Study for Variable Stars in King 18 Hojaev, Alisher; Karimov, Rivkat
Bulletin de la Société royale des sciences de Liège,
06/2024, Letnik:
93
Journal Article
Recenzirano
Odprti dostop
The preliminary results of searching and study for variable stars using TESS photometry in the intermediate age open star cluster King 18 are presented. We have investigated the light curves and ...frequency spectra of different types of variable stars located in the open cluster area. The results obtained together with prospects of study of this open cluster are briefly discussed.
Abstract
We report seven newly identified high-amplitude
δ
Scuti (HADS) stars. Among them, two stars (TIC 30977864 and TIC 387379145) exhibit pure radial pulsation without the excitation of ...non-radial modes. TIC 30977864 is classified as a double-mode HADS star, while the other four stars potentially show triple-mode HADS behavior. TIC 112682462 and TIC 255603395 closely resemble RR Lyrae stars based on their light curves, position in the period–luminosity diagram, and the period ratio diagram. However, without spectral observations, it is challenging to ascertain whether these two stars are HADS or RR Lyrae stars. TIC 281695001 exhibits a fundamental frequency amplitude smaller than that of the first overtone, suggesting the presence of intriguing phenomena that necessitate further analysis. We analyzed the relationship between metallicity and period using data provided by Netzel & Smolec. The metallicities of the 176 stars display a broad distribution ranging from −2.0 dex to 0.5 dex, with periods spanning 0.05 to 0.20 days. This random distribution of metallicities may contribute to the dispersion observed in the P1/P0 ratio. To derive more accurate conclusions, future spectroscopic observations of a larger sample of HADS stars are crucial. These observations will provide precise rotational velocities and more accurate determinations of metallicities.
Abstract
The Stellar Abundances and Galactic Evolution Survey (SAGES) of the northern sky is a specifically designed multiband photometric survey aiming to provide reliable stellar parameters with ...accuracy comparable to those from low-resolution optical spectra. It was carried out with the 2.3 m Bok telescope of Steward Observatory and three other telescopes. The observations in the
u
s
and
v
s
passband produced over 36,092 frames of images in total, covering a sky area of ∼9960 deg
2
. The median survey completenesses of all observing fields for the two bands are
u
s
= 20.4 mag and
v
s
= 20.3 mag, respectively, while the limiting magnitudes with signal-to-noise ratio of 100 are
u
s
∼ 17 mag and
v
s
∼ 18 mag, correspondingly. We combined our catalog with the data release 1 (DR1) of the first Panoramic Survey Telescope And Rapid Response System (Pan-STARRS, PS1) catalog, and obtained a total of 48,553,987 sources that have at least one photometric measurement in each of the SAGES
u
s
and
v
s
and PS1
grizy
passbands. This is the DR1 of SAGES, released in this paper. We compared our
gri
point-source photometry with those of PS1 and found an rms scatter of ∼2% difference between PS1 and SAGES for the same band. We estimated an internal photometric precision of SAGES to be of the order of ∼1%. Astrometric precision is better than 0.″2 based on comparison with DR1 of the Gaia mission. In this paper, we also describe the final end-user database, and provide some science applications.
Abstract
In this paper, we study the pulsation properties of KIC 3440495 using Kepler and TESS data. A Fourier analysis of the light curve reveals 24 pulsation modes as well as 29 frequencies ...associated with rotation. The rotation frequency is derived to be
f
rot
= 2.322909(2) day
−1
, and the rotational modulation is determined to be caused by starspots. A large frequency separation of Δ
ν
= 54.5
μ
Hz is found by using a Fourier transform, the autocorrelation function, a histogram of frequency differences, and an échelle diagram. We use the large separation to estimate the refined stellar parameters of the star to be
v
= 239, 279 km s
−1
,
M
= 1.5, 1.65
M
⊙
,
R
equator
= 2.03, 2.30
R
⊙
,
R
polar
= 1.72, 1.78
R
⊙
, and
ω
= 0.61, 0.77. The phase modulations of the pulsating frequencies show a long-term trend which may be attributed to an orbital effect of a binary system; hence, the star may be a fast rotating pulsator in a binary system. KIC 3440495 has an amplitude spectrum similar to Altair, and is identified as a potential sister of Altair. Based on studies of Altair, KIC 3330495 is presumably a young star at a similar evolutionary stage.
IC 1848 is one of the young open clusters in the giant star-forming Cas OB6 association. Several interesting aspects relating to star formation processes in giant star-forming regions attracted us to ...study the initial mass function (IMF), star formation mode and properties of pre-main-sequence (PMS) stars. A UBVI and Hα photometric study of the young open cluster IC 1848 was conducted as part of the ‘Sejong Open Cluster Survey’. We have selected 105 early-type members from photometric diagrams. Their mean reddening is 〈E(B − V)〉 = 0.660 ± 0.054 mag. Using the published photometric data with near- and mid-infrared archival data we confirmed the normal reddening law (R
V
= 3.1) towards the cluster (IC 1848). A careful zero-age main-sequence fitting gives a distance modulus of V
0 − M
V
= 11.7 ± 0.2 mag, equivalent to 2.2 ± 0.2 kpc. Hα photometry and the list of young stellar objects identified by Koenig et al. permitted us to select a large number of PMS stars comprising 196 Hα emission stars, 35 Hα emission candidates, 5 Class I, 368 Class II and 24 transition disc candidates. From the Hertzsprung–Russell diagram using stellar evolution models, we estimate an age of 5 Myr from several evolved stars and 3 Myr from the PMS stars. The IMF was derived from stars with mass larger than 3 M⊙, and the slope is slightly steeper (Γ = −1.6 ± 0.2) than the Salpeter/Kroupa IMF. Finally, we estimated the mass accretion rate of PMS stars with an ultraviolet excess. The mean mass accretion rate is about 1.4 × 10−8 M⊙ yr−1 in the mass range of 0.5–2 M⊙, whereas intermediate-mass stars (≥2.5 M⊙) exhibit a much higher accretion rate of
$\dot{M} > 10^{-6} \,\mathrm{M}_{\odot } \, \mathrm{yr}^{-1}$
.
Main belt asteroids (6070) Rheinland and (54827) 2001 NQ8 belong to a small population of couples of bodies that reside in very similar heliocentric orbits. Vokrouhlicky & Nesvorny promoted the term ...'asteroid pairs,' pointing out their common origin within the past tens to hundreds of kyr. Previous attempts to reconstruct the initial configuration of Rheinland and 2001 NQ8 at the time of their separation have led to the prediction that Rheinland's rotation should be retrograde. Here, we report extensive photometric observations of this asteroid and use the light curve inversion technique to directly determine its rotation state and shape. We confirm the retrograde sense of rotation of Rheinland, with obliquity value constrained to be >=140?. The ecliptic longitude of the pole position is not well constrained as yet. The asymmetric behavior of Rheinland's light curve reflects a sharp, near-planar edge in our convex shape representation of this asteroid. Our calibrated observations in the red filter also allow us to determine HR = 13.68 ? 0.05 and G = 0.31 ? 0.05 values of the H-G system. With the characteristic color index V -- R = 0.49 ? 0.05 for S-type asteroids, we thus obtain H = 14.17 ? 0.07 for the absolute magnitude of (6070) Rheinland. This is a significantly larger value than previously obtained from analysis of astrometric survey observations. We next use the obliquity constraint for Rheinland to eliminate some degree of uncertainty in the past propagation of its orbit. This is because the sign of the past secular change of its semimajor axis due to the Yarkovsky effect is now constrained. The determination of the rotation state of the secondary component, asteroid (54827) 2001 NQ8, is the key element in further constraining the age of the pair and its formation process.
The Stellar Abundances and Galactic Evolution Survey (SAGES) of the northern sky is a specifically-designed multi-band photometric survey aiming to provide reliable stellar parameters with accuracy ...comparable to those from low-resolution optical spectra. It was carried out with the 2.3-m Bok telescope of Steward Observatory and three other telescopes. The observations in the \(u_s\) and \(v_s\) passband produced over 36,092 frames of images in total, covering a sky area of \(\sim9960\) degree\(^2\). The median survey completeness of all observing fields for the two bands are of \(u_{\rm s}=20.4\) mag and \(v_s=20.3\) mag, respectively, while the limiting magnitudes with signal-to-noise ratio (S/N) of 100 are \(u_s\sim17\) mag and \(v_s\sim18\) mag, correspondingly. We combined our catalog with the data release 1 (DR1) of the first of Panoramic Survey Telescope And Rapid Response System (Pan-STARRS1, PS1) catalog, and obtained a total of 48,553,987 sources which have at least one photometric measurement in each of the SAGES \(u_s\) and \(v_s\) and PS1 \(grizy\) passbands, which is the DR1 of SAGES and it will be released in our paper. We compare our \(gri\) point-source photometry with those of PS1 and found an RMS scatter of \(\sim2\)% in difference of PS1 and SAGES for the same band. We estimated an internal photometric precision of SAGES to be on the order of \(\sim1\)%. Astrometric precision is better than \(0^{\prime\prime}.2\) based on comparison with the DR1 of Gaia mission. In this paper, we also describe the final end-user database, and provide some science applications.
IC 1848 is one of the young open clusters in the giant star forming Cas OB6 association. Several interesting aspects relating to star formation processes in giant star forming regions attracted us to ...study the initial mass function (IMF), star formation mode, and properties of pre-main sequence stars (PMS). A UBVI and H alpha photometric study of the young open cluster IC 1848 was conducted as part of the "Sejong Open cluster Survey" (SOS). We have selected 105 early-type members from photometric diagrams. Their mean reddening is <E(B-V)> = 0.660 +/- 0.054 mag. Using the published photometric data with near- and mid-infrared archival data we confirmed the normal reddening law (R_V = 3.1) toward the cluster (IC 1848). A careful zero-age main sequence fitting gives a distance modulus of V_0 - M_V = 11.7 +/- 0.2 mag, equivalent to 2.2 +/- 0.2 kpc. H alpha photometry and the list of young stellar objects identified by Koenig et al. permitted us to select a large number of PMS stars comprising 196 H alpha emission stars, 35 H alpha emission candidates, 5 Class I, 368 Class II, and 24 transition disk candidates. From the Hertzsprung-Russell diagram using stellar evolution models, we estimate an age of 5 Myr from several evolved stars and 3 Myr from the PMS stars. The IMF was derived from stars with mass larger than 3 M_sun, and the slope is slightly steeper (Gamma = -1.6 +/- 0.2) than the Salpeter/Kroupa IMF. Finally, we estimated the mass accretion rate of PMS stars with a UV excess. The mean mass accretion rate is about 1.4 x 10^-8 M_sun yr^-1 in the mass range of 0.5 M_sun to 2 M_sun, whereas intermediate-mass stars (>= 2.5 M_sun) exhibit a much higher accretion rate of dM/dt > 10^-6 M_sun yr^-1.
Main belt asteroids (6070) Rheinland and (54827) 2001NQ8 belong to a small population of couples of bodies which reside on very similar heliocentric orbits. Vokrouhlicky & Nesvorny (2008, AJ 136, ...280) promoted a term "asteroid pairs", pointing out their common origin within the past tens to hundreds of ky. Previous attempts to reconstruct the initial configuration of Rheinland and 2001NQ8 at the time of their separation have led to the prediction that Rheinland's rotation should be retrograde. Here we report extensive photometric observations of this asteroid and use the lightcurve inversion technique to directly determine its rotation state and shape. We confirm the retrograde sense of rotation of Rheinland, with obliquity value constrained to be >= 140 deg. The ecliptic longitude of the pole position is not well constrained as yet. The asymmetric behavior of Rheinland's lightcurve reflects a sharp, near-planar edge in our convex shape representation of this asteroid. Our calibrated observations in the red filter also allow us to determine \(H_R = 13.68\pm 0.05\) and \(G = 0.31\pm 0.05\) values of the H-G system. With the characteristic color index \(V-R = 0.49\pm 0.05\) for the S-type asteroids, we thus obtain \(H = 14.17\pm 0.07\) for the absolute magnitude of (6070) Rheinland. This a significantly larger value than previously obtained from analysis of the astrometric survey observations. We next use the obliquity constraint for Rheinland to eliminate some degree of uncertainty in the past propagation of its orbit. This is because the sign of the past secular change of its semimajor axis due to the Yarkovsky effect is now constrained. Determination of the rotation state of the secondary component, asteroid (54827) 2001NQ8, is the key element in further constraining the age of the pair and its formation process.
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