\documentstyle[twoside, epsf]{article} 
 
\input ibvs2.sty 
 
\begin{document} 
\IBVShead{5769}{4 May 2007} 
 
\IBVStitletl{Photometric Sequences and Astrometric Positions}{ for Nova C\lowercase{yg} 2007 and Nova O\lowercase{ph} 2007}
  
\IBVSauth{Henden, A.$^1$; Munari, U.$^2$}

\IBVSinst{AAVSO, American Association of Variable Star Observers, 49 Bay State Road,
Cambridge, MA 02138, USA}

\IBVSinst{INAF Osservatorio Astronomico di Padova, Sede di Asiago, I-36032 Asiago (VI), Italy}
 
\SIMBADobj{V2467 Cyg}
\SIMBADobj{V2615 Oph} 
\IBVStyp{ Nova } 
\IBVSkey{photometry} 

\begintext 

Nova Cyg 2007 (= V2467 Cyg) was discovered by A. Tago at $\sim7.4$~mag on
CCD images exposed on March 15.79 UT (cf.\ Nakano, 2007a). It was confirmed
spectroscopically on March 16.8 UT by Ayani (2007) and Naito \& Sakamoto
(2007). A detailed quantitative description of the optical spectra of the
nova for March 18.16 UT was given by Munari et al.\ (2007a).  The nova belongs
to the ``FeII'' class defined by Williams (1992). Steeghs et al. (2007)
described the identification of the progenitor at $r'=18.46
(\pm0.01$) and $i'=17.49 (\pm0.01$) mag on IPHAS survey images
obtained on August 8 and 9, 2004. According to AAVSO database, Nova Cyg 2007
was already declining when it was discovered and the true maximum occured
between the last negative observation ($V\geq12$, cf.\ Nakano 2007a) on Mar
12.80 and the discovery one on Mar. 15.79 UT.
 
Nova Oph 2007 (= V2615 Oph) was discovered by H. Nishimura  at $\sim10$~mag
on photographic film exposed on March 19.81 UT (cf.\ Nakano 2007b), and
confirmed spectroscopically by Naito \& Narusawa (2007) on March 20.84 UT as
a FeII type of nova.  Das et al.\ (2007) reported infrared spectroscopy
showing strong CO molecular bands in emission on March 28.93 UT, and a
detailed quantitative description of the optical spectra of the nova on Mar.
22.17 and 24.18 UT was provided by Munari et al.\ (2007b). According to AAVSO
database, Nova Oph 2007 reached maximum around March 27.0 at $V\sim9.0$.

In this note we present $BVR_{\rm C}I_{\rm C}$ photometric sequences
around both novae. All stars have been checked in SIMBAD for published previous 
reports on variability. To calibrate the sequences, we obtained CCD photometry
with the Sonoita Research Observatory 0.35-m robotic telescope on four
distinct photometric nights, using $BVR_{\rm C}I_{\rm C}$ filters and
an SBIG STL-1001E CCD camera.  Pixel size is 1.25\arcs/pix and
the field of view is $20\arcm\times20\arcm$.  Observations on each
photometric night included following an extinction star from low to high
airmass, along with $BVR_{\rm C}I_{\rm C}$ exposures of Landolt standard fields (Landolt
1983, 1992). The photometric sequences are presented in Figures~1 and 2.

\IBVSfig{18cm}{5769-f1.ps}{$BVR_{\rm C}I_{\rm C}$ photometric
comparison sequence around Nova Cyg 2007. The cross indicates the nova. 
$N$ is the number of nights in which the given star has been measured
in the given band. The error in $\alpha$ and $\delta$ are in arcsec. 
The panel on the left covers a $20\arcm\times20\arcm$ area centered
on the nova and shows stars down to $V=16.5$. The dashed $6\arcm\times6\arcm$ 
area is zoomed in on the right panel. $a$~=~TYC~3160-1716-1, $\alpha$~=~BD+41.3764,
$\beta$~=~BD+41.3757, $\gamma$~=~TYC~3160-1572-1, $\delta$~=~TYC~3160-1841-1,
$\epsilon$~=~BD+41.3763, $\zeta$~=~TYC~3160-1645-1}
\IBVSfigKey{5769-f1.ps}{Nova Cyg 2007}{photometric sequence}

\IBVSfig{18cm}{5769-f2.ps}{$BVR_{\rm C}I_{\rm C}$ photometric comparison sequence around Nova
Oph 2007. The cross indicates the nova.  $N$ is the number of nights in which the given star
has been measured in the given band. The error in $\alpha$ and $\delta$ are in arcsec. The
panel on the left covers a $20\arcm\times20\arcm$ area centered on the nova and shows stars
down to $V=15.8$. The dashed $6\arcm\times6\arcm$ area is zoomed in on the right panel.
$\alpha$~=~HD 160704 (B0~II)} 
\IBVSfigKey{5769-f2.ps}{Nova Oph 2007}{photometric sequence}

\vspace{-24pt}
Astrometry was performed using SLALIB (Wallace, 1994) linear plate transformation routines in
conjunction with the UCAC2 reference catalog. Errors in coordinates were typically under 0.1
arcsec in both coordinates, referred to the mean coordinate zero point of the reference stars
in each field. The coordinates we derived for Nova Cyg 2007 are:
 $$
 \alpha_{\rm J2000} = 20~28~12.492~(\pm0\farcs058)\qquad
 \delta_{\rm J2000} = +41~48~36.33~(\pm0\farcs044),
 $$ 
 close to the coordinates derived by Nishiyama \& Sakamoto (2007) at position end figures
12\fsec52 and 36\farcs5, and by Steeghs et al.\ (2007) at end figures 12\fsec47 and 36\farcs4.  
The USNO-A2.0 star closest to this position is object 1275-13944467 at position end figures
12\fsec505 and 36\farcs69, with $B=20.0$ and $R=18.5$.

The coordinates we derived for Nova Oph 2007 are:
 $$
 \alpha_{\rm J2000} = 17~42~44.013~(\pm0\farcs032)\qquad 
 \delta_{\rm J2000} = -23~40~35.05~(\pm0\farcs072),
 $$
 close to the coordinates derived by Kadota (2007) at position end figures 44\fsec00 and
35\farcs1, and by Itagaki (2007) at position end figures 43\fsec99 and 35\farcs0. Our position
is roughly halfway between that of USNO-A2.0~0600-28293794 (position end figures 44\fsec014
and 40\farcs80, $B=15.6$ and $R=12.3$) and that of USNO-A2.0~0600-28294416 (position end
figures 44\fsec353 and 28\farcs29, $B=18.6$ and $R=16.4$), the closest two USNO-A2.0 stars.

We would like to thank J. Gross, W. Cooney and D. Terrell for their help in
setting up the SRO observations and relinquishing their observing time.

\IBVSedata{5769-t1.txt}
\IBVSdataKey{5769-t1.txt}{V2467 Cyg}{photometric sequence}
\AladinChart{5769-t1}
\IBVSecomment{photometric sequence}

\IBVSedata{5769-t2.txt}
\IBVSdataKey{5769-t2.txt}{V2615 Oph}{photometric sequence}
\AladinChart{5769-t2}
\IBVSecomment{photometric sequence}

\references 

Ayani, K., 2007, {\it IAUC}, No.\ 8821

Das, R.K., et al. 2007, {\it CBET}, No.\ 925

Itagaki, K., 2007, {\it IAUC}, No.\ 8824

Kadota, K., 2007, {\it IAUC}, No.\ 8824

Landolt, A.U., 1983, {\it AJ}, {\bf 88}, 439

Landolt, A.U., 1992, {\it AJ}, {\bf 104}, 340

Munari, U., et al. 2007a, {\it CBET}, No.\ 897

Munari, U., et al. 2007b, {\it CBET}, No.\ 906

Naito, H., Sakamoto, M. 2007, {\it IAUC}, No.\ 8821

Naito, H., Narusawa, S., 2007, {\it IAUC}, No.\ 8824

Nakano, S., 2007a, {\it IAUC}, No.\ 8821

Nakano, S., 2007b, {\it IAUC}, No.\ 8824

Nishiyama, K., Sakamoto, T., 2007, {\it IAUC}, No.\ 8821

Steeghs, D., et al., 2007, {\it ATel}, No.\ 1031

Wallace, P., 1994, {\it ASP Conf.\ Ser.}, {\bf 61}, 481,
in ``Astronomical Data Analysis Software and Systems III'', 

Williams, R.E., 1992, {\it AJ}, {\bf 104}, 725

\endreferences 

\end{document}

