scholarly journals A rapidly evolving high-amplitude δ Scuti star crossing the Hertzsprung Gap

2021 ◽  
Author(s):  
Jia-Shu Niu ◽  
Hui-Fang Xue
Keyword(s):  
Main Sequence ◽  
Supernova Explosion ◽  
High Amplitude ◽  
Current Theory ◽  
Evolution Process ◽  
Single Star ◽  
Evolutionary Phase ◽  
Scuti Star ◽  
Hertzsprung Gap ◽  
Special Time

Abstract People cannot witness the stellar evolution process of a single star obviously in most cases because of its extremely secular time-scale, except for some special time nodes in it (such as the supernova explosion [1]). But in some specific evolutionary phases, we have the chances to witness such process gradually on human times-scales. When a star evolved leaving from the main sequence, the hydrogen nuclei fusion in its core is gradually transferring into the shell. In the Hertzsprung–Russell diagram, its evolutionary phase falls into the Hertzsprung gap, which is one of the most rapidly evolving phases in the life of a star [2]. Here we report a discovery of a rapidly evolving high-amplitude δ Scuti star KIC6382916 (J19480292+4146558) which is crossing the Hertzsprung gap. According to the analysis of the archival data, we find three independent pulsation modes of it, whose amplitudes and frequencies are variating distinctly in 4 years. The period variation rates of the three pulsation modes are one or two orders larger than the best seismic model constructed by the standard evolution theory, which indicates the current theory cannot precisely describe the evolution process in this rapidly evolving phase and needs further upgrades. Moreover, the frequency and amplitude interactions between the three independent pulsation modes and their harmonics/combinations open a new window to the future asteroseismology.

scholarly journals Asteroseismology of a High-amplitude δ Scuti Star GSC 4552-1498: Mode Identification and Model Fitting

2021 ◽  
Vol 922 (2) ◽  
pp. 199
Author(s):  
Xiao-Ya Sun ◽  
Zhao-Yu Zuo ◽  
Tao-Zhi Yang ◽  
Xing-Hao Chen ◽  
Hong-Rong Li
Keyword(s):  
Main Sequence ◽  
Model Fitting ◽  
Theoretical Models ◽  
High Amplitude ◽  
Radial Mode ◽  
Mode Interaction ◽  
Mode Identification ◽  
Period Increase ◽  
Stellar Parameter ◽  
Scuti Star

Abstract In this paper, the pulsation behavior of high-amplitude δ Scuti star GSC 4552-1498 was analyzed. Using the high-precision photometric data from the Transiting Exoplanet Survey Satellite, two new independent frequencies F1 = 22.6424(1) day−1 and F2 = 28.6803(5) day−1 were identified for this source, along with the fundamental one F = 17.9176(7) day−1, which was previously known. In addition, the classical O − C analysis was conducted to give a new ephemeris formula of BJDmax = T 0 + P × E = 2453321.534716(4) + 0.055811(0) × E. The O − C diagram reveals a continuous period increase, but the rate of (1/P)(dP/dt) = 1.11(3) × 10−7 yr−1 seems much larger (about hundreds) than predicted by evolution theories, which is long been noticed but not well understood, possibly related to nonlinear mode interaction. Based on frequency parameters (i.e., F, F1, and F2), a series of theoretical models were conducted by employing the stellar evolution code. It turns out that F1 should be a non-radial mode and F2 is the second overtone radial mode. Due to the mass–metallicity degeneracy, the stellar parameter of the star can however not be determined conclusively. We suggest high-resolution spectral observation is highly desired in the future to further constrain models. We note GSC 4552-1498 is located on the main sequence in the H-R diagram.

scholarly journals AE Ursae Majoris – a δ Scuti Star in the Hertzsprung Gap

2017 ◽  
pp. stx125 ◽  
Author(s):  
Jia-Shu Niu ◽  
Jian-Ning Fu ◽  
Yan Li ◽  
Xiao-Hu Yang ◽  
Weikai Zong ◽  
...  
Keyword(s):  
Scuti Star ◽  
Hertzsprung Gap

An observational study of the high-amplitude δ Scuti star V367 Cam

New Astronomy ◽  
2020 ◽  
Vol 77 ◽  
pp. 101338
Author(s):  
Elham Ziaali ◽  
Mir Hojjat Kermani ◽  
Hossein Ebadi ◽  
Vahid abbasvand
Keyword(s):  
Observational Study ◽  
High Amplitude ◽  
Scuti Star

scholarly journals The Origin of the RS CVn Binaries

1976 ◽  
Vol 73 ◽  
pp. 381-387 ◽  
Author(s):  
P. Biermann ◽  
D. S. Hall
Keyword(s):  
Angular Momentum ◽  
Star Formation ◽  
Total Mass ◽  
Total Angular Momentum ◽  
Main Sequence ◽  
Be Stars ◽  
Large Space ◽  
Single Star ◽  
The Core ◽  
Thermal Phase

We consider six possible origins for the RS CVn binaries based on the following possibilities. RS CVn binaries might now be either pre-main-sequence or post-main-sequence. A pre-main-sequence binary might not always have been a binary but might have resulted from fission of a rapidly rotating single pre-main-sequence star. The main-sequence counterparts might be either single stars or binaries.To decide which of the six origins is possible, we consider the following observed data for the RS CVn binaries: total mass, total angular momentum, lack of observed connection with regions of star formation, large space density, kinematical age, and the visual companion of WW Dra. In addition we consider lifetimes and space densities of single stars and other types of binaries.The only origin possible is that the RS CVn binaries are in a thermal phase following fission of a main-sequence single star. In this explanation the single star had a rapidly rotating core which became unstable due to the core contraction which made it begin to evolve off the main sequence. The present Be stars might be examples of such parent single stars.

scholarly journals The Delta Scuti Star GX Pegasi: A Theoretical Investigation of its Power Spectrum

1993 ◽  
Vol 134 ◽  
pp. 181-183
Author(s):  
E. Michel ◽  
M. J. Goupil ◽  
Y. Lebreton ◽  
A. Baglin
Keyword(s):  
Power Spectrum ◽  
Theoretical Investigation ◽  
Main Sequence ◽  
Main Sequence Star ◽  
Mode Identification ◽  
Star Models ◽  
Convective Core ◽  
Scuti Star ◽  
Delta Scuti Star ◽  
Delta Scuti

Target of a STEPHI multisite campaign, the Delta Scuti star GX Pegasi has been found to oscillate with at least five simultaneous, close frequencies (table I).Mode identification together with informations about the star that such an identification can provide are outlined below (see also Michel et al, 1992b).The mode identification is carried out by means of a comparison between the observed frequencies and the adiabatic frequencies of models appropriate to this star. Models that match GX Peg’s position in a Hertzsprung-Russell diagram have masses in the range 1.9 – M⊙. When included, convective core overshoot is handled as in Maeder and Meynet (1989). According to these models, GX Peg is a rather evolved, main sequence star.

scholarly journals On the Gaia DR2 distances for Galactic luminous blue variables

2019 ◽  
Vol 488 (2) ◽  
pp. 1760-1778 ◽  
Author(s):  
Nathan Smith ◽  
Mojgan Aghakhanloo ◽  
Jeremiah W Murphy ◽  
Maria R Drout ◽  
Keivan G Stassun ◽  
...  
Keyword(s):  
Main Sequence ◽  
Mass Range ◽  
Instability Strip ◽  
Single Star ◽  
Circumstellar Material ◽  
Luminous Blue Variables ◽  
Binary Evolution ◽  
Lower Luminosity ◽  
Gaia Dr2 ◽  
Wide Swath

ABSTRACT We examine parallaxes and distances for Galactic luminous blue variables (LBVs) in the Gaia second data release (DR2). The sample includes 11 LBVs and 14 LBV candidates. For about half of the sample, DR2 distances are either similar to commonly adopted literature values, or the DR2 values have large uncertainties. For the rest, reliable DR2 distances differ significantly from values in the literature, and in most cases the Gaia DR2 distance is smaller. Two key results are that the S Doradus instability strip may not be as clearly defined as previously thought, and that there exists a population of LBVs at relatively low luminosities. LBVs seem to occupy a wide swath from the end of the main sequence at the blue edge to ∼8000 K at the red side, with a spread in luminosity reaching as low as log(L/L⊙) ≈ 4.5. The lower-luminosity group corresponds to effective single-star initial masses of 10–25 M⊙, and includes objects that have been considered as confirmed LBVs. We discuss implications for LBVs including (1) their instability and origin in binary evolution, (2) connections to some supernova (SN) impostors such as the class of SN 2008S-like objects, and (3) LBVs that may be progenitors of SNe with dense circumstellar material across a wide initial mass range. Although some of the Gaia DR2 distances for LBVs have large uncertainty, this represents the most direct and consistent set of Galactic LBV distance estimates available in the literature.

Blended Visual Binaries as Tests of Low Amplitude Orbit Detection and Determination Capability in Long-Focus Photographic Astrometry

1983 ◽  
Vol 62 ◽  
pp. 45-51
Author(s):  
Sarah Lee Lippincott ◽  
John L. Hershey
Keyword(s):  
Main Sequence ◽  
Orbital Motion ◽  
Orbital Elements ◽  
Detection Capability ◽  
Single Star ◽  
Planetary Mass ◽  
Residual Series ◽  
Nearby Stars ◽  
Low Amplitude ◽  
Visual Binaries

AbstractPhotocentric orbital motions from 60-year Sproul plate series are shown for three visual binaries, ζ Her, 85 Peg and Ho 296. Mass ratios of the first two pairs, which have large-amplitude blended orbits, carry internal errors at the level of one percent. Orbital elements computed independently from the blended photographic observations agree closely with the well-determined visual orbits. Ho 296 serves as a test of the Sproul plate series to detect a 20-year orbit with an amplitude of two, or one, micron. Simulations of orbital motion in single star residual series confirm this detection capability, which corresponds to planetary mass for dark objects around nearby stars. A mass-luminosity diagram of the lower main sequence is shown, including one for invisible astrometric companions.

scholarly journals TESS observations of pulsating subdwarf B stars: extraordinarily short-period gravity modes in CD−28° 1974

2020 ◽  
Vol 493 (4) ◽  
pp. 5162-5169 ◽  
Author(s):  
M D Reed ◽  
K A Shoaf ◽  
P Németh ◽  
J Vos ◽  
M Uzundag ◽  
...  
Keyword(s):  
Main Sequence ◽  
Orbital Motion ◽  
Proper Motions ◽  
Reflection Effect ◽  
Echelle Spectrograph ◽  
Single Star ◽  
B Stars ◽  
Subdwarf B Stars ◽  
Short Period ◽  
Typical Period

ABSTRACT Transiting Exoplanet Survey Satellite (TESS) observations show CD−28° 1974 to be a gravity(g)-mode-dominated hybrid pulsating subdwarf B (sdBV) star. It shows 13 secure periods that form an ℓ = 1 asymptotic sequence near the typical period spacing. Extraordinarily, these periods lie between 1500 and 3300 s, whereas typical $\ell = 1\, g$ modes in sdBV stars occur between 3300 and 10 000 s. This indicates a structure somewhat different from typical sdBV stars. CD−28° 1974 has a visually close F/G main-sequence companion 1.33 arcsec away, which may be a physical companion. Gaia proper motions indicate a comoving pair with the same distance. A reanalysis of Ultraviolet and Visual Echelle Spectrograph (UVES) spectra failed to detect any orbital motion and the light curve shows no reflection effect or ellipsoidal variability, making an unseen close companion unlikely. The implication is that CD−28° 1974 has become a hot subdwarf via single star or post-merger evolution.

Sign in / Sign up

Export Citation Format

Share Document