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\IBVShead{5869}{12 January 2009}

\IBVStitletl{ROTSE-III Observations of Nova M31 2008-08d}{ (ROTSE3 J004548.3+430222)}


\IBVSauth{Yuan,~F.$^1$; Quimby,~R.~M.$^2$; Chamarro,~D.~C.$^1$; Uecker,~A.$^3$; Sisson,~M.~D.$^1$; Akerlof,~C.~W.$^1$; Schaefer,~B.~E.$^4$; Wheeler,~J.~C.$^5$ on behalf of the ROTSE collaboration}

\IBVSinst{University of Michigan, Ann Arbor, MI 48109, USA, e-mail: yuanfang@umich.edu}
\IBVSinst{California Institute of Technology, Pasadena, CA 91125, USA}
\IBVSinst{Indiana University of Pennsylvania, Indiana, PA 15705, USA}
\IBVSinst{Louisiana State University, Baton Rouge, LA 70803, USA}
\IBVSinst{University of Texas, Austin, TX 78712, USA}

\SIMBADobj{ROTSE3 J004548.3+430222}
\IBVStyp{ N }
\IBVSkey{photometry}
\IBVSabs{We report the photometric observations of nova M31 2008-08d}
\IBVSabs{(ROTSE3 J004548.3+430222) by ROTSE-IIIb and ROTSE-IIId.}

\begintext
 
\noindent 
Nova M31 2008-08d (ROTSE3 J004548.3+430222), with a projected distance of $\sim$25 kpc from the center of M31, was discovered in unfiltered CCD images taken with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory on August 25.23 UT, 2008. It was initially reported by Yuan et al. (2008) as an optical transient with unknown nature because of the multi-peaked early lightcurve atypical of a nova and its ambiguous correlation with an INT\footnote{The INT data were obtained from the Isaac Newton Group Archive which is maintained as part of the CASU Astronomical Data Centre at the Institute of Astronomy, Cambridge.} $V$-band archive source. Spectroscopic observation by Chornock et al. (2008) identifies it as a classical nova of Fe II type with a radial velocity consistent with a location in M31.

We report in Table~1 the complete photometric observations of this nova by ROTSE-IIIb and ROTSE-IIId at the TUBITAK National Observatory in Turkey. The ROTSE-III images were bias-subtracted and flat-fielded by the automated pipeline. Initial object detections were performed by SExtractor. The images were then processed with our custom RPHOT photometry program based on the DAOPHOT PSF-fitting photometry package (Quimby et al. 2006). The response peak of ROTSE-III CCDs covers a similar range to $R$-band. The magnitude zero point for each image was estimated from median offset of the fiducial reference stars to the USNO-B1.0 $R$-band measurements.

The ROTSE-III detections are plotted in Figure~1 together with upper limits constraining the rise and decay of the transient. The overall decaying lightcurve shows significant amount of oscillation before dropping below our detection threshold at the end of October. It is not uncommon for nova lightcurves to show variations due to dust formation (Shafter 2008), but usually on longer time-scales than observed for this object.

\IBVSfig{10.5cm}{5869-f1.eps}{ROTSE-III lightcurve of Nova M31 2008-08d (ROTSE3 J004548.3+430222). The filled squares are detections from ROTSE-IIIb and the filled triangles are detections from ROTSE-IIId. All the upper limits (downward arrows) are from ROTSE-IIIb.}

\begin{table}[!ht]
\centerline{{\bf Table~1.} Log of ROTSE-III observations}
%\footnotesize
\small
\begin{center}
\begin{tabular}{ccccc}
\hline
MJD  &  Magnitude  &  Error  &  Upper Limit & ROTSE Telescope\\
\hline
54679.32 &        &        &  20.52 &  IIIb \\
54682.29 &        &        &  20.41 &  IIIb \\
54683.29 &        &        &  20.36 &  IIIb \\
54684.28 &        &        &  20.46 &  IIIb \\
54688.26 &        &        &  19.64 &  IIIb \\
54690.44 &        &        &  19.16 &  IIIb \\
54697.32 &        &        &  18.42 &  IIIb \\
54701.99 &  18.38 &   0.12 &        &  IIId \\
54703.23 &  18.31 &   0.05 &        &  IIIb \\
54704.43 &  18.02 &   0.04 &        &  IIIb \\
54704.91 &  18.21 &   0.09 &        &  IIId \\
54706.91 &  18.87 &   0.08 &        &  IIId \\
54707.90 &  18.88 &   0.11 &        &  IIId \\
54708.90 &  19.13 &   0.12 &        &  IIId \\
54710.92 &  18.68 &   0.10 &        &  IIId \\
54711.33 &  18.55 &   0.07 &        &  IIIb \\
54714.19 &  18.32 &   0.06 &        &  IIIb \\
54715.93 &  18.43 &   0.06 &        &  IIId \\
54716.89 &  18.66 &   0.05 &        &  IIId \\
54717.92 &  19.01 &   0.10 &        &  IIId \\
54719.93 &  18.76 &   0.12 &        &  IIId \\
54720.86 &  18.65 &   0.22 &        &  IIId \\
54723.31 &  19.13 &   0.38 &        &  IIIb \\
54729.16 &  18.50 &   0.07 &        &  IIIb \\
54730.17 &  18.80 &   0.07 &        &  IIIb \\
54731.33 &  18.67 &   0.06 &        &  IIIb \\
54732.33 &  18.76 &   0.07 &        &  IIIb \\
54735.24 &  19.57 &   0.17 &        &  IIIb \\
54736.16 &  19.80 &   0.18 &        &  IIIb \\
54737.18 &  20.14 &   0.22 &        &  IIIb \\
54738.16 &  20.12 &   0.21 &        &  IIIb \\
54739.88 &  19.43 &   0.18 &        &  IIId \\
54740.16 &  19.41 &   0.07 &        &  IIIb \\
54741.16 &  19.05 &   0.08 &        &  IIIb \\
54742.16 &  19.25 &   0.08 &        &  IIIb \\
54743.29 &  19.40 &   0.10 &        &  IIIb \\
54746.16 &  19.89 &   0.20 &        &  IIIb \\
54747.16 &  20.20 &   0.17 &        &  IIIb \\
54748.16 &  20.35 &   0.42 &        &  IIIb \\
54759.16 &        &        &  20.22 &  IIIb \\
54760.19 &  20.12 &   0.33 &        &  IIIb \\
54761.19 &  19.60 &   0.10 &        &  IIIb \\
54763.15 &  20.08 &   0.24 &        &  IIIb \\
54763.84 &  19.81 &   0.17 &        &  IIId \\
54768.15 &        &        &  20.52 &  IIIb \\
54769.15 &        &        &  20.43 &  IIIb \\
54770.15 &        &        &  20.36 &  IIIb \\
54771.17 &        &        &  20.46 &  IIIb \\
54772.16 &        &        &  20.42 &  IIIb \\
54773.18 &        &        &  20.22 &  IIIb \\
54774.16 &        &        &  20.40 &  IIIb \\
54777.10 &        &        &  20.21 &  IIIb \\
54787.14 &        &        &  20.46 &  IIIb \\
54788.14 &        &        &  20.51 &  IIIb \\
54789.14 &        &        &  20.59 &  IIIb \\
54790.13 &        &        &  20.39 &  IIIb \\
54793.13 &        &        &  20.16 &  IIIb \\
54794.13 &        &        &  20.39 &  IIIb \\
54795.11 &        &        &  20.13 &  IIIb \\
\hline
\end{tabular}
\end{center}
\end{table}

\pagebreak

\references
Yuan, F., et al. 2008, {\it The Astronomer's Telegram}, {\bf 1702}

Chornock, R., Silverman, J. M., George, M. R., and Filippenko, A. V. 2008, {\it The Astronomer's Telegram}, {\bf 1708}

Quimby, R. M., et al. 2006, {\it ApJ}, {\bf 636}, 400

Shafter, A. W. 2008, Private Communication
\endreferences

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