Context :

Aims : We present a multiwavelength study of the Be/X-ray binary system XTE J1946 + 274 with the main goal of better characterizing its behavior during X-ray quiescence .
We also aim to shed light on the possible mechanisms which trigger the X-ray activity for this source .

Methods : XTE J1946 + 274 was observed by Chandra -ACIS during quiescence in 2013 March 12 .
In addition , this source has been monitored from the ground-based astronomical observatories of El Teide ( Tenerife , Spain ) , Roque de los Muchachos ( La Palma , Spain ) and Sierra Nevada ( Granada , Spain ) since 2011 September , and from the TÜBİTAK National Observatory ( Antalya , Turkey ) since 2005 April .
We have performed spectral and photometric temporal analyses in order to investigate the quiescent state and transient behavior of this binary system .

Results : Our optical study revealed that a long mass ejection event from the Be star took place in 2006 , lasting for about seven years , and another one is currently ongoing .
We also found that a large Be circumstellar disk is present during quiescence , although major X-ray activity is not observed .
We made an attempt to explain this by assuming the permanently presence of a tilted ( sometimes warped ) Be decretion disk .
The 0.3–10 keV X-ray spectrum of the neutron star during quiescence was well fitted with either an absorbed black-body or an absorbed power-law models .
The main parameters obtained for these models were kT=1.43 \pm 0.17 and \Gamma =0.9 \pm 0.4 ( with N _ { H } \sim 2–7 \times 10 ^ { 22 } cm ^ { -2 } ) .
The 0.3–10 keV flux of the source was \sim 0.8–1 \times 10 ^ { -12 } erg ^ { -1 } cm ^ { -2 } s ^ { -1 } .
Pulsations were found with P _ { pulse } =15.757 ( 1 ) s ( epoch MJD 56363.115 ) and an rms pulse fraction of 32.1 ( 3 ) \% .
The observed X-ray luminosity during quiescent periods was close to that of expected in supersonic propeller regimen .

Conclusions :