Back to the Abstract

	1 Introduction
	2 Theory
	3 Absorption models
	4 Application to the variable absorption towards PKS 1127-145
	5 Discussion
	6 Conclusions
	References
	Online Material
	Appendix A: Time scales for superluminal motion of a background source relative to an intervening absorbing medium
	Appendix B: Average power spectrum for a large number of absorbers in front of a compact source
	Appendix C: The average mean square visibility due to a random absorbing or emitting medium

List of figures