Feb 7 (Reuters) - Activist investor Elliott Management

said on Friday it has invested more than $1.5 billion in Aspen

Technology ( AZPN ), opposing the company's decision to accept

Emerson Electric's ( EMR ) tender offer.

Aspen's shares rose 4% in premarket trading.

Last month, Emerson agreed to buy the remaining shares

in software supplier Aspen that it did not already own for $7.2

billion.