Nemradiális pulzációk tanulmányozása fedési kettős csillagrendszerekben = The study of nonradial pulsations in eclipsing binary systems

A kutatási projekt célja olyan módszerek kidolgozása volt, amelyek segítségével a fedési kettőscsillagok pulzáló tagjainak pulzációs móduszai a fedés jelenségének felhasználásával feltérképezhetők, beazonosíthatók, és ezáltal lehetővé teszik a csillagbelsők asztroszeizmológiai vizsgálatát. Az ilyen rendszerek egyedülálló fontossággal bírnak, mert a pulzációk azonosítása egyedülálló csillagokban nehézkes, bonyolult csillagmodelleket és részletes spektroszkópiai méréseket igényel. A kidolgozott Dinamikai Eclipse Mapping módszer a fedések effektív felszíni mintavételezését kihasználva képszerű információt szolgáltat a csillagfelszíni pulzációs mintázatokról. Ez közvetlen és a csillagmodellektől maximálisan független móduszazonosítást tesz lehetővé; mindez pedig egyszerű fotometriai mérési sorozat alapján lehetséges. A módszer továbbfejlesztésével az ismeretlen forgástengely, valamint a forgás (de nem árapály) által eltorzított pulzációk esete is vizsgálható. Első sikeres alkalmazásként egy, a Kepler űrtávcső által mért objektum domináns pulzációit tudtam azonosítani. További eredmények az alkalmas objektumok megfelelő adatainak megjelenése ütemében várhatók. | The main goal of the project was the development of analysis methods suitable to map and identify the pulsation pattenrs on non-radial pulsation components of eclipsing binary star systems, using the binarity and the eclipses. A successful mode identification makes it potentially possible -- via asteroseismic inversion -- to peek into stellar interiors. Pulsations in eclipsing systems are unique, in that the mode identification is extremely awkward in single stars, requiring detailed stellar models and exhaustive measurements. The constructed method of Dynamic Eclipse Mapping is an indirect imaging method that uses the effective surface sampling of the eclipses to reconstruct images of the surface pulsation patterns. Such images allow a direct and maximally model-independent identification of the pulsation modes, using photometric time series only. An extension of the method allows the treatment of more complicated cases, like the simultaneous fitting of the pulsation axis, and the mapping of rotationally (but not tidally) distorted pulsations. As a first successful application, the first few dominant modes of a Kepler asteroseismic target could be identified. More applications are expected, at the rate at which appropriate data of other candidate systems are being collected and analysed

A comprehensive study of the Kepler triples via eclipse timing

We produce and analyse eclipse time variation (ETV) curves for some 2600 Kepler binaries. We find good to excellent evidence for a third body in 222 systems via either the light-travel-time (LTTE) or dynamical effect delays. Approximately half of these systems have been discussed in previous work, while the rest are newly reported here. Via detailed analysis of the ETV curves using high-level analytic approximations, we are able to extract system masses and information about the three-dimensional characteristics of the triple for 62 systems which exhibit both LTTE and dynamical delays; for the remaining 160 systems, we give improved LTTE solutions. New techniques of pre-processing the flux time series are applied to eliminate false positive triples and to enhance the ETV curves. The set of triples with outer orbital periods shorter than ˜2000 d is now sufficiently numerous for meaningful statistical analysis. We find that (i) there is a peak near im ≃ 40° in the distribution of the triple versus inner binary mutual inclination angles that provides strong confirmation of the operation of Kozai-Lidov cycles with tidal friction; (ii) the median eccentricity of the third-body orbits is e2 = 0.35; (iii) there is a deficit of triple systems with binary periods ≲1 d and outer periods between ˜50 and 200 d which might help guide the refinement of theories of the formation and evolution of close binaries; and (iv) the substantial fraction of Kepler binaries which have third-body companions is consistent with a very large fraction of all binaries being part of triples

BU Canis Minoris -- the Most Compact Known Flat Doubly Eclipsing Quadruple System

We have found that the 2+2 quadruple star system BU CMi is currently the most compact quadruple system known, with an extremely short outer period of only 121 days. The previous record holder was TIC 219006972 (Kostov et al. 2023), with a period of 168 days. The quadruple nature of BU CMi was established by Volkov et al. (2021), but they misidentified the outer period as 6.6 years. BU CMi contains two eclipsing binaries (EBs), each with a period near 3 days, and a substantial eccentricity of about 0.22. All four stars are within about 0.1 solar mass of 2.4 solar masses. Both binaries exhibit dynamically driven apsidal motion with fairly short apsidal periods of about 30 years, thanks to the short outer orbital period. The outer period of 121 days is found both from the dynamical perturbations, with this period imprinted on the eclipse timing variations (ETV) curve of each EB by the other binary, and by modeling the complex line profiles in a collection of spectra. We find that the three orbital planes are all mutually aligned to within 1 degree, but the overall system has an inclination angle near 83.5 degrees. We utilize a complex spectro-photodynamical analysis to compute and tabulate all the interesting stellar and orbital parameters of the system. Finally, we also find an unexpected dynamical perturbation on a timescale of several years whose origin we explore. This latter effect was misinterpreted by Volkov et al. (2021) and led them to conclude that the outer period was 6.6 years rather than the 121 days that we establish here.Comment: 19 pages, 8 pages, accepted to MNRA

Extensive Spectroscopy and Photometry of the Type IIP Supernova 2013ej

We present extensive optical (UBV RI, {g}\prime {r}\prime {i}\prime {z}\prime , and open CCD) and near-infrared (ZY JH) photometry for the very nearby Type IIP SN 2013ej extending from +1 to +461 days after shock breakout, estimated to be MJD 56496.9 ± 0.3. Substantial time series ultraviolet and optical spectroscopy obtained from +8 to +135 days are also presented. Considering well-observed SNe IIP from the literature, we derive UBV RIJHK bolometric calibrations from UBV RI and unfiltered measurements that potentially reach 2% precision with a B ‑ V color-dependent correction. We observe moderately strong Si ii λ 6355 as early as +8 days. The photospheric velocity ({v}{{ph}}) is determined by modeling the spectra in the vicinity of Fe ii λ 5169 whenever observed, and interpolating at photometric epochs based on a semianalytic method. This gives {v}{{ph}}=4500+/- 500 km s‑1 at +50 days. We also observe spectral homogeneity of ultraviolet spectra at +10–12 days for SNe IIP, while variations are evident a week after explosion. Using the expanding photosphere method, from combined analysis of SN 2013ej and SN 2002ap, we estimate the distance to the host galaxy to be {9.0}-0.6+0.4 Mpc, consistent with distance estimates from other methods. Photometric and spectroscopic analysis during the plateau phase, which we estimated to be 94 ± 7 days long, yields an explosion energy of 0.9+/- 0.3× {10}51 erg, a final pre-explosion progenitor mass of 15.2 ± 4.2 {M}ȯ and a radius of 250 ± 70 {R}ȯ . We observe a broken exponential profile beyond +120 days, with a break point at +183 ± 16 days. Measurements beyond this break time yield a 56Ni mass of 0.013 ± 0.001 M {}ȯ

SN 2022oqm: A Multi-peaked Calcium-rich Transient from a White Dwarf Binary Progenitor System

We present the photometric and spectroscopic evolution of SN 2022oqm, a nearby multi-peaked hydrogen- and helium-weak calcium-rich transient (CaRT). SN 2022oqm was detected 19.9 kpc from its host galaxy, the face-on spiral galaxy NGC 5875. Extensive spectroscopic coverage reveals a hot (T >= 40,000 K) continuum and carbon features observed ~1 day after discovery, SN Ic-like photospheric-phase spectra, and strong forbidden calcium emission starting 38 days after discovery. SN 2022oqm has a relatively high peak luminosity (MB = -17 mag) for CaRTs, making it an outlier in the population. We determine that three power sources are necessary to explain SN 2022oqm's light curve, with each power source corresponding to a distinct peak in its light curve. The first peak of the light curve is powered by an expanding blackbody with a power law luminosity, consistent with shock cooling by circumstellar material. Subsequent peaks are powered by a double radioactive decay model, consistent with two separate sources of photons diffusing through an optically thick ejecta. From the optical light curve, we derive an ejecta mass and 56Ni mass of ~0.89 solar masses and ~0.09 solar masses, respectively. Detailed spectroscopic modeling reveals ejecta that is dominated by intermediate-mass elements, with signs that Fe-peak elements have been well-mixed. We discuss several physical origins for SN 2022oqm and favor a white dwarf progenitor model. The inferred ejecta mass points to a surprisingly massive white dwarf, challenging models of CaRT progenitors.Comment: 33 pages, 17 figures, 5 tables, Submitted to Ap

Machine learning methods for Schlieren imaging of a plasma channel in tenuous atomic vapor

We investigate the usage of a Schlieren imaging setup to measure the geometrical dimensions of a plasma channel in atomic vapor. Near resonant probe light is used to image the plasma channel in a tenuous vapor and machine learning techniques are tested for extracting quantitative information from the images. By building a database of simulated signals with a range of plasma parameters for training Deep Neural Networks, we demonstrate that they can extract from the Schlieren images reliably and with high accuracy the location, the radius and the maximum ionization fraction of the plasma channel as well as the width of the transition region between the core of the plasma channel and the unionized vapor. We test several different neural network architectures with supervised learning and show that the parameter estimations supplied by the networks are resilient with respect to slight changes of the experimental parameters that may occur in the course of a measurement.Comment: 26 pages, 13 figures, 1 tabl

Dynamical masses, absolute radii and 3D orbits of the triply eclipsing star HD 181068 from Kepler photometry

HD 181068 is the brighter of the two known triply eclipsing hierarchical triple starsin the Kepler field. It has been continuously observed for more than 2 years with theKepler space telescope. Of the nine quarters of the data, three have been obtained inshort-cadence mode, that is one point per 58.9 s. Here we analyse this unique datasetto determine absolute physical parameters (most importantly the masses and radii)and full orbital configuration using a sophisticated novel approach. We measure eclipsetiming variations (ETVs), which are then combined with the single-lined radial velocitymeasurements to yield masses in a manner equivalent to double-lined spectroscopicbinaries. We have also developed a new light curve synthesis code that is used tomodel the triple, mutual eclipses and the effects of the changing tidal field on the stellarsurface and the relativistic Doppler-beaming. By combining the stellar masses from theETV study with the simultaneous light curve analysis we determine the absolute radiiof the three stars. Our results indicate that the close and the wide subsystems revolvein almost exactly coplanar and prograde orbits. The newly determined parametersdraw a consistent picture of the system with such details that have been beyond reachbefore