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  • richardmitnick 10:49 am on November 15, 2017 Permalink | Reply
    Tags: , , , Contracting White Dwarf Observed For The First Time, , It is widely believed based on theoretical considerations that young white dwarfs the compact remnants of solar-like stars should experience a phase of contraction in their early life, Lomonosov Moscow State University, Russian Academy of Sciences,   

    From SpaceRef: “Contracting White Dwarf Observed For The First Time” 

    SpaceRef

    SpaceRef

    November 14, 2017
    LOMONOSOV MOSCOW STATE UNIVERSITY Press Release

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    Contracting White Dwarf. LOMONOSOV MOSCOW STATE UNIVERSITY

    Astrophysicists from MSU (Russia) and [their] colleagues from Italy and Russian Academy of Sciences have found the first observational evidence for a contracting white dwarf.

    Constant high spin-up rate of a star of this type, located in an enigmatic binary system, can be easily explained if the white dwarf is contracting, the researchers argue. The discovery is reported in the Monthly Notices of the Royal Astronomical Society.

    “Thanks to this discovery, astrophysicists will be able to study and evaluate the evolution patterns of young white dwarfs — and successfully look for similar systems in the galaxy, ” — noted the main author of the article, astrophysicist Sergei Popov (SAI MSU).

    It is widely believed, based on theoretical considerations, that young white dwarfs — the compact remnants of solar-like stars, — should experience a phase of contraction in their early life. The radius of a typical white dwarf can decrease by several hundred kilometers during the first million years of its life. However, there was no observational evidence for this effect up to now. First, because most of the known white dwarf are much older. Second, because the scientists do not have a direct and precise way to measure the radii, and their variations, in these stars.

    Studying an enigmatic X-ray source in a binary system of a rare type, the scientists might have found the first observational evidence for a contracting white dwarf. The binary system HD49798/RX J0648.0-4418 is at a distance of 2000 light years, in the Puppis constellation, and has been extensively studied with optical, UV, and X-ray telescopes. It contains a massive white dwarf, which spins with a period of only 13 s, the fastest known for a white dwarf, and emits X-rays due to the accretion of matter captured from the stellar wind of its companion star.

    Sandro Mereghetti (a coauthor of the new paper) recently discovered that the rotational velocity of this white dwarf has been steadily increasing during the latest 20 years. Its spin period of 13 s is decreasing by 7 nanoseconds every year. This might seem a very small change, but it is actually a very large effect for a body weighting more than our Sun, but with a radius as small as about 5000 km (less than the Earth). Indeed, such a large spin-up rate could not be easily explained in standard ways (e.g. by the captured angular momentum of the accreting matter).

    The solution to this puzzle has been now presented by the authors of this new study. They demonstrate that the high spin-up rate can be easily explained if the white dwarf is contracting, exactly as in the case of a spinning skater that brings in her arms to rotate faster. The evolutionary calculations presented in the paper show that the white dwarf has an age of only about 2 million years. The contraction rate of about one centimeter per year expected for this age is exactly of the correct amount to explain the measured spin-up rate, showing that this is the first example of contracting white dwarf ever identified.

    “For decades it has been theoretically clear that that young white dwarfs are contracting. Yet, that very phase of contraction has never been observed “in real time”. We should thank the uniqueness of the binary system under study: the white dwarf was literally illuminated (due to the accretion of matter from the neighboring star). But it was highlighted so neatly that the accreting matter did not affect its rotation — an extremely rare phenomenon! In other similar systems, accretion is much more powerful: it determines how the white dwarf rotates, which makes it impossible to notice the beauty of contraction”, – Popov explained.

    See the full article here.

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    Founded in 1969, under the auspices of the National Academy of Sciences, Universities Space Research Association (USRA) is an independent, nonprofit research corporation which offers an avenue for government and industry to engage the expertise of the academic community together with USRA’s own technical leadership, innovative R&D, operational excellence, management of premier facilities and education programs to advance space- and aeronautics-related sciences and exploration. USRA works across disciplines including biomedicine, planetary science, astrophysics, and engineering and integrates those competencies into applications ranging from fundamental research to facility management and operations to develop and deliver sophisticated, forward-looking solutions to Federal agencies and other government sponsors.

     
  • richardmitnick 6:07 pm on February 21, 2017 Permalink | Reply
    Tags: , , , Lomonosov Moscow State University, MASTER Global Robotic Network, Supermassive black hole in the center of a galaxy known to astronomers as NGC 2617   

    From EurekaAlert: “Changes of supermassive black hole in the center of NGC 2617 galaxy” 

    eurekaalert-bloc

    EurekaAlert

    20-Feb-2017
    Lomonosov Moscow State University

    Astrophysicists study surprising changes in the appearance of a supermassive black hole.

    1
    Members of the Sternberg Astronomical Institute of the Lomonosov Moscow State University have been studying changes in the appearance of emission from around the supermassive black hole in the center of a galaxy known to astronomers as NGC 2617. The center of this galaxy, underwent dramatic changes in its appearance several years ago: it became much brighter and things that had not been seen before were seen. This sort of dramatic change can give us valuable information for understanding what the surroundings of a giant black hole are like and what is going on near the black hole. The results of these investigations have been published in the Monthly Notices of the Royal Astronomical Society, one of the world’s top-rated astronomical journals.

    Most galaxies such as our own have a giant black hole in their central nuclei. These monstrous holes have masses ranging from a million to a billion times the mass of our sun. The black hole in our galaxy is inactive, but in some galaxies, the black hole is swallowing gas that is spiraling into it and emitting enormous amounts of radiation. These galaxies are called “active galactic nuclei” or AGNs for short. The energy output from around the black holes of these AGNs can exceed that of the hundreds of billions of stars in the rest of the galaxy. Just how these galaxies get their supermassive black holes is a major mystery.

    The nuclei of galaxies where the supermassive black holes are vigorously swallowing gas are classified into two types: those where we get a direct view of the matter spiraling into the black hole at a speed that is thousands of times faster than the speed of sound, and those where the inner regions are obscured by dust and we only see more slowly moving gas much further from the black hole.

    For decades astronomers have wondered why we see the innermost regions of some active galactic nuclei but not others. A popular explanation of the two types of active galactic nuclei is that they are really the same but they appear to be different to us because we are viewing them from different angles. If they are face-on we can see the hot gas spiraling into the black hole directly. If the active galactic nucleus is tilted, then dust around the nucleus blocks our view and we can only see the more slowly moving gas a light year or more away.

    The leader of the international research team involved in the investigation, Viktor Oknyansky, a Senior Researcher at the Sternberg Astronomical Institute of the Lomonosov Moscow State University says: “Cases of object transition from one type to the other turn out to be a definite problem for this orientation model. In 1984 we found a change in the appearance of another active galactic nucleus known as NGC 4151. It was one of few known cases of this kind in the past. We now know of several dozen active galactic nuclei that have changed their type. In our recent study we have focused on one of the best cases — NGC 2617.”

    Oknyansky continues: “In 2013 a team of researchers in the US found that NGC 2617 had changed being an active galaxy where the inner regions were hidden to one where the inner regions were now exposed. We didn’t not know how long it would remain in this new unveiled state. It could last for only a short period of time or, on the other hand, for dozens of years. The title of the paper by the US astronomers was “The man behind the curtain…” When we began our study we didn’t know how long the curtain would remain open, but we’ve titled our paper “The curtain remains open…”, because we are continuing to see into the inner regions of NGC 2617.

    According to the authors there is no accepted explanation so far of what could cause us to start seeing down to the inner regions of an active galactic nucleus when it was previously hidden.

    Viktor Oknyansky comments: “It’s clear that this phenomenon isn’t very rare, on the contrary, we think it’s quite typical. We consider various possible explanations. One is that perhaps a star has come too close to the black hole and has been torn apart. However, the disruption of a star by a black hole is very rare and we don’t think that such events can explain the observed frequency of type changes of active galactic nuclei. Instead we favour a model where the black hole has started swallowing gas more rapidly. As the material spirals in towards the black holes it emits strong radiation. We speculate that this intense radiation destroys some of the dust surrounding the nucleus and permits us to see the inner regions.”

    Oknyansky continues: “Study of these rapid changes of type is very important for understanding what is going on around supermassive black holes that are rapidly swallowing gas. So, what we have concentrated on is getting observations of the various types of radiation emitted by NGC 2617. This has involved a large-scale effort.”

    The observational data for the project were obtained using the MASTER Global Robotic Network operated by Professor Vladimir Lipunov and his team, the new 2.5-m telescope located near Kislovodsk, a 2-m telescope of the observatory in Azerbajan, the Swift X-ray satellite, and some other telescopes. This research has been conducted in cooperation with colleagues from Azerbaijan, the USA, Finland, Chili, Israel and the South Africa.

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    MASTER GLOBAL Robotic Net

    NASA/SWIFT Telescope
    NASA/SWIFT Telescope

    See the full article here .

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    EurekAlert!, the premier online news source focusing on science, health, medicine and technology, is a free service for reporters worldwide.

    Since 1996, EurekAlert! has served as the leading destination for scientific organizations seeking to disseminate news to reporters and the public. Today, thousands of reporters around the globe rely on EurekAlert! as a source of ideas, background information, and advance word on breaking news stories.

    More than 1,000 peer-reviewed journals, universities, medical centers, government agencies and public relations firms have used EurekAlert! to distribute their news. EurekAlert! is an authoritative and comprehensive research news source for journalists all over the world.

     
  • richardmitnick 11:35 am on February 11, 2017 Permalink | Reply
    Tags: , , Big data for the universe, , Lomonosov Moscow State University, The Reference Catalog of galaxy SEDs   

    From EurekaAlert: “Big data for the universe” 

    eurekaalert-bloc

    EurekaAlert

    9-Feb-2017
    Lomonosov Moscow State University

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    IMAGE: RCSED design. Credit: Ivan Zolotukhin

    Astronomers at Lomonosov Moscow State University in cooperation with their French colleagues and with the help of citizen scientists have released «The Reference Catalog of galaxy SEDs» (RCSED), which contains value-added information about 800,000 galaxies. The catalog is accessible on the web and its description has been published in the Astrophysical Journal Supplement (impact factor — 11.257). Two co-authors of the research paper are undergraduate students at the Faculty of Physics, Lomonosov Moscow State University. While still working on the catalog, the team has published a few research papers based on the data from it, including a study published by the prestigious interdisciplinary journal Science.

    What can one learn using RCSED and why is it unique?

    RCSED describes properties of 800,000 galaxies derived from the elaborated data analysis. For every galaxy, it presents its stellar composition, brightness at ultraviolet, optical, and near-infrared wavelengths. From RCSED, one can also access galaxy spectra obtained by the Sloan Digital Sky Survey, measurements of spectral lines, and properties determined from them, such as the chemical composition of stars and gas, contained in those galaxies. This makes RCSED the first catalog of its kind, which contains results of detailed homogeneous analysis for such large number of objects. Dr. Igor Chilingarian, an astronomer at Smithsonian Astrophysical Observatory, USA and a Lead Researcher at Sternberg Astronomical Institute, Lomonosov Moscow State University says: “For every galaxy we also provide a small cutout image from three sky surveys, which show how the galaxy looks at different wavelengths. This provides us with the data for further investigations.” Dr. Ivan Katkov, a Senior Researcher at Sternberg Astronomical Institute adds: “The analysis of emission line profiles presented in RCSED is substantially more detailed and accurate then the data published in other catalogs”

    RCSED is really flexible and very easy to use. By simply entering the object name or its coordinates in the search field, the web site will provide in a single page all the information referring to that object contained in the catalog. One can also use the catalog through Virtual Observatory applications such as TOPCAT. The RCSED web site also provides tutorials including the one, which describes a technique that Igor Chilingarian and Ivan Zolotukhin exploited to discover new compact elliptical galaxies, which were later published in the research paper «Isolated compact elliptical galaxies: Stellar systems that ran away».

    Another interesting detail about RCSED is that the team actively used the help of citizen scientists to develop the project web site. And among them there were high-level experts in software development and web design, who have daytime jobs in the largest Russian IT-companies. Dr. Ivan Zolotukhin, a Researcher at Sternberg Astronomical Institute, explains: “Programmers sometimes get burnt out by their routine work, and they would like to do something interesting and pleasant in their spare time, for instance, to help scientists. We are very grateful to them, they have become important members of our team and significantly strengthened our project. It’s been always interesting for us to cooperate with IT specialists and we have a lot more projects where they can contribute. So if you use git, program in Python or know HTML/CSS, love stars, have a bit of spare time and are willing to help an international research team – please, contact us using the address published on the web page.

    Dr. Ivan Katkov adds: “The RCSED catalog became possible thanks to the application of an interdisciplinary Big Data approach as we had to apply very complex scientific algorithms to a large dataset in a massively parallel way. Eventually, the expertise and resources available at large IT companies would undoubtedly allow researchers to significantly increase the quality and the quantity of research results and to make many important discoveries in astrophysics”.

    The fact that the RCSED catalog has attracted serious interest in the scientific community even during its assembly phase proves its great potential. During the last three years several external researchers were given the access to the catalog on request and, using RCSED data, published over a dozen of articles in professional peer-reviewed journals (Astrophysical Journal, Astronomy & Astrophysics, MNRAS). The catalog is the world largest homogeneous value-added dataset for nearby galaxies, containing information collected with ground-based and space telescopes. The unique research material for extragalactic astrophysics contained in RCSED will certainly help astrophysicists to achieve new interesting scientific results, some of which would probably qualify for publication in the interdisciplinary journals Science and Nature.

    RCSED expansion prospects: one million galaxies will be there soon.

    The current release of the RCSED catalog could have comprised a larger number of galaxies or contained extra bits of information about the currently included objects, but at this moment the scientists have decided to focus on well-characterized datasets, which are described in detail and have known advantages and disadvantages. However, taking into account the project importance for extragalactic astronomy and observational cosmology, the RCSED team is going to move forward and expand the catalog in the near future.

    There are two principal directions of further RCSED development: the galaxy sample expansion and incorporating new data for existing objects. The team considers a possibility to include near- and mid-infrared data from the WIS? satellite all-sky survey for the entire galaxy sample. However, this requires some additional methodical work in order to homogenize the data for galaxies at different redshifts.

    Moreover, it is possible to expand the principal galaxy sample by including spectra from the latest data release of the SDSS-III survey. This will turn 800,000 to 1.5 million objects.

    Incorporating the publicly available spectral data from the Hectospec archive (Igor Chilingarian has played a major role in the Hectospec archive project) will add 300-400 thousand objects at larger distances, whose spectra were collected with the 6.5-meter MMT telescope in Arizona. The current RCSED release comprises mostly nearby galaxies (by cosmological measures), whose redshifts are smaller than 0.4, because SDSS did not include faint objects. Therefore, the early Universe is not represented in the catalog at all. The Hectospec archive will allow the team to move a little bit further in the cosmological distance scale until the redshift of 0.7. If they add several thousand galaxies from the DEEP2 survey conducted with the 10-meter Keck telescope in early 2000s, they could get insights into objects at redshift up-to 1.0, when the Universe was less than half of its present age.

    Igor Chilingarian concludes: “We shall be able to see the global picture in about ten years from now, when large surveys like DESI have collected 25-30 million galaxy spectra out to intermediate redshifts.”

    The RCSED project has been supported by the collaborative grant, provided by the Russian Foundation for Basic Research (RFBR) and The French National Center for Scientific Research (Centre National de la Recherche Scientifique, CNRS). On earlier stages the project was supported by the grants from the Russian Science Foundation (RScF), the President of the Russian Federation, along with French resources, available in the framework of the VO-Paris Data Center at the Paris Observatory.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    EurekAlert!, the premier online news source focusing on science, health, medicine and technology, is a free service for reporters worldwide.

    Since 1996, EurekAlert! has served as the leading destination for scientific organizations seeking to disseminate news to reporters and the public. Today, thousands of reporters around the globe rely on EurekAlert! as a source of ideas, background information, and advance word on breaking news stories.

    More than 1,000 peer-reviewed journals, universities, medical centers, government agencies and public relations firms have used EurekAlert! to distribute their news. EurekAlert! is an authoritative and comprehensive research news source for journalists all over the world.

     
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