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  • richardmitnick 10:27 am on August 3, 2019 Permalink | Reply
    Tags: "Star Light Star Bright", Pulsating stars, Scientists hadn’t previously predicted the existence of these stars., , , Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California   

    From UC Santa Barbara: “Star Light, Star Bright” 

    UC Santa Barbara Name bloc
    From UC Santa Barbara

    August 1, 2019
    Harrison Tasoff

    Scientists discover a new type of pulsating star.

    1
    The nebula remains of a dead giant star surround the remaining subdwarf O star, another kind of hot subdwarf.
    Photo Credit: European Southern Observatory

    Scientists can tell a lot about a star by the light it gives off. The color, for example, reveals its surface temperature and the elements in and around it. Brightness correlates with a star’s mass, and for many stars, brightness fluctuates, a bit like a flickering candle.

    A team of scientists led by UC Santa Barbara researcher Thomas Kupfer recently discovered a new class of these pulsators that vary in brightness every five minutes. Their results appeared in The Astrophysical Journal Letters.

    “Many stars pulsate, even our sun does on a very small scale,” said Kupfer, a postdoctoral scholar at UC Santa Barbara’s Kavli Institute for Theoretical Physics (KITP).

    A true pulsator can vary in brightness by some 10% due to a periodic change in its temperature, radius or both. “Those with the largest brightness changes are usually radial pulsators, ‘breathing’ in and out as the entire star changes size,” he explained. By studying pulsations in detail, scientists can learn about these stars’ interior properties.

    Initially, Kupfer and his colleagues at Caltech were searching for binary stars with periods less than an hour in observations from the Zwicky Transient Facility, a sky survey at the Palomar Observatory near San Diego.

    Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California. Courtesy Caltech Optical Observatories

    Edwin Hubble at Caltech Palomar Samuel Oschin 48 inch Telescope, (credit: Emilio Segre Visual Archives/AIP/SPL)

    Caltech Palomar Samuel Oschin 48 inch Telescope, located in San Diego County, California, United States, altitude 1,712 m (5,617 ft)

    Four stood out due to large changes in their brightness over just a few minutes. Follow-up data quickly confirmed that they were indeed pulsators, not binary pairs.

    Working with his Caltech collaborators, alongside former UC Santa Barbara doctoral student Evan Bauer and KITP Director Lars Bildsten, Kupfer has now identified the stand-out stars as hot subdwarf pulsators. A subdwarf is a star about one-tenth the diameter of the sun with a mass between 20 and 50% that of sun. They’re incredibly hot — up to 90,000 degrees Fahrenheit, compared to the sun’s 10,000 F. “These stars have certainly completed fusing all of the hydrogen in their core into helium, explaining why they are so small and can oscillate so rapidly,” said Bildsten.

    The discovery came as a surprise. Scientists hadn’t previously predicted the existence of these stars, Kupfer explained, but in retrospect they fit well into the leading models of stellar evolution.

    Because of the stars’ low masses, the team believes they started life as typical sun-like stars fusing hydrogen to helium in their cores. After exhausting the hydrogen in their cores, the stars expanded into the red giant stage. Usually, a star will reach its largest radius and begin fusing helium deep in the core. However, the scientists think these newly discovered stars had their outer material stolen by a companion before the helium became hot and dense enough to fuse.

    In the past, hot subdwarfs were almost always related to stars which became red giants, started fusing helium in their cores, and then got stripped by a companion. The new findings indicate that this group includes different types of stars. “Some do helium fusion and some don’t,” Kupfer said.

    The stars’ pulsations allow scientists to probe their masses and radii and compare these measurements to stellar models, something that was not otherwise possible previously. “We were able to understand the rapid pulsations by matching them to theoretical models with low mass cores made of relatively cold helium,” said Bauer.

    “Sky surveys are transforming astronomy, and the Zwicky Transient Facility is helping pioneer this approach,” says the National Science Foundation ‘s Richard Barvainis, who oversees the agency’s grants in support of the facility. “This latest result is a perfect example — by watching distant stars pulsate over a matter of mere minutes, astronomers have gained unexpected insights into stellar evolution.”

    Kupfer believes there’s more to come. “I expect that these large, time-domain surveys like the Zwicky Transient Facility will bring many unexpected discoveries in the future,” he said.

    These research efforts at UC Santa Barbara are supported by the National Science Foundation, as well as the Gordon and Betty Moore Foundation. The Zwicky Transient Facility is funded by the National Science Foundation, NASA and the Heising-Simons Foundation. Other contributing institutions include Caltech, the University of Washington, the University of Maryland, the Humboldt University of Berlin, the Weizmann Institute of Science and Boston University, as well as an international collaboration of additional partners.

    See the full article here .


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    UC Santa Barbara Seal
    The University of California, Santa Barbara (commonly referred to as UC Santa Barbara or UCSB) is a public research university and one of the 10 general campuses of the University of California system. Founded in 1891 as an independent teachers’ college, UCSB joined the University of California system in 1944 and is the third-oldest general-education campus in the system. The university is a comprehensive doctoral university and is organized into five colleges offering 87 undergraduate degrees and 55 graduate degrees. In 2012, UCSB was ranked 41st among “National Universities” and 10th among public universities by U.S. News & World Report. UCSB houses twelve national research centers, including the renowned Kavli Institute for Theoretical Physics.

     
  • richardmitnick 10:26 am on July 25, 2019 Permalink | Reply
    Tags: "Second-Fastest Dead Star Pair Ever Found Orbits Every Seven Minutes", , , , , , , , The second fastest orbiting pair of white dwarfs, Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California   

    From Discover Magazine: “Second-Fastest Dead Star Pair Ever Found Orbits Every Seven Minutes” 

    DiscoverMag

    From Discover Magazine

    July 24, 2019
    Korey Haynes

    1
    The two white dwarf stars orbit so close together that the whole system could fit inside the planet Saturn. (Credit: Caltech/IPAC)

    Astronomers using the Zwicky Transient Facility at Kitt Peak in Arizona [?] have discovered the second fastest orbiting pair of white dwarfs.

    Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California. Courtesy Caltech Optical Observatories

    At the end of their normal lives, our sun and other stars like it become white dwarfs. Their outer layers puff away and leave behind a hot, dense core. And if those stars started life in a binary pair, as most stars do, then then they can end up in a tight, fast orbit, as the stars age and interact.

    But in the extreme world of binary white dwarfs, this new discovery, called ZTF J1539+5027, is an extreme case. The two tiny stars orbit each other every 6.91 minutes, within a space smaller than the planet Saturn. Researchers led by graduate student Kevin Burdge from the California Institute of Technology published their findings in the journal Nature on Wednesday. They point out that the system will be a perfect target for the upcoming LISA gravitational wave detector, set to launch in 2034.

    ESA/NASA eLISA


    ESA/NASA eLISA space based, the future of gravitational wave research

    Fast Pair

    In their younger days, these stars probably orbited much farther apart. But identical twin stars are rare, and one usually starts off at least a little bigger than the other. This bigger sun then races through its life a little quicker. That means that one star reaches its large and puffy phase while the other is still star-like, and they can end up sharing – or stealing – material from each other. In many cases, this trade-off forces the pair to spiral closer together.

    In this newly-found system, one of the stars is currently slightly larger than Earth but weighs about 60 percent the mass of our sun. The other dwarf is puffier and a little larger in diameter but weighs only one-third of its companion. Already quite close, the two stars grow 10 inches closer per day, thanks to the energy they radiate away as gravitational waves.

    Such systems with clear gravitational wave emissions are expected to be common in the universe, but only a few have been positively identified so far. That may change when LISA, the Laser Interferometer Space Antenna, launches in the 2030s. Like LIGO, which found colliding black holes in 2015, the instrument will hunt for the invisible ripples in space-time caused by gravitational waves. But LISA will hunt smaller prey, like these binary systems. And unlike many of LIGO’s sources, which can only be observed through gravitational waves, binary pairs like J1539 may yield extra information, appearing both through gravitational waves and visible light.

    MIT /Caltech Advanced aLigo


    While LISA isn’t ready for launch yet, scientists are excited to have a prime observing target already picked out, and know that LISA’s prey is out there, waiting to be observed.

    See the full article here .

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  • richardmitnick 1:53 pm on July 8, 2019 Permalink | Reply
    Tags: , , Atira asteroid 2019 LF6, , , , , We only have about 20 to 30 minutes before sunrise or after sunset to find these asteroids, ZTF has so far found around 100 near-Earth asteroids and about 2000 asteroids orbiting in the Main Belt between Mars and Jupiter., Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California   

    From Caltech: “ZTF Spots Asteroid with Shortest Year” 

    Caltech Logo

    From Caltech

    Whitney Clavin
    (626) 395‑1856
    wclavin@caltech.edu

    4
    The newfound kilometer-size object orbits the sun every 151 days

    July 08, 2019

    Astronomers have spotted an unusual asteroid with the shortest “year” known for any asteroid. The rocky body, dubbed 2019 LF6, is about a kilometer in size and circles the sun roughly every 151 days. In its orbit, the asteroid swings out beyond Venus and, at times, comes closer in than Mercury, which circles the sun every 88 days. 2019 LF6 is one of only 20 known “Atira” asteroids, whose orbits fall entirely within Earth’s.

    “You don’t find kilometer-size asteroids very often these days,” says Quanzhi Ye, a postdoctoral scholar at Caltech who discovered 2019 LF6 and works with Tom Prince, the Ira S. Bowen Professor of Physics at Caltech and a senior research scientist at JPL, and George Helou, the executive director of IPAC, an astronomy center at Caltech.

    “Thirty years ago, people started organizing methodical asteroid searches, finding larger objects first, but now that most of them have been found, the bigger ones are rare birds,” he says. “LF6 is very unusual both in orbit and in size—its unique orbit explains why such a large asteroid eluded several decades of careful searches.”

    2019 LF6 was discovered via the Zwicky Transient Facility, or ZTF, a state-of-the-art camera at the Palomar Observatory that scans the skies every night for transient objects, such as exploding and flashing stars and moving asteroids. Because ZTF scans the sky so rapidly, it is well-suited for finding Atira asteroids, which have short observing windows.

    Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California. Courtesy Caltech Optical Observatories

    “We only have about 20 to 30 minutes before sunrise or after sunset to find these asteroids,” says Ye.

    To find the Atira asteroids, the ZTF team has been carrying out a dedicated observing campaign, named Twilight after the time of day best suited for discovering the objects. Twilight was developed by Ye and Wing-Huen Ip of the National Central University in Taiwan. So far, the program has discovered one other Atira asteroid, named 2019 AQ3. Before 2019 LF6 came along, 2019 AQ3 had the shortest known year of any asteroid, orbiting the sun roughly every 165 days.

    “Both of the large Atira asteroids that were found by ZTF orbit well outside the plane of the solar system,” says Prince. “This suggests that sometime in the past they were flung out of the plane of the solar system because they came too close to Venus or Mercury,” says Prince.

    In addition to the two Atira objects, ZTF has so far found around 100 near-Earth asteroids and about 2,000 asteroids orbiting in the Main Belt between Mars and Jupiter.

    Ye says he hopes the Twilight program will lead to more Atira discoveries, and he looks forward to the possible selection by NASA of the Near-Earth Object Camera (NEOCam) mission, a proposed spacecraft designed to look for asteroids closer to the sun than previous surveys. NEOCam would pick up the infrared, or heat, signatures of asteroids. (Ye works at IPAC, which would process and archive data for the NEOCam mission, but is not part of that team.)

    “Because Atira asteroids are closer to the sun and warmer than other asteroids, they are brighter in the infrared,” says Helou.”NEOCam has the double advantage of its location in space and its infrared capability to find these asteroids more easily than telescopes working at visible wavelengths from the ground.”

    The International Astronomical Union Minor Planet Center listing for 2019 LF6 is at https://minorplanetcenter.net/mpec/K19/K19M45.html.

    ZTF is funded by the National Science Foundationand an international collaboration of partners. Additional support comes from the Heising-Simons Foundation, and Caltech itself. ZTF data are processed and archived by IPAC. NASA supports ZTF’s search for near-Earth objects through the Near-Earth Object Observations program.

    See the full article here .


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    Please help promote STEM in your local schools.


    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

     
  • richardmitnick 7:11 pm on March 6, 2019 Permalink | Reply
    Tags: , , , , , , , The transient AT2018zr triggered a ZTF alert on 6 March 2018, With many more events like AT2018zr we can hope to build a large sample of flares that will finally shed light on TDE processes, ZTF began its first major public observing survey in mid-March 2018, Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California   

    From AAS NOVA: “First Disrupted Star for a New Survey” 

    AASNOVA

    From AAS NOVA

    6 March 2019
    Susanna Kohler

    1
    Artist’s impression of a glowing stream of material produced when a star is shredded by a supermassive black hole. [NASA/JPL-Caltech]

    What happens when a black hole makes a meal out of a passing star? So far, we’ve only detected a few dozen candidate tidal disruption events to help us answer this question — but now a new player is in the observing game.

    Snacks for Black Holes

    When a star passes within the tidal radius of a supermassive black hole, things don’t end well for the star. After the unfortunate object is torn apart by gravitational forces, some of the resulting debris accretes onto the black hole, causing a multi-wavelength flare.

    To date, we’ve observed this flare emission from several dozen candidate tidal disruption events (TDEs), but many of them were only noticed significantly after the moment of disruption, when the flare emission is already ramping back down again. We also have only a handful of detections of TDEs across multiple wavelengths.

    Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California. Courtesy Caltech Optical Observatories

    In short, TDE observations thus far — though tantalizing — aren’t yet enough to help us complete the picture of what happens when a star is torn apart by a supermassive black hole. Clearly, the next step is to gather many more such observations! Luckily, a new tool has recently come online that will help us do exactly that: the Zwicky Transient Facility (ZTF)

    A New Player

    ZTF is a wide-field optical survey that hunts for transient objects in our night sky. ZTF images image the entire northern sky once every three nights, and the plane of the Milky Way twice a night. By scanning the same regions frequently, the survey can detect and monitor rapidly changing objects — like a suddenly rising tidal disruption flare.

    ZTF began its first major public observing survey in mid-March 2018. In the weeks before that, ZTF was still in its commissioning phase, testing the camera and the alert pipeline. It was in this time that the survey detected its first tidal disruption event candidate, AT2018zr.

    2
    ZTF optical and Swift ultraviolet and optical light curves for AT2018zr. The data capture both the sudden rise and gradual decay of the flare. [van Velzen et al. 2019]

    NASA Neil Gehrels Swift Observatory

    Early View of Destruction

    The transient AT2018zr triggered a ZTF alert on 6 March 2018. In the weeks that followed, it was observed by additional telescopes across a number of wavelength bands. In a new publication led by Sjoert van Velzen (University of Maryland and New York University), team members detailed the ZTF and multi-wavelength follow-up observations of AT2018zr.

    By reprocessing earlier ZTF image frames, van Veltzen and collaborators found that ZTF had actually captured this tidal disruption event starting in early February, 50 days before the peak of the flare light curve. These detailed optical observations, combined with the broadband follow-up, provide an unusually complete view of this flare.

    3
    The host of AT2018zr, as observed by the Sloan Digital Sky Survey before the TDE occurred. [SDSS]

    SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude2,788 meters (9,147 ft)

    Harbingers of Data to Come

    With many more events like AT2018zr, we can hope to build a large sample of flares that will finally shed light on TDE processes. ZTF is conveniently poised to start producing those observations; estimates suggest that, now that ZTF is fully operational, it will produce ~30 TDE detections per year.

    What’s more, ZTF is providing researchers with a chance to test clever analysis techniques in advance of an even larger flood of data: the upcoming Large Synoptic Survey Telescope (LSST) is expected to detect ~1,000 TDEs per year!

    LSST


    LSST Camera, built at SLAC



    LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.


    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    While only one event, AT2018zr is likely something more — the beginning of a new era for TDE observations.
    Citation

    “The First Tidal Disruption Flare in ZTF: From Photometric Selection to Multi-wavelength Characterization,” Sjoert van Velzen et al 2019 ApJ 872 198.
    https://iopscience.iop.org/article/10.3847/1538-4357/aafe0c/meta

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
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