c********************************************************************
	
	SUBROUTINE t_vif(v,dv,i,di,fesh,dfesh,teff,dteff)
	
c routine PUBLIC du module mod_photo
		
c calcul de la Teff en utilisant les Mv, Mi et [Fe/H]
c Alonso et al. A&A 313, 873, 1996 (formule 6),

c Auteur: P. Morel, Laboratoire Lagrange, O.C.A., CESAM2k

c entrées
c	v, dv, i, di: magnitudes absolues V et I et precision
c	fesh, dteff : [Fe/H] et precision

c sorties
c	teff : Teff

c------------------------------------------------------------------------

	USE mod_kind
	
	IMPLICIT NONE
	
	REAL (kind=dp), INTENT(in) :: v, dv, i, di, fesh, dfesh
	REAL (kind=dp), INTENT(out) :: teff, dteff
	
	REAL (kind=dp) :: vmi, teta, dteta_vmi
	
	LOGICAL :: ok, init=.TRUE.
 	
c-----------------------------------------------------------------------
	
	if(init)THEN	!initialisations
	 init=.FALSE. 
	 WRITE(*,10)
10	 FORMAT('calcul de la Teff en utilisant les Mv, Mi et [Fe/H]',/,
	1 'suivant Alonso et al. A&A 313, 873, 1996 (formule 6)',/)
	ENDIF

	vmi=v-i	

	ok=(0.5d0 <= vmi .AND. vmi <= 2.5d0) .AND.
	1 (0.5d0 >= fesh .AND. fesh > -0.5d0)
	ok=ok .OR. (0.6d0 <= vmi .AND. vmi <= 1.3d0) .AND.
	1 (-0.5d0 >= fesh .AND. fesh > -1.5d0)
	ok=ok .OR. (0.7d0 <= vmi .AND. vmi <= 1.3d0) .AND.
	1 (-1.5d0 >= fesh .AND. fesh > -2.5d0)
	ok=ok .OR. (0.65d0 <= vmi .AND. vmi <= 1.2d0) .AND.
	1 (-2.5d0 >= fesh .AND. fesh > -3.5d0) 
	
	teta=0.424d0+vmi*(0.610d0-vmi*0.096d0)
	dteta_vmi=0.610d0-0.192d0*vmi
	
	teff=5040.d0/teta
	dteff=teff/teta*SQRT((dteta_vmi*dv)**2+(dteta_vmi*di)**2)
	dteff=ABS(dteff)

	RETURN
		
	END SUBROUTINE t_vif