Transcript Diapositiva 1

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  104

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)