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In the latest Gaia third data release one can find extremely small proper motion components for the star HD 7977. This, together with the radial velocity measurement lead to the conclusion that this star passed very close to the Sun in the recent past. Such a very close approach of a one solar mass star must result in noticeable changes in the motion of all Solar System bodies, especially those on less tight orbits, namely long-period comets (LPCs) and Kuiper belt objects. We estimate and present these effects. Our current knowledge on the stellar surroundings of the Sun found in the latest Gaia catalogues allowed us to perform numerical integrations and prepare a list of potential stellar perturbers of LPCs. We use this list, made available in the StePPeD database. To study the past motion of LPCs under the simultaneous action of the Galactic potential and passing stars, we use precise original cometary orbits taken from the current CODE catalogue. We examine the reliability of the extremely small proper motion of HD 7977 concluding that this star can be an unresolved binary but according to the astrometry covering more than a century, the current Gaia results cannot be ruled out. We present the parameters of a very close passage of this star near the Sun. We also show examples of the strong influence of this passage on the past motion of some LPCs. We also discuss the possible influence of this perturber on other Solar System bodies. It is possible that 2.47 Myr ago the one solar mass star HD 7977 passed as close as one thousand au from the Sun. Such an event constitutes a kind of dynamical horizon for all studies of the past Solar System bodies' dynamics., Comment: 15 pages, 13 figures, 5 tables, submitted to A&A

Long gamma-ray bursts (GRB), explosions of very massive stars, provide crucial information on stellar and galaxy evolution, even at redshifts z ~ 8 - 9.5, when the Universe was only 500-600 million years old. Recently, during observations of a galaxy at a redshift of z ~ 11 (400 million years after the Big Bang), a bright signal, named GN-z11-flash, shorter than 245 s was detected and interpreted as an ultraviolet flash associated with a GRB in this galaxy, or a shock-breakout in a Population III supernova. Its resulting luminosity would be consistent with that of other GRBs, but a discussion based on probability arguments started on whether this is instead a signal from a man-made satellite or a Solar System object. Here we show a conclusive association of GN-z11-flash with Breeze-M upper stage of a Russian Proton rocket on a highly elliptical orbit. This rules out GN-z11-flash as the most distant GRB ever detected. It also implies that monitoring of a larger sample of very high redshift galaxies is needed to detect such distant GRBs. This also highlights the importance of a complete database of Earth satellites and debris, which can allow proper interpretation of astronomical observations., Comment: Submitted to Nature Astronomy; 12 pages, 2 figures

We report the discovery of two massive eccentric systems with BRITE data, $\tau$ Ori and $\tau$ Lib, showing heartbeat effects close to the periastron passage. $\tau$ Lib exhibits shallow eclipses that will soon vanish due to the apsidal motion in the system. In neither system, tidally excited oscillations were detected., Comment: 3 pages, 1 figure, to appear in the Proceedings of the 3rd BRITE Science Conference

In this paper we describe the echelle spectrograph of the 2 meter telescope of the Rozhen National Astronomical Observatory. The spectrograph is a cross-dispersed, bench-mounted, fiber-fed instrument giving a resolution from $\sim$30000 to $\sim$45000. The spectral range obtained in one single image is from 3900 to 9000 {\AA}. We describe the parameters of the fiber injection and the guiding unit, of the spectrograph itself, and of the detector. The identified orders and the resulting resolving power are presented. The opportunity to increase of the resolution by using a narrower slit is discussed and the corresponding loss of flux is calculated. The expected signal-to-noise ratio for a set of stars of different magnitudes was derived. Some of the first results obtained with ESpeRo are shortly described., Comment: 24 pages, 17 figures, accepted for publication in Bulgarian Astronomical Journal, Vol. 26, http://www.astro.bas.bg/AIJ/issues/n26/index.html

Obtaining accurate photometry of bright stars from the ground remains tricky because of the danger of overexposure of the target and/or lack of suitable nearby comparison star. The century-old method of the objective wire mesh used to produce multiple stellar images seems attractive for precision CCD photometry of such stars. Our tests on beta Cep and its comparison star differing by 5 magnitudes prove very encouraging. Using a CCD camera and a 20 cm telescope with objective covered with a plastic wire mesh, located in poor weather conditions we obtained differential photometry of precision 4.5 mmag per 2 min exposure. Our technique is flexible and may be tuned to cover as big magnitude range as 6 - 8 magnitudes. We discuss the possibility of installing a wire mesh directly in the filter wheel., Comment: 15 pages, 4 figures, AJ accepted

The Hyades K2V+WD system 471 Tau is a prototype post-common envelope system and a likely cataclysmic binary progenitor. We present 10 days of nearly continuous optical photometry by the MOST (Microvariability & Oscillations of STars) satellite and partly simultaneous optical spectroscopy from DDO (David Dunlap Observatory) of the binary. The photometric data indicate that the spot coverage of the K dwarf component was less than observed in the past, suggesting that we monitored the star close to a minimum in its activity cycle. Despite the low spot activity, we still detected seven flare-like events whose estimated energies are among the highest ever observed in V471 Tau and whose times of occurrence do not correlate with the binary orbital phase. A detailed O-C analysis of the times of eclipse over the last ~35 years reveals timing variations which could be explained in several ways, including perturbations by an as-yet-undetected third body in the system or by a small orbital eccentricity inducing slow apsidal motion. The DDO spectra result in improved determinations of the K dwarf projected rotation velocity, V_K sin i = 92 km s^-1, and the orbital amplitude, K_K=150.5 km s^-1. The spectra also allow us to measure changes in H_alpha emission strength and radial velocity (RV) variations. We measure a larger H_alpha velocity amplitude than found previously suggesting that the source of the emission in V471 Tau was less concentrated around the sub-white-dwarf point on the K star than had been observed in previous studies., Comment: accepted for publication in AJ