| Abstract : | We present a detailed H-band spectroscopic study of Herbig Ae/Be stars using
APOGEE DR17 data. Although detailed H and K band studies are performed
for classical Be stars, studies of Herbig Ae/Be stars are lacking in
literature. We compiled a master list of known Herbig stars from Vioque et al.
(2019) and Nidhi et al. (in prep), which consists of spectral types ranging from B0
to F5. Of ~400 Herbig stars queried, H-band spectra were available for 52 stars.
We visually examined the spectra and found that only 8 Herbig stars show Brackett series in emission. Single-peak as well as double-peak profiles in Br11-Br20 were
identified. Owing to high-resolution (R ~ 22,500) of APOGEE spectrum, peak
separation and V/R ratios were estimated. In addition, we complement APOGEE
spectra with other archival optical/IR spectra (such as XShooter) to study the
variability of profiles and emission strengths. It was seen in some stars that even though Hα EW is reported to be high (> 100 Å), Brackett lines were not seen in the
H-band spectrum. To study the dependence of Brackett emission on stellar properties, we examined the correlation between spectral type, infrared excess and HI emission line strengths. Furthermore, we perform Brackett decrement (Br11-Br20) calculations using the case-B recombination scenario and diagnose the density and temperature in the hot, circumstellar environment where these lines originate.
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