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\IBVShead{4785}{3 November 1999}

\IBVStitle{The Precursor of Nova Aquilae 1999 = V1493 A\lowercase{ql}}


\IBVSauth{D.~MORO$^1$, U.~MUNARI$^1$, T.~TOMOV$^1$, A.~HENDEN$^2$}

\IBVSinst{Padova and Asiago Astronomical Observatories, I-36012 Asiago (VI), Italy}

\IBVSinst{Universities Space Research Association/U. S. Naval Observatory
Flagstaff Station, P. O. Box 1149, Flagstaff AZ 86002-1149, USA}

\SIMBADobj{Nova Aql 1999}
\IBVSkey{photometry}
\IBVSabs{The pre-outburst photometric evolution of the precursor of Nova Aql}
\IBVSabs{1999 is investigated via the plate archive of the Asiago Schmidt telescopes}

\begintext

Nova Aql 1999 (V1493 Aql) was discovered in outburst by A. Tago (cf.\ IAU Circ No.\ 7223) on July 13.6, 1999. Detailed spectral observations by Tomov et al.\ (1999) for the days immediately following the maximum brightness set the expansion velocity of the nova at $\sim 1700$ km\,sec$^{-1}$; note the strong NaI~D interstellar lines which suggest a large reddening and classify the nova among the {\sl Fe~II class} of Williams (1992).

A detailed photometric monitoring of the nova evolution has been provided by VSNET\@. It shows the nova reached a maximum brightness $V \sim 9$ mag and has had a complex decline over three months to $V \sim 15.5$ mag.

An important parameter for any nova is the identification of the precursor and consequently the measure of the outburst amplitude. An accurate position for the nova ($\alpha_{\rm J2000}=19\hr 7\mm 36\fsec90$, $\delta_{\rm J2000}=+12\deg 31\arcm 26\farcs6$) has been provided independently by N.~James and G.~Masi (cf.\ IAU Circ No.\ 7228). This corresponds to an empty position both in DSS-1 and DSS-2, with the closest stars at 4\arcs{} and 8\arcs{} distance, as shown in Figure~1. The corresponding Palomar plates were taken on May 25, 1952 and May 31, 1987 respectively. The 35 year time span is long enough to detect large proper motions of the field stars and to extrapolate their position to the year 1999. The matching of the two plates does not reveal for any nearby star a proper motion large enough to bring it to the position of the nova for the epoch 1999.

The precursor of Nova Aql 1999 must have been fainter than the plate limits for both DSS-1 and DSS-2, which set the amplitude of the outburst in the $\Delta m \geq 12$ mag range. However, the precursor may have become bright enough to show up on Schmidt patrol plates if it underwent the smaller amplitude outbursts that characterize dwarf novae (DN)\@. A tight link between the binary system properties of DN and classical novae is widely accepted in literature and there are classical novae (for example GK Per = Nova Per 1901) that once back to quiescence conditions are showing DN outbursts (cf.\ Warner 1995). This note describes the results of our search for such DN outbursts of the precursor of Nova Aql over some decades before the 1999 eruption, by inspection of archive plates from the two Schmidt telescopes of the Padova and Asiago Astronomical Observatories.

The two Schmidt telescopes (40/50 and 67/92 cm) have collected more than 35,000 plates since 1955. In their plate archive we have found 40 plates covering the field of Nova Aql 1999. The basic parameters for the plates are summarized in Table~1. The limiting magnitude of the plates has been derived by comparison with a deep $UBVRI$ comparison sequence calibrated at USNOFS by one of us (AH) which will be published elsewhere.

\IBVSfig{8.7cm}{4785-f1.ps}{Comparison of the same $120\times30$ arcsec region around the position of Nova Aql 1999 (indicated by the empty circle
in the center) from the Palomar DSS-1 and DSS-2.}

The progenitor was too faint in quiescence to be recorded by the 1.2-m Palomar Schmidt, and so it has been for the smaller Asiago Schmidt telescopes. Also, no outburst of the progenitor of Nova Aql 1999 has been recorded on the Asiago plates, whose limiting magnitudes cluster around 17.5 mag as shown in Table~1.

There are two basic possibilities to account for the negative detection
of DN outbursts for the progenitor of the Nova Aql 1999:

\begin{itemize}
\item the progenitor did not experience DN outbursts 
in the decades preceding its eruption as a classical nova; 

\item the progenitor indeed went through DN outbursts, but they
have not been recorded on the patrol plates because:

\begin{itemize}
\item they were of limited amplitude and the progenitor never became bright
enough to be recorded on the plates, or

\item the DN outbursts of the progenitor were of normal amplitude
but the progenitor itself is so faint in quiescence that even at outburst
maximum it is still too faint to be recorded on the plates, or finally

\item the outbursts are normal but rare and took place when we were not observing.
\end{itemize}
\end{itemize}

With the data in hand it is not possible to distinguish among these different possibilities. However it seems fair at least to conclude that the nova progenitor did not have frequent outbursts of large amplitude.

We have already performed a similar investigation for the precursor of Nova Cas 1993 which was bright enough in quiescence to be easily recorded by the Asiago patrol plates (Munari et al.\ 1993). As in the current study of Nova Aql 1999, the search for DN outbursts in Nova Cas 1993 before its eruption as a classical nova gave negative results.

\begin{table}
\caption{Schmidt plates from the Asiago archive containing the field of
Nova Aql 1999. The last column gives the limiting magnitude of the plate (in the band of the $UBVRI$ system closest to the emulsion+filter combination) estimated against a deep $UBVRI$ sequence (see text).}
\begin{center}
\begin{tabular}{rcccrcccc}
\hline
 plate \# & date & emulsion & filter & exp.~t. & lim.~mag \\
\hline
 2666 & 14/03/1962 & 103a-O & -- & 10\mm & 18.0 \\ 
 2923 & 02/07/1962 & 103a-O & -- & 8\mm & 17.7 \\ 
 2943 & 07/07/1962 & 103a-O & -- & 8\mm & 17.9 \\ 
 2960 & 09/07/1962 & 103a-O & -- & 8\mm & 17.5 \\ 
 4145 & 16/10/1963 & 103a-O & -- & 12\mm & 17.9 \\ 
 4163 & 19/10/1963 & 103a-O & -- & 10\mm & 18.0 \\ 
 4223 & 07/11/1963 & 103a-O & -- & 10\mm & 17.5 \\ 
 4240 & 17/11/1963 & 103a-O & -- & 10\mm & 18.0 \\ 
 4956 & 05/11/1964 & 103a-O & GG 13 & 15\mm & 18.2 \\ 
 5585 & 23/10/1965 & 103a-O & GG 13 & 20\mm & 18.3 \\ 
 5938 & 16/07/1966 & 103a-O & -- & 15\mm & 18.0 \\ 
 6030 & 22/09/1966 & 103a-O & GG 13 & 10\mm & 16.9 \\ 
 6369 & 30/06/1967 & 103a-O & -- & 15\mm & 18.0 \\ 
 6381 & 04/07/1967 & 103a-O & GG 13 & 20\mm & 17.9 \\ 
 6436 & 24/11/1967 & 103a-O & -- & 15\mm & 18.0 \\ 
 6752 & 22/07/1968 & Pan.Royal& GG 13 & 15\mm & 18.0 \\ 
 6775 & 24/08/1968 & 103a-O & GG 13 & 10\mm & 18.1 \\ 
 6807 & 24/09/1968 & 103a-O & GG 13 & 15\mm & 17.9 \\ 
 6930 & 22/11/1968 & 103a-O & GG 13 & 15\mm & 17.5 \\ 
 7373 & 17/08/1969 & Pan.Royal& GG 14 & 20\mm & 16.4 \\ 
 7408 & 11/09/1968 & Pan.Royal& GG 14 & 20\mm & 15.7 \\ 
 7409 & 11/09/1969 & 103a-O & GG 13 & 6\mm & 17.5 \\ 
 7557 & 29/10/1969 & 103a-O & GG 13 & 15\mm & 17.9 \\ 
 7562 & 01/11/1969 & Pan.Royal& GG 14 & 20\mm & 16.2 \\ 
 7619 & 28/11/1969 & 103a-O & GG 13 & 14\mm & 17.7 \\ 
 8125 & 05/07/1970 & Tri-X & GG 14 & 20\mm & 16.4 \\ 
 8162 & 09/09/1970 & 103a-O & GG 13 & 15\mm & 17.5 \\ 
 8314 & 26/10/1970 & Tri-X & GG 14 & 15\mm & 17.9 \\ 
 8315 & 26/10/1970 & 103a-O & GG 13 & 10\mm & 17.9 \\ 
 8741 & 30/03/1971 & 103a-O & GG 13 & 10\mm & 15.8 \\ 
 8969 & 29/08/1971 & Tri-X & GG 14 & 15\mm & 15.7 \\ 
 9128 & 20/10/1071 & Tri-X & GG 14 & 20\mm & 16.7 \\ 
A 1611 & 13/09/1974 & 103a-O & GG 13 & 8\mm & 18.0 \\ 
 9519 & 05/06/1978 & 103a-D & OG 2 & 30\mm & 17.5 \\ 
 9520 & 05/06/1978 & 103a-E & RG 1 & 30\mm & 17.9 \\ 
13998 & 19/06/1979 & Tri-X & GG 14 & 15\mm & 16.4 \\ 
13999 & 19/06/1979 & 103a-O & GG 13 & 5\mm & 17.5 \\ 
14637 & 29/06/1981 & 103a-O & GG 13 & 8\mm & 17.5 \\ 
14658 & 03/08/1981 & 103a-O & GG 13 & 10\mm & 17.5 \\ 
14877 & 20/07/1982 & Tri-X & -- & 15\mm & 17.5 \\
\hline
\end{tabular}
\end{center}
\end{table}

Our understanding of the physics of the eruptions of classical novae would
undoubtedly benefit from a broader knowledge of the photometric behaviour of their progenitor in quiescence. For example the detection, frequency and brightness of DN outbursts may be used to estimate the mass-transfer rate onto the accreting white dwarf prior to the nova eruption (cf.\ Cannizzo 1993).

The Schmidt telescopes in use around the world generally have sufficiently
faint limiting magnitudes to be of interest in the study of nova progenitors, as we have shown for Nova Cas 1993 and Nova Aql 1999, and such investigations on the largest possible set of novae should be encouraged.

\references

Cannizzo, J.K., 1993, {\it ApJ}, {\bf 419}, 318

Munari, U., Tomov, T., Hric, L., Hazucha, P., 1993, {\it IBVS}, No.\ 3977

Tomov, T., Moro, D., Munari, U., 1999, {\it IAU Circ.}, No.\ 7225

Warner, B., 1995, {\sl Cataclysmic Variable Stars}, Cambridge Univ.\ Press

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

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