The issuance of senior notes by Essex Property Trust introduces new debt to the company's financial structure, which could have mixed effects. On one hand, it could provide the company with necessary capital for growth or refinancing existing debt, potentially positive for the stock. On the other hand, the increase in debt and associated interest expenses could be a concern for some investors, especially considering the fixed interest rate of 5.500%. The net impact on the stock price in the short term is uncertain, hence the neutral score.