On 26 September 2022, the Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos. This demonstrated the efficacy of a kinetic impactor for planetary defense by changing the orbital period of Dimorphos by 33 minutes (Thomas et al. 2023). Measuring the period change relied heavily on a coordinated campaign of lightcurve photometry designed to detect mutual events (occultations and eclipses) as a direct probe of the satellite's orbital period. A total of 28 telescopes contributed 224 individual lightcurves during the impact apparition from July 2022 to February 2023. We focus here on decomposable lightcurves, i.e. those from which mutual events could be extracted. We describe our process of lightcurve decomposition and use that to release the full data set for future analysis. We leverage these data to place constraints on the post-impact evolution of ejecta. The measured depths of mutual events relative to models showed that the ejecta became optically thin within the first ~1 day after impact, and then faded with a decay time of about 25 days. The bulk magnitude of the system showed that ejecta no longer contributed measurable brightness enhancement after about 20 days post-impact. This bulk photometric behavior was not well represented by an HG photometric model. An HG1G2 model did fit the data well across a wide range of phase angles. Lastly, we note the presence of an ejecta tail through at least March 2023. Its persistence implied ongoing escape of ejecta from the system many months after DART impact.

GRB~230812B is a bright and relatively nearby ($z =0.36$) long gamma-ray burst (GRB) that has generated significant interest in the community and has thus been observed over the entire electromagnetic spectrum. We report over 80 observations in X-ray, ultraviolet, optical, infrared, and sub-millimeter bands from the GRANDMA (Global Rapid Advanced Network for Multi-messenger Addicts) network of observatories and from observational partners. Adding complementary data from the literature, we then derive essential physical parameters associated with the ejecta and external properties (i.e. the geometry and environment) of the GRB and compare with other analyses of this event. We spectroscopically confirm the presence of an associated supernova, SN2023pel, and we derive a photospheric expansion velocity of v $\sim$ 17$\times10^3$ km s$^{-1}$. We analyze the photometric data first using empirical fits of the flux and then with full Bayesian Inference. We again strongly establish the presence of a supernova in the data, with a maximum (pseudo-)bolometric luminosity of $5.75 \times 10^{42}$ erg/s, at $15.76^{+0.81}_{-1.21}$ days (in the observer frame) after the trigger, with a half-max time width of 22.0 days. We compare these values with those of SN1998bw, SN2006aj, and SN2013dx. Our best-fit model favours a very low density environment ($\log_{10}({n_{\rm ISM}/{\rm cm}^{-3}}) = -2.38^{+1.45}_{-1.60}$) and small values for the jet's core angle $\theta_{\rm core} = 1.54^{+1.02}_{-0.81} \ \rm{deg}$ and viewing angle $\theta_{\rm obs} = 0.76^{+1.29}_{-0.76} \ \rm{deg}$. GRB 230812B is thus one of the best observed afterglows with a distinctive supernova bump.

In 2015–2021 we carried out observations of the Seyfert 1 galaxy (SyG 1) NGC 7469 in Bessell UBVRI filters with the 1.5-m telescope of the Maidanak Observatory, which have continued the monitoring of NGC 7469 since 1990. We took UBVRI CCD frames and performed standard frame processing, including bias correction, sky background subtraction, flat fielding, cosmic-ray particle removal, etc. All our data were obtained on CCD cameras with deep cooling and subarcsecond seeing. We carried out the calibrations using several standard stars in the same frame as the galaxy. The results of our photometry in a 13.5 arcsec aperture are presented graphically in the visibility windows of the observed period. A slow (S) flare was detected on the constructed variability curves in the UBVRI filters; a slow increase in brightness is observed since 2015, reaching a maximum in 2019. The amplitude of the S flare is 0.5 mag in the U filter and decreases to zero in the I filter. On the color–color (U-B)/(B-V) diagrams the colors in a 5 arcsec aperture are bluer than those in a 30 arcsec aperture.

В статье приведены результаты фотометрического исследования наблюдательных данныхчетырехкомпонентного гравитационно-линзированного квазара GRAL J024848.7+191331в Майданакской обсерватории. Показаны кривые блеска системы в целом и ее отдельныхкомпонентов. Система в целом показала умеренную амплитуду переменности, однакоблеск компонентов меняется более активно, до 0.25m звездных величин. Явных признаковмикролинзирования не обнаружено. Вычислены наиболее вероятные значения временныхзадержек: ΔtAB=−1.7±1.6 дней, ΔtAC=−2.2±1.8 дней, ΔtAD=–4.8±2.8 дней. Эти величины согласуются с найденными ранее модельными расчетами.

Aims. We present a campaign designed to train the Global Rapid Advanced Network Devoted to the Multi-messenger Addicts (GRANDMA) network and its infrastructure to follow up on transient alerts and detect their early afterglows. In preparation for O4 II campaign, we focused on gamma-ray burst (GRB) alerts since they are expected to serve as the electromagnetic counterpart of gravitational-wave events. Our goal was to improve our response to the alerts and to start prompt observations as soon as possible, so that we may better prepare the GRANDMA network for the fourth observational run of LIGO-Virgo-Kagra (launched at the end of May 2023) and future missions such as SM. Methods. We set up a dedicated infrastructure and organized a rota of follow-up advocates (FAs) to guarantee round-the-clock assistance to our telescope teams, with an aim to receive, manage, and send out observational plans to our partner telescopes. To ensure a large number of observations, we focused on Swift GRBs whose localization errors were generally smaller than the GRANDMA telescopes’ field of view. This allowed us to bypass the transient identification process and focus on the reaction time and efficiency of the network. Results. During the ‘Ready for O4 II’ phase, 11 Swift /INTEGRAL GRB triggers were selected. Of these, nine fields had been observed and three afterglows had been detected (GRB 220403B, GRB 220427A, GRB 220514A) with 17 GRANDMA telescopes and 17 amateur astronomers from the citizen science project Kilonova-Catcher. Here, we highlight the GRB 220427A analysis, where our long-term follow-up of the host galaxy allowed us to obtain a photometric redshift of z = 0.82 ± 0.09 and its lightcurve evolution, as well as to fit the decay slope of the afterglows and study the properties of the host galaxy. Conclusions. During this eight-week-long GRB follow-up campaign, we successfully fulfilled our goal of training telescope teams for O4 and improving the associated technical toolkits. For seven of the GRB alerts, our network was able to start the first observations less than one hour after the GRB trigger time. We also characterized the network efficiency to observe GRB afterglow given the resulting time delay and limiting magnitude, and to its light curve evolution based on the observation of GRB 220427A.

We analyze variability in 15-season optical lightcurves from the doubly imaged lensed quasar SDSS J165043.44+425149.3 (SDSS1650), comprising five seasons of monitoring data from the Maidanak Observatory (277 nights in total, including the two seasons of data previously presented in Vuissoz et al.), five seasons of overlapping data from the Mercator telescope (269 nights), and 12 seasons of monitoring data from the US Naval Observatory, Flagstaff Station at lower cadence (80 nights). We update the 2007 time-delay measurement for SDSS1650 with these new data, finding a time delay of Delta t AB = - 55.1 - 3.7 + 4.0 days, with image A leading image B. We analyze the microlensing variability in these lightcurves using a Bayesian Monte Carlo technique to yield measurements of the size of the accretion disk at lambda rest = 2420 angstrom, finding a half-light radius of log(r 1/2/cm) = 16.19 - 0.58 + 0.38 assuming a 60 degrees inclination angle. This result is unchanged if we model 30% flux contamination from the broad-line region. We use the width of the Mg ii line in the existing Sloan Digital Sky Survey spectra to estimate the mass of this system's supermassive black hole, finding M BH = 2.47 x 109 M circle dot. We confirm that the accretion disk size in this system, whose black hole mass is on the very high end of the M BH scale, is fully consistent with the existing quasar accretion disk size-black hole mass relation.

The article presents the results of long-term photometric monitoring of two binary gravitationally lensed quasars, SDSS J2124 + 1632 and SDSS J0806 + 2006, carried out at the Maidanak Observatory in 2017–2022. The obtained light curves of the lensed components of both systems are analyzed. The variability of SDSS J2124 + 1632 turned out to be quite large: up to 0m.50 for the system as a whole and up to 0m.75 for component A. Long-term microlensing was found against the background of a general increase in the apparent brightness of the quasar source. The brightness variations in SDSS J0806 + 2006 are less intense: the range is about 0m.20 for the system as a whole, and up to 0m.25 for both components. Analysis of the light curves did not show the presence of microlensing here. We also calculated the probable values of the time delay: Δ t_AB=102± 20 days (component B is in the lead) and Δ t_AB=-53.0± 6.0 days (component A is in the lead) in SDSS J2124 + 1632 and SDSS J0806 + 2006, respectively. The value of Δ t_AB for SDSS J2124 + 1632 is consistent with previously found time delays for binary gravitationally lensed systems. In the case of the second system, the time delay is consistent with earlier theoretical calculations, which suggested that the time delay should be about 50 days.

Context. GRB 221009A, initially detected as an X-ray transient by Swift, was later revealed to have triggered the Fermi satellite about an hour earlier, marking it as a post-peak observation of the event’s emission. This GRB distinguished itself as the brightest ever recorded, presenting an unparalleled opportunity to probe the complexities of GRB physics. The unprecedented brightness, however, challenged observation efforts, as it led to the saturation of several high-energy instruments. Aims. Our study seeks to investigate the nature of the INTEGRAL-detected GRB 221009A and elucidate the environmental conditions conducive to these exceptionally powerful bursts. Moreover, we aim to understand the fundamental physics illuminated by the detection of teraelectronvolt (TeV) photons emitted by GRB 221009A. Methods. We conducted detailed analyses of early photometric and spectroscopic observations that span from the Fermi trigger through to the initial days following the prompt emission phase in order to characterize GRB 221009A’s afterglow, and we complemented these analyses with a comparative study. Results. Our findings from analyzing INTEGRAL data confirm GRB 221009A as the most energetic event observed to date. Early optical observations during the prompt phase negate the presence of bright optical emissions with internal or external shock origins. Spectroscopic analyses enabled us to measure GRB 221009A’s distance and line-of-sight properties. The afterglow’s temporal and spectral analysis suggests prolonged activity of the central engine and a transition in the circumburst medium’s density. Finally, we discuss the implications for fundamental physics of detecting photons as energetic as 18 TeV from GRB 221009A. Conclusions. Early optical observations have proven invaluable for distinguishing between the potential origins of optical emissions in GRB 221009A, underscoring their utility in GRB physics studies. However, the rarity of such data underscores the need for dedicated telescopes capable of synchronous multiwavelength observations. Additionally, our analysis suggests that the host galaxies of TeV GRBs share commonalities with those of long and short GRBs. Expanding the sample of TeV GRBs could further solidify these findings.

Three light curves of the V1059 Cep eclipsing binary obtained in 2012, 2013, and 2021 were analyzed. We found the rapid apsidal motion in this system at the rate dω/dt = 7.2^∘ per year. Assuming the equality of observed and theoretical apsidal motion rates we estimated physical characteristics of the components based on the data on their temperatures from the literature. According to our calculations the components are two very similar stars of the B7V–B7.5V spectral type with masses ≈ 1pt (3.4 ± 0.3) 1ptM_⊙ and age 180 ± 30 million years.

We present a campaign designed to train the GRANDMA network and its infrastructure to follow up on transient alerts and detect their early afterglows. In preparation for O4 II campaign, we focused on GRB alerts as they are expected to be an electromagnetic counterpart of gravitational-wave events. Our goal was to improve our response to the alerts and start prompt observations as soon as possible to better prepare the GRANDMA network for the fourth observational run of LIGO-Virgo-Kagra (which started at the end of May 2023), and future missions such as SM. To receive, manage and send out observational plans to our partner telescopes we set up dedicated infrastructure and a rota of follow-up adcates were organized to guarantee round-the-clock assistance to our telescope teams. To ensure a great number of observations, we focused on Swift GRBs whose localization errors were generally smaller than the GRANDMA telescopes' field of view. This allowed us to bypass the transient identification process and focus on the reaction time and efficiency of the network. During 'Ready for O4 II', 11 Swift/INTEGRAL GRB triggers were selected, nine fields had been observed, and three afterglows were detected (GRB 220403B, GRB 220427A, GRB 220514A), with 17 GRANDMA telescopes and 17 amateur astronomers from the citizen science project Kilonova-Catcher. Here we highlight the GRB 220427A analysis where our long-term follow-up of the host galaxy allowed us to obtain a photometric redshift of $z=0.82\pm0.09$, its lightcurve elution, fit the decay slope of the afterglows, and study the properties of the host galaxy.

Представлены результаты анализа многоволновых наблюдений длинного космического гамма-всплеска GRB 200829A. Красное смещение всплеска \(z\approx 1.29\pm 0.04\) определено фотометрическим методом на стадии послесвечения. В гамма-диапазоне событие является одним из самых ярких (в изотропном эквиваленте) \(E_{\textrm{iso}}\gtrsim 10^{54}\) эрг. Многоцветная кривая блеска послесвечения GRB 200829A характеризуется хроматизмом и наличием плато, плавно переходящего в степенное падение потока, которое можно также интерпретировать как квазисинхронную неоднородность (вспышку). Мы предполагаем, что наличие хроматической неоднородности в послесвечении не противоречит теории структурированного джета.

The Stellar Abundances and Galactic Evolution Survey (SAGES) of the northern sky is a specifically designed multiband photometric survey aiming to provide reliable stellar parameters with accuracy comparable to those from low-resolution optical spectra. It was carried out with the 2.3 m Bok telescope of Steward Observatory and three other telescopes. The observations in the u s and v s passband produced over 36,092 frames of images in total, covering a sky area of ∼9960 deg 2 . The median survey completenesses of all observing fields for the two bands are u s = 20.4 mag and v s = 20.3 mag, respectively, while the limiting magnitudes with signal-to-noise ratio of 100 are u s ∼ 17 mag and v s ∼ 18 mag, correspondingly. We combined our catalog with the data release 1 (DR1) of the first Panoramic Survey Telescope And Rapid Response System (Pan-STARRS, PS1) catalog, and obtained a total of 48,553,987 sources that have at least one photometric measurement in each of the SAGES u s and v s and PS1 grizy passbands. This is the DR1 of SAGES, released in this paper. We compared our gri point-source photometry with those of PS1 and found an rms scatter of ∼2% difference between PS1 and SAGES for the same band. We estimated an internal photometric precision of SAGES to be of the order of ∼1%. Astrometric precision is better than 0.″2 based on comparison with DR1 of the Gaia mission. In this paper, we also describe the final end-user database, and provide some science applications.

We present the results of our analysis of multiwavelength observations for the long gamma-ray burst GRB 200829A. The burst redshift z≈ 1.29± 0.04 has been determined photometrically at the afterglow phase. In gamma rays the event is one of the brightest (in isotropic equivalent), E_iso≳ 10^54 erg. The multicolor light curve of the GRB 200829A afterglow is characterized by chromatic behavior and the presence of a plateau gradually transitioning into a power-law decay that can also be interpreted as a quasi-synchronous inhomogeneity (flare). We assume that the presence of a chromatic inhomogeneity in the early afterglow is consistent with the model of a structured jet.

The progenitor system of Type Ia supernovae (SNe Ia) is expected to be a close binary system consisting of a carbon/oxygen white dwarf (WD) and a nondegenerate star or another WD. Here, we present results from high-cadence monitoring observations of SN 2021hpr in a spiral galaxy, NGC 3147, and constraints on the progenitor system based on its early multicolor light-curve data. First, we classify SN 2021hpr as a normal SN Ia from its long-term photometric and spectroscopic data. More interestingly, we found a significant “early excess” in the light curve over a simple power-law ∼ t 2 evolution. The early light curve evolves from blue to red to blue during the first week. To explain this, we fitted the early part of the BVRI -band light curves with a two-component model consisting of ejecta–companion interaction and a simple power-law model. The early excess and its color can be explained by shock-cooling emission due to a companion star having a radius of 8.84 ± 0.58 R ⊙ . We also examined Hubble Space Telescope preexplosion images, finding no detection of a progenitor candidate, consistent with the above result. However, we could not detect signs of a significant amount of stripped mass from a nondegenerate companion star (≲0.003 M ⊙ for H α emission). The early excess light in the multiband light curve supports a nondegenerate companion in the progenitor system of SN 2021hpr. At the same time, the nondetection of emission lines opens the door for other methods to explain this event.

The nuclear transient AT2019cuk/Tick Tock/SDSS J1430+2303 has been suggested to harbor a supermassive black hole (SMBH) binary near coalescence. We report results from high-cadence NICER X-ray monitoring with multiple visits per day from 2022 January to August, as well as continued optical monitoring during the same time period. We find no evidence of periodic/quasiperiodic modulation in the X-ray, UV, or optical bands; however, we do observe exotic hard X-ray variability that is unusual for typical active galactic nuclei (AGN). The most striking feature of the NICER light curve is repetitive hard (2–4 keV) X-ray flares that result in distinctly harder X-ray spectra compared to the nonflaring data. In its nonflaring state, AT2019cuk looks like a relatively standard AGN, but it presents the first case of day-long, hard X-ray flares in a changing-look AGN. We consider a few different models for the driving mechanism of these hard X-ray flares, including (1) corona/jet variability driven by increased magnetic activity, (2) variable obscuration, and (3) self-lensing from the potential secondary SMBH. We prefer the variable corona model, as the obscuration model requires rather contrived timescales and the self-lensing model is difficult to reconcile with a lack of clear periodicity in the flares. These findings illustrate how important high-cadence X-ray monitoring is to our understanding of the rapid variability of the X-ray corona and necessitate further high-cadence, multiwavelength monitoring of changing-look AGN like AT2019cuk to probe the corona-jet connection.

GRB 221009A is the brightest Gamma-Ray Burst (GRB) detected in more than 50 years of study. In this paper, we present observations in the X-ray and optical domains after the GRB obtained by the GRANDMA Collaboration (which includes observations from more than 30 professional and amateur telescopes) and the Insight-HXMT Collaboration. We study the optical afterglow with empirical fitting from GRANDMA+HXMT data, augmented with data from the literature up to 60 days. We then model numerically, using a Bayesian approach, the GRANDMA and HXMT-LE afterglow observations, that we augment with Swift-XRT and additional optical/NIR observations reported in the literature. We find that the GRB afterglow, extinguished by a large dust column, is most likely behind a combination of a large Milky-Way dust column combined with moderate low-metallicity dust in the host galaxy. Using the GRANDMA+HXMT-LE+XRT dataset, we find that the simplest model, where the observed afterglow is produced by synchrotron radiation at the forward external shock during the deceleration of a top-hat relativistic jet by a uniform medium, fits the multi-wavelength observations only moderately well, with a tension between the observed temporal and spectral evolution. This tension is confirmed when using the extended dataset. We find that the consideration of a jet structure (Gaussian or power-law), the inclusion of synchrotron self-Compton emission, or the presence of an underlying supernova do not improve the predictions, showing that the modelling of GRB22109A will require going beyond the most standard GRB afterglow model. Placed in the global context of GRB optical afterglows, we find the afterglow of GRB 221009A is luminous but not extraordinarily so, highlighting that some aspects of this GRB do not deviate from the global known sample despite its extreme energetics and the peculiar afterglow evolution.

GRANDMA is a world-wide collaboration with the primary scientific goal of studying gravitational-wave sources, discovering their electromagnetic counterparts and characterizing their emission. GRANDMA involves astronomers, astrophysicists, gravitational-wave physicists, and theorists. GRANDMA is now a truly global network of telescopes, with (so far) 30 telescopes in both hemispheres. It incorporates a citizen science programme (Kilonova-Catcher) which constitutes an opportunity to spread the interest in time-domain astronomy. The telescope network is an heterogeneous set of already-existing observing facilities that operate coordinated as a single observatory. Within the network there are wide-field imagers that can observe large areas of the sky to search for optical counterparts, narrow-field instruments that do targeted searches within a predefined list of host-galaxy candidates, and larger telescopes that are devoted to characterization and follow-up of the identified counterparts. Here we present an overview of GRANDMA after the third observing run of the LIGO/VIRGO gravitational-wave observatories in 2019-2020 and its ongoing preparation for the forthcoming fourth observational campaign (O4). Additionally, we review the potential of GRANDMA for the discovery and follow-up of other types of astronomical transients.

В работе представлены результаты фотометрической обработки цифровых изображенийнового двойного гравитационно-линзированного квазара SDSS J2124+1632, наблюдавшаяся в Майданакской обсерватории. Кривые блеска показали, что яркость компонентов в течение 2018-2021 г.г. имеет активную переменность, вызванную, в том числе, микролинзированием. Вычислено вероятное значение времени задержки ∆tAB = 105.3±18.8 дней, причем лидирующим оказался компонент В. Эта величина согласуется с ранее найденнымивременными задержками для двойных гравитационно-линзированных квазаров с подобнойконфигурацией.

We present our follow-up observations with GRANDMA of transient sources revealed by the Zwicky Transient Facility (ZTF). Over a period of six months, all ZTF triggers were examined in real time by a dedicated science module implemented in the Fink broker, which will be used for the data processing of the Vera C. Rubin Observatory. In this article, we present three selection methods to identify kilonova candidates. Out of more than 35 million candidates, a hundred sources have passed our selection criteria. Six were then followed-up by GRANDMA (by both professional and amateur astronomers). The majority were finally classified either as asteroids or as supernovae events. We mobilized 37 telescopes, bringing together a large sample of images, taken under various conditions and quality. To complement the orphan kilonova candidates (those without associated gamma-ray bursts, which were all), we included three additional supernovae alerts to conduct further observations of during summer 2021. We demonstrate the importance of the amateur astronomer community that contributed images for scientific analyzes of new sources discovered in a magnitude range r'=17-19 mag. We based our rapid kilonova classification on the decay rate of the optical source that should exceed 0.3 mag/day. GRANDMA's follow-up determined the fading rate within 1.5+/-1.2 days post-discovery, without waiting for further observations from ZTF. No confirmed kilonovae were discovered during our observing campaign. This work will be continued in the coming months in the view of preparing for kilonova searches in the next gravitational-wave observing run O4.