Extremely red objects , identified in the early Spitzer Space Telescope observations of the bright-rimmed globule IC 1396A and photometrically classified as Class I protostars Class II T Tauri stars based on their mid-infrared colors , were observed spectroscopically at 5.5–38 \mu m ( Spitzer InfraRed Spectrograph ) , at the 22 GHz water maser frequency ( NRAO Green Bank Telescope ) , and in the optical ( Palomar Hale 5-m ) , to confirm their nature and further elucidate their properties .
The sources photometrically identified as Class I , including IC1396A : \alpha , \gamma , \delta , \epsilon , and \zeta , are confirmed as objects dominated by accretion luminosity from dense envelopes , with accretion rates 1–10 \times 10 ^ { -6 } M _ { \odot } Â yr ^ { -1 } and present stellar masses 0.1–2 M _ { \odot } .
The Class I sources have extremely red continua , still rising at 38 \mu m , with a deep silicate absorption at 9–11 \mu m , weaker silicate absorption around 18 \mu m , and weak ice features including CO _ { 2 } at 15.2 \mu m and H _ { 2 } O at 6 \mu m. The ice/silicate absorption ratio in the envelope is exceptionally low for the IC 1396A protostars , compared to those in nearby star-forming regions , suggesting the envelope chemistry is altered by the radiation field or globule pressure .
Only one 22 GHz water maser was detected in IC 1396A ; it is coincident with a faint mid-infrared source , offset from near the luminous Class I protostar IC 1396A \gamma .
The maser source , IC 1396A \gamma _ { b } , has luminosity < 0.1 L _ { \odot } , the first H _ { 2 } O maser from such a low-luminosity object .
Two near-infrared H _ { 2 } knots on opposite sides of IC 1396A : \gamma reveal a jet , with axis clearly distinct from the H _ { 2 } O maser of IC 1396A : \gamma _ { b } .

The objects photometrically classified as Class II , including IC1396A : \beta , \theta , 2MASSJ 21364964+5722270 , 2MASSJ 21362507+5727502 , LkH \alpha 349c , Tr 37 11-2146 and Tr 37 11-2037 , are confirmed as stars with warm , luminous disks , with a silicate emission feature at 9–11 \mu m , and bright H \alpha emission , so they are young , disk-bearing , classical T Tauri stars .
The disk properties change significantly with source luminosity : low-mass ( G–K ) stars have prominent 9–11 emission features due to amorphous silicates while higher-mass ( A–F ) stars have weaker features requiring abundant crystalline silicates .
A mineralogical model that fits the wide and low-amplitude silicate feature of IC1396A : \theta requires small grains of crystalline olivine ( 11.3 \mu m peak ) and another material to to explain the its 9.1 \mu m peak ; reasonable fits are obtained with a phyllosilicate , quartz , or relatively large ( > 10 \mu m ) amorphous olivine grains .

The distribution of Class I sources is concentrated within the molecular globule , while the Class II sources are more widely scattered .
Combined with the spectral results , this suggests two phases of star formation , the first ( 4 Myr ago ) leading to the widespread Class II sources and the central O star of IC 1396 , and the second ( < 1 Myr ago ) occurring within the globule .
The recent phase was likely triggered by the wind and radiation of the central O star of the IC 1396 H ii region .