arXiv subjects

Mark G. Blackford

Publications and source records attributed to Mark G. Blackford.

11 recordsLinked to original sources

arXiv2026

The Close Binary V486 Carinae

The hitherto neglected close binary V486 Car is studied with the aid of newly applied satellite photometry (HIPPARCOS and TESS), high dispersion spectrometry (HERCULES) and ground-based B and V photometry. While the sinusoidal light variations are suggestive of a near-contact system, the stars have only shallow eclipse, so highly confident parametrization becomes challenging. We find: $M_1 = 2.1 \pm 0.1$, $M_2 = 0.4 \pm 0.1$; $R_1 = 3.20 \pm 0.02$, $R_2 = 1.48 \pm 0.01$; (${\odot}$); $T_{e1} = 10000 \pm 500$, $T_{e2} = 6200 \pm 200$ (K); distance = 162 $\pm$ 12 (pc). New times of minima for V486 Car have been examined, including recent observations from TESS. The role of the relatively significant O'Connell effect is examined. As well as the conspicuous asymmetry from the main effect of about 0.036 mag (V), a jitter, with amplitude of about 0.005 V mag and quasi-period of order $\sim$ 10 d is noticed. There is a tendency for such photometric excursions at one maximum to precede those at the other. As well, the O -- C data indicate the presence of a low mass star $\sim$0.3 M$_{\odot}$ in an orbit separated by a few AU from the close binary. More accurate and plentiful spectroscopic data would be requisite for further investigations. A brief discussion reviews possible approaches to understanding the system in the context of near-contact binary scenarios.

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arXiv2026

BSN-VI: Multiband Light Curve Modeling of Four W UMa-Type Contact Binaries I. Revisiting Energy Transfer Mechanisms and Luminosity Behavior

We presented the first high-precision, detailed photometric analysis of four W Ursae Majoris (W UMa)-type contact binaries, Linear 10772300, Linear 11150338, Linear 20372537 and DM Cir. In addition to ground-based multiband photometric observations, data from the Transiting Exoplanet Survey Satellite (TESS) were employed for the analysis of the DM Cir system. New ephemeris and linear fit to the O-C diagrams were derived using extracted times of minima and additional literature. The light curve modeling was performed using the PHysics Of Eclipsing BinariEs (PHOEBE) Python code and the BSN application, employing a Markov Chain Monte Carlo approach. In each systems, the two stellar components exhibited minimal temperature differences ($ΔT<150$ K), confirming efficient energy exchange within their common convective envelopes. Absolute parameters were estimated using the Gaia Data Release 3 (Gaia DR3) parallax and astrophysical equations. Based on effective temperatures and component masses, two systems were classified as W-subtype systems, while others belonged to the A-subtype. We computed the initial masses of the primary ($M_{1i}$) and secondary ($M_{2i}$) components for four target systems using a method based on the observational properties of overluminous secondary components. We found initial primary masses in the range 0.6-1.0$M_\odot$ and initial secondary masses in the range 0.9-1.7$M_\odot$ with mass loss $<1.0M_{\odot}$. We investigated the relative energy transfer rates ($U_{1}$ and $U_{2}$) and nuclear luminosities ($L_{10}$ and $L_{20}$) based on the physical parameters of 411 W UMa-type contact binaries, including the four systems analyzed in this study, through wide range of mass ratios. The results for all systems provided a comprehensive view of energy transfer behavior throughout different evolutionary stages of contact binaries.

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arXiv2024

Comparative study of the W UMa type binaries S Ant and Epsilon CrA

Contact binaries challenge contemporary stellar astrophysics with respect to their incidence, structure and evolution. We explore these issues through a detailed study of two bright examples: S Ant and Eps CrA, that permit high-resolution spectroscopy at a relatively good S/N ratio. The availability of high-quality photometry, including data from the TESS satellite as well as Gaia parallaxes, allows us to apply the Russell paradigm to produce reliable up-to-date information on the physical properties of these binaries. As a result, models of their interactive evolution, such as the thermal relaxation oscillator scenario, can be examined. Mass transfer between the components is clearly evidenced, but the variability of the O'Connell effect over relatively short time scales points to irregularities in the mass transfer or accretion processes. Our findings indicate that S Ant may evolve into an R CMa type Algol, while the low mass ratio of Eps CrA suggests a likely merger of its components in the not-too-distant future.

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arXiv2023

The enigmatic multiple star VV Ori

New photometry, including TESS data, have been combined with recent spectroscopic observations of the Orion Ib pulsating triple-star system VV Ori. This yields a revised set of absolute parameters with increased precision. Two different programs were utilized for the light curve analysis, with results in predictably close agreement. The agreement promotes confidence in the analysis procedures. The spectra were analysed using the {\sc FDBinary} program. The main parameters are as follows: $M_1 = 11.6 \pm 0.14$ and $M_2 = 4.8 \pm 0.06$ (M$_\odot$). We estimate an approximate mass of the wide companion as $M_3 = 2.0 \pm 0.3$ M$_\odot$. Similarly, $R_{1} = 5.11 \pm 0.03$, $R_2 = 2.51 \pm 0.02$, $R_3 = 1.8 \pm 0.1$ (R$_\odot$); $T_{\rm e 1} = 26600 \pm 300$, $T_{\rm e 2} = 16300 \pm 400$ and $T_{\rm e 3} = 10000 \pm 1000$ (K). The close binary's orbital separation is $a= 13.91$ (R$_\odot$); its age is $8 \pm 2$ (Myr) and its photometric distance is $396 \pm 7$ pc. The primary's $β$ Cep type oscillations support these properties and confirm our understanding of its evolutionary status. Examination of the well-defined $λ$6678 He I profiles reveals the primary to have a significantly low projected rotation: some 80\% of the synchronous value. This can be explained on the basis of the precession of an unaligned spin axis. This proposal can resolve also observed variations of the apparent inclination and address other longer-term irregularities of the system reported in the literature. This topic invites further observations and follow-up theoretical study of the dynamics of this intriguing young multiple star.

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arXiv2023

The First Multiband Photometric Light Curve Solutions of the V Gru Binary System from the Southern Hemisphere

The first multiband photometric solutions of the short-period V Gru eclipsing binary from the southern hemisphere is presented in this study. Light curves of the system were observed through BVI filters at the Congarinni Observatory in Australia for 15 nights. In addition to the new ground-based data, we also used the TESS observations in two sectors. We analyzed the light curves of the system using the PHysics Of Eclipsing BinariEs (PHOEBE) 2.4.7 version code to achieve the best accordance with the photometric observations. The solutions suggest that V Gru is a near-contact binary system with q=1.302(81) mass ratio, f1=0.010(23), f2=-0.0.009(21), and i=73.45(38). We considered the two hot spots on the hotter and cooler components for the light curve analysis. We extracted the minima times from the light curves based on the Markov Chain Monte Carlo (MCMC) approach. Using our new light curves, TESS, and additional literature minima, we computed the ephemeris of V Gru. The system's eclipse timing variation trend was determined using the MCMC method. This system is a good and challenging case for future studies.

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arXiv2022

V410 Puppis: A useful laboratory for early stellar evolution

New spectrometric (HERCULES) and ground-based multi-colour photometric data on the multiple star V410 Puppis are combined with satellite photometry (HIPPARCOS and TESS), as well as historic astrometric observations. Absolute parameters for V410 Pup Aab are derived: $M_{Aa}$ = $3.15 \pm 0.10$, $M_{Ab}$ = $1.83 \pm 0.08$ (M$_{\odot}$); $R_{Aa}$ = $2.12 \pm 0.10$, $R_{Ab}$ = $1.52 \pm 0.08$ (R$_\odot$); $a$ = $6.57 \pm 0.04$ R$_\odot$; $T_{Aa}$ = $12500 \pm 1000$, $T_{Ab}$ = $9070 \pm 800$ (K), and photometric distance $350 \pm 10$ (pc). We report the discovery of a low-amplitude SPB variation in the light curve and also indications of an accretion structure around V410 Pup B as well as emission cores in V410 Pup C. We argue that V410 Pup is probably a young formation connected with the Vela 2 OB Association. The combined evidence allows an age in the range 7-25 Myr from comparisons with standard stellar evolution modelling.

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arXiv2022

The Photometric Study of Six W UMa Systems and Investigation of the Mass-Radius Relations for Contact Binary Stars

We present the photometric analysis of six short-period systems (EI Oct, V336 TrA, NX Boo, V356 Boo, PS Boo, and V2282 Cyg). This is the first photometric analysis of these systems except for V336 TrA. Observations were conducted for 27 nights at three observatories in the northern and southern hemispheres. We calculated a new ephemeris for each of the systems using our minimum times and additional literature. The Markov Chain Monte Carlo (MCMC) approach was used to determine the eclipse timing variation trends of the systems. We found a likely orbital growth for V336 TrA and PS Boo; four other systems show a linear trend in orbital period changes, which is most likely due to the accumulation of measurement errors in their linear ephemeris parameters. The light curve analysis was performed using the Physics of Eclipsing Binaries (PHOEBE) 2.3.59 version code with the MCMC approach. The absolute parameters of the systems were calculated by using the Gaia Early Data Release 3 (EDR3) parallax. The positions of the systems were also depicted on the Hertzsprung-Russell (H-R) and $logJ_0-logM$ diagrams. According to a sample, we were able to present relations for the mass-radius (M-R) relationships of contact binary systems. There is also a strong relationship between the mass ratio and the radius ratio in the W UMa systems for which we also provided a new relation. We compared the M-R updated relationships in this study with seven systems in other studies obtained using the spectroscopic method. In addition, we estimated some of the absolute parameters for 1734 EW systems, based on the new relationships.

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arXiv2022

The First Photometric Study of AH Mic Contact Binary System

The first multi-color light curve analysis of the AH Mic binary system is presented. This system has very few past observations from the southern hemisphere. We extracted the minima times from the light curves based on the Markov Chain Monte Carlo (MCMC) approach and obtained a new ephemeris. To provide modern photometric light curve solutions, we used the Physics of Eclipsing Binaries (Phoebe) software package and the MCMC approach. Light curve solutions yielded a system temperature ratio of 0.950, and we assumed a cold star-spot for the hotter star based on the O'Connell effect. This analysis reveals that AH Mic is a W-subtype W UMa contact system with a fill-out factor of 21.3% and a mass ratio of 2.32. The absolute physical parameters of the components are estimated by using the Gaia Early Data Release 3 (EDR3) parallax method to be M_h(M_Sun)=0.702(26), M_c(M_Sun)=1.629(104), R_h(R_Sun)=0.852(21), R_c(R_Sun)=1.240(28), L_h(L_Sun)=0.618(3) and L_c(L_Sun)=1.067(7). The orbital angular momentum of the AH Mic binary system was found to be 51.866(35). The components' positions of this system are plotted in the Hertzsprung-Russell (H-R) diagram.

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arXiv2021

The New Ephemeris and Light Curve Analysis of V870 Ara by the Ground-Based and TESS Data

New CCD photometric observations and their investigation of the W UMa-type binary, V870 Ara, are presented. Light curves of the system were taken through BVI filters from the Congarinni Observatory in Australia. The new ephemeris is calculated based on seven new determined minimum times, together with the TESS data and others compiled from the literature. Photometric solutions determined by the Wilson-Devinney (W-D) code are combined with the Monte Carlo simulation to determine the adjustable parameters' uncertainties. These solutions suggest that V870 Ara is a contact binary system with a mass ratio of 0.082, a fillout factor of 96+-4 percent, and an inclination of 73.60+-0.64 degrees. The absolute parameters of V870 Ara were determined by combining the Gaia EDR3 parallax and photometric elements.

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arXiv2021

BVRI Photometric Observations, Light Curve Solutions and Orbital Period Analysis of BF Pav

A new ephemeris, period change analysis and light curve modeling of the W UMa-type eclipsing binary BF Pav are presented in this study. Light curves of the system taken in BVRI filters from two observatories in Australia and Argentina were modeled using the Wilson-Devinney code. The results of this analysis demonstrate that BF Pav is a contact binary system with a photometric mass ratio q=1.460+_0.014, a fillout factor f=12.5%, an inclination of 87.97+_0.45 deg and a cold spot on the secondary component. By using the distance modulus formula, the distance of BF Pav was calculated to be d=268+_18 pc which is in good agreement with the Gaia EDR3 distance. We obtain an orbital period increase at a rate of 0.142 s/century due to a quadratic trend in the O-C diagram. Also, an alternative sudden period jump probably has occurred which could be interpreted as a rapid mass transfer from the lower mass star to its companion about DeltaM=2.45*10^(-6) Msun. Furthermore, there is an oscillatory behavior with a period of 18.3+_0.3 yr. Since BF Pav does not seem to have significant magnetic activity, this behavior could be interpreted as the light-time effect caused by an undetected third body in this system. In this case, the probability for the third body to be a low mass star with M>=0.075 Msun or a brown dwarf is 5.4% and 94.6% respectively. If we assume i'=90deg, a_3=8.04+_0.33 AU. The mass of the secondary component was also determined using two different methods which result close to each other.

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arXiv2021

Absolute Parameters of Young Stars: V Puppis

New spectrometric data on V Pup are combined with satellite photometry (HIPPARCOS and recent TESS) to allow a revision of the absolute parameters with increased precision. We find: $M_1$ = 14.0$\pm$0.5, $M_2$ = 7.3$\pm$0.3 (M$_\odot$); $R_{1}$ = 5.48$\pm$0.18, $R_2$ = 4.59$\pm$0.15 (R$_\odot$); $T_{1}$ 26000$\pm 1000$, $T_2$ 24000 $\pm$1000 (K), age 5 $\pm$1 (Myr), photometric distance 320 $\pm$10 (pc). The TESS photometry reveals low-amplitude ($\sim$0.002 mag) variations of the $β$ Cep kind, consistent with the deduced evolutionary condition and age of the optical primary. This fact provides independent support to our understanding of the system as in a process of Case A type interactive evolution that can be compared with $μ^1$ Sco. The $\sim$10 M$_{\odot}$ amount of matter shed by the over-luminous present secondary must have been mostly ejected from the system rather than transferred, thus taking angular momentum out of the orbit and keeping the pair in relative close proximity. New times of minima for V Pup have been studied and the results compared with previous analyses. The implied variation of period is consistent with the Case A evolutionary model, though we offer only a tentative sketch of the original arrangement of this massive system. We are not able to confirm the previously reported cyclical variations having a 5.47 yr period with the new data, though a direct comparison between the HIPPARCOS and TESS photometry points to the presence of third light from a star that is cooler than those of the close binary, as mentioned in previous literature.

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