WR~21a was known as a massive spectroscopic binary composed of an O2.5If*/WN6ha primary and an O3V((f*))z secondary. Although a minimum value, the mass estimated for the primary placed it as one of the most massive stars found in our Galaxy. We repor
t the discovery of photometric variations in the time series observations carried out by the Transiting Exoplanet Survey Satellite (TESS). These light variations are interpreted as formed by two main components: a sharp partial eclipse of the O3 by the O2.5/WN6 star, and tidally excited oscillations. Based on the light minima a new ephemeris for the system is calculated. The system configuration is detached and the observed eclipse corresponds to the periastron passage. During the eclipse, the light curve shape suggests the presence of the heartbeat effect. The frequencies derived for the tidally excited oscillations are harmonics of the orbital period. Combining new and previously published radial velocity measurements, a new spectroscopic orbital solution is also obtained. Using the PHOEBE code we model the TESS light curve and determine stellar radii of R_O2.5/WN6=23.3 Rsun and R_O3=14.8 Rsun, and an orbital inclination i=61.8+/-1.5 deg. The latter combined with the spectroscopic minimum masses lead to absolute masses of M_O2.5/WN6=94.4 Msun and M_O3=53.6 Msun, which establishes WR 21a as belonging to the rare group of the very massive stars.
In this work, we study the lepton flavor and lepton number violating $B_{c}$ meson decays via two intermediate on-shell Majorana neutrinos $N_j$ into two charged leptons and a charged pion $B_{c}^{pm} to mu^{pm} N_j to mu^{pm} tau^{pm} pi^{mp}$. We
evaluated the possibility to measure the modulation of the decay width along the detector length produced as a consequence of the lepton flavor violating process, in a scenario where the heavy neutrinos masses range between $2.0$ GeV $leq M_N leq 6.0$ GeV. We study some realistic conditions which could lead to the observation of this phenomenon at futures $B$ factories such HL-LHCb.
The KM3NeT research infrastructure is under construction in the Mediterranean Sea. KM3NeT will study atmospheric and astrophysical neutrinos with two multi-purpose neutrino detectors, ARCA and ORCA, primarily aimed at the GeV-PeV energy scale. Thanks
to the multi-photomultiplier tube design of the digital optical modules, KM3NeT is capable of detecting the neutrino burst from a Galactic or near-Galactic core-collapse supernova. This potential is already exploitable with the first detection units deployed in the sea. This paper describes the real-time implementation of the supernova neutrino search, operating on the two KM3NeT detectors since the first months of 2019. A quasi-online astronomy analysis is introduced to study the time profile of the detected neutrinos for especially significant events. The mechanism of generation and distribution of alerts, as well as the integration into the SNEWS and SNEWS 2.0 global alert systems are described. The approach for the follow-up of external alerts with a search for a neutrino excess in the archival data is defined. Finally, an overview of the current detector capabilities and a report after the first two years of operation are given.
Light axion-like particles (ALPs) are expected to be abundantly produced in core-collapse supernovae (CCSNe), resulting in a $sim$10-second long burst of ALPs. These particles subsequently undergo conversion into gamma-rays in external magnetic field
s to produce a long gamma-ray burst (GRB) with a characteristic spectrum peaking in the 30--100-MeV energy range. At the same time, CCSNe are invoked as progenitors of {it ordinary} long GRBs, rendering it relevant to conduct a comprehensive search for ALP spectral signatures using the observations of long GRB with the textit{Fermi} Large Area Telescope (LAT). We perform a data-driven sensitivity analysis to determine CCSN distances for which a detection of an ALP signal is possible with the LATs low-energy (LLE) technique which, in contrast to the standard LAT analysis, allows for a a larger effective area for energies down to 30~MeV. Assuming an ALP mass $m_a lesssim 10^{-10}$~eV and ALP-photon coupling $g_{agamma} = 5.3times 10^{-12}$ GeV$^{-1}$, values considered and deduced in ALP searches from SN1987A, we find that the distance limit ranges from $sim!0.5$ to $sim!10$~Mpc, depending on the sky location and the CCSN progenitor mass. Furthermore, we select a candidate sample of twenty-four GRBs and carry out a model comparison analysis in which we consider different GRB spectral models with and without an ALP signal component. We find that the inclusion of an ALP contribution does not result in any statistically significant improvement of the fits to the data. We discuss the statistical method used in our analysis and the underlying physical assumptions, the feasibility of setting upper limits on the ALP-photon coupling, and give an outlook on future telescopes in the context of ALP searches.
Terahertz (THz) technology has been a great candidate for applications, including pharmaceutic analysis, chemical identification, and remote sensing and imaging due to its non-invasive and non-destructive properties. Among those applications, penetra
ting-type hyperspectral THz signals, which provide crucial material information, normally involve a noisy, complex mixture system. Additionally, the measured THz signals could be ill-conditioned due to the overlap of the material absorption peak in the measured bands. To address those issues, we consider penetrating-type signal mixtures and aim to develop a textit{blind} hyperspectral unmixing (HU) method without requiring any information from a prebuilt database. The proposed HYperspectral Penetrating-type Ellipsoidal ReconstructION (HYPERION) algorithm is unsupervised, not relying on collecting extensive data or sophisticated model training. Instead, it is developed based on elegant ellipsoidal geometry under a very mild requirement on data purity, whose excellent efficacy is experimentally demonstrated.
AQ Col (EC~05217-3914) is one of the first detected pulsating subdwarf B (sdB) stars and has been considered to be a single star. However, its periodic pulsation timing variations indicate that AQ Col may not be a single star. We present pulsation pe
riod variations observed over twenty-four years and derived orbital characteristics these would imply if these were a consequence of AQ Col being a pulsating hot subdwarf in a long-period binary. The derived orbital period is P = 486.0 days. In the sdB star binary evolution scenario, a Roche lobe overflow channel results in long period (450 < P < 1400 d) for sdB + Main Sequence (MS) binaries. However the derived orbital eccentricity of the system is 0.424, which is too large for a typical long period sdB+MS system. The Skymapper u - z vs. z - WISE W1 diagram is incompatible with sdB+MS binary systems, and suggests the system contains a white dwarf or other hot and faint object. The expected radial velocity amplitude of AQ Col due to this orbital motion is ~15 km/s. However, the radial velocity amplitude differences obtained from spectroscopy show that the amplitude could be more than ~300 km/s, which indicates the possibility that AQ Col also has a short period companion with orbital period of ~1 day. Therefore, the AQ Col system may be a triple star system. Because such systems have not yet been studied in detail, AQ Col may offer unique insight into the production of sdB stars and this system deserves continued time-series and spectroscopic monitoring.
Home automation in modern smart home platforms is often facilitated using trigger-action routines. While such routines enable flexible automation, they also lead to an instance of the integrity problem in these systems: untrusted third-parties may us
e platform APIs to modify the abstract home objects (AHOs) that privileged, high-integrity devices such as security cameras rely on (i.e., as triggers), thereby transitively attacking them. As most accesses to AHOs are legitimate, removing the permissions or applying naive information flow controls would not only fail to prevent these problems, but also break useful functionality. Therefore, this paper proposes the alternate approach of home abstraction endorsement, which endorses a proposed change to an AHO by correlating it with certain specific, preceding, environmental changes. We present the HomeEndorser framework, which provides a policy model for specifying endorsement policies for AHOs as changes in device states, relative to their location, and a platform-based reference monitor for mediating all API requests to change AHOs against those device states. We evaluate HomeEndorser on the HomeAssistant platform, finding that we can derive over 1000 policy rules for HomeEndorser to endorse changes to 6 key AHOs, preventing malice and accidents for less than 10% overhead for endorsement check microbenchmarks, and with no false alarms under realistic usage scenarios. In doing so, HomeEndorser lays the first steps towards providing a practical foundation for ensuring that API-induced changes to abstract home objects correlate with the physical realities of the users environment.
Shannons Index of Difficulty ($SID$), a logarithmic relation between movement-amplitude and target-width, is reputable for modelling movement-time in pointing tasks. However, it cannot resolve the inherent speed-accuracy trade-off, where emphasizing
accuracy compromises speed and vice versa. Effective target-width is considered as spatial adjustment, compensating for accuracy. However, for compensating speed, no significant adjustment exists in the literature. Real-life pointing tasks are both spatially and temporally unconstrained. Spatial adjustment alone is insufficient for modelling these tasks due to several human factors. To resolve this, we propose $ANTASID$ (A Novel Temporal Adjustment to $SID$) formulation with detailed performance analysis. We hypothesized temporal efficiency of interaction as a potential temporal adjustment factor ($t$), compensating for speed. Considering spatial and/or temporal adjustments to $SID$, we conducted regression analyses using our own and benchmark datasets in both controlled and uncontrolled scenarios. The $ANTASID$ formulation showed significantly superior fitness values and throughput in all the scenarios.
Context: To investigate how the content of massive OB stars affects the long-term evolution of young open clusters and their tidal streams, and how such an effect influences the constraint of initial conditions by looking at the present-day observati
ons. Aims: OB stars are typically in binaries, have a strong wind mass loss during the first few Myr, and many become black holes. These affect the dynamical evolution of an open star cluster and impact its dissolution in a given Galactic potential. We investigate the correlation between the mass of OB stars and the observational properties of open clusters. Hyades-like star clusters are well represented in the Solar neighborhood and thus allow comparisons with observational data. Methods: We perform a large number of star-by-star numerical $N$-body simulations of Hyades-like star clusters by using the high-performance $N$-body code textsc{petar} combined with textsc{galpy}. We also developed the tool to transfer the simulation data to mock observations of Gaia. Results: We find that OB stars and black holes have a major effect on star cluster evolution. Star clusters with the same initial conditions, but a different initial content of OB stars, follow very different evolutionary paths. Thus, the initial total mass and radius of an observed star cluster cannot be unambiguously determined unless the initial content of OB stars is known. We show that the stellar counts in the corresponding tidal tails, that can be identified in the Gaia data, help to resolve this issues. We thus emphasise the importance of exploring not only star-clusters, but also their corresponding tidal tails. These findings are relevant for studies of the formation of massive stars.
We consider the propagation of short waves which generate waves of much longer (infinite) wave-length. Model equations of such long wave-short wave resonant interaction, including integrable ones, are well-known and have received much attention becau
se of their appearance in various physical contexts, particularly fluid dynamics and plasma physics. Here we introduce a new long wave-short wave integrable model which generalises those first proposed by Yajima-Oikawa and by Newell. By means of its associated Lax pair, we carry out the linear stability analysis of its continuous wave solutions by introducing the stability spectrum as an algebraic curve in the complex plane. This is done starting from the construction of the eigenfunctions of the linearised long wave-short wave model equations. The geometrical features of this spectrum are related to the stability/instability properties of the solution under scrutiny. Stability spectra for the plane wave solutions are fully classified in the parameter space together with types of modulational instabilities.
