Gone in a Flash. The Transient Radio Universe. Michael J. Kavic (Long Island University-Brooklyn)

Transcription

1 Gone in a Flash The Transient Radio Universe Michael J. Kavic (Long Island University-Brooklyn)

2 Outline Radio transient basics How we search Long Wavelength Array (LWA) Eight-meter-wavelength Array (ETA) The All Sky Transient Array (ASTRA) What we are searching for Black Hole-Pulsar Binaries Searching for Warped Extra Spatial Dimensions

3 Radio Transients A short timescale (1 second or less) burst of radio waves from an astronomical source.

4 A Single Dispersed Pulse

5 How we search.

6 Early Radio Telescope Arrays & the Discovery of Pulsars Pulsars where discovered in 1967 using a radio telescope array built by Cambridge University. Jocelyn Bell Burnell, a graduate student, operated the telescope array and was responsible for the first observation of a pulsar. The signal was initially labeled LGM-1 for Little Green Men because it was suspected the signal may be extra-terrestrial in origin. The Nobel Prize was awarded in 1974 to Antony Hewish (Bell s advisor) and Martin Ryle but not Bell herself.

7 Early Radio Telescope Arrays & the Discovery of Pulsars

8 All-Sky Radio telescopes at very low frequency can observe the entire sky above the horizon. This is particularly useful for detecting transient events which can come from a seemingly random part of the sky. Traditional astrophysical observations have tended to focus on imaging a single source for an extended period of time. These techniques have proven extremely successful for studying static astronomical objects but could miss transient events. A λ 2

9 Long Wavelength Array (LWA) The LWA is low-frequency radio telescope, sensitive to a bandwidth of MHz. The first station of the LWA (LWA-1) is composed of an array of 256 dualpolarization dipole antennas laid out in a 100m diameter aperture. Initial observations have recently begun!

10 LWA-direct-sampling receiver outrigger stands 528 Analog Receivers Analog-to-Digital converters (196 million samples per second). Data stored on DRSU hard drive arrays. (5Tb~10 hours of data)

11 LWA-beam forming LWA-1 is configurable in a variety of different data collection modes including an all-sky and a DRX beamforming configuration. Beam-forming involves synchronizing the signal from multiple antennas for increased sensitivity to a particular portion of the sky, a phased-array.

12 Eight-meter-wavelength Transient Array (ETA) The ETA is composed of 16 dualpolarization dipole antennas. It is sensitive to a bandwidth of MHz. An upgrades ETA located in western Virginia, will observe coincidently with LWA. (a baseline of ~2400 km)

13 All Sky Transient Radio Array A planned radio telescope array composed of 4 dual polarization dipole antennas being built on the LIU-Post campus. Sensitive to a bandwidth of MHz Adapted to RFI poor environments (can be on/near a college campus). Construction and operation can be carriedout entirely with a team of undergraduate researchers. Built with equipment provided by the LWA collaboration Capable of independent observation as well as conducting coincident observations with LWA/ETA (ASTRA)

14 Radio Jove NASA supported effort centered on construction of dipole radio antennas at educational institutions around the world. Radio Jove telescopes search for radio transients within the solar system such as Jovian radio burst and solar storms. Observations are conducted ~20 MHz.

15 Radio Jove - Goals Educate students about planetary and solar radio astronomy, space physics, and the scientific method Provide teachers and students with a hands-on radio astronomy exercise as a science curriculum support activity Create an on-line radio observatory that provides real time observations and data for those with Internet access Allow interactions among participating schools by facilitating exchanges of ideas, data, and observing experiences

16 Typical Setup + + = Science Knowledge Fun

17 Antenna Schematic

18 Radio Jove Construction

19 Solar Storms Solar burst are causes by strong variation in the suns magnetic field. These events can be accompanied by the release of a large number of charged particles in an event called a Coronal Mass Ejection (CME). Earth-bound CMEs can cause severe damage to electronic equipment (and astronauts!) as well as disrupt communications.

20 Solar Storms with Radio Jove

21 Solar Radio Observations

22 Jupiter & Io

23 Storm Occurrence Probability

24 L-Burst S-Burst

25 Radio Jove Spectral Analysis

26 What we are searching for.

27 Astronomical Sources of Radio Transients Gamma-Ray Bursts Black Hole Collisions Primordial Black Holes (PBHs) Cosmic Strings Supernovae Pulsars

28 Testing Quantum Gravitational Models Black Hole--Neutron Star Binaries Primordial Black Holes Cosmic Superstrings Extra Spatial Dimensions Calabi-Yau

29 Warped Extra Dimensions x Randall-Sundrum 2 (1999) y bulk infinite 4 th spatial dimension Our brane --- flat, positive cosmological constant (tension), standard model particles/forces confined to the brane The bulk --- AdS: vacuum, negative cosmological constant, gravity only, warped (redshift scaling factor confines gravitons near our brane) No stable BH solutions on the brane, due to enhanced Hawking radiation modes

30 Emparan, Fabbri, Kaloper (2002) Emparan, García-Bellido, Kaloper (2003) Enhanced black hole evaporation rate in RS 2 braneworld, due to a greatly enhanced number of emission modes (gravitons propagating into the bulk, i.e., Kaluza-Klein gravitons) BH m m BH L M* y M* 10m (L is the length scale of warp) Lifetimes for stellar-mass black holes < age of the universe

31 The Binary Pulsar PSR Weisberg and Taylor 2005 a p sin i = (8) s e = (4) P = days (7.75 hours) M pulsar = / M * M companion = / M * dp/dt = ( / ) dp/dt GR unlikely to improve (a) Limited by galactic acceleration term (b) Will lose the pulsar beam in ~ 10 years (geodetic precession)

32 Black hole is losing mass Intuitively: decreasing gravitational binding angular momentum conserved Increasing orbital radius Increasing orbital period

33 The Assembled Ingredients a a m m a m BH m BH m NS BH m m BH L M y M 10m A Binary Pulsar ballpark P = 7.75 hours BH mass = 3 M * NS mass = 1.4 M * a m 3.25 R* (KIII)

34 m m y 2 1 * 2 * 1 L M m m M m R a a NS BH BH m hours y 0.40 ms 2 1 * 2 * 1 L M m m M m P P NS BH BH must satisfy Kepler s third law at any moment, so m BH m NS m a P and,, a a P a a m m a a P P

35 Precision on orbital period determination for PSR / ms y ms y -1 / ms y -1 = 25 sigma Accepting 3 sigma results for a BH-NS binary system, we could set limits to L ~ 3.5 microns

36 Summary Low frequency radio telescope arrays are opening a new window on our Universe allowing us to more effectively search for transient radio signals. The LWA and ETA are part of a new generation of radio telescope arrays. They are composed of dual polarization dipole antennas with state of the art signal processing capabilities. The ETA has completed its first science run and the LWA has recently begun observations. A planned radio telescope to be constructed on the campus of LIU-Post, the All Sky Transient Radio Array (ASTRA) will conduct independent observations as well as joint observations with LWA/ETA. There are a wide variety astronomical sources of radio transients. The progenitors of theses signals are often highly exothermic, explosive events such as the final explosion outburst of a primordial black hole or a supernova. Observations of Black hole-pulsar systems can be used search warped extra spatial dimensions with a high degree of sensitivity. We are entering a new era of discovery in which the transient radio observation will open a new view on our Universe!

37 Collaborators Dr. Steven Ellingson Virginia Tech LWA/ETA Dr. Gregory Taylor University of New Mexico LWA Dr. John Simonetti Virginia Tech ETA Dr. Tanmay Vachaspati University of Arizona Dr. Cameron Patterson Virginia Tech ETA Dr. Peter Shawhan University of Maryland LIGO

38 Thank you!!!

39 NASA supported effort centered on construction of dipole radio antennas at educational institutions around the world. Radio Jove telescopes search for radio transients within the solar system such as Jovian radio burst and solar storms. Observations are conducted ~20 MHz. (The same frequency range as ETA/LWA) Radio Jove

40 What the future holds.

41 ETA-Spectrogram Preliminary ETA data: Before (Upper Panel) and After (Lower Panel) RFI Mitigation

42 Undergraduate Researchers Wanted!

43 IMPRESS-Ed: Getting Future Teachers into Research IMPRESS-Ed is a summer research program focused on pre-service K-12 education majors who are interested in teaching science. Participants are given special training in the space and earth sciences and participate in a mentored research experience. Financial support is provided to participants (~$ per person, 5 students per summer)

44 Undergraduate Researchers Wanted! Undergraduates students are wanted and needed to help explore the transient radio Universe and to make this research effort a success. Students will have the opportunity to construct and operate ASTRA, collect and reduce data taken by LWA/ETA/ASTRA, and to investigate astrophysical sources of radio transients. Students will have the chance to participate directly in all research activities including being co-authors and traveling to conferences. Will require students with a diversity of interests.

45 Solar Storms Solar burst are causes by strong variation in the suns magnetic field. These events can be accompanied by the release of a large number of charged particles in an event called a Coronal Mass Ejection (CME). Earth-bound CMEs can cause severe damage to electronic equipment (and astronauts!) as well as disrupt communications. LWA/ETA can observe such events as they are emitted, track them through interplanetary space, and observe them as they interact with the Earth s ionosphere.

46 LIGO Sensitivity

47 A Three-Point Plan Astronomical sources of radio transients Testing models of quantum gravity Coincident detection of gravitational waves

48 The Laser Interferometer Gravitational-Wave Observatory (LIGO) Observatory dedicated to the direct detection of gravitational waves. 2 large laser interferometers located in Washington State and Louisiana Several science runs have been completed without a positive detection. LIGO is a truly all-sky instrument, seeing both above and below the horizon. LIGO data is logged and searched for positive detections much like LWA/ETA data.

49 Coincident Detection of Gravitational Waves Gravitational waves (GWs) are a form of radiation generated by oscillations of space-time. The vast majority of astrophysical sources of radio transients are also strong sources of GWs. GWs do not disperse and would outpace a simultaneously released radio signal. Radio transient detection could help to identify GW signals in LIGO data.

50 Undergraduate Researchers Wanted!

51 Hawking Radiation GR + basic QM + Stat Mech: Black holes should lose energy like blackbody radiators kt ~ hc ~ hc 2GM 2 c T 3 c 8Gk 1 M

52 An EMP from a PBH

53 Ionospheric Observations A phase delay is introduced as a radio signal transverse the ionosphere. This variation in phase is directly related the Total Electron Content (TEC). This can cause distortion in astronomical images, but can also allow from imaging of the ionosphere.

54 Black holes have a size Consequence of General Relativity R S 2GM c 2 Schwarzschild Radius

55 Antony Hewish Jocelyn Bell Nobel Prize 1974 M = 1.4 M * R = 10 km

56 Galactic Noise

57

58 Aviation GPS Navigation & the Ionosphere The distortion introduced by variations in the ionosphere can interfere with and in the case of solar storms even completely disrupt radio signals from GPS satellites. This can cause sever difficulties for aviation navigation. Observations of solar storms and the ionosphere will help us to better understand and adapt to this kind of disturbance.

59 Black holes are bald! A black hole in 4- dimensions can be uniquely & entirely described by it mass, charge and angular momentum. This property fails if we consider higher dimensions.