Letter to the Editor

Spectral signatures of ultra-rapidly varying objects in spectroscopic surveys

Centre d'Optique, Photonique et Laser, and Centre de Recherche en Astrophysique du Québec, Département de Physique, Université Laval, Québec, Qc, Canada G1K 7P4 e-mail: borra@phy.ulaval.ca

Received: 15 December 2009
Accepted: 11 February 2010

Abstract

Context. Astronomy is an observationally-led subject where chance discoveries play an important role. The time domain is the least explored in astronomy.

Aims. We alert spectroscopists, particularly those involved in surveys, that rapidly varying sources can induce periodic patterns in spectra.

Methods. The analytical treatment is based on standard Fourier theory. It is used to predict the shapes of features introduced by intensity pulses in spectra. These are the shapes that one must look for in spectral surveys. The theoretical analysis is supported by published experiments that measured the spectral modulation, in the visible wavelength region, caused by pairs of 150 femtosecond laser pulses separated by time periods varying between 5 10^-13 s and 3 10^-11 s.

Results. Detection of spectral signatures would allow the detection of new classes of objects that emit bursts of pulses separated by time intervals that are too short to be detected with conventional techniques. The principal advantage of the technique is that there is no need for specialized instruments or surveys: one must only incorporate algorithms capable of searching for periodic spectroscopic signals, such as those shown in a figure in this article, into existing data analyzis software and use it with standard spectroscopic surveys (including existing ones).