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High time resolution astrophysics

High time resolution astrophysics. J. Cortina, Thursday meeting, March 2008. Cuando contemplo el cielo
 de innumerables luces adornado…. Quien mira el gran concierto
 de aquestos resplandores eternales,
 su movimiento cierto
 sus pasos desiguales
 y en proporci ón concorde tan iguales;

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High time resolution astrophysics

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  1. High time resolution astrophysics J. Cortina, Thursday meeting, March 2008

  2. Cuando contemplo el cielo
 de innumerables luces adornado…. Quien mira el gran concierto
 de aquestos resplandores eternales,
 su movimiento cierto
 sus pasos desiguales
 y en proporción concorde tan iguales; --Fray Luis de León When I behold upon the sky Decorated with innumerable lights…. Whoever watches this grand concert Of eternal splendor, Its certain pace, Its unequal steps Still so equal in its harmonic proportions --Fray Luis de León

  3. The inmutable sky • Eternal, long-lived, ever-lasting. • The sky has always been a reference for mankind. We’ve used for sailing, for harvesting… • Aristotle and the Catholic Church were essentially right: to a first order approximation, the sky doesn’t change. • Supernovae, comets, etc are weirdos. Bright stars are there season after season for thousands of years, the phases of the moon repeat every month, the sun doesn’t stop shining.

  4. The inmutable OPTICAL sky • Our natural detectors (the human eyes) are tuned to the wrong frequency. The optical sky is definitely boring.

  5. The X-ray sky • X-rays are absorbed in the atmosphere so we had to wait for satellites to see the X-ray sky. • In fact the first detectors were mounted on balloons and rockets, and took data for only hours or days. • What they first detected was hard to believe. First X-ray detector: White Sands Missile Range in New Mexico with a V-2 rocket in 1949.

  6. The X-ray sky • To start with, nobody expected to see anything in the sky in X-rays. Stars are black-body emitters and one can easily predict the flux at X-rays: 0. • Then: the X-ray celestial sources came and go! • They are so-called transient.

  7. The X-ray sky

  8. Similar in -rays or radio… • Apparently the sky is only inmutable in optical or near-optical frequencies. • Well, it’s only natural, right?: the evolution has equipped us with eyes which work on a stable and reliable source of light. • The Sun is always there (at day) and optical photons can traverse the atmosphere. • It would be stupid to evolve X-ray eyes.

  9. THE MUTABLE SKY

  10. NEOs • Near-Earth Objects. • The atmospheric, geological, and biological effects of cosmic impact have become apparent only since the early 1980s, when the likely cause of the Cretaceous-Tertiary extinction was first linked to the impact of a 10-km asteroid. • NASA has supported a groundbased program to identify the NEOs larger than 1 km in diameter. This task is about 50 percent complete, with estimates for the date of completion ranging from 2010 to 2020 and beyond. Asteroid Mathilde: 59 by 47 km (image by NEAR spacecraft) Asteroid 2004 FH Missed us by 43 000 km

  11. NEOs • The high-altitude explosion of an 80-m-diameter body above Tunguska, Siberia, in 1908 flattened trees over a broad area. A differently aimed impact of this scale could flatten a modern city • Bodies larger than about 300 m in size cause ground-level explosions in the gigaton range. Such impacts would devastate whole countries. • There is about a 1 percent chance that a >300 m impact will occur in the next century. A higher chance for >80 m impacts. • These bodies are too faint to have been detected by the current surveys, and almost all remain undetected.

  12. Extrasolar planets We look for extrasolar planets using 9 different techniques. Popular ones are: ▪Astrometry: If the star has a planet, then the gravitational influence of the planet will cause the star itself to move in a tiny orbit about their common center of mass. ▪Radial velocity or Doppler method: Variations in the speed with which the star moves towards or away from Earth can be deduced from Doppler effect. This has been by far the most productive technique used. ▪Transit method: If a planet transits in front of its parent star's disk, then the observed brightness of the star drops by a small amount. The amount by which the star dims depends on its size and on the size of the planet. ▪Gravitational microlensing: Microlensing occurs when the gravitational field of a star acts like a lens, magnifying the light of a distant background star. Possible planets orbiting the foreground star can cause detectable anomalies in the lensing event light curve.

  13. Extrasolar planets: -lensing • In 1991 Mao and Paczyński (Princeton) first proposed using gravitational microlensing to look for exoplanets. • In 2002 when astronomers from Warsaw and Paczyński (project OGLE, 1.3m telescope in Las Campanas) developed a workable technique. • Since then, 8 (?) confirmed extrasolar planets have been detected using microlensing. • Only method capable of detecting planets of Earth-like mass around ordinary stars. • Problem: microlensing events happen only once!

  14. Extrasolar planets: transits • So far 11 cases of planetary transits were discovered first photometrically and confirmed spectroscopically later. • Most of them were detected with 10 cm (!) telescopes: TrES-1 (Alonso et al. 2004), XO-lb (McCullough et al. 2006), TrES-2 (O’Donovan et al. 2006), HAT-P-1b (Bakos et al. 2006), WASP-1b and WASP-2b (Collier et al. 2006).

  15. Extrasolar planets: transits • COROT: First space mission targetted at planetary transits. • 27 cm diameter telescope. • Launched December 2006, reported first light January 2007. • Detected its first extrasolar planet, COROT-Exo-1b, May 2007. • Sensitivity allows to detect Earth-like planets.

  16. Extrasolar planets:Dysonian SETI See my last Thursday meeting…. • Astrophys. J. 627 (2005) 534: look for structure in planetary transit lightcurves. • Proposed Kepler mission expects to survey 105 stars and detect hundreds of planets through transits. Sensitive to non-spherical object shapes.

  17. Gamma Ray Bursts • The Vela satellites (May 1969 - June 1979) were a series of satellites launched by the US Air Force to monitor compliance with the Nuclear Test Ban Treaty. • These satellites were sensitive to -radiation, since a nuclear blast in the Earth's atmosphere would produce a large amount of -rays. • Surprisingly enough, they detected lots of -ray explosions! By 1979, they had detected 70. • But they could triangulate their position and it was way out of our solar system: “Gamma Ray Bursts”.

  18. Serendipity "It was once when I read a silly fairy tale, called The Three Princes of Serendip: as their highnesses travelled, they were always making discoveries, by accidents and sagacity, of things which they were not in quest of: for instance, one of them discovered that a mule blind of the right eye had travelled the same road lately, because the grass was eaten only on the left side….” -Horace Walpole on 28 January 1754

  19. Serendipity • The greatest act of serendipity in Human History took place in Spain 500 years ago when a stubborn Italian came with the idea of traveling West to make it to the Far East. • Strictly speaking, he should have given the money back to the Funding Agency: he never achieved his goals. • First he was confronted with a “Committee of Experts” in the University of Salamanca. • Quite rightfully, the experts argued that the Earth was round and its perimeter was about 40000 km, so it was suicidal to sail through 20000 km of empty ocean. • Columbus ignored the “Committee of Experts” and went directly to the “Funding Agency” a.k.a. as Queen of Castile. • The Queen, out of political arguments, funded his project. • Columbus never made it to the Far East. But, serendipitously, he found America on the way...

  20. Gamma Ray Bursts • In the 80s and most of the 90s, GRB were one of the biggest misteries in Astronomy. We knew NOTHING. • All kind of theories: from objects in the comet cloud around the solar system to black holes in our galaxy or cosmological explosions. • Observational breakthroughs: • CGRO/BATSE maps thousands of GRBs and they are isotropic. • Beppo-Sax measures redshifts and they are at cosmological distances.

  21. Gamma Ray Bursts • GRBs are the most luminouselectromagnetic events occurring in the universe since the Big Bang. • Propotypical “transient”: typically a few seconds, although can range from a few milliseconds to minutes. Essentially two kinds:short(<2s)andlong. The origin is uncertain for both of them: • Short GRB may be neutron star and neutron star/black hole mergers. Or they may be “magnetars”. • Long GRBs are associated to Supernovae. Probably come from some sort of “super-supernova”: “hypernova” or “collapsar”.

  22. GRB060614: a new type of GRB But the show goes on: • GRB060614isneither short nor long. • It waslong(102s),but hadnoassociatedsupernova. • ItalsoresidedinagalaxythatappearstobeatypicalwhencomparedtohostsofpreviouslystudiedlongGRBs. • ThisGRBmaywellrequireanewprocesstoexplainit: • amassivestarthatisverydifferentfromthosethatmakeeitherlongGRBs(andwhichdoesnotendupasasupernova), • acompactbinarymergerthatcanproducelong-livedradiation • somethingtotallynew.

  23. Easter Egg: GRB080319B • The show goes on (even on holidays). I found out about GRB080319B one week ago in “El País”. • The most luminous GRB ever recorded. • It reached <6m, i.e. visible with naked eye. • Redshift z=0.9. Could have been detected in -rays by GLAST out to z=5 and in X-rays by EXIST out to z=12. • GRBs probes of first stars in the universe...

  24. Orphan GRBs • Can we see all GRBs? • Some GRBs may not emit -rays (!). • Off-axis or otherwise. Very likely, given current understanding of jets, in GRBs. • Their detection and identification would allow the full understanding of GRB jets and source populations, which in turn may prove necessary for using GRBs as tracers of star formation rates out to large z. • Nakar et al have estimated that these will be optimally detected (at highest rates) at V,R ~20-22.

  25. The Crab Pulsar

  26. Radio and optical pulsars • A. Hewish built a funny array of radio antennas to study interstellar scintillation. • In 1967, one of his PhD students, Jocelyn Bell, found a suspicious pulsation in the data. • She had discovered the first radio “pulsar”… Years later Hewish, not her, would get the Nobel Prize. (Students: beware your advisors.)

  27. Radio and optical pulsars • Bell’s discovery got the astronomers crazy. A race set in to find more pulsars. • In a month Australians found a second one close to a Supernova Remnant. And then a pulsar at the Crab Nebula with 33 ms period. • Problem: radiotelescope had a poor angular resolution. You couldn’t tell where the source really was. • Optical telescopes did better, • A device to very fast fold light with a period (like a stroboscope) was installed at an optical telescope at Kitt Peak. • Pointed at the so-called “Baade’s star” in the center of the Crab Nebula… and there it was! A star blinking with 33 ms period!

  28. Radio Pulsars • There are now more than 1000 radio pulsars and more every day. • The phenomenology is wild: each pulse in a pulsar is different, there are giant pulses, sometimes the period jumps (glitch). • There are extremely magnetized pulsars (“magnetars”), pulsars with extremely fast periods in binary systems (“ms pulsars”) and pulsars which pulse only every now and then (“RRATs”)….. • Pulsars are used to measured distance, and have been used to detect Earth-like planets, to prove the existence of gravitational waves,and recently also as gravitational wave detectors.

  29. Radio Pulsars New phenomena are frequent: Nature 422 (2003) 141. Equipped radiotelescope in Arecibo with faster digitizer & data storage to allow ns sampling. Crab: discovered giant radio pulses lasting for 2 ns! Theplasma structures responsible for these emissions <1min size, the smallestobjects ever detected outside the Solar System. They are also the brightest transient radio sources in the sky.

  30. Radio transients in general: a zoo Nature 434, 50-52 (3 March 2005) Trasient near the Galactic Center: GCRT J1745-3009. Repeated bursts with 77 min period Nature 439, 817-820 (16 February 2006) • Eleven objects characterized by single, dispersed bursts having durations between 2 and 30 ms. • The average time intervals between bursts range from 4 min to 3 h with radio emission typically detectable for <1 s per day. • Periodicities in the range 0.4-7 s for ten of the eleven sources, suggesting origins in rotating neutron stars.

  31. Parkes’ radio transient Science 318/2 (2007) 777 • Analyzed archival Parkes radio survey data and found a 30-jansky burst, lessthan 5 ms in duration, 3ºfrom the Small Magellanic Cloud. • So bright it overloaded the detector! • Models forthe free electron content in the universe imply that the burst is less than 1 Gpc away. • Expect hundreds of such events occur throughout the sky every day. • New method to measure baryon component of the universe? • Origin?? Came out of the blue…

  32. WATCH THE UNIVERSE

  33. Limited instrumentation (1) • Optical telescopes look at the most boring window to the Universe. • By definition…. Stars, life…

  34. Limited instrumentation (2) • One century ago we moved to photographic plates and then to CCDs. • These devices improve on sensitivity by integrating for minutes or hours, so by definition they are not sensitive to faster events.

  35. Limited instrumentation (3) • We have increased the sensitivity at the cost of the Field of View: the more we zoom, the smaller the FOV. • Optical FOV>5º are hard to accomplish: optics and size of instrumentation (huge expensive CCDs). • Radio: multibeam receivers are just starting. Small FOV. • X-rays, -rays: expensive cameras, problems with optics. Hubble Ultra Deep Field: 800 exposures, 36.7 square arcminutes, 1/13 000 000 of the sky

  36. Optical: CONCAM • A CONCAM is a CONtinuous CAMera that is placed somewhere in the world with a fisheye lenses to watch the entire sky every night. • Each camera takes a 180-second exposure every 4 minutes, then relays the data back to nightskylive.net.

  37. CONCAM: Night sky live • Collectively, these physical CONCAM devices are part of the Night Sky Live project that also includes people, data, web pages, etc. • The Night Sky Live project aims to make these images and data available to those who are interested.

  38. Optical: ASAS The All Sky Automated Survey • Final goal is photometric monitoring of approx. 107 stars brighter than 14 magnitude all over the sky. • The initial idea for the project is due to Bohdan Paczynski (Princeton) • The prototype instrument, located at the Las Campanas Observatory (operated by the Carnegie Institution of Washington), and the data pipeline were developed at the Warsaw University. • Recently developed ASAS-N at Faulkes North site at the Haleakalaon Maui (Hawaii) to cover all sky. • Papers using ASAS data in ADS Database: 192 entries.

  39. ASAS • It uses telescopes with the aperture of 7 cm, the focal length of 20 cm, 2K x 2K CCD cameras 3 with 15m pixels from Apogee. • Standard V-band and I-band filters. • The I-band data are still being processed but all V-band data have already been converted to catalogs of variable stars. • ASAS reaches 14-mag stars in 2 minute exposures over a field of view of (9º)2 degrees.

  40. Sloan Digital Sky Survey • The SDSS uses a dedicated, 2.5-meter telescope on Apache Point, New Mexico. • A pair of spectrographs can measure spectra of (and hence distances to) more than 600 galaxies and quasars in a single observation. • However the 120-megapixel camera can image 1.5 square degrees of sky at a time. • This means that it took SDSS five years to scan 8,000 square degrees (20%) of the sky.

  41. Optical: LSST • The Large Synoptic Survey Telescope (LSST) is a proposed 8.4-m, 10 square-degree-field telescope. • In a relentless campaign of 15 second exposures, LSST will cover the available sky every three nights. • Will also be used to trace billions of remote galaxies and measure gravitational lensing produced by Dark Matter.

  42. LSST Funny funding for the time being: Jan 2008:LSST Receives $30M from Charles Simonyi and Bill Gates July 2007:LSST Receives $3 Million from Keck and TABASGO Foundations Jan 2007:Google joins Large Synoptic Survey Telescope Project Sept 2005:LSST receives $14.2 Million from NSF. Now they only need $400 million more from NSF…

  43. LSST: a data challenge • CCD pixel count: 3.2 Gpixels • Readout time: 2 sec • Dynamic range: 16 bits • Nominal exposure time: 15 seconds • Nightly data generation rate: 15 Tbytes. • Yearly data generation rate (average): 6.8 Pbytes

  44. Radio: Allen Telescope Array • Joint project between the SETI Institute and the UC Berkeley. • 90 miles northeast of San Francisco. • Concept: many small (6m ) cheap antennas. When completed: 350. First phase with 42 antennas operational since 2007. • Field of View 2.5ºat λ = 21 cm (17x VLA), complete instantaneous frequency coverage from 0.5 to 11.2 GHz • Donation of $12 million by Paul Allen, co-founder of Microsoft.

  45. Radio: LOFAR • LOw Frequency ARray: array for detection <250 MHz. • Half of it funded and under construction in the Netherlands. • LOFAR uses an array of simple omni-directional antennas instead of mechanical signal processing with a dish antenna. It looks at the whole sky!

  46. Radio: LOFAR • The electronic signals from the antennas are digitised, transported to a central digital processor, and combined in software to emulate a conventional antenna. • In the core of CEP is IBM’slatest supercomputer, the BlueGene/L system. • Data transport requirements are in the range of many Tera-bits/sec and the processing power needed is tens of Tera-FLOPS. • The cost is dominated by the cost of electronics and follows Moore's law. • LOFAR is an IT-telescope.

  47. The antennas are simple enough but there are a lot of them - 25000 in the full LOFAR design. To make radio pictures of the sky with adequate sharpness, the antennas are spread out over an area of ultimately 350 km in diameter.

  48. X-ray: SWIFT • The state of the art X-ray survey instrument is the US/UK/Italian satellite detector SWIFT. • Main goal: look for GRB with a 1.4 sr FOV (1/6th of the sky), inmediate alert sent worldwide. • Will fly until 2011. • Very succesful: • 330 GRBs. • 65 Supernovae. • Catalogue of AGNs. • Constant monitoring of 514 variable sources.

  49. X-rays: Black Hole Finder Probes: EXIST • No instrument foreseen for the next future. Only advanced proposals by NASA, so-called “BHFPs”. • The best candidate right now, EXIST, could be launched in 2015.

  50. X-rays: Black Hole Finder Probes: EXIST • Energy range: 4-300 keV • Field of View: 160ºx 70º= 3 sr (25% of the sky). • Much better sensitivity over SWIFT or INTEGRAL.

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