New photoelectric observations of the interacting binary V367 Cyg were made during two consecutive seasons, 1996 and 1997, using the two-channel photometer at Mt. Suhora Observatory. The BVRI light ...curves are analyzed and system parameters are derived for two alternative models: with and without an accretion disk. A contact configuration is obtained for the no-disk model. The semidetached model, with a disk around the invisible component gives a better fit and, in addition, explains most of the observed features of V367 Cyg. The disk in V367 Cyg has a radius of about $R_{\rm d}=23 R_{\odot}$, almost completely filling the secondary component's Roche lobe. Mass is transferred from the less massive ($3.3 M_{\odot}$) to the more massive ($4.0 M_{\odot}$) star at a high rate of 5-7 10-5} M_{\odot/yr.
Context. The physical characterization of trans-Neptunian objects is essential for improving our understanding of the formation and evolution of our Solar System. Stellar occultation is a ...ground-based technique that can be successfully used to determine some of the TNOs' fundamental physical properties with high precision, such as size and shape. Aims: This work is aimed at constraining the size, shape, and geometric albedo of the dwarf planet candidate (307261) 2002 MS4 through the analysis of nine stellar occultation events. Using multichord detection, we also study the object's topography by analyzing the obtained limb and residuals between the observed chords and the best-fit ellipse. Metods. We predicted and organized the observational campaigns of nine stellar occultations by 2002 MS4 between 2019 and 2022, resulting in two single-chord events, four double-chord detections, and three events with between 3 and 61 positive chords. We derived the occultation light curves using differential aperture photometry, from which the star ingress and egress instants were calculated. Using 13 selected chords from the 8 August 2020 event, we determined the global elliptical limb of 2002 MS4. The best-fit ellipse, combined with the object's rotational information from the literature, sets constraints on the object's size, shape, and albedo. Additionally, we developed a new method to characterize the topography features on the object's limb. Results: The global limb has a semi-major axis of a′ = 412 ± 10 km, a semi-minor axis of b′= 385 ± 17 km, and the position angle of the minor axis is 121° ± 16°. From this instantaneous limb, we obtained 2002 MS4's geometric albedo of pV = 0.1 ± 0.025, using HV = 3.63 ± 0.05 mag and a projected area-equivalent diameter of 796 ± 24 km. Significant deviations from the fitted ellipse in the northernmost limb were detected from multiple sites, highlighting three distinct topographic features: one 11 km depth depression, followed by a 25−5+4 km height elevation next to a crater-like depression, with an extension of 322 ± 39 km and 45.1 ± 1.5 km deep. Conclusions: Our results indicate the presence of an object that is ≈138 km smaller in diameter than that derived from thermal data, possibly indicating the presence of a thus-far unknown satellite. However, within the error bars, the geometric albedo in the V-band is in agreement with the results published in the literature, even with the radiometric-derived albedo. This stellar occultation has allowed for the first multichord measurement of a large topography in a TNO. Tables B.1-B.5 are available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/678/A167
We present the results of extensive time-series photometry of the pulsating subdwarf B star KPD 2109 + 4401. Our data set consists of 29 data runs with a total length of 182.6 h over 31 d, collected ...at five observatories in 2004. These data comprised high signal-to-noise ratio observations acquired with larger telescopes and wider time-coverage observations obtained with smaller telescopes. They are sufficient to resolve the pulsation structure to 0.4 μHz and are the most extensive data set for this star to date. With these data, we identify eight pulsation frequencies extending from 4701 to 5481 μHz, corresponding to periods of 182–213 s. The pulsation frequencies and their amplitudes are examined over several time-scales with some frequencies showing amplitude variability.
Context.
The physical characterization of trans-Neptunian objects is essential for improving our understanding of the formation and evolution of our Solar System. Stellar occultation is a ...ground-based technique that can be successfully used to determine some of the TNOs’ fundamental physical properties with high precision, such as size and shape.
Aims.
This work is aimed at constraining the size, shape, and geometric albedo of the dwarf planet candidate (307261) 2002 MS
4
through the analysis of nine stellar occultation events. Using multichord detection, we also study the object’s topography by analyzing the obtained limb and residuals between the observed chords and the best-fit ellipse.
Metods.
We predicted and organized the observational campaigns of nine stellar occultations by 2002 MS
4
between 2019 and 2022, resulting in two single-chord events, four double-chord detections, and three events with between 3 and 61 positive chords. We derived the occultation light curves using differential aperture photometry, from which the star ingress and egress instants were calculated. Using 13 selected chords from the 8 August 2020 event, we determined the global elliptical limb of 2002 MS
4
. The best-fit ellipse, combined with the object’s rotational information from the literature, sets constraints on the object’s size, shape, and albedo. Additionally, we developed a new method to characterize the topography features on the object’s limb.
Results.
The global limb has a semi-major axis of
a
′ = 412 ± 10 km, a semi-minor axis of
b
′= 385 ± 17 km, and the position angle of the minor axis is 121° ± 16°. From this instantaneous limb, we obtained 2002 MS
4
’s geometric albedo of
p
V
= 0.1 ± 0.025, using
H
V
= 3.63 ± 0.05 mag and a projected area-equivalent diameter of 796 ± 24 km. Significant deviations from the fitted ellipse in the northernmost limb were detected from multiple sites, highlighting three distinct topographic features: one 11 km depth depression, followed by a 25
−5
+4
km height elevation next to a crater-like depression, with an extension of 322 ± 39 km and 45.1 ± 1.5 km deep.
Conclusions.
Our results indicate the presence of an object that is ≈138 km smaller in diameter than that derived from thermal data, possibly indicating the presence of a thus-far unknown satellite. However, within the error bars, the geometric albedo in the V-band is in agreement with the results published in the literature, even with the radiometric-derived albedo. This stellar occultation has allowed for the first multichord measurement of a large topography in a TNO.
O-C Analysis of Selected 3-Body Systems Ogłoza, W.; Kreiner, J. M.; Stachowski, G. ...
Proceedings of the International Astronomical Union,
07/2011, Letnik:
7, Številka:
S282
Journal Article
Recenzirano
Odprti dostop
This paper presents the results of the analysis of (O-C) diagrams of four eclipsing variables. The diagrams are based on times of minima collected in the Cracow database, which contains times of ...minima found in the literature, from observations at Mt. Suhora and Ulupinar Observatories, or determined using publicly-available photometric surveys (NSVS, ASAS etc).
PG 0014+067 is one of the most promising pulsating subdwarf B stars for seismic analysis, as it has a rich pulsation spectrum. The richness of its pulsations, however, poses a fundamental challenge ...to understanding the pulsations of these stars, as the mode density is too complex to be explained only with radial and nonradial low-degree (l < 3) p-modes without rotational splittings. One proposed solution, suggested by Brassard et al. in 2001 for the case of PG 0014+067 in particular, assigns some modes with high degree (l= 3). On the other hand, theoretical models of sdB stars suggest that they may retain rapidly rotating cores, and so the high mode density may result from the presence of a few rotationally split triplet (l = 1) and quintuplet (l = 2) modes, along with radial (l = 0) p-modes. To examine alternative theoretical models for these stars, we need better frequency resolution and denser longitude coverage. Therefore, we observed this star with the Whole Earth Telescope for two weeks in 2004 October. In this paper we report the results of Whole Earth Telescope observations of the pulsating subdwarf B star PG 0014+067. We find that the frequencies seen in PG 0014+067 do not appear to fit any theoretical model currently available; however, we find a simple empirical relation that is able to match all of the well-determined frequencies in this star.
We present results from an observational campaign on the close binary system 2MASS J16211735+4412541 and a preliminary model based on the photometric data gathered during the quiescent and outburst ...levels. The modeling, done with the Wilson-Devinney code and its improvements, failed to reproduce the observational properties of the system. A secondary minimum obtained within the stellar model that is too shallow, as well as the evidence provided by the spectroscopic observations performed at outburst and quiescence, point toward an accretion disk surrounding one component, likely a white dwarf, as the cause of the outburst. Using a simple disk model, we modeled the observed multicolor light curves taken two (2016 August) and eight (2017 March) months after the outburst. We obtained a reasonable fit to the 2016 August light curves but those from 2017 March cannot be explained with the same parameters. We conclude that J1621 is an eclipsing cataclysmic binary, with an accretion disk still present almost a year after outburst, and not a contact-type system as previously classified. The binary is seen at an inclination of about 84° and there is evidence of changing accretion rates and disk parameters as a result of the outburst. Our results indicate that more cataclysmic variables may be hidden among contact binaries.
Context. Stellar occultations have become one of the best techniques to gather information about the physical properties of trans-Neptunian objects (TNOs), which are critical objects for ...understanding the origin and evolution of our Solar System. Aims: The purpose of this work is to determine, with better accuracy, the physical characteristics of the TNO (84922) 2003 VS2 through the analysis of the multichord stellar occultation on 2019 October 22 and photometric data collected afterward. Methods: We predicted, observed, and analyzed the multichord stellar occultation of the Second Gaia Data Release (Gaia DR2) source 3449076721168026624 (mυ = 14.1 mag) by the plutino object 2003 VS2 on 2019 October 22. We performed aperture photometry on the images collected and derived the times when the star disappeared and reappeared from the observing sites that reported a positive detection. We fit the extremities of such positive chords to an ellipse using a Monte Carlo method. We also carried out photometric observations to derive the rotational light curve amplitude and rotational phase of 2003 VS2 during the stellar occultation. Combining the results and assuming a triaxial shape, we derived the 3D shape of 2003 VS2. Results: Out of the 39 observatories involved in the observational campaign, 12 sites, located in Bulgaria (one), Romania (ten), and Serbia (one), reported a positive detection; this makes it one of the best observed stellar occultations by a TNO so far. Considering the rotational phase of 2003 VS2 during the stellar occultation and the rotational light curve amplitude derived (Am = 0.264 ± 0.017 mag), we obtained a mean area-equivalent diameter of DAeq = 545 ± 13 km and a geometric albedo of 0.134 ± 0.010. By combining the rotational light curve information with the stellar occultation results, we derived the best triaxial shape for 2003 VS2, which has semiaxes a = 339 ± 5 km, b = 235 ± 6 km, and c = 226 ± 8 km. The derived aspect angle of 2003 VS2 is θ = 59° ± 2° or its supplementary θ = 121° ± 2°, depending on the north-pole position of the TNO. The spherical-volume equivalent diameter is DVeq = 524 ± 7 km. If we consider large albedo patches on its surface, the semi-major axis of the ellipsoid could be ~ 10 km smaller. These results are compatible with the previous ones determined from the single-chord 2013 and four-chord 2014 stellar occultations and with the effective diameter and albedo derived from Herschel and Spitzer data. They provide evidence that 2003 VS2's 3D shape is not compatible with a homogeneous triaxial body in hydrostatic equilibrium, but it might be a differentiated body and/or might be sustaining some stress. No secondary features related to rings or material orbiting around 2003 VS2 were detected. The photometric data used to obtain the rotational light curve of (84922) 2003 VS2 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/663/A121
Context.
Stellar occultations have become one of the best techniques to gather information about the physical properties of trans-Neptunian objects (TNOs), which are critical objects for ...understanding the origin and evolution of our Solar System.
Aims.
The purpose of this work is to determine, with better accuracy, the physical characteristics of the TNO (84922) 2003 VS
2
through the analysis of the multichord stellar occultation on 2019 October 22 and photometric data collected afterward.
Methods.
We predicted, observed, and analyzed the multichord stellar occultation of the Second
Gaia
Data Release
(Gaia
DR2) source 3449076721168026624
(m
υ
= 14.1 mag) by the plutino object 2003 VS
2
on 2019 October 22. We performed aperture photometry on the images collected and derived the times when the star disappeared and reappeared from the observing sites that reported a positive detection. We fit the extremities of such positive chords to an ellipse using a Monte Carlo method. We also carried out photometric observations to derive the rotational light curve amplitude and rotational phase of 2003 VS2 during the stellar occultation. Combining the results and assuming a triaxial shape, we derived the 3D shape of 2003 VS2.
Results.
Out of the 39 observatories involved in the observational campaign, 12 sites, located in Bulgaria (one), Romania (ten), and Serbia (one), reported a positive detection; this makes it one of the best observed stellar occultations by a TNO so far. Considering the rotational phase of 2003 VS
2
during the stellar occultation and the rotational light curve amplitude derived (Am = 0.264 ± 0.017 mag), we obtained a mean area-equivalent diameter of
D
Aeq
= 545 ± 13 km and a geometric albedo of 0.134 ± 0.010. By combining the rotational light curve information with the stellar occultation results, we derived the best triaxial shape for 2003 VS2, which has semiaxes
a
= 339 ± 5 km,
b
= 235 ± 6 km, and
c
= 226 ± 8 km. The derived aspect angle of 2003 VS
2
is
θ
= 59
°
± 2
°
or its supplementary
θ
= 121
°
± 2
°
, depending on the north-pole position of the TNO. The spherical-volume equivalent diameter is
D
Veq
= 524 ± 7 km. If we consider large albedo patches on its surface, the semi-major axis of the ellipsoid could be ~ 10 km smaller. These results are compatible with the previous ones determined from the single-chord 2013 and four-chord 2014 stellar occultations and with the effective diameter and albedo derived from
Herschel
and
Spitzer
data. They provide evidence that 2003 VS
2
’s 3D shape is not compatible with a homogeneous triaxial body in hydrostatic equilibrium, but it might be a differentiated body and/or might be sustaining some stress. No secondary features related to rings or material orbiting around 2003 VS2 were detected.
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