Multiple areas involving photometric studies experience a flood of raw telescopic data, that need to be processed automatically. Although many software solutions exist, few of them are capable of making automated detection and precise measurements of moving targets. In this study we developed a modular package to automate photometric procedures in Python. Our package can reduce image frames, estimate drift and rotation between the frames, and/or perform aperture photometry for accurate light curves. We also integrated tools for detecting and tracking moving objects, particularly asteroids. Utilizing this package, we processed a large volume of data, extracting over a hundred asteroid light curves, validating its robustness.
We present an analysis of the photometric data of new main belt comet P/2023 JN16 (Lemmon) observed with the 1.35-m SkyMapper telescope at Siding Spring Observatory in 2024 during July-September. The faint object showed dusty activity during a long period. Some photometric parameters, such as SkyMapper r-band magnitudes, Af rho parameters, and absolute magnitude were estimated. We estimate the nuclear radius for comet P/2023 JN16 to be less than 0.5 km. The activity of the object is possibly driven by the release of large, slow-moving particles.
We present a search for visual companions of multiple systems with the LITE effect using DR3 data from the Gaia mission. Then, we verified if we can determine the relative positions and velocities of the two components in three-dimensional space with sufficient accuracy. Finally, we checked if closed orbits are possible for such values. We used fits of clone orbits with a scatter consistent with the errors of the parameters determined. We used covariance matrices provided by Gaia to create the normal distribution of the astrometric parameters. Most of the visual companions found are already listed in publications and catalogs. In some cases the positions in the three-dimensional space of the two components of the visual pair were unambiguous, i.e., the uncertainty ranges did not overlap. We selected a group of eight objects from among those in Zakirov's catalog, for which the positions and velocities of the main system and the visual companion are very similar. In most cases, we were able to find closed orbits by calculating the orbits of clones. In addition, we selected a wider group of 40 candidates with slightly worse parameters determined. Three of them were also studied in detail.
In this study, the astrophysical parameters of four sparsely studied open clusters: ASCC 6, ASCC 13, ASCC 16, and ASCC 108 were determined and updated. Cluster memberships were analysed using the UPMASK algorithm, while cluster ages and color excesses were estimated through the PARSEC isochrone-fitting method. The parameters of the four clusters were obtained by selecting data from contemporary open cluster catalogs, refining their coordinates using the latest Gaia DR3 data release, and subsequently incorporating the results into the scientific literature. The calculated distances for the clusters are as follows: ASCC 6 at d = 1844 +/- 88 pc, ASCC 13 at d = 1104 +/- 70 pc, ASCC 16 at d = 2.878 +/- 0.005 pc, and ASCC 108 at d = 1142 +/- 54 pc. Among the clusters studied, ASCC 108 is an older cluster with an estimated age of 265 +/- 5 Myr. The other three clusters, ASCC 6, ASCC 13, and ASCC 16 are young open clusters with ages calculated as 30 +/- 5, 85 +/- 5, and 7 +/- 1 million years, respectively.
We present N-body simulations of open clusters covering a time span starting from birth and ending after 200 Myr. These clusters initially contain 5000 stars and are set up with both 3D and fractal geometries. The structural parameters are intentionally chosen so as to allow lifetimes exceeding 100 Myr. The results are analyzed with regard to bulk properties such as mass, size, number of stars, virial ratio and binary fraction, and the internal structure as evidenced by the radial profiles of mass density and stellar number density. Thus, we are able to characterize the progress of evolutionary features like mass segregation, virialization and two-body relaxation. We find that mass segregation proceeds more quickly in clusters without primordial mass segregation, likely because these allow for closer contact between low and high mass stars as two-body relaxation sets in. By studying the long-term evolution of the virial ratio, we have found that this is on average larger than the equilibrium value and shows an oscillating behavior with a characteristic frequency, possibly caused by periodic trapping of high-velocity stars in the high density region close to the center. Using simulated surface brightness profiles, we show that our cluster models are consistent with observed core radii in young clusters. We find indications that the binary fraction decreases with time in clusters without primordial mass segregation and increases in primordially mass segregated clusters. We find evidence that binary destruction and formation are continually ongoing phenomena. Primordial binaries tend to either be destroyed within 40 Myr or to exist until 200 Myr. In fractal clusters we observe both an increased binary destruction rate and an increased binary formation rate during the early times as compared to 3D clusters. This is likely due to the stars being concentrated to filaments with super-high densities.
We report photometry results of a frequently outbursting dwarf nova, ER Ursae Majoris. We carried out analyses of the light curve, periodograms, and O-C diagrams, to measure the outburst parameters of the system. We investigated the system's behavior using the ground-based optical data and the Transiting Exoplanet Survey Satellite data. During these observing runs, we scrutinized three superoutbursts and several normal outbursts. We detected ordinary and late superhumps during each of the investigated superoutbursts. We derived the period excess value epsilon approximate to 3.0(1)%. This suggests that over the last 30 yr, ER UMa has not shifted on the evolutionary path toward period-bounce objects. Between 1992 and 2022, the interval between two successive superoutbursts (the supercycle length) changed significantly from 42.1 d to 59.6 d, what indicates that the mean mass-transfer rate of ER UMa has been decreasing over this period.
A comprehensive evolution study was conducted on a carefully selected sample of near-contact binaries (NCBs) with more massive components filling the Roche lobes, utilizing the best-known basic parameters and indications of ongoing mass transfer. The results and discussion highlight that several NCBs with total masses exceeding 2 M-circle dot survive only a short time after mass exchange as contact binaries (CBs), with both components eventually merging to form a rapidly rotating giant, akin to FK Com. Less massive NCBs transition into typical CBs and remain in this phase for up to 2 Gyr before ending their binary evolution as systems with extremely low mass ratios, susceptible to Darwin instability. However, this does not fully explain the existence of low-mass CBs with masses in the range of 1--1.5 M-circle dot. It is noted that there exists a population of low-mass binaries, nearly filling their Roche lobes. Their overall properties suggest that they could be progenitors of low-mass CBs.
We present the discovery of a free-floating planet microlensing event KMT-2024-BLG-0816/ OGLE-2024-BLG-0519. The event shows finite-source effect, significant blending light, and no microlensing signal from a putative planet host. Among the free-floating planet events with finite source effects, this is the only event with unresolved blending light. We discuss how follow-up observations can be used to determine whether the blending light originates from a putative planet host.
Long secondary period (LSP) variable stars are a subclass of long-period variables (LPV) that exhibit additional long-term variability alongside pulsations. Despite being observed in over 30% of LPVs, the reason behind the LSP phenomenon is still debated. The most favored explanation, supported by recent growing evidence, is binarity, where the pulsating giant star has a substellar-mass companion. To further test this hypothesis, it is important to identify bright LSP variables, for which high-quality spectroscopic and interferometric observations can be obtained more easily. Motivated by the absence of a catalog of bright nearby LSPs, we searched the All Sky Automated Survey data in the V-band magnitude range 5.5-14 mag, and for declinations < +28(degrees). The resulting catalog contains 23 LSPs, 13 of which are new discoveries. We compare our catalog with the LSP lists available in the literature.
Photometry of t Bo & ouml;tis A acquired by MOST satellite shows variations, which could be explained by the presence of a spot on the host star surface, potentially induced by its planetary companion. We used the Wilson-Devinney method for modeling the light curve. The results from the literature describing the star-planet system were used. Although t Bo & ouml; is a non-transiting system, the masses, radii, and orbital inclination are known. The dominating factor in the light curve is the stellar spot effect. The ellipsoidal variations and reflected light influence are not visible or very small. Modeling shows a strong correlation between co-latitude and spot size. There is a group of solutions that fits the data well. If we suppose that the spot is on the star's equator we could find an unambiguous solution. The spot is shifted due to the sub-planetary point in the rotation direction. The longitude of the circular spot center is 62.degrees 75 +/- 0.03. The temperature contrast of the spot is very low, only a few degrees below ambient temperature. The spots cover a significant part of the stellar surface, its radius is 56 degrees +/- 4. We also presented a second solution, which better fits the data, for a much smaller spot at latitude approximate to 30 degrees and radius of 9.degrees 7 +/- 0.1. The influence of light reflected from the day side of the planet was also analyzed.
Blue Large-Amplitude Pulsators (BLAPs) are rare short-period (P less than or similar to 80 min) pulsating variable stars exhibiting large-amplitude brightness variations (typically between 0.1 mag and 0.4 mag). As a recently discovered class of radial-mode pulsators, the origin and nature of these variables remain the subject of ongoing investigations. Here, we present a comprehensive summary of all BLAPs identified in the data of the Optical Gravitational Lensing Experiment (OGLE), including the discovery of 87 new BLAPs in the inner Galactic bulge fields. We performed a systematic search for periodic signals in the I-band light curves of more than 400 million stars with magnitudes down to I= 21. Our search effectively doubles the number of these variables to almost 200. The detected BLAPs exhibit pulsation periods between roughly 5 min and 76 min. The analyzed dataset covers a timespan from 2001 to 2024, with some stars observed up to 20000 times, providing the temporal coverage needed to study period and amplitude variations. We report on three objects that show enormous period changes, at a rate of 10(-5) yr(-1) , which could provide important clues to the evolutionary status of BLAPs. Full dataset is incorporated into the publicly available OGLE Collection of Variable Stars (OCVS), enabling future studies of these enigmatic objects.
In a recent paper, Hawkins and Garc & iacute;a-Bellido raised doubts on the results of 20-yr long OGLE photometric monitoring, which did not find a large number of gravitational microlensing events in the direction of the Magellanic Clouds. These results implied that primordial black holes and other compact objects with masses from 10-8 to 103 M circle dot cannot comprise a substantial fraction of the Milky Way dark matter halo. Unfortunately, the Hawkins and Garc & iacute;a-Bellido paper contained a number of scientific misrepresentations of our work. Here, we demonstrate that their arguments lack a solid basis or are simply incorrect. As we show below, and yet they are not found - compact objects (including primordial black holes) in the dark halo of the Milky Way remain undetected, despite extensive searches.
We present an independent spectroscopic and radial velocity analysis for nine stars from the Pennsylvania-Torun Planet Search. For BD+24 4697, we present an updated true companion's mass (0.16 +/- 0.02 M-circle dot) as well as evidence of stellar activity. For BD+54 1640 and BD+65 1241 we present true masses of companions, m = 0.15 +/- 0.04 M-circle dot and m = 0.091 +/- 0.005 M-circle dot, respectively. For BD+63 974 and BD+69 935 we find low mass companions with m sin i = 0.046 +/- 0.001 M-circle dot and m sin i = 0.090 +/- 0.005 M-circle dot. For BD+52 1281, BD+54 1382, TYC 2704-2680-1, and TYC 3525-02043-1 we present evidence of low-mass companions with m sin i of 0.115 +/- 0.006 M-circle dot, 0.083 +/- 0.007 M-circle dot, 0.279 +/- 0.009 M-circle dot, and 0.064 +/- 0.006 M-circle dot, respectively. Consequently, BD+54 1382, BD+63 974, BD+65 1241, BD+69 935 and TYC 3525-02043-1 appear to be brown dwarf host candidates.
We present the ultimate I-band calibration of the tip of the red giant branch (TRGB) standard candle. Our calibration is based on photometry from the outer parts of the Large Magellanic Cloud, 2.(degrees)75 < r < 6.(degrees)5 from the center, collected during the OGLE-IV phase of the Optical Gravitational Lensing Experiment. Outer regions of the LMC have large advantages compared to the previous attempts of the TRGB calibrations using the red giants from the central parts of this galaxy. The interstellar reddening in these regions is much lower and more uniform, stellar crowding is lower and the outer parts of the LMC can be accurately described as a flat disk within the reasonable distance from the LMC center. The number of red giants in the upper part of the red giant branch in our LMC region is large, approximate to 140000, making it possible to determine of the tip magnitude with high accuracy. Our ultimate I-band calibration of the TRGB is: M-I,M-TRGB = -4.022 +/- 0.006 (stat) +/- 0.033 (syst) mag. We also provide its values for different techniques of the determination of the tip magnitude. The accuracy of our calibration is mostly limited by the accuracy of the distance to the LMC ( approximate to 1%) and can be improved in the future. We test our calibration by comparing it with the TRGB in the Small Magellanic Cloud and NGC 4258, i.e., the galaxies with precise geometric distance determination, and find excellent agreement. Finally, we refine the main determinations of the Hubble constant, H-0 , with the TRGB using our new calibration of the I-band TRGB brightness.
We have obtained spectroscopic observations for four short-period variable objects detected in ZTF, Gaia, and Pan-STARRS (ZGP) data and classified as Blue Large-Amplitude Pulsators (BLAPs) in McWhirter and Lam (2022): ZGP-BLAP-03, ZGP-BLAP-04, ZGP-BLAP-10, and ZGP-BLAP-15. The variables have periods between 46 and 56 min, full amplitudes of 0.13-0.22 mag in the r band, and light curve shapes typical for radially pulsating stars. Three of them were found at high galactic latitudes (|b|>30 deg). We have identified object ZGP-BLAP-03 as an early F-type star, while objects ZGP-BLAP-04 and ZGP-BLAP-15 as low-metallicity late A-type stars. These are the three objects found at high galactic latitudes and located several kiloparsecs from the Sun. Thus, they are SX Phoenicis-type variable stars residing in the Galactic halo. In the case of low-latitude object ZGP-BLAP-10, we report the presence of helium lines in its spectrum and atmospheric parameters in agreement with known BLAPs. This and other results indicate that BLAPs are absent in metal-poor environments.
Gravitational microlensing depends primarily on the lens mass and presents a larger occurrence rate in crowded regions, which makes it the best tool to uncover the initial mass function (IMF) of low-mass stars in the Galactic bulge. The bulge IMF can be obtained from the luminosity function measured with the Hubble Space Telescope if one knows the statistics of binary stellar systems in the bulge. We aim to analyze a statistically significant number of binary-lens/single-source and singlelens/binary-source events, in order to explore the lower-mass end of the bulge IMF even in unresolved binary systems. This paper deals with events with clearly separated bumps and no caustic crossing or approach, whereas other types will be analyzed in following works. A fully-automated approach in the search and modeling of binary events was implemented. Event detection was carried out with a modified version of the algorithm used in previous studies. Model fitting was carried out with Markov chain Monte Carlo and nested sampling methods, in order to find the most probable solution among binary lens or binary source models. We retrieved 107 binary events in the Optical Gravitational Lensing Experiment (OGLE) light curves spanning ten years in 9 high-cadence and 112 low-cadence fields toward the bulge. Several criteria were applied to reduce false positives, resulting in 59 most likely binary lenses and 48 binary sources. The tools were effective in detecting a bona-fide sample of binary events, with a distribution of Einstein timescales around 35-40 d and flat distributions for mass ratio and source flux ratio. After proper consideration of detection efficiency, the statistics for binary fraction and mass ratio will provide valuable constraints for the bulge IMF.
We present the results of our analysis of Gaia19dke, an extraordinary microlensing event in the Cygnus constellation that the Gaia satellite discovered. This event featured a strong microlensing parallax effect, resulting in multiple light curve peaks. We conducted extensive photometric, spectroscopic, and high-resolution imaging follow-up observations to determine the mass and nature of the invisible lensing object. Using the Milky Way priors on the density and proper motion of lenses, we found that the lens is likely to be located at a distance of D-L = 3.3(-1.7)(+2.1) kpc, and has a mass of M-L = 0.50(-0.27)(+0.82) M-circle dot. Based on its low luminosity and mass, we propose that the lens in the Gaia19dke event is either a main sequence star or an isolated white dwarf. Due to its brightness, longevity, and lack of blending, Gaia19dke is a target for which the forthcoming Gaia Data Release 4 data will help to constrain the parameters of the lens.
New CCD photometry combined with published and unpublished archival observations have been used to study ten RR Lyr-type variable stars in the globular cluster M13. The periods have been updated and U, B, V, R-C , I-C-band light curves and their characteristics derived. Fourier analysis of the CCD observations showed that variables V31 and V36 are multiperiodic RRc stars with additional frequencies grouped close to the frequency of the overtone mode, but not forming equidistant triplets. For V36, we detect an additional weak component for which the period ratio with the overtone indicates variability of the RR0.61 kind. This makes M13 the third globular cluster, besides M3 and NGC 6362, where such RRc stars are known. We confirm V34 to be a biperiodic variable with very close frequencies. Searches for period changes using the (O-C) method for observations spanning up to 120 yr show that the cluster's only RRab star (V8) has undergone a very large period decrease, but rather than decreasing at a steady rate it most likely experienced an abrupt period decrease around 1970. Two of the nine RRc variables show steady period increases, one a period decrease, and five no significant period change. Rapid irregular light-curve phase changes observed for four of the RRc stars can be explained by their multiperiodicity. Expected evolutionary rates of period change have been determined for the RR Lyr stars using the PISA evolutionary tracks for horizontal branch models. The observed rates mostly do not agree with the theoretical ones, both in sign and in absolute value. The results for V25, however, indicate that this RRc star is much more evolved than other RR Lyr stars in M13 with its observed period change rate of 0.5 d/Myr being consistent with that predicted by theory. A comparison of the derived physical properties from different approaches suggests problems with the theory. Of most concern is the inconsistency found for the RR Lyr stars between the predictions from HB evolutionary tracks and the well-determined observational parameters of these stars.
In this study, we present the results of an investigation of the the physical properties, abundances, and photoionization modeling of planetary nebula (PN) candidates from the HASH database having small angular sizes (<8'' with one exception) and located in the Northern sky hemisphere. We collected new spectroscopic data of these objects. We confirmed 12 PNe using diagnostic diagrams, emission line ratios and calculated their physical conditions such as extinction coefficient, electron density, and electron temperature. We conducted elemental abundance calculations for the PNe and found that their abundances align with both solar and Galactic values. Additionally, utilizing photoionization models developed with the Cloudy code, we obtained the effective temperatures of central stars, which span from 40 000 K to 250 000 K, along with luminosities ranging from 400 L-circle dot to 10 000 L-circle dot. We determined the initial mass values of the PNe to be in the 0.8-4.5 M-circle dot range on the HR diagram with post-AGB evolutionary tracks using their T-eff and luminosity values. Considering the final masses of these PNe, their mass losses were estimated to be approximately between 0.3 M-circle dot and 3.6 M-circle dot. Notably, we found that the ages of the PNe, determined from post-AGB evolutionary tracks, varied from 120 to 34 000 yr, consistently with the earlier findings.
Transient noise (glitches) in LIGO data hinders the detection of gravitational waves (GW). The Gravity Spy project has categorized these noise events into various classes. With the O3 run, there is the inclusion of two additional noise classes and, thus, a need to train new models for effective classification. We aim to classify glitches in LIGO data into 22 existing classes from the first run plus 2 additional noise classes from O3a using the Vision Transformer (ViT) model. We train a pre-trained Vision Transformer (ViT-B/32) model on a combined dataset consisting of the Gravity Spy dataset with the additional two classes from the LIGO O3a run. We achieve a classification efficiency of 92.26%, demonstrating the potential of Vision Transformer to improve the accuracy of gravitational wave detection by effectively distinguishing transient noise.
