On the ultracompact nature of 4U 1822-000

We report the discovery of a periodic modulation in the optical lightcurve of the candidate ultracompact X-ray binary 4U 1822-000. Using time-resolved optical photometry taken with the William Herschel Telescope we find evidence for a sinusoidal modulation with a semi-amplitude of 8 per cent and a period of 191 min, which is most likely close to the true orbital period of the binary. Using the van Paradijs & McClintock relation for the absolute magnitude and the distance modulus allowing for interstellar reddening, we estimate the distance to 4U 1822-000 to be 6.3 kpc. The long orbital period casts severe doubts on the ultracompact nature of 4U 1822-000.

An Address of members of the House of Representatives of the Congress of the United States, to their constituents, on the subject of the war with Great Britain. --

Signed by George Sullivan and thirty-three other Federalist members.

Proposed statutes of the Caribbean Congress of Information Professionals

Includes bibliography

Las principales tesis presentadas y discutidas en el VII Congreso de Sociología sobre Sociología Urbana = The main arguments concerning urban sociology presented and discussed at the seventh National Congress of Sociology

Los documentos del Seminario fueron publicados por UNESCO en 1961 con el título: La urbanización en América Latina/Urbanization in Latin America