Title: INTEGRAL observations of classical novae


Proposal ID: 0120052
Subject category: Nucleosynthesis
Principal investigator: Hernanz
Institute: Institut d'Estudis Espacials de Catalunya (IEEC-CSIC)

Abstract

Detection of gamma-ray emission from classical novae would provide a unique proof of the thermonuclear runaway model for these explosions. Up to now, no nova has been detected in gamma-rays. Two different types of emission are expected: prompt emission (related to e-e+ annihilation, with positrons emitted by the short-lived radioactive isotopes13N and 18F at the very early epochs of the explosion), and long-lasting emission, produced by the decay of medium-lived isotopes (22Na and 7Be). The first type of emission consists of a 511 keV line plus a continuum between 20-30 keV and 511 keV, whereas the second type consists of lines at 1275 and 478 keV. Both types of emission provide a direct insight of the amount of radioactive nuclei in the expanding nova envelope, an information only obtainable through the observation of gamma-rays. In addition, the prompt emission carries crucial information about the dynamic properties of the expanding envelope. The simultaneous observation with the X-ray and optical monitors of INTEGRAL would provide important complementary data about the explosion mechanism. Two different types of observation strategies are suggested for novae unknown before INTEGRAL launch. 1) A pointed observation done around one month after TOO alert (external trigger from optical discovery of a nova bright and close enough); its main goal would be the detection of the 1275 keV line from 22Na (tau=3.75 years), and its second objective the 478 keV line from 7Be (tau=66days), which is harder to detect; the dominant type of line depends on the nova class (ONe or CO, respectively). 2) An "a posteriori" analysis of data, to search for the 511 keV line and the continuum, provided that INTEGRAL was pointing to the nova position at the epoch close (but previous) to the optical discovery. We also propose to observe Nova Velorum 1999 and the novae discovered from now up to INTEGRAL's launch (at distances short enough), to search for 1275 keV emission.