Survey
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* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Some thoughts on the astronomical time domain and… related issues with… (m ?)satellites Giuseppe Longo* Salvatore Capozziello Maurizio Paolillo Ester Piedipalumbo Giovanni d’Angelo et al… Dipartimento di Scienze Fisiche Università Federico II di Napoli •INFN – Sezione di Napoli & INAF – Sezione di Napoli Also from talks with C. Barbieri (INAF) What makes un(less)expensive a satellite No steering (no pointing capabilities) Small weight and size pointed observations (hence Small field of view) and …. Limited scope either long integration (non multi-purpose) or …. Must require little amount of technological development very high sampling rate HIGH SCIENTIFIC IMPACT may come only from new openings in the astronomical parameter space Astronomical parameter space Flux Non-EM … Morphology / Surf.Br. Time Wavelength Proper motion Polarization RA What is the coverage? Where are the gaps? Where do we go next? Why are space observations needed? Dec (® G.S. Djorgovski – Caltech) Parameters defining the TIME DOMAIN at a given l Defines aliasing 1. Time coverage Tcov (start/end of observations SPACE 2. Sampling (Dt) (average interval between two subsequent observations 3. Integration (Tint) exposure time of typical data taking (maximum lenght of detectable variations) Defines sparseness of events and accuracy of period reconstruction Defines minimum time scale of events TYPES OF DATA – A SIMPLE VIEW Large f.o.v Pointed observations Surveys Poor sampling (uneven and months/years) SPACE Large Dt Poor sampling (uneven and months/years) Deep but low accuracy Finalised science Deep but low accuracy Huge statistics and data flow Data flow depending on sampling Small angular resolution (to avoid large and expensive entrance pupil) High S/N ratio sources Time domain is “big business” in the optical Whole sky POSS I & II, SDSS, UKIRT, etc. (optical, NIR, Palomar QUEST and Palomar NEAT LSST (USA) Finalized OGLE, MACHO, SLOTT-AGAPE (optical) Solar system patrols (optical) Supernovae searches (optical) GRB monitoring (optical and other) AGN monitoring (radio, little optical) limited wavelenght coverage fairly deep poor and uneven sampling long time baseline (months/years) What do you find in surveys? (months to hours time scales – INAF domain…) • Mainly serendipitous discovery of new phenomena • Better understanding of old phenomena (SN, distance scale, deceleration, etc.) • Statistically significant samples (NEAR, asteroids, Kuiper belt, etc… up to clusters) • Better characterization of some physical parameters • Might lead to some exciting new physics (cf. Amendola) but… Megaflares on normal MS stars (DPOSS) Faint, fast transients (Tyson et al. What do you find in pointed observations? (months to hours time scales… INAF domain) • Monitoring campaigns lead to variability (from short to long term) studies for selected objects • Possible periodic behaviors • Correlations among variations at different wavelenghts Periodic light curve of Blazar (binary black hole) Ciaramella et al. 2004 INFN domain INAF domain The “seconds” to “milliseconds” domain Nebula around Vela pulsar (P=89 ms) X-ray image from Chandra Kilohertz quasiperiodic oscillations in Sco X-1, (Miller, Strohmayer, Zhang & van der Klis, RXTE) “milliseconds” to “m-seconds” • Tidally-driven transport in accretion disks in close binary systems (J. M. Blondin, Hydrodynamics on supercomputers: Interacting Binary Stars) • Photon Bubble Oscillations in Accretion, Klein, Arons, Jernigan & Hsu ApJ 457, L85 (1996) GRO J1744228 presents quasi-periodic oscillations (QPOs) of intensities in the energy band 3–12 keV • Non radial oscillations in neutron stars, Mc Dermott, Van Horn & Hansen, ApJ 325, 725 (1988) • Fluctuations of Pulsar Emission with SubMicrosecond Time-Scales, J. Gil, ApSS 110, 293 (1985) • etc… The nanoseconds domain • Nanosecond radio bursts from strong plasma turbulence in the Crab pulsar, Hankins, Kern, Weatherhill & Eilek, Nature 422, 141 (2003) Nanoseconds astrophysics is already ongoing within INFN Pierre AUGER Fluorescence Detector are producing light curves at 435 nm for ca. 200 stars with a time sampling of 100 ns. (Ambrosio M., Aramo C., Guarino F., Laurino O, Longo G., 2005) • Small (1 m size) resolution of stellar structure through coherence A POSSIBLE EXPERIMENT (which could be possibly done with a very low cost satellite using existing INFN/INAF know-how) Measuring the time delay of multiple QSO images with second accuracy Quasars time delay from multiple images Dlij l j li Dtij H 0 Dtij Tf i ,obs , j ,obs , zlens , zsource ) Dt H0 T T depends on cosmology F depends on the lens mass model Dt H0 accuracy 104 Additional benefits: • Detailed structure and mass model of the lens through microturbulence • High spatial resolution study of the QSO structure Why are X-rays important ? Lower statistics hence lower S/N but…. • Continuous coverage • Lower background, no atmosphere • Strong QSO variability • Possibility to measure individual photons and… to measure polarization (Bellazzini ?) QSO RX J0911.4+0551 404 photons in 29 ks (0.7 to 7.0 keV) • In the assumption that we can measure polarization of individual photons • There are mechanisms which entangle photons (ask Capozziello …) but also on non entangled photons works with slightly lower accuracy using light curve shapes Optical path n.1 Dt Optical path n.2 Time delay with an accuracy of ~ 40 s • Angular resolution is not an issue ! (overlapping sequences present a trivial problem of crittography) • Contamination from non entangled photons may be tackled (simulations are needed)