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Jakub Klencki

Jakub Klencki contributes to research discovery and scholarly infrastructure.

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Published work

7 published item(s)

preprint2026arXiv

Traditional statistical representations outperform generative AI in identifying expert peer reviewers

The exponential growth of scientific submissions has strained the peer review system. Despite the rapidly expanding global pool of researchers, this unprecedented scale has rendered the previous approach of manual expert identification unfeasible. Therefore, institutions have naturally turned to Large Language Models (LLMs) to automate intricate processes like expert reviewer identification. However, the reliability of these new models in accurately identifying domain experts lacks rigorous evaluation. We conduct a comprehensive empirical evaluation of statistical and AI-driven expertise identification methodologies to benchmark their reliability and limitations. Framing expert identification as an information retrieval problem, we utilize the distributed peer review system of a major international astronomical observatory, where proposal authorship serves as our proxy ground truth for domain expertise. Evaluating six retrieval methodologies utilized across observatories and computer science conferences, we demonstrate that traditional statistical representations outperform generative AI. Specifically, Term Frequency-Inverse Document Frequency successfully identified a labeled expert within the top 25 recommendations 79.5% of the time, compared to 51.5% for GPT-4o mini. Our results highlight that distinguishing subfield expertise requires fine-grained vocabulary, which is obscured by the semantic smoothing in generative methods. By establishing a rigorous evaluation framework for automated peer review, we demonstrate that transparent and reproducible statistical representations still outperform computationally expensive LLMs in specialized scientific tasks.

preprint2022arXiv

Partial-envelope stripping and nuclear-timescale mass transfer from evolved supergiants at low metallicity

Stable mass transfer from a massive post-main sequence (post-MS) donor is thought to be a short-lived event of thermal-timescale mass transfer which strips the donor star of nearly its entire H-rich envelope, producing a hot helium star. This long-standing picture is based on stellar models with Hertzprung gap (HG) donors. Motivated by a finding that in low-metallicity binaries, post-MS mass transfer may instead be initiated by core-helium burning (CHeB) donors, we use the MESA code to compute grids of detailed massive binary models at three metallicities: Solar and that of the Large and the Small Magellanic Cloud (LMC, SMC). We find that metallicity strongly influences the course and outcome of mass transfer. We identify two novel types of post-MS mass transfer: (a) mass exchange on the long nuclear timescale that continues until the end of the CHeB phase, and (b) rapid mass transfer leading to detached binaries with mass-losers that are only partially stripped of their envelopes. In neither (a) or (b) does the donor become a fully stripped helium star by the end of CHeB. Boundaries between the different types of post-MS mass transfer are associated with the degree of rapid post-MS expansion and, for a given metallicity, are sensitive to the assumptions about internal mixing. At low metallicity, we predict fewer hot fully stripped stars formed through binary interactions and higher compactness of pre-supernova cores. Nuclear-timescale post-MS mass transfer suggests a strong preference for metal-poor host galaxies of ultra-luminous X-ray sources with black-hole (BH) accretors and massive donors, some of which might be the immediate progenitors of binary BH mergers. It also implies a population of interacting binaries with blue and yellow supergiant donors. Partially-stripped stars could potentially explain the puzzling nitrogen-enriched slowly-rotating (super)giants in the LMC.

preprint2022arXiv

Stellar response after stripping as a model for common-envelope outcomes

Binary neutron stars have been observed as millisecond pulsars, gravitational-wave sources, and as the progenitors of short gamma-ray bursts and kilonovae. Massive stellar binaries that evolve into merging double neutron stars are believed to experience a common-envelope episode. During this episode, the envelope of a giant star engulfs the whole binary. The energy transferred from the orbit to the envelope by drag forces or from other energy sources can eject the envelope from the binary system, leading to a stripped short-period binary. In this paper, we use one-dimensional single stellar evolution to explore the final stages of the common-envelope phase in progenitors of neutron star binaries. We consider an instantaneously stripped donor star as a proxy for the common-envelope phase and study the star's subsequent radial evolution. We determine a range of stripping boundaries which allow the star to avoid significant rapid re-expansion and which thus represent plausible boundaries for the termination of the common-envelope episode. We find that these boundaries lie above the maximum compression point, a commonly used location of the core/envelope boundary. We conclude that stars may retain fractions of a solar mass of hydrogen-rich material even after the common-envelope episode. If we consider orbital energy as the only energy source available, all of our models would overfill their Roche lobe after ejecting the envelope, whose binding energy includes gravitational, thermal, radiation, and recombination energy terms.

preprint2022arXiv

The circumstellar material around the Type IIP SN 2021yja

The majority of Type II-plateau supernovae (SNe IIP) have light curves that are not compatible with the explosions of stars in a vacuum; instead, the light curves require the progenitors to be embedded in circumstellar matter (CSM). We report on the successful fitting of the well-observed SN IIP 2021yja as a core-collapse explosion of a massive star with an initial mass of ~15 Msun and a pre-explosion radius of 631 Rsun. To explain the early-time behaviour of the broad-band light curves, the presence of 0.55 Msun CSM within ~2x10^14 cm is needed. Like many other SNe IIP, SN 2021yja exhibits an early-time flux excess including ultraviolet wavelengths. This, together with the short rise time (<2 days) in the gri bands, indicates the presence of a compact component in the CSM, essentially adjacent to the progenitor. We discuss the origin of the pre-existing CSM, which is most likely a common property of highly convective red supergiant envelopes. We argue that the difficulty in fitting the entire light curve with one spherical distribution indicates that the CSM around the SN 2021yja progenitor was asymmetric.

preprint2022arXiv

The luminous red nova AT 2018bwo in NGC 45 and its binary yellow supergiant progenitor

Luminous Red Novae (LRNe) are astrophysical transients associated with the partial ejection of a binary system&#39;s common envelope (CE) shortly before its merger. Here we present the results of our photometric and spectroscopic follow-up campaign of AT2018bwo (DLT18x), a LRN discovered in NGC45, and investigate its progenitor system using binary stellar-evolution models. The transient reached a peak magnitude of $M_r=-10.97\pm0.11$ and maintained this brightness during its optical plateau of $t_p = 41\pm5$days. During this phase, it showed a rather stable photospheric temperature of ~3300K and a luminosity of ~$10^{40}$erg/s. The photosphere of AT2018bwo at early times appeared larger and cooler than other similar LRNe, likely due to an extended mass-loss episode before the merger. Towards the end of the plateau, optical spectra showed a reddened continuum with strong molecular absorption bands. The reprocessed emission by the cooling dust was also detected in the mid-infrared bands ~1.5 years after the outburst. Archival Spitzer and Hubble Space Telescope data taken 10-14 years before the transient event suggest a progenitor star with $T_{prog}\sim 6500$K, $R_{prog}\sim 100R_{\odot}$ and $L_{prog}\sim 2\times10^4L_{\odot}$, and an upper limit for optically thin warm (1000 K) dust mass of $M_d<10^{-6}M_{\odot}$. Using stellar binary-evolution models, we determined the properties of binary systems consistent with the progenitor parameter space. For AT2018bwo, we infer a primary mass of 12-16 $M_{\odot}$, which is 9-45% larger than the ~11$M_{\odot}$ obtained using single-star evolution models. The system, consistent with a yellow-supergiant primary, was likely in a stable mass-transfer regime with -2.4<log ($\dot{M}/M_{\odot}$/yr)<-1.2 a decade before the main instability occurred. During the dynamical merger, the system would have ejected 0.15-0.5$M_{\odot}$ with a velocity of ~500 km/s.

preprint2020arXiv

Massive donors in interacting binaries: effect of metallicity

Metallicity is known to significantly affect the radial expansion of a massive star: the lower the metallicity, the more compact the star, especially during its post-MS evolution. We study this effect in the context of binary evolution. Using the stellar-evolution code MESA, we computed evolutionary tracks of stars at different metallicities, exploring variations of factors known to affect the radial expansion (e.g. semiconvection, overshooting, rotation). We find observational support for an evolution in which already at metallicity $0.2Z_{\odot}$ massive stars remain relatively compact during the Hertzprung-Gap (HG) phase and most of their expansion occurs during core-helium burning (CHeB). Consequently, we show that metallicity has a strong influence on the type of mass transfer evolution in binary systems. At solar metallicity, a case-B mass transfer is initiated shortly after the end of MS, and a giant donor is almost always a rapidly expanding HG star. At lower metallicity, the parameter space for mass transfer from a more evolved CHeB star increases dramatically. This means that envelope stripping and formation of helium stars in low-metallicity environments occurs later in the evolution of the donor, implying a much shorter duration of the Wolf-Rayet phase (even by an order of magnitude) and higher final core masses. This metallicity effect is independent of the impact of metallicity-dependent stellar winds. At very low metallicities, a significant fraction of massive stars in binaries engages in the first episode of mass transfer very late into their evolution, when they already have a well-developed CO core. The remaining lifetime ($< 10^4$ yr) is unlikely to be enough to strip the entire H-rich envelope. We also briefly discuss the extremely small parameter space for mass transfer from massive convective-envelope donors in the context of binary black hole merger formation.

preprint2018arXiv

High mass X-ray binaries as progenitors of gravitational wave sources

X-ray binaries with black hole (BH) accretors and massive star donors at short orbital periods of a few days can evolve into close binary BH systems (BBH) that merge within the Hubble time through stable mass transfer evolution. From observational point of view, upon the Roche-lobe overflow, such systems will most likely appear as ultra-luminous X-ray sources (ULXs). To study this connection, we compute the mass transfer phase in systems with BH accretors and massive star donors ($M > 15 \,M_\odot$) at various orbital separations and metallicities using the MESA stellar evolution code. In the case of core-hydrogen and core-helium burning donors (cases A and C of mass transfer) we find the typical duration of super-Eddington mass transfer of up to $10^6$ and $10^5 \, \rm yr$ , with rates of $10^{-6}$ and $10^{-5} \,M_\odot \, \rm yr^{-1}$ , respectively. Given that roughly $0.5$ ULXs are found per unit of star formation rate ($\,M_\odot \, \rm yr^{-1}$), and assuming that $10\%$ of all the observed ULXs form merging BBH, we estimate the rate of BBH mergers from stable mass transfer evolution to be at most $10 {\rm ~Gpc}^{-3} {\rm ~yr}^{-1}$.