The rich culture of old Maya gave birth to a very complicated and complex calendar; they also recorded important historical events and many significant astronomical phenomena. The main source of information is represented by Dresden Codex (DC), one of the four preserved Mayan hieroglyphic literal legacies. DC roughly covers the interval between 280 and 1325 AD. The old problem of precise Mayan dating with respect to our calendar is traditionally called correlation; it expresses the difference in days between the Long Count of the Mayan calendar and the Julian Date, used in presentday astronomy. There exist more than fifty published correlations that differ one from the other by as much as several centuries. Historians mostly accept the so called Goodman-Mart?nez-Thompson (GMT) value of 584 283 days, which is based mostly on historical events extracted from the sources of a postclassical period of Mayan history. On the contrary, brothers B?hm used precisely dated astronomical data from classical period to derive the B?hm correlation (BB) of 622 261 days. Unlike the GMT correlation it is in excellent agreement with the astronomical phenomena recorded in DC. Since then we published several papers supporting the validity of BB correlation and its advantage over GMT in the classical period of Mayan history. To this end, we used more records of astronomical phenomena discovered in DC. This study describes six records of planetary conjunctions that we found recently on p. 37 of DC that concern planets Mercury, Venus, Mars, Jupiter, and Saturn. All of these records coincide with the real occurrences of these phenomena within several days, if BB correlation is applied.

We report on the search results of Fast Radio Bursts (FRBs) from three Gamma- ray Bursts (GRBs) at 2256 MHz using the 40-m radio telescope located at the YunNan Astronomical Observatory (YNAO). The search for signals was triggered by the Burst Alert Telescope (BAT) on- board the Swift satellite. Radio single pulses are searched in the data over a large range of dispersion measure from 0 to 5000 pc/cm3 in step of 50 pc/cm3. No FRB-like emission from the prompt phase of GRBs are detected with significance > 5?. If there are FRBs related to the GRBs, we set an upper limit on the ux density of radio pulses of 2.5 Jy for GRB140512A and 8.0 Jy for GRBs 140629A and 140703A with the sensitivity of the telescope. A statistical analysis of the GRB data reveals that the events detected above 5? are consistent with the thermal noise uctuations.

We present the results of 58 detailed evolutionary models of massive single stars and close binary systems with the Solar and Small Magellanic Cloud (SMC) metallicity computed with the MESA (Modules for Experiments in Stellar Astrophysics) numerical code. Helium core masses of single stars (30 M? - 75 M?) with metallicities of 0.02 and 0.0021 are in the range of 9.26 M? - 29.56 M? and 11.62 M? - 33.96 M?, respectively. Their carbon-oxygen (CO) core masses are between 5.44 M? and 25.04 M? vs. 8.23 M? and 28.38 M? for the Solar vs. SMC metallicity, accounting for an average difference of 25%. To investigate the influence of metallicity on helium and carbon-oxygen core masses in massive close Case A binary systems, detailed evolutionary models of binary systems in the mass range of 30 M? to 40 M? are calculated. The initial orbital period is set to 3 days and the accretion efficiency to 10%. The helium core mass range for primary stars with lower metallicity is 10.61 - 16.21 M? vs. 7.94 - 11.69 M? for z = 0.02. The resulting CO core masses of primary stars for the SMC metallicity are on average about 50% larger than for the Solar metallicity, so the effect is more prominent than in the case of single stars. The black hole formation limit for primary stars with the SMC metallicity is under 30 M?. While the least massive primary stars with Solar metallicity end up as neutron stars, all primary stars with the SMC metallicity and all secondary stars complete their evolution as black holes. The double compact objects resulting from the presented models are of two types: mixed neutron star-black hole systems (4 models) and double black holes (18 models). We also derive the relation between the final helium core mass and the carbon-oxygen core mass and show that it does not depend on metallicity. We confirm the CO/helium core mass ratio to be larger in binary systems than for single stars.

The Late Heavy Bombardment (LHB) represents a period of time in which an increased number of impactors collided with the Earth. While there were continuous collisions of impactors globally, these would be perceived by populations of life as locally infrequent, as they occurred at different times and locations across the planet. These impactions presented a severe and unpredictable environmental pressure on life, as they could at any moment destroy organisms and their local habitats. However, such an environment could potentially lead to the selection of a particular evolutionary strategy, bet hedging, which is an adaptation to unpredictability itself. Thus, a model for analysing this has been put forward in the form of a system of rings arising from an impact-consisting of the inner primary and outer secondary rings, which demonstrates the dynamic interplay between the external pressure from impact dynamics and life's evolutionary response towards it. The model demonstrates that there is a longer relaxed period where organisms thrive and a short violent period where they must survive three violent events and respond to a potentially different environment. This evolutionary strategy consistently results in a higher number of surviving organisms compared to other evolutionary strategies; thus, it may have played a crucial role in life's endurance through the LHB-an insight relevant to astrobiology.

For studies of the long-term evolution of small Solar System objects, it is fundamental to add the Yarkovsky and Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effects in the dynamical model. Still, implementations of these effects in publicly available N-body codes is either lacking, or the effects are implemented using significantly simplified models. In this paper, we present an implementation of the coupled Yarkovsky/YORP effects in the mercury and orbfit N-body codes. Along with these two effects, we also included the effects of non-destructive collisions and rotationally induced breakups to model the asteroid spin state properly. Given the stochastic nature of many incorporated effects, the software is suitable for statistical dynamical studies. Here we primarily explained the scientific aspect of the implementation, while technical details will be made freely available along with the source codes.

In the present manuscript we consider the possibility of conducting SETI with small-size (with diameters less than 1 m) optical telescopes. Calculations are performed for typical parameters of the mentioned type of telescopes. In particular, we show that the techno-signatures of Type-2.x and Type-3.x civilizations might be detected. It is demonstrated that it is possible to detect hot megastructures (up to 4000 K) built around Main Sequence stars and pulsars, as well as von Neumann extraterrestrial probes.

Stellar streams and shells are observed in halos of spiral galaxies. In this paper, we investigated the formation of these structures due to mergers between the host spiral galaxy and its dwarf satellite galaxies. We run the N-body simulations with two morphological models of a dwarf galaxy for different initial positions. One model is a spheroidal dwarf, dSph, and the other is a dwarf with a disk. We found that both models form stellar shells and streams and, in the case of the progenitor with a disk, streams are more prominent. After several pericentric passages, there is a possibility of formation of several streams. The remnant of the progenitor is more likely to disrupt later into the merger in the case of spiral progenitor than in the case of dSph.

Using a recently introduced synthetic method to compute the asteroid secular frequencies (Knezevic and Milani 2019), in this paper we survey the locations of secular resonances in the 9 dynamically distinct zones of the asteroid belt. Positions of all resonances up to order four, of a significant fraction of the order six resonances, and of a several order eight ones were determined, plotted in the space of proper elements, and discussed in relation to the local dynamics and to the structure and shape of the nearby asteroid collisional families. Only the resonant combinations with fundamental frequencies of Jupiter and Saturn were considered, with a few special cases involving other planets and largest asteroids. Accuracy of the polynomial fit to determine the frequencies was found to be satisfactory for the purpose of determination of secular resonance positions. This enabled a precise identification of dynamical mechanisms affecting the computation of frequencies (close vicinity of the mean motion resonances and libration in secular resonances), and of the ?cycle slips? as a primary technical drawback causing deterioration of the results. For each zone we also presented and discussed a fairly complete sample of recent works dealing with interaction of the secular resonances with asteroid families present in that zone. Finally, a few words were devoted to possibilities for future work.

Stellar coronal mass ejections (CMEs) are a growing research field, especially during the past decade. The large number of so far detected exoplanets raises the open question for the CME activity of stars, as CMEs may strongly affect exoplanetary atmospheres. In addition, as CMEs contribute to stellar mass and angular momentum loss and are therefore relevant for stellar evolution, there is a need for a better characterization of this phenomenon. In this article we review the different methodologies used up to now to attempt the detection of stellar CMEs. We discuss the limitations of the different methodologies and conclude with possible future perspectives of this research field.

This paper presents a comparative study of physical properties of a sample of 89 blue early-type galaxies (ETGs) from the local universe by fitting SEDs to their multi-wavelength photometric and spectroscopic data. The detailed template-based SED fitting analysis using the MAGPHY S and SED3FIT codes on the interstellar dust extinction corrected UV-to-far-IR spectro-photometric data enabled us to trace the evolutionary sequence of the blue ETGs on the color-magnitude diagram. This study evidenced a decreasing trend of the SFR, sSFR, dust mass, and dust mass fraction over the sequence from the SF - to - the Seyferts - to - the LINERs. The UV-optical colors also enabled us to estimate the look-back time of the last starburst phase in SF, Seyfert, and LINER galaxies, probably pointing towards the evolutionary sequence of the blue ETGs. Despite the blue colors and strong emission lines in the optical regime of the electromagnetic spectrum, the blue ETGs in the present sample occupy a position off the main sequence, commonly known as the green valley, on the CMD plot and hence indicate the transitional state of their non-secular evolution. A marginal positive correlation was noticed between SFR per unit dust mass and the temperature of the cool ISM. The declining trend of the cold dust temperature Tc over the sequence from the SF-to-Seyfert-to-LINER implies that the AGNs in the systems are not enough powerful to affect the cold component of the ISM.