GALACTIC ASTRONOMY (II): PULSARS _____________________________ Jon Marcaide ASI, Castel San Pietro Terme, 18 September 2001

GALACTIC ASTRONOMY (II): PULSARS JON MARCAIDE ASI, 18 Sept 2001 Castel San Pietro Terme

Pulsar VLBI observations are (gated) phase-delay observations (phase referenced observations)

Campbell´s enumeration of possible uses of pulsars: (1) DISTANCES, along with independent dispersion measures, can yield the electron density integrated along the light of sight and thus check on models of Galactic electron density distribution obtained with pulsar timing techniques

Campbell´s enumeration of possible uses of pulsars: (2) DISTANCES, along with independent measures of the angular diameter of pulsars´ scattering disks at two or more frequencies, can determine similarly integrated values for the coefficient and exponent of the power-law spectrum of the electron density spatial fluctuations, which may provide insights into the mechanisms driving turbulence in the ISM.

Campbell´s enumeration of possible uses of pulsars: (3) DISTANCES and PROPER MOTIONS, along with independent age estimates, can provide bounds on the birth places of pulsars

Campbell´s enumeration of possible uses of pulsars: (4) POSITIONS, along with independent pulse time-of-arrival data, can contribute toward a tie between the extragalactic (Earth-rotation-based) and dynamic (Earth-orbit-based ) reference frames.

Where are we in Campbell´s enumeration? (1) Compatibility on electron density estimates starting to appear around 2000 (2) I do not know (3) Attempts being made (4) Frames tied to 0.3 mas level

Tests Chatterjee’99 VLBA Scientific Memo #18 How accurate is phase referencing at L-band? In-beam (12’); nodding calibrator (4 deg) SUCCESS WILL DEPEND ON THE DAY

Day 1

Day 2

How about a black hole!!!!! proper motion?????? Mirabel et al. Nature, 13 September 2001!!!