The S&P/ASX 200 Index (ASX: XJO) is having a strong finish to the week. In afternoon trade, the benchmark index is up 0.65% to 8,351.2 points.

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

Appen Ltd (ASX: APX)

The Appen share price is up over 23% to $1.52. Investors have been buying this artificial intelligence data services company's shares following the release of a guidance update at its annual general meeting. Appen revealed that it is expecting revenue between $235 million and $260 million. This implies flat to 10.9% growth for the year. It also expects positive underlying EBITDA for FY 2025.

Aspen Group Ltd (ASX: APZ)

The Aspen Group share price is up 8% to $3.25. This has been driven by the completion of an institutional placement raising $70.2 million. The company raised these funds at $2.90 per share thanks to very strong support from investors. Management advised: "Proceeds will be used for debt reduction, to strengthen Aspen's position to pursue new organic and acquisition opportunities that add value and drive continued strong growth in earnings and net asset value."

Catalyst Metals Ltd (ASX: CYL)

The Catalyst Metals share price is up 5% to $6.86. This morning, this gold miner announced that it has received the final environmental approval for development of the Trident Gold Project. This means that Catalyst Metals now has all environmental approvals in place to commence mining activities. The company's CEO, James Champion de Crespigny, commented: "Trident has been inching closer to development for some time.  This milestone makes it more real. We now have all the mining approvals in place to allow Catalyst to bring online the mines necessary to double production at the Plutonic Gold Belt."

Core Lithium Ltd (ASX: CXO)

The Core Lithium share price is up 6% to 10 cents. Investors have been buying this lithium miner's shares since the release of its restart study results for the Finniss Lithium Project. Those results revealed that the project could reduce its operating costs materially and generate strong free cash flow. This is based on a spodumene 6% price of US$1,300 per tonne. Though, it is worth noting that the current spot price is US$735 per tonne. This could mean that a final investment decision on the project is still some way off. Commenting on the study, Core Lithium's CEO, Paul Brown, said: "The Study outlines a lower-cost, longer-life, and scalable operating plan that generates free cash flow of $1.2 billion, representing a six-fold return on pre-production capital."