Astronomy exhibition of AIRA at Sun Plaza

The Astronomical Institute of the Romanian Academy, in partnership with Sun Plaza, Association “Astronomia 21” and Bucharest Astroclub, presents a new astronomy exhibition inside the commercial galleries of Sun Plaza in Bucharest. The event will be hosted in this location in between 15.04 - 27.05.2022, and aims to give the public an insight about the historical endeavor and the current research activities of the Astronomical Institute of the Romanian Academy (AIRA). In this respect, the emphasis of this cultural project falls on the rich patrimonial heritage of AIRA in Bucharest, represented by a large scientific and educational park that integrates several buildings and many specific instruments.

A messenger beyond words about the dynamic scientific evolution of Romania in the field of astronomy, the representative selections of our patrimony forms the core of this exposition hosted by Sun Plaza. For any visitor that is eager to learn more about the astronomical research done by Romanians and, generally, about astronomy as a “science of sciences”, seeing our new exhibition is a good place to continue this amazing journey.

Inside several display cases, some rare and valuable scientific instruments are exposed for the public, together with printed panels where the visitor can read and understand about their particular role in the Romanian astronomical research. Among these cultural items are a few ultra-precise clocks and recording devices, which were used as a reference in the continuous efforts of the Romanian research crews to calculate different types of scientific time, such as the sidereal time, solar time, including the calculation and nationwide reporting from Bucharest of the Legal Time of Romania. In the exhibition are also presented to the public several calculating machines, coming form the old mechanical ones to the electric machines that were used at AIRA up to the PC era.

As a close educational partner of AIRA, the Bucharest Astroclub, contributed to this exhibition by displaying some interesting meteorite fragments and a few telescopes used today by the amateur astronomers.

Exhibition presented by the Astronomical Institute of the Romanian Academy at Sun Plaza Commercial Center in Bucharest
Figure illustrating the variable stars of this article.

Discovery of new short period variable stars in open clusters using OmegaWhite data

Variable stars are cosmic sources of light that change their brightness in time due to various physical phenomena like atmospheric pulsations and/or geometrical configurations like eclipses.

The OmegaWhite (OW) is a wide-field high-cadence synoptic survey that is searching the Galactic Plane and Bulge for intriguing rare variable stars like the interacting ultra-compact binary systems (also known as AM CVn stars). These are pairs of white dwarf stars that exchange mass. The key point of the survey is that it was designed to explore a new space of parameters: namely to search for faint, low-amplitude stars that exhibit short sinusoidal modulations in their light curves, with periods shorter than 20 min. These are the rarest types of AM CVn stars and also the hardest to be detected by typical transient and spectroscopic surveys due to their observing properties (only 7 are known today).

OW started in 2011, and uses the OmegaCAM detector on the 2.5 m VLT Survey Telescope in Chile. A large number of intriguing variable stars was discovered and several have been followed-up. The most interesting examples like the progenitor of an AM CVn system, the second warm magnetic carbon white dwarf, etc. have been reported in several publications.

The latest study reports on the searching for variable stars with periods shorter than 1 hr in open clusters that happen to overlap the OW fields. Open Clusters (OCs) are gravitationally bound groups of tens to hundreds of stars that reside in the thin disk of our Milky Way. The novelty of this study is that no other open clusters survey has explored the faint stars in the space searched by the OW. The importance of this work is significant since a star that physically belongs to an OC has more known parameters (e.g. the same distance and age as the cluster) and can be used to test stellar physics theories. OCs population studies can also be used to trace the structure and evolution of our Galaxy.

A number of 92 variable stars were found into a set of 20 OCs. Several stellar catalogues were used, including the newest derived from data released by the Gaia mission, to assess if our stars are cluster members. Of these, only 12 have the highest probability to be members, 6 more have unknown status and the remaining are field stars. From spectroscopic follow-up data and studies of the Gaia colour-magnitude diagram, 12 members are low-amplitude delta Scuti pulsators - one of the most common class of variable stars, as expected. The shortest period star found is a 29.8 min delta Scuti with a chance of only 66 percent to belong to an OC. Most of the stars discovered are longer periodic variables. The Gaia Hertzsprung-Russell Diagram (Fig. 1) indicates that the new found cluster members (shown as red star symbols) are located on the main-sequence and beyond; the latter are evolved pulsators. Among the field stars (pink dots), there could also be main-sequence high-amplitude delta Scutis and eclipsing binaries. As reference, all the field stars within 50 pc from the Sun (smaller dark dots) are shown. It is assumed that these closer field stars are not affected by reddening. The report concludes that the new results are in agreement with the literature: there is a relative small number of delta Scuti stars that are members of OCs.

More information: The most recent project was presented in a new published paper in the Monthly Notices of the Royal Astronomical Society Journal: The OmegaWhite Survey for Short Period Variable Stars VI. Open Clusters, by Toma et al. https://doi.org/10.1093/mnras/stac802.

The first radio burst type II detected at Bucharest CALLISTO Station

The solar activity is increasing beyond the predictions for the solar cycle 25. Following a M4 class solar flare in the active region AR12975 occurred at 11:28 UTC, there was a radio burst type II and an Earth direction Coronal Mass Ejection (CME). The type II radio burst was detected and recorded by the CALLISTO radio spectrometer installed at AIRA Bucharest, a custom device for this kind of radio observations, developed by Christian Monstein (IRSOL, Switzerland).

Type II radio are characterized by a slow drift in frequency and two distinct bands of fundamental and harmonic frequencies of the hot plasma emissions. The electrons are accelerated by the shock-wave in front of a CME so these phenomena are strong correlated. In the picture, the blue to red contiguous zones represent the emissions and the other smaller lines and zones are Radio Frequencies Interference (RFI) caused by various terrestrial sources like computers, switching power supply, radio communications, static noise and so on.

A custom software was used to extract the relevant signal from the background noise, provided by Christian Monstein to all e-callisto network stations. More information on: http://www.e-callisto.org/. Contact: oblagoi (at) astro.ro

Radio burst type II detected at AIRA
Summer time observing in Romania

Summer Time in Romania - 2022

As daylight time gets longer this period of the year, summer time in Europe will begin in Romania on Sunday, 27 March 2022, at 3 a.m. EET, when clocks will be set one hour ahead. This corresponds to the practice of Daylight Saving Time (DST) applied in the US, Canada, parts of Australia and to some other countries of the world. Today, only a minority of the world’s population uses DST, respectively a number of states located, in general, north or south of the tropics where daylight lasts shorter in the winter and longer in summer.

Regardless on how this is known as - Summer Time in Europe or Daylight Saving Time in other places of the world, this practice basically aims to save energy by the usage of more natural light in all human activities and less artificial light, which is energy consuming. As we still use to a significant extent fossil fuels to produce our energy, such a simple, conventional procedure like summer time observing leads to a significant cut in energy consumption and consequentially, of our carbon footprint on Earth.

Summer time in Europe is applied in most European countries, excepting Turkey, Iceland, Belarus and Russia.

This solution of making human activities more energy-effective was introduced in Germany in 1916, during the military and economic crisis of the First World War. However, for almost half a century afterwards, this practice was discontinued and then reintroduced at times in various places of the globe. The energy crisis of the late 1960s-1970s changed this dynamics ever since, and the European Summer Time is now used every year on most of our continent.

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