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) Some thoughts on the astronomical time domain and… related issues with… (  satellites

No steering (no pointing capabilities) Small weight and size (hence Small field of view) Limited scope (non multi-purpose) Must require little amount of technological development What makes un(less)expensive a satellite pointed observations and …. either long integration or …. very high sampling rate HIGH SCIENTIFIC IMPACT may come only from new openings in the astronomical parameter space

RA Dec Wavelength Time Flux Proper motion Non-EM … Polarization Morphology / Surf.Br. What is the coverage? Where are the gaps? Where do we go next? Why are space observations needed? Astronomical parameter space (® G.S. Djorgovski – Caltech)

Parameters defining the TIME DOMAIN at a given 1.Time coverage T cov (start/end of observations 2.Sampling (  t) (average interval between two subsequent observations 3.Integration (T int ) exposure time of typical data taking Defines aliasing (maximum lenght of detectable variations) Defines sparseness of events and accuracy of period reconstruction Defines minimum time scale of events SPACE

TYPES OF DATA – A SIMPLE VIEW Large f.o.v Surveys Pointed observations Poor sampling (uneven and months/years) Deep but low accuracy Finalised science Data flow depending on sampling Small angular resolution (to avoid large and expensive entrance pupil) High S/N ratio sources Poor sampling (uneven and months/years) Deep but low accuracy Huge statistics and data flow Large  t SPACE

Time domain is “big business” in the optical Whole skyPOSS 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)

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… Faint, fast transients (Tyson et al. Megaflares on normal MS stars (DPOSS) What do you find in surveys? (months to hours time scales – INAF domain…)

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

INAF domain INFN domain

The “seconds” to “milliseconds” domain X-ray image from Chandra Nebula around Vela pulsar (P=89 ms) Kilohertz quasiperiodic oscillations in Sco X-1, (Miller, Strohmayer, Zhang & van der Klis, RXTE)

“milliseconds” to “  -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 J 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 Sub- Microsecond Time-Scales, J. Gil, ApSS 110, 293 (1985) etc…

Nanosecond radio bursts from strong plasma turbulence in the Crab pulsar, Hankins, Kern, Weatherhill & Eilek, Nature 422, 141 (2003) The nanoseconds domain

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 Optical path n. 1= l 1 Optical path n. 2 = l 2

Quasars time delay from multiple images T depends on cosmology F depends on the lens mass model 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 ? QSO RX J photons in 29 ks (0.7 to 7.0 keV) 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 ?)

Optical path n.2 Optical path n.1 tt 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) 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