The S&P/ASX 200 Index (ASX: XJO) is on form again on Wednesday and on course to record another decent gain. In afternoon trade, the benchmark index is up 0.55% to 7,866.3 points.

Four ASX shares that are rising more than most today are listed below. Here's why they are climbing:

The Electro Optic Systems share price is up over 3% to $1.69. This morning, this defence and space company announced that it has completed a debt repayment of $20.5 million on schedule. This follows the repayment of $26.9 million in September 2023 under a separate 12 month working capital facility. As a result, this means that Electro Optic Systems has now repaid 50% of the principal amounts originally due to Washington H. Soul Pattinson (ASX: SOL) and 100% of the working capital facility amounts. The only outstanding amount now relates to a term loan facility.

The Novonix share price is up 8% to $1.08. A number of battery materials shares are having a strong session today following a solid night on Wall Street for lithium miners. In addition, this morning Novonix revealed that members of its executive team are scheduled to participate in a number of investor events in April. Investors may believe that these events could increase interest in the battery materials and technology company and be supportive of its share price.

The St Barbara share price is up 14% to 26.2 cents. As well as getting a boost from another rise from the gold price, the release of drilling results from its Simberi Operations in Papua New Guinea has got investors excited. Commenting on the drilling, the gold miner's managing director and CEO, Andrew Strelein, said: "We are getting positive results by applying more than 10 years of improvement in geological knowledge and targeting insufficiently drilled areas from drill pad locations now available because of more than 10 years of oxide mining."

The Whitehaven Coal share price is up 4% to $7.67. This appears to have been driven by a broker note out of UBS this morning. According to the note, the broker has upgraded this coal miner's shares to a buy rating with an improved price target of $8.70. It believes the company is well-positioned for the future thanks to a positive outlook for metallurgical coal. Particularly given the recent acquisition of Blackwater and Daunia. UBS's price target implies potential upside of 13% from current levels.