does the seller own the accrued dividend after ex-dividend day? does the seller also own accrued dividend before ex-dividend day?
Yes and yes.
suppose seller sell the asset to buyer before ex-dividend day, you mean after ex-dividend day, he can still claw back the dividend from buyer?
I think you’re confusing accrued interest for fixed income securities with ex-dividend for equities. They’re not the same.
If I own a fixed income security that pays a coupon semi-annually, and I sell it to you 60 days before the next coupon, then I accrued 120 days (or 2/3, generally speaking) worth of interest on that fixed income security. So you would pay 2/3 of the next coupon to me as part of the purchase price.
Now if I own XYZ stock and it pays a dividend, then whoever was holding that stock as of the ex-date will be entitled to the dividend. So if I sell the stock to you two days before the ex-date, then you will own both the stock and the upcoming dividend. I, the seller, will not receive any part of that dividend since I was not holding the stock on ex-dividend date.
for the bond, if you sell me 60 days after coupon day, I need to pay you the 60 days interest ? is this called as dirty price?