\documentstyle[twoside, epsf]{article}

\input ibvs2.sty

\begin{document}

\IBVShead{5783}{30 July 2007}

\IBVStitle{Quiescent Photometry of V5115 Sgr}

\IBVSauth{HENDEN, A.$^1$; DI SCALA, G.$^2$}

\IBVSinst{AAVSO, 49 Bay State Road, Cambridge, MA 02138 USA, e-mail: arne@aavso.org}
\IBVSinst{Carnes Hill Obs., 34 Perisher St., Horningsea Park, NSW, Sydney Australia, e-mail: lgdiscala@aapt.net.au}

\SIMBADobjAlias{V5115 Sgr}{Nova Sgr 2005}
\IBVStyp{ N }
\IBVSkey{photometry}
\IBVSabs{This paper gives details on the color evolution and current}
\IBVSabs{identification of V5115 Sgr (Nova Sgr 2005)}


\begintext

V5115 Sgr (Nova Sgr 2005) was independently discovered by Nishimura (2005)
and Sakurai (2005).  At peak, it reached a visual magnitude of 7.8 on
March 29.7, in 2005.  The AAVSO light curve for this nova is given in Figure 1.

\IBVSfig{8cm}{5783-f1.eps}{AAVSO light curve of V5115 Sgr.  Points are a mixture of visual observations and CCD V-band observations.}
\IBVSfigKey{5783-f1.eps}{V5115 Sgr}{light curve}

\vspace*{-0.5cm}

Kiss and Derekas (2005) confirmed the nova classification based on
H-alpha emission with a strong P-Cyg profile with full-width-zero-intensity  exceeding
5000 km/s.  The Na D doublet was saturated, indicating high
interstellar reddening.  Rudy et al. (2005) indicate that the
reddening derived from the NIR O I lines was $E(B-V) = 0.53$.
Likewise, the Schlegel et al. (1998) galactic extinction maps give
$E(B-V) = 0.586$mag, and a total extinction of 1.942mag
at $V$-band.  The light curve looks like a typical fast nova,
with the time to drop 3 magnitudes ($t_3$) of about 12 days.

Several independent astrometric positions were given for the nova,
as given in Table 1.  Three additional measurements are given there,
based on new astrometric measurements of $B$-band images taken by
Di Scala (DSI),  reduced using the UCAC2 astrometric catalog
(Zacharias et al. 2004), and also recent imagery from the
U.S. Naval Observatory, Flagstaff Station (NOFS) as described
later.

\begin{table}[!hr]
\centerline{Table 1. V5115 Sgr  astrometric positions}
\begin{center}
\begin{tabular}{cccc}
\hline
Observer   &  Epoch & RA(J2000)  &  DEC(J2000) \\
 
\hline
Nakano (2005a) & 2005.33 & 18:16:59.04 & $-$25:56:38.8 \\
Nakano (2005b) & 2005.33 & 18:16:58.96 & $-$25:56:38.9 \\
Nakano (2005b) & 2005.33 & 18:16:58.97 & $-$25:56:39.1 \\
DSI            & 2005.58 & 18:16:58.95 & $-$25:56:39.7 \\
DSI            & 2005.66 & 18:16:58.96 & $-$25:56:39.6 \\
NOFS           & 2007.40 & 18:16:58.96 & $-$25:56:39.6 \\
\hline
\end{tabular}
\end{center}
\end{table}

As this is a very crowded region near the center of the Galaxy
(galactic longitude 6.0464 degrees; latitude $-$4.5674 degrees) and
is heavily reddened, no progenitor was identified in the IAUC.  Yamaoka (2005)
noted that there was a nearby bright infrared source in the 2MASS
catalog.

Other than these initial reports, no additional information has been
published on this nova.  Hans-Guenter Diederich asked on the BAV
mail list on May 8, 2007, about the proper identification for
V5115 Sgr now that it has faded.  In addition, late-time photometry
for novae is often neglected.  For these reasons, we made further observations
of V5115 Sgr at NOFS in May, 2007.

DSI observed V5115 Sgr during the outburst, using a 30cm telescope,
SBIG ST-6 CCD camera and Custom Scientific $BVR_c$ filters.  Standard
dark subtraction and flatfielding were performed.  Stars were
extracted using {\tt AIP4WIN} software. First order extinction corrections as well as 
transformation coefficients were applied.  Since this field was not yet calibrated, the
DSI observations are all-sky, using SA109-747 as the primary
standard.  Table 2 gives the $BVR_c$ photometry during outburst.

The field of V5115 Sgr was also observed at $BVR_cI_c$ on May 26, 2007 (UT) and
at $BV$ on May 28, 2007, using the 1.0m R/C telescope at NOFS.
Conditions were photometric.
A $BVR_cI_c$ calibration of the field was obtained, with results given
in Table 3 (available through the IBVS website as {\tt 5783-t3.txt}).  
For each night, multiple Landolt (1983, 1992) fields
were observed to both obtain the transformation coefficients as
well as extinction.  As this field is at $-$25 degrees declination,
it transits at relatively high airmass, so the quality of the
calibration is not as high as for other fields.  In addition, the
high airmass results in poorer image quality; the typical seeing
on these two nights was about 2.5arcsec for this field.  Note that
automated starfinding routines were used to generate Table 3, and
that many spurious objects will be present due to blending.  Take
care when using this table to identify isolated objects.

\IBVSedata{5783-t3.txt}
\IBVSdataKey{5783-t3.txt}{V5115 Sgr}{sequence}
\AladinChart{5783-t3}
\IBVSecomment{photometric sequence}



Each image was bias subtracted and flatfielded using standard
procedures.  The images were then
psf-fit using DAOPHOT (Stetson, 1987) as implemented in IRAF.
The photometry was calculated using 
inhomogeneous ensemble photometry techniques similar to Honeycutt (1992).
Astrometry was performed using the SLALIB astronomical library
(Wallace, 2002) along with UCAC2.

This is a very crowded region and exposures were shorter than necessary
for high-precision photometry.  However, we report the new photometry for
V5115 Sgr also in Table 2.
 

\begin{table}[!hr]
\centerline{Table 2. V5115 Sgr multifilter data from DSI and NOFS}
\begin{center}
\begin{tabular}{cccccccc}
\hline
JD   &  $V$  &  err & ($B-V$)   &  err  &  ($V-R_c$) &  err  &  Observer  \\
\hline
2453498.2049  & 12.05 & 0.05 & 0.25 & 0.10 & 1.40 & 0.10 & DSI \\
2453505.2479  & 12.40 & 0.02 & --   &  -- & 1.18 & 0.04 & DSI \\ 
2453519.1458  & 12.83 & 0.02 & 0.07 & 0.04 & 1.16 & 0.04 & DSI \\
2453525.1417  & 12.94 & 0.02 & 0.05 & 0.03 & 1.06 & 0.03 & DSI \\
2453533.1875  & 12.99 & 0.02 & 0.18 & 0.04 & 0.85 & 0.04 & DSI \\
2453539.1188  & 13.11 & 0.02 & 0.10 & 0.04 & 0.97 & 0.04 & DSI \\
2453555.0451  & 13.27 & 0.02 & 0.32 & 0.04 & 0.80 & 0.04 & DSI \\
2453582.0090  & 13.60 & 0.02 & 0.36 & 0.04 & 0.50 & 0.04 & DSI \\
2453595.0833  & 13.87 & 0.03 & --   & --   & 0.55 & 0.05 & DSI \\
2453595.9507  & 13.90 & 0.02 & 0.29 & 0.04 & 0.58 & 0.04 & DSI \\
2453621.0278  & 14.06 & 0.02 & 0.43 & 0.04 & 0.69 & 0.04  & DSI \\
2454246.9038  & 18.50 &  0.06 & 0.50 &  0.08 & -- & -- & NOFS \\
2454248.9211  & 18.42 &  0.08 & 0.29 &  0.09 & -- & -- & NOFS \\
\hline
\end{tabular}
\end{center}
\end{table}

Yamaoka (2005) noted that there was a nearby bright infrared source
in the 2MASS catalog.  The recent $BVR_cI_c$ images make it clear that
V5115 Sgr has a red companion about 4.2arcsec due west of the variable.
The $BVR_cI_c$ photometry for the red companion is given in
Table 4.  Table 5 gives the astrometry for the companion from
existing catalogs as well as from the recent NOFS images.
The NOFS astrometry has internal errors around 50mas.
Based on the astrometry shown in the Table, there is no detectable
proper motion for the red companion.

\begin{table}[!hr]
\centerline{Table 4. Red companion optical photometry}
\begin{center}
\begin{tabular}{cccccccc}
\hline
$V$ & err & ($B-V$) & err & ($V-R_c$) & err & ($R_c-I_c$) & err \\
\hline
17.154 & 0.022 & 2.409 & 0.086 & 2.491 & 0.023 & 2.358 & 0.015 \\
\hline
\end{tabular}
\end{center}


\small
\centerline{Table 5. Red companion information}
\vspace*{-0.2cm}
\begin{center}
\begin{tabular}{p{1.3cm}p{0.8cm}p{1.3cm}p{1.4cm}cccccccc}
\hline
Source   & Epoch & RA(J2000) & Dec(J2000) & i' & err & J & err & H & err & K & err \\
\hline
USNO-B   & 1969.7 & 18:16:58.63 & $-$25:56:38.6 & -- & -- & -- & -- & -- & -- & -- & -- \\
GSC2.3.2 & 1996.70 & 18:16:58.65 & $-$25:56:39.1 & -- & -- & -- & -- & -- & -- & -- & -- \\
DENIS & 1999.52 & 18:16:58.62 & $-$25:56:38.3 & 12.263 & 0.03 & 9.297 & 0.06 & -- & -- & 7.764 & 0.09 \\
2MASS    & 2000.82 & 18:16:58.67 & $-$25:56:39.0 & -- & -- & 9.243 & 0.048 & 8.142 & 0.036 & 7.690 & 0.026 \\
NOFS     & 2007.40 & 18:16:58.66 & $-$25:56:39.2 & -- & -- & -- & -- & -- & -- & -- & -- \\
\hline
\end{tabular}
\end{center}
\end{table}

The MACHO and OGLE databases were searched for progenitor photometry, with
none found.  Likewise, ASAS does not show any outbursts of this nova, including
the 2005 outburst to $V$=8.  This may be due to the continuing hard drive
failures that the system is having.
No CFHT, Gemini, HST, AAT or ING images were found during CADC searches
that covered the field of V5115 Sgr.

We examined available Schmidt plate material from the
PMM archive at NOFS, and see no progenitor for V5115 Sgr to
their plate limit (about 21mag).
These plate searches indicate that any progenitor must have
been $V$=21 or fainter, indicating that the full amplitude of the
outburst is greater than 13 magnitudes.

Figure 2 is a $B$-band image from NOFS identifying V5115 Sgr and
its red companion.  Figure 3 is the corresponding field from
a POSS-I survey plate, showing the red companion and the lack
of a progenitor.

\IBVS2fig{7.5cm}{5783-f2.eps}{NOFS 1.0m $B$ image of field. FOV 2$\times$2arcmin. V=variable; C=companion}{5783-f3.eps}{POSS-I $O$(blue) image of field.FOV 2$\times$2arcmin}
\IBVSfigKey{5783-f2.eps}{V5115 Sgr}{finding chart}
\IBVSfigKey{5783-f3.eps}{V5115 Sgr}{finding chart}


V5115 Sgr appears to be a typical fast nova, with an amplitude
exceeding 13 magnitudes.  No progenitor is known.  It currently
is at $V$=18.5, still above the quiescent level, but any new photometry
must account for the nearby bright red companion and the otherwise
extremely crowded field.

This research has made use of the SIMBAD database, operated at CDS,
Strasbourg, France.  This research made use of the facilities of
the U.S. Naval Observatory, Flagstaff, Arizona USA.  The astronomical
catalog facility of VizieR (Ochsenbein et al. 2000) was also used.

\references

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Ochsenbein, F., Bauer, P., Marcout, J. 2000, {\it A\&AS}, {\bf 143}, 23

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Zacharias, N., Urban, S. E., Zacharias, M. I., et al., 2004, {\it AJ}, {\bf 127}, 3043

\endreferences

\end{document}

