ABSTRACT
V752 Cen is a triple-lined spectroscopic contact binary. Its multicolour light curves were obtained in the years 1971 and 2018, independently. Photometric analyses reveal that the two sets ...of light curves produce almost consistent results. It contains a W-subtype totally eclipsing binary, and its mass ratio and fill-out factor are q = 3.35(1) and $f = 29(2)\, {{\rm per\, cent}}$. The absolute elements of its two-component stars were determined to be M1 = 0.39(2) M⊙, M2 = 1.31(7) M⊙, R1 = 0.77(1) R⊙, R2 = 1.30(2) R⊙, L1 = 0.75(3) L⊙, and L2 = 2.00(7) L⊙. The period of V752 Cen is 0.37023198 d. The 0.37-d period remained constant from its first measurement in 1971 until the year 2000. However, it changed suddenly around the year 2000 and has been increasing continuously at a rate of dP/dt = +5.05 × 10−7 d yr−1 since then, which can be explained by mass transfer from the less massive component star to the more massive one with a rate of $\frac{\mathrm{ d}M_{2}}{\mathrm{ d}t}=2.52\times {10^{-7}}\,\mathrm{ M}_\odot\,{\rm yr}^{-1}$. The period variation of V752 Cen over the 48 yr in which the period has been monitored is really unusual, and is potentially related to effects from the possible presence of a nearby third star or of a pair of stars in a second binary.
Abstract
We present a timing study of the short-period eclipsing cataclysmic variable (CV) HT Cas. Based on new eclipse times derived from our photometric monitoring and archival optical data, ...combined with historical timings, spanning ∼42 yr, we detect a secular decrease in the orbital period at a rate of
P
̇
=
−
1.32
×
10
−
12
ss
−
1
and a cyclic period wiggle with an amplitude of 79.3 s and a period of 30.28 yr. We find that neither gravitational radiation nor magnetic braking can explain the observed decrease rate, suggesting the presence of additional angular momentum loss (AML). The empirical consequential AML (eCAML) model developed by Schreiber et al. can well match the observed orbital decay in HT Cas, and the physical mechanism for eCAML is most likely attributable to the frictional AML following nova eruptions. As for the cyclic variation, the best explanation is the influence of an unseen companion in orbit around the binary. The derived orbital parameters reveal that the hypothetical third body could be a giant planet with mass of
M
3
≃ 14
M
Jup
that is moving on a highly eccentric orbit (
e
= 0.82). Taken together the results of the present study suggest that HT Cas is a unique triple system containing a high-eccentricity giant planet and it has the potential to become an ideal laboratory in which to test models of CV evolution.
Abstract
V606 Centauri (V606 Cen) is an early B-type close binary with an orbital period of 1.4950935 days, and its complete light curves are very difficult to observe on the ground. By analyzing the ...continuous light curve obtained by TESS, we found that it is a marginal contact binary with a very low fill-out factor of about 2%. The
O
−
C
diagram of V606 Cen is constructed for the first time based on 118.8 yr of eclipse times. The
O
−
C
diagram has been found to show a downward parabolic change together with a cyclic oscillation with a semiamplitude of 0.0545 days and a period of 88.3 yr. The downward parabolic variation reveals a linear period decrease at a rate of
dP
/
dt
= −2.08 × 10
−7
days yr
−1
that can be explained by the mass transfer from the more massive component to the less massive one. Both the marginal contact configuration and the continuous period decrease suggest that V606 Cen is a newly formed contact binary via Case A mass transfer. The cyclic change in the
O
−
C
diagram can be explained by the light-travel time effect via the presence of a third body. The lowest mass of the tertiary companion is determined to be
M
3
= 4.51 (±0.43)
M
⊙
and the tertiary is orbiting around the central eclipsing binary in a nearly circular orbit (
e
= 0.33). All of the results indicate that V606 Cen is a newly formed massive contact binary in a hierarchical triple system.
ABSTRACT
We homogeneously analyse ∼3.2 × 105 photometric measurements for ∼1100 transit light curves belonging to 17 exoplanet hosts. The photometric data cover 16 years (2004–2019) and include ...amateur and professional observations. Old archival light curves were reprocessed using up-to-date exoplanetary parameters and empirically debiased limb-darkening models. We also derive self-consistent transit and radial-velocity fits for 13 targets. We confirm the non-linear transit timing variation (TTV) trend in the WASP-12 data at a high significance, and with a consistent magnitude. However, Doppler data reveal hints of a radial acceleration of about −7.5 ± 2.2 m s−1 yr−1, indicating the presence of unseen distant companions, and suggesting that roughly 10 per cent of the observed TTV was induced via the light-travel (or Roemer) effect. For WASP-4, a similar TTV trend suspected after the recent TESS observations appears controversial and model dependent. It is not supported by our homogeneous TTV sample, including 10 ground-based EXPANSION light curves obtained in 2018 simultaneously with TESS. Even if the TTV trend itself does exist in WASP-4, its magnitude and tidal nature are uncertain. Doppler data cannot entirely rule out the Roemer effect induced by possible distant companions.
ABSTRACT V2051 Oph is a deeply eclipsing dwarf nova with an orbital period below the period gap of cataclysmic variables (CVs). It has been photometrically monitored since 2008 June and 24 ...mid-eclipse times of the white dwarf have been obtained. The changes in the orbital period are investigated using all of the available mid-eclipse times. A continuous period decrease with a rate of was discovered to be superimposed on a periodic variation with a small amplitude of 0 000329 and a period of 21.64 years. The standard theory predicted that the evolution of CVs below the period gap is driven by gravitational radiation. However, angular momentum loss (AML) via gravitational radiation is insufficient to explain this decrease, and additional AML via magnetic braking that is about five times the gravitational radiation rate is required. This is consistent with the theoretical requirement indicating that magnetic braking of the fully convective star is not completely stopped. The cyclic oscillation was interpreted as the variation of the arriving eclipse time via the presence of a third body because the required energy for the Applegate mechanism is much larger than that radiated from the secondary in 10 years. Its mass is derived as Jupiter mass. For orbital inclinations it would be a planetary object. The giant circumbinary planet is orbiting around V2051 Oph at an orbital separation of about 9.0 astronomical units (AU) in an eccentric orbit (e′ = 0.37). These conclusions support the ideas that some planets could survive stellar late evolution and that dwarf novae are also planetary hosting stars.
Initially on an elliptical orbit, C/2021 A1 experimented significant changes in its orbital configuration due to planetary perturbations upon entering the planetary region. Images of the comet C/2021 ...A1 (Leonard) obtained in March 2022 allow to estimate that its disintegration occurred in December 2021. The aim of this paper is to analyze the comet’s dust behavior during the period when its disintegration is presumed to have commenced, so a series of images of this comet on the broadband B, V, and R filters were taken on December 21 and 23, 2021 with the 0.6 m Helen Sawyer Hogg (HSH) telescope at the Complejo Astronómico El Leoncito (CASLEO) to do a morphological, photometric, and numerical analysis of this comet. Analysis of the magnitudes and dust production rate suggests a significant increase in activity on December 21 compared to two days later, indicating a potential outburst. Digital filters were applied to enhance contrast in the cometary images, revealing two active regions on opposite sides of the nucleus. Additionally, the A(0°)fρ parameter was obtained for this comet. Finally, to gain deeper insights into Leonard’s dust behavior, observations were fitted to a newly developed theoretical model for studying dust comas. Combined with photometric data and gas production information from the literature, the analysis suggests that the comet’s activity on December 21, 2021, may mark the beginning of its disintegration.
•Comet C/2021 A1 (Leonard) dust behavior study.•Images taken on December 21 and 23, 2021 with HSH telescope at CASLEO.•Morphological, photometric, and numerical analysis.•Leonard’s dust activity on 2021/12/21, may mark the beginning of its disintegration.
Context.
The TeV BL Lac object
PG 1553+113
is one of the primary candidates for a binary supermassive black hole system.
Aims.
We study the flux and spectral variability of
PG 1553+113
on intra-night ...to long-term timescales using (i)
BVRI
data collected over 76 nights from January 2016 to August 2019 involving nine optical telescopes and (ii) historical
VR
data (including ours) obtained for the period from 2005 to 2019.
Methods.
We analysed the light curves using various statistical tests, fitting and cross-correlation techniques, and methods for the search for periodicity. We examined the colour-magnitude diagrams before and after the corresponding light curves were corrected for the long-term variations.
Results.
Our intra-night monitoring, supplemented with literature data, result in a low duty cycle of ∼(10–18)%. In April 2019, we recorded a flare, which marks the brightest state of
PG 1553+113
for the period from 2005 to 2019:
R
≃ 13.2 mag. This flare is found to show a clockwise spectral hysteresis loop on its
VR
colour-magnitude diagram and a time lag in the sense that the
V
-band variations lead the
R
-band ones. We obtain estimates of the radius, the magnetic field strength, and the electron energy that characterize the emission region related to the flare. We find a median period of (2.21 ± 0.04) years using the historical light curves. In addition, we detect a secondary period of about 210 days using the historical light curves corrected for the long-term variations. We briefly discuss the possible origin of this period.
Context. The ESO public survey VISTA variables in the Vía Láctea (VVV) started in 2010. VVV targets 562 sq. deg in the Galactic bulge and an adjacent plane region and is expected to run for about ...five years. Aims. We describe the progress of the survey observations in the first observing season, the observing strategy, and quality of the data obtained. Methods. The observations are carried out on the 4-m VISTA telescope in the ZYJHKs filters. In addition to the multi-band imaging the variability monitoring campaign in the Ks filter has started. Data reduction is carried out using the pipeline at the Cambridge Astronomical Survey Unit. The photometric and astrometric calibration is performed via the numerous 2MASS sources observed in each pointing. Results. The first data release contains the aperture photometry and astrometric catalogues for 348 individual pointings in the ZYJHKs filters taken in the 2010 observing season. The typical image quality is ~ \hbox{$0\farcs9{-}1\farcs0$} 0 . ″ 9 − 1 . ″ 0 . The stringent photometric and image quality requirements of the survey are satisfied in 100% of the JHKs images in the disk area and 90% of the JHKs images in the bulge area. The completeness in the Z and Y images is 84% in the disk, and 40% in the bulge. The first season catalogues contain 1.28 × 108 stellar sources in the bulge and 1.68 × 108 in the disk area detected in at least one of the photometric bands. The combined, multi-band catalogues contain more than 1.63 × 108 stellar sources. About 10% of these are double detections because of overlapping adjacent pointings. These overlapping multiple detections are used to characterise the quality of the data. The images in the JHKs bands extend typically ~4 mag deeper than 2MASS. The magnitude limit and photometric quality depend strongly on crowding in the inner Galactic regions. The astrometry for Ks = 15−18 mag has rms ~35−175 mas. Conclusions. The VVV Survey data products offer a unique dataset to map the stellar populations in the Galactic bulge and the adjacent plane and provide an exciting new tool for the study of the structure, content, and star-formation history of our Galaxy, as well as for investigations of the newly discovered star clusters, star-forming regions in the disk, high proper motion stars, asteroids, planetary nebulae, and other interesting objects.
We present a new set of radial velocity measurements of the spectroscopic binary HD 165052 obtained by disentangling high-resolution optical spectra. The longitude of the periastron (ϖ = 60 ± 2°) ...shows a variation with respect to previous studies. We have determined the apsidal motion rate of the system,
yr−1, which was used to calculate the absolute masses of the binary components: M
1 = 22.5 ± 1.0 M and M
2 = 20.5 ± 0.9 M. Analysing the separated spectra, we have reclassified the components as O7Vz and O7.5Vz stars.
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