keyword(s):  
Fundamental Mode ◽  
Variable Stars ◽  
Scale Height ◽  
Eclipsing Binaries ◽  
Image Subtraction ◽  
Orbital Periods ◽  
Many Sources ◽  
Scuti Stars ◽  
Δ Scuti Stars ◽  
Gaia Dr2

ABSTRACT We characterize an all-sky catalogue of ∼8400 δ Scuti variables in ASAS-SN, which includes ∼3300 new discoveries. Using distances from Gaia DR2, we derive period–luminosity relationships for both the fundamental mode and overtone pulsators in the WJK, V, Gaia DR2 G, J, H, Ks, and W1 bands. We find that the overtone pulsators have a dominant overtone mode, with many sources pulsating in the second overtone or higher order modes. The fundamental mode pulsators have metallicity-dependent periods, with log10(P) ∼ −1.1 for $\rm [Fe/H]\lt -0.3$ and log10(P) ∼ −0.9 for $\rm [Fe/H]\gt 0$, which leads to a period-dependent scale height. Stars with $P\gt 0.100\, \rm d$ are predominantly located close to the Galactic disc ($\rm |\mathit{ Z}|\lt 0.5\, kpc$). The median period at a scale height of $Z\sim 0\, \rm kpc$ also increases with the Galactocentric radius R, from log10(P) ∼ −0.94 for sources with $R\gt 9\, \rm kpc$ to log10(P) ∼ −0.85 for sources with $R\lt 7\, \rm kpc$, which is indicative of a radial metallicity gradient. To illustrate potential applications of this all-sky catalogue, we obtained 30 min cadence, image subtraction TESS light curves for a sample of 10 fundamental mode and 10 overtone δ Scuti stars discovered by ASAS-SN. From this sample, we identified two new δ Scuti eclipsing binaries, ASASSN-V J071855.62−434247.3 and ASASSN-V J170344.20−615941.2 with short orbital periods of Porb = 2.6096 and 2.5347 d, respectively.

scholarly journals The pulsation properties of λ bootis stars I. the southern TESS sample

2020 ◽  
Vol 495 (2) ◽  
pp. 1888-1912
Author(s):  
S J Murphy ◽  
E Paunzen ◽  
T R Bedding ◽  
P Walczak ◽  
D Huber
Keyword(s):  
Stellar Evolution ◽  
Fundamental Mode ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Mode Identification ◽  
Regular Sequences ◽  
Stellar Ages ◽  
Scuti Stars ◽  
Δ Scuti Stars ◽  
Gaia Dr2

ABSTRACT We analyse TESS light curves for 70 southern λ Boo stars to identify binaries and to determine which of them pulsate as δ Scuti stars. We find two heartbeat stars and two eclipsing binaries among the sample. We calculate that 81 per cent of λ Boo stars pulsate as δ Sct variables, which is about twice that of normal stars over the same parameter space. We determine the temperatures and luminosities of the λ Boo stars from photometry and Gaia DR2 parallaxes. A subset of 40 λ Boo stars have 2-min TESS data, reliable temperatures and luminosities, and δ Sct pulsation. We use Petersen diagrams (period ratios), échelle diagrams, and the period–luminosity relation to identify the fundamental mode in 20 of those 40 stars and conclude that a further 8 stars are not pulsating in this mode. For the remaining 12, the fundamental mode cannot be unambiguously identified. Further mode identification is possible for 12 of the fundamental mode pulsators that have regular sequences of pulsation overtones in their échelle diagrams. We use stellar evolution models to determine statistically that the λ Boo stars are only superficially metal weak. Simple pulsation models also better fit the observations at a metallicity of Z = 0.01 than at Z = 0.001. The TESS observations reveal the great potential of asteroseismology on λ Boo stars, for determining precise stellar ages and shedding light on the origin(s) of the λ Boo phenomenon.

scholarly journals Do the Pre-Main Sequence δ Scuti Stars Really Exist?

2002 ◽  
Vol 185 ◽  
pp. 346-347
Author(s):  
J.H. Peña ◽  
R. Peniche ◽  
J.C. Plascencia ◽  
M.A. Hobart ◽  
C. de la Cruz ◽  
...  
Keyword(s):  
Main Sequence ◽  
Variable Stars ◽  
Current Status ◽  
Excellent Review ◽  
Scuti Stars ◽  
Δ Scuti Stars

Recently, new views of the current status of δ Scuti stars have been developed by Rodríguez & Breger (2001) who carried out an excellent review, listing 8 pre-main-sequence (PMS) δ Scuti candidates and examined the possibility of the existence of PMS δ Scuti variable stars. Here we discuss the nature of 4 stars from their list: 2 said to be members of NGC 2264 and 2 of NGC 6823.

scholarly journals Kepler eclipsing binaries with δ Scuti components and tidally induced heartbeat stars

2015 ◽  
Vol 11 (A29B) ◽  
pp. 648-652
Author(s):  
Zhao Guo ◽  
Douglas R. Gies ◽  
Rachel A. Matson
Keyword(s):  
Binary Stars ◽  
High Frequency ◽  
Eclipsing Binaries ◽  
Frequency Separation ◽  
High Frequency Oscillations ◽  
Orbital Frequency ◽  
Scuti Stars ◽  
Large Frequency ◽  
Δ Scuti Stars ◽  
Stellar Density

Abstractδ Scuti stars are generally fast rotators and their pulsations are not in the asymptotic regime, so the interpretation of their pulsation spectra is a very difficult task. Binary stars, especially eclipsing systems, offer us the opportunity to constrain the space of fundamental stellar parameters. Firstly, we show the results of KIC9851944 and KIC4851217 as two case studies. We found the signature of the large frequency separation in the pulsational spectrum of both stars. The observed mean stellar density and the large frequency separation obey the linear relation in the log-log space as found by Suarez et al. (2014) and García Hernández et al. (2015). Second, we apply the simple ‘one-layer model’ of Moreno & Koenigsberger (1999) to the prototype heartbeat star KOI-54. The model naturally reproduces the tidally induced high frequency oscillations and their frequencies are very close to the observed frequency at 90 and 91 times the orbital frequency.

scholarly journals Re-classification of ROTSE-I δ Scuti stars

2004 ◽  
Vol 193 ◽  
pp. 279-282
Author(s):  
H. Jin ◽  
S.-L. Kim ◽  
C.-U. Lee ◽  
D.-J. Lee ◽  
K.-S. Kim
Keyword(s):  
Decomposition Analysis ◽  
Variable Stars ◽  
Fourier Decomposition ◽  
Eclipsing Variable Stars ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractWe present new multiband photometric results for ROTSE-I δ Sct stars and the Fourier decomposition analysis. Our result shows that most of the stars classified as ROTSE-I δ Sct stars seem to be W UMa type eclipsing variable stars.

scholarly journals Variable stars in young open cluster NGC 2244

2019 ◽  
Vol 487 (3) ◽  
pp. 3505-3522 ◽  
Author(s):  
Gabriela Michalska
Keyword(s):  
Near Infrared ◽  
Open Cluster ◽  
Variable Stars ◽  
Eclipsing Binaries ◽  
Class I ◽  
Be Stars ◽  
Membership Probability ◽  
Young Open Cluster ◽  
Stellar Sources ◽  
Scuti Stars

ABSTRACT We present results of a UBVIC variability survey in the young open cluster NGC 2244. In total, we found 245 variable stars. Most of them, 211 stars, are variables with irregular variations. Furthermore, 23 periodic variables were found. We also detected four candidates for δ Scuti stars and seven eclipsing binaries. Based on the mid-infrared Spitzer and WISE photometry and near infrared JHKS 2MASS photometry, we classified 104 young stellar sources among our variables: 1 Class I object, 1 Class I/flat spectrum object, 4 flat spectrum objects, 91 Class II objects, and 7 transition disc objects. This classification, together with r′i′Hα IPHAS photometry and JHK UKIDSS photometry, were used for identification of pre-main sequence stars among irregular and periodic variables. In this way, 97 CTTS candidates (96 irregular and one periodic variable), 68 WTTS candidates (54 irregular and 14 periodic variables), and 6 Herbig Ae/Be stars were found. For 223 variable stars we calculated membership probability based on proper motions from Gaia DR2 catalogue. Majority of them, 143 stars, are cluster members with probability greater than 70 per cent. For only 36 variable stars the membership probability is smaller than 20 per cent.

scholarly journals Delta Scuti Stars in Open Clusters: w2 and w20 in NGC 2264 and h501 and h906 in α Per

2000 ◽  
Vol 176 ◽  
pp. 465-466
Author(s):  
J. H. Peña ◽  
R. Peniche ◽  
F. Cervantes ◽  
R. M. García ◽  
J. P. Sareyan
Keyword(s):  
Chemical Composition ◽  
Effective Temperature ◽  
Variable Stars ◽  
Open Clusters ◽  
Early Type ◽  
Early Type Stars ◽  
Delta Scuti ◽  
Scuti Stars ◽  
Δ Scuti Stars

There are many advantages to studying variable stars in open clusters; the parameters that determine the evolution of the stars, such as chemical composition and age, can be considered to be the same for all the stars in the cluster. These data, along with the mass, effective temperature and superficial gravity, allow us to better determine the physics which explain the pulsation mechanisms. In the present paper the variable stars h501 and h906 in α Per and w2 and w20 in NGC 2264 are studied. In particular, the reasons why δ Scuti stars coexist with early type stars in NGC 2264 is examined.

scholarly journals Frequency analysis of δ Scuti stars towards the Galactic bulge

2021 ◽  
Author(s):  
H Netzel ◽  
P Pietrukowicz ◽  
I Soszyński ◽  
M Wrona
Keyword(s):  
Frequency Analysis ◽  
Gravitational Lensing ◽  
Fundamental Mode ◽  
Statistical Properties ◽  
Galactic Bulge ◽  
Homogeneous Sample ◽  
Theoretical Predictions ◽  
Scuti Stars ◽  
Δ Scuti Stars

Abstract We have performed a frequency analysis of 10,092 δ Scuti-type stars detected in the fourth phase of the Optical Gravitational Lensing Experiment (OGLE) towards the Galactic bulge, which is the most numerous homogeneous sample of δ Scuti stars observed so far. The main goal was to search for stars pulsating in at least two radial modes simultaneously. We have found 3083 candidates for such stars, which is the largest set obtained to date. Among them, 2655 stars pulsate in two radial modes, 414 stars pulsate in three radial modes, and 14 stars pulsate in four radial modes at the same time. We report the identification of 221 δ Scuti stars pulsating in the fundamental mode, first overtone, and third overtone simultaneously. We show the most populated Petersen and Bailey diagrams and discuss statistical properties of the identified frequencies based on this numerous sample. Additionally, we present theoretical predictions of period ratios for δ Scuti stars pulsating in overtones from the fourth to the seventh.

scholarly journals Double Mode Pulsating Stars and Opacity Changes

1989 ◽  
Vol 111 ◽  
pp. 248-248
Author(s):  
G.K. Andreasen
Keyword(s):  
Physical Properties ◽  
Variable Stars ◽  
Period Ratio ◽  
Pulsating Stars ◽  
Temperature Range ◽  
Ratio Data ◽  
Mass Calibration ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractThe basic physical properties of double mode Cepheids and double mode δ Scuti stars are still highly controversial. Based on results of very recent opacity calculations a detailed consistent, possible solution of the problem of the nature of double mode variable stars has been developed. Extensive studies have been performed to establish the rules governing the morphology of the period ratio diagrams. An ideal reproduction of the period ratio data for both stellar types are obtained assuming an increase of the Cox-Steward opacity by a factor of about 2.5 in the temperature range from 1.5 X 105K to 8.0 X 105K. Consequences for the mass calibration of Petersen diagrams are evaluated.

scholarly journals How to separate the low amplitude δ Scuti variation from the instrumental ones in CoRoT data?

2015 ◽  
Vol 11 (A29B) ◽  
pp. 529-531
Author(s):  
József M. Benkő ◽  
Margit Paparó
Keyword(s):  
Real Data ◽  
High Amplitude ◽  
Variable Stars ◽  
South Atlantic ◽  
Frequency Range ◽  
South Atlantic Anomaly ◽  
Fourier Spectra ◽  
Low Amplitude ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractRich regular frequency patterns were found in the Fourier spectra of low-amplitude δ Scuti stars observed by CoRoT satellite (see Paparó et al. in prep.). The CoRoT observations are, however, influenced by the disturbing effect of the South Atlantic Anomaly. The effect is marginal for high amplitude variable stars but it could be critical in the case of low amplitude variables, especially if the frequency range of the intrinsic variation overlaps the interval of the instrumental frequencies. Some tests were carried out both on synthetic and real data for distinguishing technical and stars' frequencies.

scholarly journals The Apsidal Motion of the Eclipsing Binary Systems GSC 4487 0347 and GSC 4513 2537

2011 ◽  
Vol 7 (S282) ◽  
pp. 93-94
Author(s):  
V. S. Kozyreva ◽  
A. V. Kusakin ◽  
T. Krajci ◽  
J. Menke ◽  
T. M. Tsvetkova
Keyword(s):  
Binary Systems ◽  
Variable Stars ◽  
Eclipsing Binaries ◽  
Tien Shan ◽  
Astronomical Institute ◽  
Ccd Array ◽  
Photometric Observations ◽  
Sternberg Astronomical Institute ◽  
The Crimea ◽  
Orbital Periods

AbstractThe eclipsing variable stars GSC 44870347 and GSC 4513 2537 are recently discovered binary systems (Otero et al., 2006) with orbital periods 1d.99 and 6d.33 days. We carried out the photometric observations of these eclipsing binaries from 2009-2010 using a CCD-array at the Tien-Shan Observatory in Kazakstan, at the Crimea Station of the Sternberg Astronomical Institute, at the Astrokolkhoz Observatory in New Mexico (AAVSO), while the spectrophotometric observations were obtained at the Starlight Farm Observatory in Barnesville, USA.

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