New Massive Contact Twin Binary in a Radio-quiet HII Region Associated
  with the M17 Complex
  Early-B stars may create an HII region that appears as radio-quiet. We report
the identification of new early-B stars associated with the radio-quiet HII
region G014.645--00.606 in the M17 complex. The ratio-quiet HII region
G014.645--00.606 is adjacent to three radio-quiet WISE HII region candidates.
The ionizing sources of the radio-quiet HII regions are expected to later than
B1V, given the sensitivity about 1-2 mJy of the MAGPIS 20 cm survey. The stars
were first selected if their parallaxes of GAIA EDR3 match that of the 22 GHz
H$_2$O maser source within the same region. We used the color-magnitude diagram
made from the ZTF photometric catalog to select the candidates for massive
stars because the intrinsic $g-r$ colors of massive stars change little from
B-type to O-type stars. Five stars lie in the areas of the color-magnitude
diagram where either reddened massive stars or evolved post-main sequence stars
of lower masses are commonly found. Three of the five stars, sources 1, 2, and
3, are located at the cavities of the three IR bubbles, and extended H$\alpha$
emission is detected around the three IR bubbles. We suggest that sources 1, 2,
and 3 are candidates for early-B stars associated with the radio-quiet region
G014.645--00.606. Particularly, source 1 is an EW type eclipsing binary with a
short period of 0.825 day, while source 2 is an EA type eclipsing binary with a
short period of 0.919 day. The physical parameters of the two binary systems
have been derived through the PHOEBE model. Source 1 is a twin binary of two
stars with T~23,500 K, and source 2 contains a hotter component (T~20,100 K)
and a cooler one (T~15,500 K). The $O-C$ values of source 1 show a trend of
decline, implying that the period of the source is deceasing. Source 1 is
likely a contacting early-B twin binary, for which mass transfer might cause
its orbit to shrink.
