pro write_arf,fname,h1,e_lo,e_hi,effarea,expos,specresp,h=h

	if n_params(0) eq 0 then begin
	  print,'write_arf,fname,h1,e_lo,e_hi,effarea,expos,specresp,h=h
	  retall
	endif

	if n_elements(h) eq 0 then fxhmake,h,/ext
	n = n_elements(e_lo)
	if n eq 0 then return
        fxwrite,fname,h
	fxbcreate,unit,fname,h1
	for i=0,n-1 do begin
	  fxbwrite,unit,e_lo(i),1,i+1
	  fxbwrite,unit,e_hi(i),2,i+1
	  fxbwrite,unit,effarea(i),3,i+1
	  if n_elements(expos) gt 0 then fxbwrite,unit,expos(i),4,i+1
	  if n_elements(specresp) gt 0 then fxbwrite,unit,specresp(i),5,i+1
	endfor
	fxbfinish,unit
	return
	end