Giuseppe Longo*Salvatore CapozzielloMaurizio PaolilloEster PiedipalumboGiovanni 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

WavelengthTime

Flux

Propermotion

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 Tcov

(start/end of observations

2. Sampling (t)(average interval between two subsequent observations

3. Integration (Tint)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 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 coveragefairly deep poor and uneven samplinglong 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 normalMS 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

INA

F d

om

ain

INF

N d

om

ain

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 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 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= l1

Optical path n. 2 = l2

Quasars time delay from multiple images

ij j i ijl l l t

0 , ,, , ,ij i obs j obs lens sourceH t Tf z z T depends on cosmology

F depends on the lens mass model

t 0

0

HtH

T

410accuracy

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 J0911.4+0551

404 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

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