arXiv subjects

K. G. Hełminiak

Publications and source records attributed to K. G. Hełminiak.

At least 37 records · Page 2Linked to original sources

arXiv2018

The Hyper Suprime-Cam SSP Survey: Overview and Survey Design

Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2m Subaru telescope on the summit of Maunakea in Hawaii. A team of scientists from Japan, Taiwan and Princeton University is using HSC to carry out a 300-night multi-band imaging survey of the high-latitude sky. The survey includes three layers: the Wide layer will cover 1400 deg$^2$ in five broad bands ($grizy$), with a $5\,σ$ point-source depth of $r \approx 26$. The Deep layer covers a total of 26~deg$^2$ in four fields, going roughly a magnitude fainter, while the UltraDeep layer goes almost a magnitude fainter still in two pointings of HSC (a total of 3.5 deg$^2$). Here we describe the instrument, the science goals of the survey, and the survey strategy and data processing. This paper serves as an introduction to a special issue of the Publications of the Astronomical Society of Japan, which includes a large number of technical and scientific papers describing results from the early phases of this survey.

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arXiv2017

Project Solaris, a Global Network of Autonomous Observatories: Design, Commissioning, and First Science Results

We present the design and commissioning of Project Solaris, a global network of autonomous observatories. Solaris is a Polish scientific undertaking aimed at the detection and characterization of circumbinary exoplanets and eclipsing binary stars. To accomplish this, a network of four fully autonomous observatories has been deployed in the Southern Hemisphere: Solaris-1 and Solaris-2 in the South African Astronomical Observatory in South Africa; Solaris-3 in Siding Spring Observatory in Australia; and Solaris-4 in Complejo Astronomico El Leoncito in Argentina. The four stations are nearly identical and are equipped with 0.5-m Ritchey-Crétien (f/15) or Cassegrain (f/9, Solaris-3) optics and high-grade 2 K x 2 K CCD cameras with Johnson and Sloan filter sets. We present the design and implementation of low-level security; data logging and notification systems; weather monitoring components; all-sky vision system, surveillance system; and distributed temperature and humidity sensors. We describe dedicated grounding and lighting protection system design and robust fiber data transfer interfaces in electrically demanding conditions. We discuss the outcomes of our design, as well as the resulting software engineering requirements. We describe our system's engineering approach to achieve the required level of autonomy, the architecture of the custom high-level industry-grade software that has been designed and implemented specifically for the use of the network. We present the actual status of the project and first photometric results; these include data and models of already studied systems for benchmarking purposes (Wasp-4b, Wasp-64b, and Wasp-98b transits, PG 1663-018, an eclipsing binary with a pulsator) as well J024946-3825.6, an interesting low-mass binary system for which a complete model is provided for the first time.

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arXiv2017

High-resolution spectroscopy and abundance analysis of Delta Scuti stars near the Gamma Doradus instability strip

$δ$ Scuti stars are remarkable objects for asteroseismology. In spite of decades of investigations, there are still important questions about these pulsating stars to be answered, such as their positions in $\log$$T_{\rm eff}$ $-$ $\log g$ diagram, or the dependence of the pulsation modes on atmospheric parameters and rotation. Therefore, we performed a detailed spectroscopic study of $41$ $δ$ Scuti stars. The selected objects are located near the $γ$ Doradus instability strip to make a reliable comparison between both types of variables. Spectral classification, stellar atmospheric parameters ($T_{\rm eff}$, $\log g$, $ξ$) and $v \sin i$ values were determined. The spectral types and luminosity classes of stars were found to be A1$-$F5 and III$-$V, respectively. The $T_{\rm eff}$ ranges from $6600$ to $9400$ K, whereas the obtained $\log g$ values are from $3.4$ to $4.3$. The $v \sin i$ values were found between $10$ and $222$ km s$^{-1}$. The derived chemical abundances of $δ$ Scuti stars were compared to those of the non-pulsating stars and $γ$ Doradus variables. It turned out that both $δ$ Scuti and $γ$ Doradus variables have similar abundance patterns, which are slightly different from the non-pulsating stars. These chemical differences can help us to understand why there are non-pulsating stars in classical instability strip. Effects of the obtained parameters on pulsation period and amplitude were examined. It appears that the pulsation period decreases with increasing $T_{\rm eff}$. No significant correlations were found between pulsation period, amplitude and $v \sin i$.

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arXiv2017

KIC 4150611: a rare multi-eclipsing quintuple with a hybrid pulsator

We present the results of our analysis of KIC 4150611 (HD 181469) - an interesting, bright quintuple system that includes a hybrid $δ$ Sct/$γ$ Dor pulsator. Four periods of eclipses - 94.2, 8.65, 1.52 and 1.43 d - have been observed by the Kepler satellite, and three point sources (A, B, and C) are seen in high angular resolution images. From spectroscopic observations made with the HIDES spectrograph attached to the 1.88-m telescope of the Okayama Astrophysical Observatory (OAO), for the first time we calculated radial velocities (RVs) of the component B - a pair of G-type stars - and combined them with Kepler photometry in order to obtain absolute physical parameters of this pair. We also managed to directly measure RVs of the pulsator, also for the first time. Additionally, we modelled the light curves of the 1.52 and 1.43-day pairs, and measured their eclipse timing variations (ETVs). We also performed relative astrometry and photometry of three sources seen on the images taken with the NIRC2 camera of the Keck II telescope. Finally, we compared our results with theoretical isochrones. The brightest component Aa is the hybrid pulsator, transited every 94.2 days by a pair of K/M-type stars (Ab1+Ab2), which themselves form a 1.52-day eclipsing binary. The components Ba and Bb are late G-type stars, forming another eclipsing pair with a 8.65 day period. Their masses and radii are $M_{Ba}=0.894\pm0.010$ M$_\odot$, $R_{Ba}=0.802\pm0.044$ R$_\odot$ for the primary, and $M_{Bb}=0.888\pm0.010$ M$_\odot$, $R_{Bb}=0.856\pm0.038$ R$_\odot$ for the secondary. The remaining period of 1.43 days is possibly related to a faint third star C, which itself is most likely a background object. The system's properties are well-represented by a 35 Myr isochrone. There are also hints of additional bodies in the system.

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arXiv2017

HIDES spectroscopy of bright detached eclipsing binaries from the $Kepler$ field - I. Single-lined objects

We present results of our spectroscopic observations of nine detached eclipsing binaries (DEBs), selected from the $Kepler$ Eclipsing Binary Catalog, that only show one set of spectral lines. Radial velocities (RVs) were calculated from the high resolution spectra obtained with the HIDES instrument, attached to the 1.88-m telescope at the Okayama Astrophysical Observatory, and from the public APOGEE archive. In our sample we found five single-lined binaries, with one component dominating the spectrum. The orbital and light curve solutions were found for four of them, and compared with isochrones, in order to estimate absolute physical parameters and evolutionary status of the components. For the fifth case we only update the orbital parameters, and estimate the properties of the unseen star. Two other systems show orbital motion with a period known from the eclipse timing variations (ETVs). For these we obtained parameters of outer orbits, by translating the ETVs to RVs of the centre of mass of the eclipsing binary, and combining with the RVs of the outer star. Of the two remaining ones, one is most likely a blend of a faint background DEB with a bright foreground star, which lines we see in the spectra, and the last case is possibly a quadruple bearing a sub-stellar mass object. Where possible, we compare our results with literature, especially with results from asteroseismology. We also report possible detections of solar-like oscillations in our RVs.

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arXiv2017

HIDES spectroscopy of bright detached eclipsing binaries from the $Kepler$ field - II. Double- and triple-lined objects

We present the results of our spectroscopic observations of eight detached eclipsing binaries (DEBs), selected from the $Kepler$ Eclipsing Binary Catalog. Radial velocities (RVs) were calculated from high resolution spectra obtained with the HIDES pectrograph, attached to the 1.88-m telescope of the Okayama Astrophysical Observatory, and were used to characterize the targets in combination with the $Kepler$ light curves. For each binary we obtained a full set of orbital and physical parameters, reaching precision below 3% in masses and radii for 5 pairs. By comparing our results with theoretical models, we assess the distance, age and evolutionary status of the researched objects. We also study eclipse timing variations of selected objects, and identify a new system with a $γ$Dor pulsator. Two systems are triples, and show lines coming from three components. In one case the motion of the outer star and the perturbation in the RVs of the inner binary are clearly visible and periodical, which allows us to directly calculate the mass of the third star, and inclination of the outer orbit. In the second case we only see a clear motion of the tertiary, and investigate two scenarios: that it is a linear trend coming from the orbital motion around the inner binary, and that it is caused by a planetary mass companion. When possible, we also compare our results with the literature, and conclude that only by combining photometry with RVs it is possible to obtain correct physical parameters of both components of a DEB.

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arXiv2016

SEEDS direct imaging of the RV-detected companion to V450 Andromedae, and characterization of the system

We report the direct imaging detection of a low-mass companion to a young, moderately active star V450 And, that was previously identified with the radial velocity method. The companion was found in high-contrast images obtained with the Subaru Telescope equipped with the HiCIAO camera and AO188 adaptive optics system. From the public ELODIE and SOPHIE archives we extracted available high-resolution spectra and radial velocity (RV) measurements, along with RVs from the Lick planet search program. We combined our multi-epoch astrometry with these archival, partially unpublished RVs, and found that the companion is a low-mass star, not a brown dwarf, as previously suggested. We found the best-fitting dynamical masses to be $m_1=1.141_{-0.091}^{+0.037}$ and $m_2=0.279^{+0.023}_{-0.020}$ M$_\odot$. We also performed spectral analysis of the SOPHIE spectra with the iSpec code. The Hipparcos time-series photometry shows a periodicity of $P=5.743$ d, which is also seen in SOPHIE spectra as an RV modulation of the star A. We interpret it as being caused by spots on the stellar surface, and the star to be rotating with the given period. From the rotation and level of activity, we found that the system is $380^{+220}_{-100}$ Myr old, consistent with an isochrone analysis ($220^{+2120}_{-90}$ Myr). This work may serve as a test case for future studies of low-mass stars, brown dwarfs and exoplanets by combination of RV and direct imaging data.

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arXiv2016

Orbital and physical parameters of eclipsing binaries from the ASAS catalogue -- IX. Spotted pairs with red giants

We present spectroscopic and photometric solutions for three spotted systems with red giant components. Absolute physical and orbital parameters for these double-lined detached eclipsing binary stars are presented for the first time. These were derived from the V-, and I-band ASAS and WASP photometry, and new radial velocities calculated from high quality optical spectra we obtained with a wide range of spectrographs and using the two-dimensional cross-correlation technique (TODCOR). All of the investigated systems (ASAS J184949-1518.7, BQ Aqr, and V1207 Cen) show the differential evolutionary phase of their components consisting of a main sequence star or a subgiant and a red giant, and thus constitute very informative objects in terms of testing stellar evolution models. Additionally, the systems show significant chromospheric activity of both components. They can be also classified as classical RS CVn-type stars. Besides the standard analysis of radial velocities and photometry, we applied spectral disentangling to obtain separate spectra for both components of each analysed system which allowed for a more detailed spectroscopic study. We also compared the properties of red giant stars in binaries that show spots, with those that do not, and found that the activity phenomenon is substantially suppressed for stars with Rossby number higher than $\sim$1 and radii larger than $\sim$20 R$_\odot$.

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arXiv2015

Multiples among detached eclipsing binaries from the ASAS catalog

For more than three years now we have been conducting a spectroscopic survey of detached eclipsing binaries (DEBs) from the All-Sky Automated Survey (ASAS) database. Thousands of high-resolution spectra of over 300 systems were secured, and used for radial velocity measurements and spectral analysis. In our sample we found a zoo of multiple systems, such as spectroscopic triples and quadruples, visual binaries with eclipsing components, and circumbinary low-mass companions, including sub-stellar-mass candidates

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arXiv2015

Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue - VII. V1200 Centauri: a bright triple in the Hyades moving group

We present the orbital and physical parameters of the detached eclipsing binary V1200~Centauri (ASAS~J135218-3837.3) from the analysis of spectroscopic observations and light curves from the \textit{All Sky Automated Survey} (ASAS) and SuperWASP database. The radial velocities were computed from the high-resolution spectra obtained with the OUC 50-cm telescope and PUCHEROS spectrograph and with 1.2m Euler telescope and CORALIE spectrograph using the cross-correlation technique \textsc{todcor}. We found that the absolute parameters of the system are $M_1= 1.394\pm 0.030$ M$_\odot$, $M_2= 0.866\pm 0.015$ M$_\odot$, $R_1= 1.39\pm 0.15$ R$_\odot$, $R_2= 1.10\pm 0.25$ R$_\odot$. We investigated the evolutionary status and kinematics of the binary and our results indicate that V1200~Centauri is likely a member of the Hyades moving group, but the largely inflated secondary's radius may suggest that the system may be even younger, around 30 Myr. We also found that the eclipsing pair is orbited by another, stellar-mass object on a 351-day orbit, which is unusually short for hierarchical triples. This makes V1200 Cen a potentially interesting target for testing the formation models of multiple stars.

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arXiv2014

Orbital and physical parameters of eclipsing binaries from the ASAS catalogue - VIII. The totally-eclipsing double-giant system HD 187669

We present the first full orbital and physical analysis of HD 187669, recognized by the All-Sky Automated Survey (ASAS) as the eclipsing binary ASAS J195222-3233.7. We combined multi-band photometry from the ASAS and SuperWASP public archives and 0.41-m PROMPT robotic telescopes with our high-precision radial velocities from the HARPS spectrograph. Two different approaches were used for the analysis: 1) fitting to all data simultaneously with the WD code, and 2) analysing each light curve (with JKTEBOP) and RVs separately and combining the partial results at the end. This system also shows a total primary (deeper) eclipse, lasting for about 6 days. A spectrum obtained during this eclipse was used to perform atmospheric analysis with the MOOG and SME codes in order to constrain physical parameters of the secondary. We found that ASAS J195222-3233.7 is a double-lined spectroscopic binary composed of two evolved, late-type giants, with masses of $M_1 = 1.504\pm0.004$ and $M_2=1.505\pm0.004$ M$_\odot$, and radii of $R_1 = 11.33\pm0.28$ and $R_2=22.62\pm0.50$ R$_\odot$, slightly less metal abundant than the Sun, on a $P=88.39$ d orbit. Its properties are well reproduced by a 2.38 Gyr isochrone, and thanks to the metallicity estimation from the totality spectrum and high precision in masses, it was possible to constrain the age down to 0.1 Gyr. It is the first so evolved galactic eclipsing binary measured with such a good accuracy, and as such is a unique benchmark for studying the late stages of stellar evolution.

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arXiv2014

BACHES - a compact échelle spectrograph for radial velocity surveys with small telescopes

We evaluate a pre-production BACHES échelle spectrograph in terms of its usefulness for radial velocity surveys of binary stars with small telescopes in a remote and autonomous. We use the Solaris-4 observatory located in Casleo, Argentina, that is part of a global network of autonomous observatories as the test-bed for the instrument. The setup is designed in such a way that spectroscopy and photometry can be carried out using the same telescope without the need to mechanically modify the imaging train. We observe single spectroscopic standard stars as well as binary stars up to 9.75 mag. We present results of mechanical tests of the instruments and spectroscopic observations carried out between Nov 26th and Dec 8th 2013. We conclude that BACHES is a very compact and capable spectrograph well suited for remote and autonomous operation. Coupled to a 0.5-m telescope it is capable of obtaining spectra of 10 mag targets with a SNR of 20 for 30-minute exposures. This is a very good result considering the price and size of the instrument. It brings new possibilities to the scientific community and opens a whole new range of research opportunities available to new and existing observatories.

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arXiv2014

The VVV Templates Project. Towards an Automated Classification of VVV Light-Curves. I. Building a database of stellar variability in the near-infrared

Context. The Vista Variables in the Vía Láctea (VVV) ESO Public Survey is a variability survey of the Milky Way bulge and an adjacent section of the disk carried out from 2010 on ESO Visible and Infrared Survey Telescope for Astronomy (VISTA). VVV will eventually deliver a deep near-IR atlas with photometry and positions in five passbands (ZYJHK_S) and a catalogue of 1-10 million variable point sources - mostly unknown - which require classifications. Aims. The main goal of the VVV Templates Project, that we introduce in this work, is to develop and test the machine-learning algorithms for the automated classification of the VVV light-curves. As VVV is the first massive, multi-epoch survey of stellar variability in the near-infrared, the template light-curves that are required for training the classification algorithms are not available. In the first paper of the series we describe the construction of this comprehensive database of infrared stellar variability. Methods. First we performed a systematic search in the literature and public data archives, second, we coordinated a worldwide observational campaign, and third we exploited the VVV variability database itself on (optically) well-known stars to gather high-quality infrared light-curves of several hundreds of variable stars. Results. We have now collected a significant (and still increasing) number of infrared template light-curves. This database will be used as a training-set for the machine-learning algorithms that will automatically classify the light-curves produced by VVV. The results of such an automated classification will be covered in forthcoming papers of the series.

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arXiv2014

Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue - VI. AK Fornacis - a rare, bright K-type eclipsing binary

We present the results of the combined photometric and spectroscopic analysis of a bright (V=9.14), nearby (d=31 pc), late-type detached eclipsing binary AK Fornacis. This P=3.981 d system has not been previously recognised as a double-lined spectroscopic binary, and this is the first full physical model of this unique target. With the FEROS, CORALIE and HARPS spectrographs we collected a number of high-resolution spectra in order to calculate radial velocities of both components of the binary. Measurements were done with our own disentangling procedure and the TODCOR technique, and were later combined with the photometry from the ASAS and SuperWASP archives. We also performed an atmospheric analysis of the component spectra with the Spectroscopy Made Easy (SME) package. Our analysis shows that AK For consists of two active, cool dwarfs having masses of $M_1=0.6958 \pm 0.0010$ and $M_2=0.6355 \pm 0.0007$ M$_\odot$ and radii of $R_1=0.687 \pm 0.020$ and $R_2=0.609 \pm 0.016$ R$_\odot$, slightly less metal abundant than the Sun. Parameters of both components are well reproduced by the models. AK For is the brightest system among the known eclipsing binaries with K or M type stars. Its orbital period is one of the longest and rotational velocities one of the lowest, which allows us to obtain very precise radial velocity measurements. The precision in physical parameters we obtained places AK For among the binaries with the best mass measurements in the literature. It also fills the gap in our knowledge of stars in the range of 0.5-0.8 M$_\odot$, and between short and long-period systems. All this makes AK For a unique benchmark for understanding the properties of low-mass stars.

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arXiv2013

Orbital and physical parameters of eclipsing binaries from the ASAS catalogue - V. Investigation of subgiants and giants: the case of ASAS J010538-8003.7, ASAS J182510-2435.5, and V1980 Sgr

We present absolute physical and orbital parameters for three double-lined detached eclipsing binary systems from the All Sky Automated Survey (ASAS) catalogue with subgiant and giant components. These parameters were derived from archival V-band ASAS photometry and new radial velocities. The radial velocities were calculated from high quality optical spectra we obtained with the 8.2 m Subaru/HDS, ESO 3.6 m/HARPS, 1.9 m Radcliffe/GIRAFFE, CTIO 1.5 m/CHIRON, and 1.2 m Euler/CORALIE using the two-dimensional cross-correlation technique (TODCOR) and synthetic template spectra chosen for every system separately as references. The physical and orbital parameters of the systems were derived with the PHOEBE and JKTEBOP codes. We checked the evolutionary status of the systems with several sets of isochrones and determined distances for each system. The derived uncertainties for individual masses of ASAS J010538-8003.7, ASAS J182510-2435.5, and V1980 Sgr components vary from 0.7% to 3.6% while the radii are in the range 1% to 24%. For all of the investigated systems such a detailed orbital and physical analysis is presented for the first time.

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arXiv2013

Tracing the structure of the Milky Way with detached eclipsing binaries from the VVV survey - I. The method and initial results

We present the first results of a project aiming to trace the spatial structure of the Milky Way using detached eclipsing binaries (DEBs) as distance indicators. A sample of DEBs from the OGLE-II catalogue was selected and their near infrared photometry was taken from the Vista Variables in the Via Lactea (VVV) survey. The I band OGLE-II light curves are used to create models of the DEBs, which together with the VVV photometry are compared with a set of theoretical isochrones. After correcting for stellar reddening, we find a set of absolute physical parameters of components of a given binary, including absolute magnitudes and distances. With this approach we can calculate the distances with the precision better than 5 per cent. Even though we have a few systems, the distribution is not homogeneous along the line of sight, and appears to follow the overall structure of the Galaxy - several spiral arms and the Bulge are distinguishable. A number of systems can be seen behind the Bulge, reaching even the distance to the Sagittarius dwarf galaxy.

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arXiv2013

Non-Keplerian effects in precision radial velocity measurements of double-line spectroscopic binary stars: numerical simulations

Current precision in radial velocity (RV) measurements of binary stars reaches $\sim$2 ms$^{-1}$. This level of precision means that RV models have to take into account additional non-Keplerian effects such as tidal and rotational distortion of the components of a binary star, relativistic effects and orbital precession. We generate synthetic binaries using Yonsei-Yale stellar models. For typical representatives we investigate the impact of various orbital orientations and different non-Keplerian effects on the RV curves. To this end we simulate RV observations with an added white noise of different scale. Subsequently we try to reconstruct the input orbital parameters and their errors by fitting a model using a standard least-squares method. In particular we investigate the connection between the tidal distortion of the shape of the stars and the best-fit orbital eccentricity, the possibility of deriving orbital inclination of a non-eclipsing binary star by exploiting relativistic effects and the circumstances in which the orbital precession can be detected. We confirm that the method proposed by to obtain orbital inclination with use of the relativistic effect does work in favourable cases and that it can be used even for orbital configurations far from an edge-on orientation. We show that the RV variations imposed by tidally distorted stars can mimic non-zero eccentricity in some binaries. The scale of such an effect depends on the RV accuracy. Finally, we demonstrate that the apsidal precession can be easily detected with precision RVs. In particular we can detect orbital precession of $10^{-4}$ rad yr$^{-1}$, $10^{-3}$ rad yr$^{-1}$ for precision of RVs of 1 ms$^{-1}$ and 10 ms$^{-1}$ respectively.

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arXiv2012

Orbital and physical parameters of eclipsing binaries from the ASAS catalogue - IV. A 0.61 + 0.45 M_sun binary in a multiple system

We present the orbital and physical parameters of a newly discovered low-mass detached eclipsing binary from the All-Sky Automated Survey (ASAS) database: ASAS J011328-3821.1 A - a member of a visual binary system with the secondary component separated by about 1.4 seconds of arc. The radial velocities were calculated from the high-resolution spectra obtained with the 1.9-m Radcliffe/GIRAFFE, 3.9-m AAT/UCLES and 3.0-m Shane/HamSpec telescopes/spectrographs on the basis of the TODCOR technique and positions of H_alpha emission lines. For the analysis we used V and I band photometry obtained with the 1.0-m Elizabeth and robotic 0.41-m PROMPT telescopes, supplemented with the publicly available ASAS light curve of the system. We found that ASAS J011328-3821.1 A is composed of two late-type dwarfs having masses of M_1 = 0.612 +/- 0.030 M_sun, M_2 = 0.445 +/- 0.019 M_sun and radii of R_1 = 0.596 +/- 0.020 R_sun, R_2 = 0.445 +/- 0.024 R_sun, both show a substantial level of activity, which manifests in strong H_alpha and H_beta emission and the presence of cool spots. The influence of the third light on the eclipsing pair properties was also evaluated and the photometric properties of the component B were derived. Comparison with several popular stellar evolution models shows that the system is on its main sequence evolution stage and probably is more metal rich than the Sun. We also found several clues which suggest that the component B itself is a binary composed of two nearly identical ~0.5 M_sun stars.

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