High–redshift quasars and blazars are among the most powerful sources in the Universe and among the highest luminosity sources, as in optical, so as in X–ray, UV, IR and radio range. We have created a full sample of blazars and high–redshift quasars (z≥2.15). The evolutionary relation of high–redshift quasars and blazars to high–redshift galaxies is discussed using the luminosity evolution.

We present high-quality power spectra of oscillations in the quiet solar chromosphere measured from the Ca II H line. They show unambiguously that the network does not participate in chromospheric three-minute oscillations, but that instead it oscillates in slow wave motions which are neither present in the surrounding non-magnetic chromosphere, nor in the underlying photosphere.

Coulomb interactions for the Free Helmholtz energy and the pressure are studied in a partial new formulation which described more exactly the numerical evaluation of many body theories.

Observational contraints on the evolution and instabilities of massive stars at very low metallicities are limited. Most of the information come from HST observations of one target, I Zw 18. Recent distance estimates of I Zw 18 put it at 17 Mpc, moving detailed studies of single stars clearly beyond the range of current ground based telescopes. Since massive stars with metallcities of 1/10 of solar and below are our best proxies for massive stars in (proto-) galaxies around the time of reionization, finding them and studying their evolution and instabilities is of premium importance for our understanding of galaxy formation, feedback, and the IGM reionization. Here we present pilot study results of variable stars in two more nearby extremely low metallicity galaxies, UGC 5340 and UGCA 292, and comment on the possibilities of more detailed studies of variable massive stars with new ground-based instrumentation.

We have obtained radio continuum observations of an HH object, known as the “streamer” in Orion using the VLA in a number of configurations at λ2, 6 and 20cm. This object is located several arc-minutes to the north of HH34 in L1641 cloud and exhibits a remarkably long and narrow structure with dimensions of 5′ × 10′ in optical photographs unlike the morphology of any other HH object. Based on radio continuum observations, we have detected a significant linearly polarized emission at λ6cm from the core of the streamer indicating highly uniform magnetic field geometry. This unusual result suggests that the source responsible for producing the nebulosity is a nonthermal-emitting radio source. Because of the presence of a number of newly born low-mass stars in L1641 and because of the detection of a highly reddened 2μm source coincident with the synchrotron source, it is likely that the source at the core of the streamer is a low-mass star responsible for the non-thermal emission and the HH nebulosity. Presence of synchrotron emission associated with a newly born star supports further view that the magnetic field plays a strong role in the early phase of star formation.

The impact of relativistic theories of space, time and gravitation on the problem of reference systems is reviewed.

First, the concept of inertial systems is discussed from the point of view of the special and the general theory of relativity. Then, relativistic corrections of Doppler, laser and VLBI, and similar effects are reviewed; they are usually on the order of 10-8. Finally, the problem of a possible variation of the gravitational constant G (on the order of 10-11/year) is outlined; such a variation does not occur in special and general relativity, but is implied by certain generalized field theories which are less commonly accepted.

Observations of gamma rays around 1012 eV (= 1 TeV) from pulsars are reviewed and the results are discussed and compared with emission at other wavelengths. Very high energy gamma rays do not appear to be modulated with the pulsar period, which suggests that a major part of the VHE emission is not from the pulsar magnetosphere.

In the past, Western academic astronomy has conceived in a very specific way its interests. However, in recent decades there has been a promising openness to the rest of the society, in the context of areas such as education, heritage and outreach. Despite this, there has not been an adequate scientific approach to do it, which would imply taking into account the social sciences and a truly interdisciplinary perspective. Here we want to develop the idea that this interdisciplinary approach already exists and it is called: Cultural Astronomy. Unfortunately, in the context of academic astronomy it has been only seen as a study of the “astronomies of others”, intended as previous stages or failed attempts of Western academic astronomy. We will seek to show that Cultural Astronomy, as a critical reflection on the social character of the astronomical knowledge, is key to the success of these opening efforts.

In this review the oldest known advanced astronomical instrument and dedicated analogue computer is presented, in context. The Antikythera Mechanism a mysterious device, assumed to be ahead of its time, probably made around 150 to 100 BCE, has been found in a 1st century BCE shipwreck near the island of Antikythera in a huge ship full of Greek treasures that were on their way to Rome. The Antikythera Mechanism is a clock-like device made of bronze gears, which looks much more advanced than its contemporary technological achievements. It is based on mathematics attributed to the Hipparchus and possibly carries knowledge and tradition that goes back to Archimedes, who according to ancient texts constructed several automata, including astronomical devices, a mechanical planetarium and a celestial sphere. The Antikythera Mechanism probably had a beautiful and expensive box; looking possibly like a very elaborate miniature Greek Temple, perhaps decorated with golden ornaments, of an elegant Hellenistic style, even perhaps with automatic statuettes, ‘daemons’, functioning as pointers that performed some of its operations. Made out of appropriately tailored trains of gears that enable to perform specialised calculations, the mechanism carries concentric scales and pointers, in one side showing the position of the Sun in the ecliptic and the sky, possibly giving the time, hour of the day or night, like a clock. The position of the Moon and its phase is also shown during the month. On the other side of the Mechanism, having probably the size of a box (main part 32×20×6 cm), are two large spiral scales with two pointers showing the time in two different very long calendars, the first one concerning the eclipses, and lasting 18 years 11 days and 8 hours, the Saros period, repeating the solar and lunar eclipses, and enabling their prediction, and the 19 year cycle of Meton, that is the period the Moon reappears in the same place of the sky, with the same phase. An additional four-year dial shows the year of all Greek Festivities, the so-called ‘games’ (Olympic, Pythian, Isthmian etc). Two additional dials give the Exeligmos, the 54 year and 34 day cycle, which provides a more accurate prediction of eclipses. It is possible that the Mechanism was also equipped with a planetary show display, as three of the planets and their motion (stationary points) are mentioned many times in the manual of the instrument, so it was also a planetarium. From the manual we have hints that the mechanism was probably also an observational instrument, as having instructions concerning a viewfinder and possibly how to orient the viewfinder to pass a sunbeam through it, probably measuring the altitude of the Sun. There are fragmented sentences that probably give instructions on how to move the pointers to set the position of the Sun, the Moon and the planets in their initial places in the ecliptic, on a specific day, or how to measure angular distances between two celestial bodies or their coordinates. This mechanism is definitely not the first one of its kind. The fact that it is accompanied with instructions means that the constructor had in its mind to be used by somebody else and one posits that he made at least another similar instrument.

Although late stage gap formation reduces the surface density in the vicinity of protoplanets, simulations suggest gas may continue to leak through the protoplanets tidal barrier, replenishing the gas supply and allowing protoplanets to acquire masses comparable to or larger than that of Jupiter. Global gas depletion is a possible explanation for gaseous planets with lower masses in weak-line T-Tauri disks and ice giants in our own solar system, but it is unlikely to have stalled the growth of multiple systems around nearby stars that contain relatively low-mass, close-in planets along with more massive and longer period companions. Here, we suggest a potential solution. We show that supersonic infall of surrounding gas onto a protoplanet is only possible interior to both its Bondi and Roche radii. Although the initial Bondi radius is much smaller than its Roche radius, the former overtakes the latter during its growth. Thereafter, a positive pressure gradient is required to induce the gas to enter the Roche lobe of the protoplanet and flow is significantly reduced. We present the results of analysis and numerical simulations to show that the accretion rate increases rapidly with the ratio of the protoplanets Roche to Bondi radii. Based on these results we suggest that in regions with low geometric aspect ratios gas accretion is quenched, resulting in relatively low protoplanetary masses.

The Far-Infrared Radio Correlation (FRC) is the tightest and most universal correlation known among global parameters of galaxies. Here we present the results of our investigation of the 70 μm FRC of starforming galaxies in the Extended Chandra Deep Field South (ECDFS) out to z > 2. In order to quantify the evolution of the FRC we used both survival analysis and stacking techniques, which gave similar results. We also calculated the FRC using total infrared luminosity and rest-frame radio luminosity, qTIR, and find that qTIR is constant (within 0.22) over the redshift range 0 - 2. We see no evidence for evolution in the FRC at 70 μm, which is surprising given the many factors that are expected to change this ratio at high redshifts.

This contribution describes high-velocity clouds (HVCs), neutral hydrogen moving with velocities inexplicable by differential galactic rotation. They have been invoked as evidence for infall of gas to the Galaxy, as manifestations of a galactic fountain, as energy source for the formation of supershells, etc. It is becoming clear that a single model will not suffice to explain all HVCs. A better understanding is mainly hampered by the fact that the distance remains unknown. Many aspects to the study of HVCs will be discussed here.

Astronomy has changed from data-starving science to data-flooding science about 20 years ago due to advances of observational technology in all the wavelength regimes of electromagnetic waves. This paper gives a historical overview of galaxy surveys. We start from the impact of the technology development. Then, old imaging surveys and redshift surveys based on photography, especially using Schmidt telescopes, in the era of data-starving science are described in some detail. Several features of modern surveys are given and two highlights obtained from the exploitation of modern galaxy surveys are introduced.

The Herschel Space Observatory was the fourth cornerstone mission in the European Space Agency (ESA) science programme with excellent broad band imaging capabilities in the sub-mm and far-infrared part of the spectrum. Although the spacecraft finished its observations in 2013, it left a large legacy dataset that is far from having been fully scrutinised and still has a large potential for new scientific discoveries. This is specifically true for the photometric observations of the PACS and SPIRE instruments. Some source catalogues have already been produced by individual observing programs, but there are many observations that risk to remain unexplored. To maximise the science return of the SPIRE and PACS data sets, we are in the process of building the Herschel Point Source Catalogue (HPSC) from all primary and parallel mode observations. Our homogeneous source extraction enables a systematic and unbiased comparison of sensitivity across the different Herschel fields that single programs will generally not be able to provide. The catalogue will be made available online through archives like the Herschel Science Archive (HSA), the Infrared Science Archive (IRSA), and the Strasbourg Astronomical Data Center (CDS).

Magnetars are neutron stars with exceptionally strong dipole magnetic fields which are observed to display a range of x-ray flaring behavior, but the flaring mechanism is not well understood. The third observing run of Advanced LIGO and Virgo extended from April 1, 2019 to March 27, 2020, and contained x-ray flares from known magnetar SGR 1935+2154, as well as the newly-discovered magnetar, Swift J1818-1607. We search for gravitational waves coincident with these magnetar flares with minimally modeled, coherent searches which specifically target both short-duration gravitational waves produced by excited f-modes in the magnetar’s core, as well as long-duration gravitational waves motivated by the Quasi-Periodic Oscillations observed in the tails of giant flares. In this talk, we report on the methods and sensitivity estimates of there searches, and the astrophysical implications.

We present the very first detection of N2H+J = (1 – 0) and CH3OH(2k−1k) line emission on 5″ scales in the circumnuclear disk (CND) around Sgr A*. The emission matches the position and shape of the dark clouds in the near-infrared. Our findings suggest that these molecular clouds in the eastern CND are significantly colder and denser than the rest of the CND, and partially shocked. The research on these dark clouds will contribute to understanding the processes of star formation close to a supermassive black hole.

A catalogue of galactic novae and an atlas of finding charts are under preparation and will be published in 1984. The status of the project is described.

Satellite observations of the Merope and Barnard's Loop nebulae in the 1050 to 4250 Å spectral region show that the increase in the albedo of interstellar grains below 2000 Å occurs in individual reflection nebulae as well as in the general interstellar medium. Evidence for differences in the composition and size distribution of grains due to variations in the local radiation field is presented.

The LIGO-Virgo gravitational wave detectors have confidently observed 4 events involving neutron stars: two binary neutron star (BNS) mergers (GW170817 and GW190425), and two neutron star-black hole mergers (GW200105 and GW200115). However, our theoretical understanding of the remnant properties of such systems is incomplete due to the complexities related to the modeling of matter effects and the very high computational cost of corresponding numerical relativity simulations. An important such property is the recoil velocity, which is imparted onto the remnant due to the anisotropic emission of gravitational radiation and the dynamical ejection of matter in the kilonova. In this work, we combine gravitational radiation as well as dynamical ejecta distributions, computed by the Computational Relativity numerical simulations, to get accurate estimates for BNS remnant recoil velocities. We find that recoils due to ejection of matter dominate those caused by gravitational wave emission. Knowledge of BNS remnant recoil velocities is important in determining if the remnant is retained by its environment for future hierarchical mergers which, in turn, can form binaries with black holes in the so-called lower mass gap of ∼ 3 – 5M⊙.

Recently it has been possible to perform computer calculations with sufficiently high resolution to obtain the response of the gas in galaxies to a tightly wound spiral potential due to a stellar density wave. Previously for pitch angles ~ 10° the problem had to be simplified using the tightly wound approximation, with gradients parallel to the arms neglected compared to perpendicular gradients, yielding a quasi-1-dimensional calculation. This paper reports the early results of a 2-dimensional calculation, and compares them with the 1-dimensional results.