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  • richardmitnick 2:32 pm on August 3, 2017 Permalink | Reply
    Tags: , , , , , SN 2017egm, Superluminous Supernova   

    From CfA: “Astronomers Discover “Heavy Metal” Supernova Rocking Out” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    July 31, 2017
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

    Peter Edmonds
    Harvard-Smithsonian Center for Astrophysics
    +1 617-571-7279
    pedmonds@cfa.harvard.edu

    1

    Many rock stars don’t like to play by the rules, and a cosmic one is no exception. A team of astronomers has discovered that an extraordinarily bright supernova occurred in a surprising location. This “heavy metal” supernova discovery challenges current ideas of how and where such super-charged supernovas occur.

    Supernovas are some of the most energetic events in the Universe. When a massive star runs out of fuel, it can collapse onto itself and create a spectacular explosion that briefly outshines an entire galaxy, dispersing vital elements into space.

    In the past decade, astronomers have discovered about fifty supernovas, out of the thousands known, that are particularly powerful. These explosions are up to 100 times brighter than other supernovas caused by the collapse of a massive star.

    Following the recent discovery of one of these “superluminous supernovas”, a team of astronomers led by Matt Nicholl from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., has uncovered vital clues about where some of these extraordinary objects come from.

    Cambridge University’s Gaia Science Alerts team discovered this supernova, dubbed SN 2017egm, on May 23, 2017 with the European Space Agency’s Gaia satellite.

    ESA/GAIA satellite


    Nordic Optical telescope, at Roque de los Muchachos Observatory, La Palma in the Canary Islands, Spain


    A team led by Subo Dong of the Kavli Institute for Astronomy and Astrophysics at Peking University used the Nordic Optical Telescope to identify it as a superluminous supernova.

    SN 2017egm is located in a spiral galaxy about 420 million light years from Earth, making it about three times closer than any other superluminous supernova previously seen. Dong realized that the galaxy was very surprising, as virtually all known superluminous supernovas have been found in dwarf galaxies that are much smaller than spiral galaxies like the Milky Way.

    Building on this discovery, the CfA team found that SN 2017egm’s host galaxy has a high concentration of elements heavier than hydrogen and helium, which astronomers call “metals”. This is the first clear evidence for a metal-rich birthplace for a superluminous supernova. The dwarf galaxies that usually host superluminous supernovas are known to have a low metal content, which was thought to be an essential ingredient for making these explosions.

    “Superluminous supernovas were already the rock stars of the supernova world,” said Nicholl. “We now know that some of them like heavy metal, so to speak, and explode in galaxies like our own Milky Way.”

    “If one of these went off in our own Galaxy, it would be much brighter than any supernova in recorded human history and would be as bright as the full Moon,” said co-author Edo Berger, also of the CfA. “However, they’re so rare that we probably have to wait several million years to see one.”

    The CfA researchers also found more clues about the nature of SN 2017egm. In particular, their new study supports the idea that a rapidly spinning, highly magnetized neutron star, called a magnetar, is likely the engine that drives the incredible amount of light generated by these supernovas.

    While the brightness of SN 2017egm and the properties of the magnetar that powers it overlap with those of other superluminous supernovas, the amount of mass ejected by SN 2017egm may be lower than the average event. This difference may indicate that the massive star that led to SN 2017egm lost more mass than most superluminous supernova progenitors before exploding. The spin rate of the magnetar may also be slower than average.

    These results show that the amount of metals has at most only a small effect on the properties of a superluminous supernova and the engine driving it. However, the metal-rich variety occurs at only about 10% of the rate of the metal-poor ones. Similar results have been found for bursts of gamma rays associated with the explosion of massive stars. This suggests a close association between these two types of objects.

    From July 4th, 2017 until September 16th, 2017 the supernova is not observable because it is too close to the Sun. After that, detailed studies should be possible for at least a few more years.

    “This should break all records for how long a superluminous supernova can be followed”, said co-author Raffaella Margutti of Northwestern University in Evanston, Illinois. “I’m excited to see what other surprises this object has in store for us.”

    6
    The CfA team observed SN 2017egm on June 18th with the 60-inch telescope at the Smithsonian Astrophysical Observatory’s Fred Lawrence Whipple Observatory in Arizona.

    A paper by Matt Nicholl describing these results was recently accepted for publication in The Astrophysical Journal Letters, and is available online. In addition to Berger and Margutti, the co-authors of the paper are Peter Blanchard, James Guillochon, and Joel Leja, all of the CfA, and Ryan Chornock of Ohio University in Athens, Ohio.

    See the full article here .

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    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 2:00 pm on July 21, 2017 Permalink | Reply
    Tags: Cosmic high noon, Superluminous Supernova, Supernova DES15E2mlf,   

    From UCSC: “Superluminous supernova marks the death of a star at cosmic high noon” 

    UC Santa Cruz

    UC Santa Cruz

    July 21, 2017
    Tim Stephens
    stephens@ucsc.edu

    At a distance of 10 billion light years, a supernova detected by the Dark Energy Survey team is one of the most distant ever discovered and confirmed.

    1
    The yellow arrow marks the superluminous supernova DES15E2mlf in this false-color image of the surrounding field. This image was observed with the Dark Energy Camera (DECam) gri-band filters mounted on the Blanco 4-meter telescope on December 28, 2015, around the time when the supernova reached its peak luminosity. (Observers: D. Gerdes and S. Jouvel)

    The death of a massive star in a distant galaxy 10 billion years ago created a rare superluminous supernova that astronomers say is one of the most distant ever discovered. The brilliant explosion, more than three times as bright as the 100 billion stars of our Milky Way galaxy combined, occurred about 3.5 billion years after the big bang at a period known as “cosmic high noon,” when the rate of star formation in the universe reached its peak.

    Superluminous supernovae are 10 to 100 times brighter than a typical supernova resulting from the collapse of a massive star. But astronomers still don’t know exactly what kinds of stars give rise to their extreme luminosity or what physical processes are involved.

    The supernova known as DES15E2mlf is unusual even among the small number of superluminous supernovae astronomers have detected so far. It was initially detected in November 2015 by the Dark Energy Survey (DES) collaboration using the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory in Chile.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam

    Follow-up observations to measure the distance and obtain detailed spectra of the supernova were conducted with the Gemini Multi-Object Spectrograph on the 8-meter Gemini South telescope.

    Gemini Observatory GMOS on Gemini South


    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile

    The investigation was led by UC Santa Cruz astronomers Yen-Chen Pan and Ryan Foley as part of an international team of DES collaborators. The researchers reported their findings in a paper published July 21 in the Monthly Notices of the Royal Astronomical Society.

    The new observations may provide clues to the nature of stars and galaxies during peak star formation. Supernovae are important in the evolution of galaxies because their explosions enrich the interstellar gas from which new stars form with elements heavier than helium (which astronomers call “metals”).

    “It’s important simply to know that very massive stars were exploding at that time,” said Foley, an assistant professor of astronomy and astrophysics at UC Santa Cruz. “What we really want to know is the relative rate of superluminous supernovae to normal supernovae, but we can’t yet make that comparison because normal supernovae are too faint to see at that distance. So we don’t know if this atypical supernova is telling us something special about that time 10 billion years ago.”

    Previous observations of superluminous supernovae found they typically reside in low-mass or dwarf galaxies, which tend to be less enriched in metals than more massive galaxies. The host galaxy of DES15E2mlf, however, is a fairly massive, normal-looking galaxy.

    “The current idea is that a low-metal environment is important in creating superluminous supernovae, and that’s why they tend to occur in low mass galaxies, but DES15E2mlf is in a relatively massive galaxy compared to the typical host galaxy for superluminous supernovae,” said Pan, a postdoctoral researcher at UC Santa Cruz and first author of the paper.

    Foley explained that stars with fewer heavy elements retain a larger fraction of their mass when they die, which may cause a bigger explosion when the star exhausts its fuel supply and collapses.

    “We know metallicity affects the life of a star and how it dies, so finding this superluminous supernova in a higher-mass galaxy goes counter to current thinking,” Foley said. “But we are looking so far back in time, this galaxy would have had less time to create metals, so it may be that at these earlier times in the universe’s history, even high-mass galaxies had low enough metal content to create these extraordinary stellar explosions. At some point, the Milky Way also had these conditions and might have also produced a lot of these explosions.”

    “Although many puzzles remain, the ability to observe these unusual supernovae at such great distances provides valuable information about the most massive stars and about an important period in the evolution of galaxies,” said Mat Smith, a postdoctoral researcher at University of Southampton. The Dark Energy Survey has discovered a number of superluminous supernovae and continues to see more distant cosmic explosions revealing how stars exploded during the strongest period of star formation.

    In addition to Pan, Foley, and Smith, the coauthors of the paper include Lluís Galbany of the University of Pittsburgh, and other members of the DES collaboration from more than 40 institutions. This research was funded the National Science Foundation, The Alfred P. Sloan Foundation, and the David and Lucile Packard Foundation.

    The Dark Energy Survey is a collaboration of more than 400 scientists from 26 institutions in seven countries. Its primary instrument, the 570-megapixel Dark Energy Camera, is mounted on the 4-meter Blanco telescope at the National Optical Astronomy Observatory’s Cerro Tololo Inter-American Observatory in Chile, and its data are processed at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign. Funding for the DES Projects has been provided by the U.S. Department of Energy Office of Science, U.S. National Science Foundation, Ministry of Science and Education of Spain, Science and Technology Facilities Council of the United Kingdom, Higher Education Funding Council for England, ETH Zurich for Switzerland, National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, Kavli Institute of Cosmological Physics at the University of Chicago, Center for Cosmology and Astro-Particle Physics at Ohio State University, Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and Ministério da Ciência e Tecnologia, Deutsche Forschungsgemeinschaft, and the collaborating institutions in the Dark Energy Survey, the list of which can be found at http://www.darkenergysurvey.org/collaboration.

    See the full article here .

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    UCO Lick Shane Telescope
    UCO Lick Shane Telescope interior
    Shane Telescope at UCO Lick Observatory, UCSC

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    UC Santa Cruz campus
    The University of California, Santa Cruz, opened in 1965 and grew, one college at a time, to its current (2008-09) enrollment of more than 16,000 students. Undergraduates pursue more than 60 majors supervised by divisional deans of humanities, physical & biological sciences, social sciences, and arts. Graduate students work toward graduate certificates, master’s degrees, or doctoral degrees in more than 30 academic fields under the supervision of the divisional and graduate deans. The dean of the Jack Baskin School of Engineering oversees the campus’s undergraduate and graduate engineering programs.

    UCSC is the home base for the Lick Observatory.

    Lick Observatory's Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building
    Lick Observatory’s Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building

    Search for extraterrestrial intelligence expands at Lick Observatory
    New instrument scans the sky for pulses of infrared light
    March 23, 2015
    By Hilary Lebow
    1
    The NIROSETI instrument saw first light on the Nickel 1-meter Telescope at Lick Observatory on March 15, 2015. (Photo by Laurie Hatch) UCSC Lick Nickel telescope

    Astronomers are expanding the search for extraterrestrial intelligence into a new realm with detectors tuned to infrared light at UC’s Lick Observatory. A new instrument, called NIROSETI, will soon scour the sky for messages from other worlds.

    “Infrared light would be an excellent means of interstellar communication,” said Shelley Wright, an assistant professor of physics at UC San Diego who led the development of the new instrument while at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics.

    Wright worked on an earlier SETI project at Lick Observatory as a UC Santa Cruz undergraduate, when she built an optical instrument designed by UC Berkeley researchers. The infrared project takes advantage of new technology not available for that first optical search.

    Infrared light would be a good way for extraterrestrials to get our attention here on Earth, since pulses from a powerful infrared laser could outshine a star, if only for a billionth of a second. Interstellar gas and dust is almost transparent to near infrared, so these signals can be seen from great distances. It also takes less energy to send information using infrared signals than with visible light.

    5
    UCSC alumna Shelley Wright, now an assistant professor of physics at UC San Diego, discusses the dichroic filter of the NIROSETI instrument. (Photo by Laurie Hatch)

    Frank Drake, professor emeritus of astronomy and astrophysics at UC Santa Cruz and director emeritus of the SETI Institute, said there are several additional advantages to a search in the infrared realm.

    “The signals are so strong that we only need a small telescope to receive them. Smaller telescopes can offer more observational time, and that is good because we need to search many stars for a chance of success,” said Drake.

    The only downside is that extraterrestrials would need to be transmitting their signals in our direction, Drake said, though he sees this as a positive side to that limitation. “If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”

    Scientists have searched the skies for radio signals for more than 50 years and expanded their search into the optical realm more than a decade ago. The idea of searching in the infrared is not a new one, but instruments capable of capturing pulses of infrared light only recently became available.

    “We had to wait,” Wright said. “I spent eight years waiting and watching as new technology emerged.”

    Now that technology has caught up, the search will extend to stars thousands of light years away, rather than just hundreds. NIROSETI, or Near-Infrared Optical Search for Extraterrestrial Intelligence, could also uncover new information about the physical universe.

    “This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales,” said Dan Werthimer, UC Berkeley SETI Project Director. “The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”

    NIROSETI will also gather more information than previous optical detectors by recording levels of light over time so that patterns can be analyzed for potential signs of other civilizations.

    “Searching for intelligent life in the universe is both thrilling and somewhat unorthodox,” said Claire Max, director of UC Observatories and professor of astronomy and astrophysics at UC Santa Cruz. “Lick Observatory has already been the site of several previous SETI searches, so this is a very exciting addition to the current research taking place.”

    NIROSETI will be fully operational by early summer and will scan the skies several times a week on the Nickel 1-meter telescope at Lick Observatory, located on Mt. Hamilton east of San Jose.

    The NIROSETI team also includes Geoffrey Marcy and Andrew Siemion from UC Berkeley; Patrick Dorval, a Dunlap undergraduate, and Elliot Meyer, a Dunlap graduate student; and Richard Treffers of Starman Systems. Funding for the project comes from the generous support of Bill and Susan Bloomfield.

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    UCSC is the home base for the Lick Observatory.

     
  • richardmitnick 3:01 pm on April 29, 2016 Permalink | Reply
    Tags: , , , Superluminous Supernova   

    From DES- “From the DArchive: A Newly Discovered Superluminous Supernova” 

    Dark Energy Icon

    The Dark Energy Survey

    April 29, 2016
    Mathew Smith
    Edited by R.C. Wolf & R. Cawthon

    Science paper:
    DES14X3taz: A Type I Superluminous Supernova Showing a Luminous, Rapidly Cooling Initial Pre-Peak Bump

    In this paper we present DES14X3taz, a newly discovered superluminous supernova (SLSN). This particular SLSN is very unusual – if you look at the evolution of its brightness over time, or its light curve, there are two peaks (most only have one)! In our analysis, we attempt to explain what physical process might cause such an occurrence and determine if this is truly a unique event or common to all SLSNe.

    Although the initial DECam data was fairly indicative that this was a particularly interesting object, we had to use additional information to confirm our discovery. By combining optical light-curve data from DES and its sister survey, the Survey Using Decam for Superluminous Supernovae (SUDSS), we were able to plot the evolution of brightness over time (light-curve) of DES14X3taz and find its brightest point. We then used spectra obtained on the Gran Telescopino Canarias (GTC) in La Palma, Spain to estimate the distance to this event, and thus its peak brightness, and unambiguously confirmed that it is a SLSNe.

    Gran Telescopino Canarias exterior
    Gran Telescopino de Canaries interior
    Gran Telescopino de Canaries

    What really distinguishes DES14X3taz from previously discovered SLSNe is the presence of an early “bump” in the light curve prior to the main light-curve. The figure below shows these features for DES14X3taz.

    1

    In addition to detecting this bump, we were lucky to have observed this SLSN before explosion and to have observed it at many points during its lifetime; most other observed SLSNe have been discovered post-explosion or do not have such a large a sample of measurements.

    Our observations with DECam allowed us to obtain colour information, from observations in several filters, of the bump. This enabled us to probe the physical processes driving these super-luminous events by comparing our data to pre-existing theoretical models. In the figure below, the colored-circle points are real data, and the dashed lines represent theoretical observations for different physical processes that we think might be motivating this behavior.

    2

    Fitting models to the main curve show that the physical mechanism driving the explosion is consistent with a magnetar, a rapidly rotating neutron star (as seen in the match to the Extended Material Around the Star). In the figure, this is consistent with the solid lines. Fitting black-body curves to the DES data of DES14X3taz, we show that the initial peak cools rapidly, before a period of reheating, which drives the main part of the light-curve. Using chi-squared statistics, we compare photometric data of the initial peak with various models of shock-cooling and find that shock from material at an extended radius is consistent with observations. We also find a sample of previously discovered SLSNe that also exhibit this early bump in their light curves; therefore, we believe our findings suggest a unified physical interpretation for all SLSNe.

    SLSNe are a new class of transient event, with potentially exciting consequences for cosmology. Recent work (Inserra & Smartt 2014) has suggested that these events may even be “standardisable candles”, and thus useful to measure distances to the high redshift Universe. As these events are more luminous than traditional Type Ia supernovae they have the potential to extend SN cosmology to larger distances than currently possible. However, little is well-understood about the explosion mechanism driving these events and we will need to understand more about the origin of SLSNe as we explore utilizing them as cosmological probes.

    See the full article here .

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    DECam, built at FNAL
    DECam, built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
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