COMMISSION 27 AND 42 OF THE IAU
                   INFORMATION BULLETIN ON VARIABLE STARS
                               Number 3842

                                                         Konkoly Observatory
                                                         Budapest
                                                         12 February 1993

                                                         HU ISSN 0374 - 0676


                       NSV10848: A PROBLEMATIC STAR

Estimating the magnitudes of the variable stars in the field of M16-M17 listed
in Maffei (1975), we found that the variable M150 (NSV10848) is almost always
invisible.  More precisely the star is visible only on two infrared plates as
shown below.


   Date          J.D.           m_I     m_B
1967.09.05   2439739.3384      <16.0
1967.09.25       759.2798       14.5
1967.10.03       767.2790       14.4   <17.4
1968.07.04     40042.4876      <15.5


                                 [FIGURE 1]

                          Figure 1. Finding chart


   We examined 65 infrared plates (I-N hypers.+RG5) taken with the 65/90 cm
Schmidt telescope at Asiago Astrophysical Observatory in the years: 1962,
1967, 1968, 1969, 1970, 1971, 1975 and 1990  The star is invisible also on an
infrared UKSTU plate (IV-N+RG715) taken at the date 1984.06.03. The infrared
limit magnitude of this plate is 18.0.
   We enclose the finding chart, till now not published. North is at the top.
The infrared magnitudes of two comparison stars are indicated.
   The star might be a nova. In this case it would be very important to search
for it on plates obtained near the epoch in which the star was visible during
our observations. On the other side this object may be a cataclysmic star. If
so, we believe that its true nature could be shown only by a deep monitoring.


                          Paolo MAFFEI and Gino TOSTI
                          Osservatorio Astronomico
                          Universita di Perugia,
                          06100 Perugia, Italia



Reference:

Maffei, P., 1975, IBVS, No. 985.