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\input{ibvs2.sty}

\begin{document}

\IBVShead{5137}{12 July 2001}

\IBVStitletl{On the identifications of V391 S\lowercase{ct}, V2435 S\lowercase{gr}}{ and Maffei's infrared variables}

\IBVSauth{Kato, Taichi}

\IBVSinsto{Dept.\ of Astronomy, Kyoto University, Kyoto 606-8502, Japan,
e-mail: tkato@kusastro.kyoto-u.ac.jp}

\SIMBADobj{V391 Sct}
\SIMBADobj{V2435 Sgr}
\IBVStyp{ M:, M }
\IBVSkey{long-period variable, identification}

\begintext

V391 Sct is one of new variable stars discovered by Maffei (1975).
The object was classified as a possible dwarf nova by Maffei (1975).
However, owing to the lack of a finding chart, the exact identification
remained uncertain. Downes et al.\ (1997) even considered the variable
to be lost.

The reason of the difficulty of finding an identification has been
partly because that Maffei (1975) used infrared plates to search for
variable stars. Many of new variable stars by Maffei (1975) are
not registered in USNO catalogs, probably because of their red colors
and interstellar extinction. The recent release of 2MASS point source
catalog (released by IPAC/UMass 2000) has removed much of these
difficulties. A sample extraction of variable stars by Maffei (1975)
has revealed that remarkably bright infrared sources are almost always
present at the exact locations reported by Maffei (1975), making unique
identifications possible. Table 1 lists all objects in the table of
Maffei (1975) which have 2MASS counterparts brighter than $J = 11$ and
$K_s = 9$. However, the 2MASS release has covered only a small part of
the survey by Maffei (1975), which does not contain the field of
V391 Sct. The most recent release of the Midcourse Space
Experiment (MSX5C) Point Source Catalog (Egan 1999) has dramatically
improved this situation. The author has found many variables by Maffei
(1975) have conspicuous MSX5C counterparts, as are also listed in Table 1.

\begin{table}
\caption{Maffei's objects identified with bright 2MASS sources}
\begin{center}
\begin{tabular}{rlcccccc}
\hline
No.$^a$ & Object & \multicolumn{2}{c}{2MASS position$^b$}
 & \multicolumn{2}{c}{MSX5C$^{b}$}
 & \multicolumn{2}{c}{Maffei$^{b}$} \\
\hline
 2 & GU Ser & 18\hr09\mm39\fsec53 & $-$14\deg55\arcm38\farcs9
 & 39.5 & 44 & 39.5 & 37 \\
 3 & GO Ser & 18 08 51.93 & $-$14 08 33.3 & 51.8 & 37 & 51.6 & 31 \\
 15 & V405 Sct & 18 29 22.48 & $-$15 07 59.8 & 22.5 & 57 & 22.7 & 57 \\
 30 & GH Ser & 18 08 21.56 & $-$15 24 01.9 & 21.8 & 05 & 22.1 & 02 \\
 31 & GL Ser & 18 08 34.39 & $-$15 07 38.6 & - & - & 34.8 & 37 \\
 32 & GN Ser & 18 08 40.03 & $-$15 09 39.3 & - & - & 39.8 & 36 \\
 65 & V404 Sct & 18 29 12.84 & $-$15 37 37.7 & - & - & 12.3 & 40 \\
 67 & V400 Sct & 18 28 42.36 & $-$15 22 52.6 & 42.3 & 51 & 42.0 & 53 \\
 76 & V421 Sct & 18 30 50.93 & $-$15 37 29.0 & - & - & 51.3 & 29 \\
 77 & V424 Sct & 18 31 36.26 & $-$15 26 58.2 & 36.3 & 58 & 36.1 & 56 \\
 78 & V422 Sct & 18 31 25.26 & $-$15 18 22.7 & 25.2 & 22 & 24.9 & 20 \\
 79 & V402 Sct & 18 29 00.73 & $-$14 43 55.1 & 00.9 & 51 & 01.2 & 52 \\
 80 & V401 Sct & 18 28 54.18 & $-$14 29 20.2 & 54.2 & 16 & 53.9 & 20 \\
 84 & V415 Sct & 18 03 13.42 & $-$14 25 19.2 & 13.5 & 17 & 13.8 & 16 \\
 90 & GI Ser & 18 08 26.39 & $-$15 35 11.9 & 26.3 & 11 & 26.4 & 06 \\
 92 & GM Ser & 18 08 35.81 & $-$15 04 01.6 & 35.7 & 03 & 35.7 & 59 \\
100 & GQ Ser & 18 09 18.03 & $-$14 38 12.7 & 17.8 & 15 & 18.2 & 10 \\
101 & GG Ser & 18 08 11.04 & $-$14 34 27.9 & 10.9 & 30 & 12.1 & 19 \\
102 & FY Ser & 18 07 53.49 & $-$14 31 26.4 & 53.4 & 30 & 54.0 & 24 \\
103 & GK Ser & 18 08 25.49 & $-$14 18 07.7 & 25.2 & 10 & 25.8 & 06 \\
104 & GT Ser & 18 09 34.93 & $-$14 26 40.8 & 34.7 & 42 & 34.9 & 38 \\
134 & V406 Sct & 18 29 23.30 & $-$15 47 34.8 & 23.7 & 25 & 23.5 & 29 \\
135 & V407 Sct & 18 29 32.18 & $-$15 48 39.6 & 32.1 & 40 & 32.5 & 40 \\
136 & V413 Sct & 18 30 02.33 & $-$15 28 30.1 & 02.3 & 28 & 02.1 & 30 \\
137 & V414 Sct & 18 30 13.85 & $-$15 27 22.4 & 13.7 & 21 & 14.1 & 23 \\
151 & V409 Sct & 18 29 40.00 & $-$14 00 17.9 & - & - & 40.3 & 18 \\
152 & V412 Sct & 18 29 58.81 & $-$14 10 10.3 & 58.9 & 08 & 58.5 & 11 \\
153 & V419 Sct & 18 30 36.29 & $-$14 16 24.9 & 36.4 & 19 & 36.6 & 21 \\
154 & V418 Sct & 18 30 28.97 & $-$14 21 35.4 & 29.2 & 33 & 28.7 & 34 \\
163 & GP Ser & 18 09 09.81 & $-$15 51 20.2 & 09.7 & 19 & 09.7 & 19 \\
164 & GR Ser & 18 09 24.40 & $-$15 19 36.4 & 24.3 & 36 & 24.0 & 32 \\
165 & NSV10266 & 18 09 06.05 & $-$15 18 37.2 & - & - & 06.0 & 34 \\
172 & NSV10251 & 18 08 36.17 & $-$14 47 34.1 & - & - & 36.4 & 34 \\
173 & FZ Ser & 18 08 01.93 & $-$14 44 15.0 & 01.7 & 16 & 02.3 & 09 \\
174 & NSV10271 & 18 09 14.51 & $-$14 29 48.4 & 14.4 & 50 & 14.0 & 46 \\
198 & V403 Sct & 18 29 02.73 & $-$14 46 58.3 & 02.9 & 55 & 02.2 & 56 \\
199 & V410 Sct & 18 29 53.01 & $-$14 57 53.4 & 53.0 & 52 & 53.5 & 52 \\
200 & V425 Sct & 18 34 42.33 & $-$15 12 14.3 & 42.2 & 13 & 41.7 & 12 \\
201 & V408 Sct & 18 29 38.97 & $-$14 46 12.4 & - & - & 39.2 & 08 \\
202 & V417 Sct & 18 30 15.72 & $-$14 31 26.6 & 15.8 & 24 & 15.9 & 25 \\
205 & V416 Sct & 18 30 14.76 & $-$14 21 33.9 & 14.9 & 30 & 14.7 & 33 \\
206 & V423 Sct & 18 31 25.23 & $-$14 43 50.3 & 25.3 & 47 & 25.2 & 47 \\
\hline
\end{tabular}

\normalsize
%\begin{tabular}{l@{ }l}
$^{a}$ Maffei Var.\ Number (Maffei 1975); \qquad $^{b}$ J2000.0 position
%\end{tabular}
\end{center}
\end{table}

The author noticed the presence of MSX5C G016.1479-02.1803 at the
exact location reported by Maffei (1975). Based on secure identifications
of other variables with MSX5C sources, we consider that this MSX5C source
is the true counterpart of V391 Sct. The source is subsequently identified
with a GSC star (GSC 6266.2259) with $V = 12.8$, not resolved in the USNO
catalog. A large difference between the USNO $r$ magnitude of 15.5 (combined
magnitude with a nearby star) and the GSC value also supports that the
optical counterpart is a large-amplitude variable star. Combined with the
infrared detection, the object is most likely a large-amplitude, Mira-type
variable. Table 2 lists the reported positions in J2000.0.

\begin{table}
\caption{Positions of V391 Sct}
\begin{center}
\begin{tabular}{ccc}
\hline
Source & R.A. & Decl. \\
\hline
Maffei & 18\hr 28\mm 06\fsec 7 & $-$15\deg 54\arcm 49\arcs \\
MSX5C & 18 28 06.6 & $-$15 54 42 \\
GSC 1.1 & 18 28 06.6 & $-$15 54 45 \\
\hline
\end{tabular}
\end{center}

\caption{Positions of V2435 Sgr}
\begin{center}
\begin{tabular}{lcc}
\hline
Source & R.A. & Decl. \\
\hline
Original$^a$ & 17\hr 58\mm 54\fsec 98 & $-$29\deg 00\arcm 37\farcs 8 \\
2MASS & 17 58 54.98 & $-$29 00 37.8 \\
ISOGAL & 17 58 55.1\phantom{0} & $-$29 00 37\phantom{.0} \\
\hline
\end{tabular}

\normalsize
\begin{tabular}{l@{ }l}
$^{a}$ & Position by Downes et al.\ (1997), based on \\
 & the chart in Oosterhoff and Ponsen (1968) \\
\end{tabular}
\end{center}
\end{table}

V2435 Sgr is one of variables discovered by Oosterhoff and Ponsen (1968),
and was classified as a possible dwarf nova. The author noticed
that the object is identified with a bright 2MASS star ($J = 9.63$, $H = 8.50$,
$K_s =8.14$) and a variable star ISOGAL P J175855.1-290037 with a
$\log P({\rm d})=1.718$ detected by the ISOGAL project (Schultheis et al.\ 2000).
These identifications have not been reported in the previous literature.
The variable is thus a long-period variable rather than a dwarf nova.
Table 3 lists the reported positions in J2000.0.

\references

Downes, R., Webbink, R. F., Shara, M. M., 1997, {\it PASP}, {\bf 109}, 345

Egan, M. P., Price, S. D., Moshir, M. M., Cohen, M., Tedesco, E.,
Murdock, T. L., Zweil, A., Burdick, S., Bonito, N., Gugliotti, G. M.,
Duszlak J., 1999, The Midcourse Space Experiment Point Source Catalog,
Version 1.2

Maffei, P., 1975, {\it IBVS}, No.\ 985

Oosterhoff, P. Th., Ponsen, J., 1968, {\it Bull.\ Astron.\ Inst.\ of the Netherlands,
Suppl.}, {\bf 3}, 79

Schultheis, M., Ganesh, S., Glass, I. S., Omont, A., Ortiz, R., Simon, G.,
van Loon, J. Th., Alard, C., Blommaert, J. A. D. L., Borsenberger, J.,
Fouqu\'e, P., Habing, H. J., 2000, {\it A\&A}, {\bf 362}, 215

\end{document}

