GFORTRAN sending .o files in separate directory

I am using gfortran and want to send .o files in separate directory.

Currently I have the following in a bash script. The .mod files are handled ok, but the .o files are still created in the same directory as the source code

fsrc="newunit.f08 math.f08 tString.f08 prout.f08 prary.f08 apodization.f08"
swth="-std=f2008 -Wextra -Wall -pedantic -fbounds-check"

objDir="./bin/objBin"
modDir="./bin/modBin"

fobj="$objDir/newunit.o $objDir/math.o $objDir/tString.o $objDir/prout.o $objDir/prary.o"
fobj="$fobj $objDir/apodization.o"

gfortran $swth -c $fsrc -J $modDir

Where do you specify the object file? I don't think you do.

Use a makefile and forget the shell script unless you're using it to call make.