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We present a case study of using a novel method to identify red supergiant(RSG) candidates in NGC 6822, based on their 1.6 $\mu$m "H-bump". We collected32 bands of photometric data for NGC 6822 ranging from optical to MIR. By usingthe theoretical spectra from MARCS, we demonstrate that there is a prominentdifference around 1.6 $\mu$m ("H-bump") between low-surface-gravity (LSG) andhigh-surface-gravity (HSG) targets. Taking advantage of this feature, weidentify efficient color-color diagrams (CCDs) of rzH and rzK to separate HSGand LSG targets from crossmatching of optical and NIR data. Moreover, syntheticphotometry from ATLAS9 also give similar results. Further separating RSGcandidates from the rest of the LSG candidates is done by using semi-empiricalcriteria on NIR CMDs and resulted in 323 RSG candidates. Meanwhile, thesimulation of foreground stars from Besan\c{c}on models also indicates that ourselection criteria is largely free from the contamination of Galactic giants.In addition to the "H-bump" method, we also use the traditional BVR method as acomparison and/or supplement, by applying a slightly aggressive cut to selectas much as possible RSG candidates (358 targets). Furthermore, the Gaiaastrometric solution is used to constrain the sample, where 181 and 193 targetswere selected from the "H-bump" and BVR method, respectively. The percentagesof selected targets in both methods are similar as $\sim$60\%, indicating thecomparable accuracy of the two methods. In total, there are 234 RSG candidatesafter combining targets from both methods with 140 ($\sim$60\%) of them incommon. The final RSG candidates are in the expected locations on the MIR CMDs,while the spatial distribution is also coincident with the FUV-selected starformation regions, suggesting the selection is reasonable and reliable.

Evolved Massive Stars at Low-metallicity IV. Using 1.6 $\mu$m "H-bump" to identify red supergiant stars: a case study of NGC 6822