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\documentclass{aa}
%\documentclass[referee]{aa}
\usepackage{graphicx}
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\usepackage{txfonts}
\usepackage{amstext}
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\usepackage{longtable}
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\usepackage{hyperref}
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\hypersetup{
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 urlcolor     = blue, %Colour for external hyperlinks
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\begin{document}

\newcommand{\bu}{$\bullet$ }
\newcommand{\omicron}{o}
\newcommand{\ksi}{\xi}
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\newcommand{\Mnom}{\hbox{$\mathcal{M}^{\mathrm N}_\odot$}}
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\newcommand{\tria}{\hbox{$\bigtriangleup$}}
\newcommand{\ubv}{\hbox{$U\!B{}V$}}
\newcommand{\ubvr}{\hbox{$U\!B{}V\!R$}}
\newcommand{\bv}{\hbox{$B\!-\!V$}}
\newcommand{\ub}{\hbox{$U\!-\!B$}}
\newcommand{\hp}{$H_{\rm p}$}

\newcommand{\p}{$\pm$}
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\newcommand{\hip}{$Hipparcos$}
\newcommand{\ond}{Ond\v{r}ejov}


\title{Half a century of \ubv\ photometry at Hvar:\\
Auxiliary materials
\thanks{Based on photometric observations from
the Hvar Observatory and ESA Hipparcos Satellite.
 } }
\author{
H.~Bo\v{z}i\'c\inst{1}\and
P. Harmanec\inst{2}\and
J.~Horn\thanks{Ji\v{r}\'\i\ Horn passed away on Dec. 13, 1994}\inst{3}\and
K.~Juza\thanks{Karel Juza passed away on March 13, 1994}\inst{3}\and
P.~Koubsk\'y\inst{3}\and
S.~K\v{r}\'\i\v{z}\thanks{Svatopluk K\v{r}\'\i\v{z} passed away on Feb. 23, 2018}\inst{3}\and
P.~Mayer\thanks{Pavel Mayer passed away on Nov. 7, 2018}\inst{2}\and
P.~Hadrava\inst{4}\and
D.~Ru\v{z}djak\inst{1}\and
D.~Sudar\inst{1}\and
S.~\v{S}tefl\thanks{Stanislav \v{S}tefl passed away on June 11, 2014}\inst{3}\and
M.~Wolf\inst{2}\and
P.~Zasche\inst{2}\and
M.~Bro\v{z}\inst{2}\and
J.~Havelka\thanks{Josef Havelka passed away on June 19, 2009}\inst{3}\and
J.~Honsa\inst{3}\and
V.~Kocourek\inst{3}\and
M.~Tlamicha\inst{3}\and
F.~\v{Z}\v{d}\'arsk\'y\inst{3}\and
A.~Harmanec\inst{5}\and
J.~Jon\'ak\inst{2}\and
A.~Opli\v{s}tilov\'a\inst{2}\and
I.~Piantschitsch\inst{6,7,8}\and
I.~Skoki\'c\inst{1}\and
J.~\v{S}vr\v{c}kov\'a\inst{2}\and
K.~Vitovsk\'y\inst{2}\and
D.~Vr\v{s}nak\inst{9}\and
M.~Zummer\inst{5}
}
\institute{
Hvar Observatory, Faculty of Geodesy, Zagreb University,
Ka\v ci\'ceva~26, HR-10000 Zagreb, Croatia
  \and
Astronomical Institute, Faculty of Mathematics and Physics,
Charles University, V~Hole\v{s}ovi\v{c}k\'ach~2,\\
CZ-180~00~Praha~8, Czech Republic
  \and
Astronomical Institute of the Czech Academy of Sciences, Fri\v{c}ova~298,
CZ-251~65~Ond\v{r}ejov, Czech Republic
  \and
Astronomical Institute of the Czech Academy of Sciences, Bo\v{c}n\'\i~II~1401/1,
CZ-141~00 Praha~4, Czech Republic
 \and
Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
 \and
Institute of Physics, University of Graz, Universit\"atsplatz 5, A-8010 Graz,
Austria
 \and
Departament de F\'\i sica, Universitat de les Illes Balears (UIB), E-07122, Spain
 \and
Institute of Applied Computing \& Community Code (IAC3), UIB, Spain
 \and
Faculty of Electrical Engineering and Computing, University of Zagreb,
 Unska~3, HR-10000 Zagreb, Croatia
}
\date{Received \today}

%\abstract {We present a summary report on 52 years of systematic photoelectric
%\ubv\ observations of selected eclipsing, ellipsoidal and spectroscopic
%binaries, CP stars and some miscellaneous variables, secured by a~number of mainly
%Croatian and Czech observers at the Hvar Observatory.
%All these observations were reduced to the standard \ubv\ system defined by
%the Johnson standard stars through the nonlinear transformation formul\ae.
%In many cases, Hvar observations were complemented by the Hipparcos \hp\ photometry
%transformed to Johnson $V$ passband, since these observations conveniently fill
%the gap in Hvar observations. This paper is a continuation of previous study,
%which dealt with metodology and observations of emission-line stars.
%}

\keywords{stars: early-type --
  stars: emission-lne(Be) --
  stars: chemically peculiar (CP) --
  binaries: eclipsing --
  binaries: ellipsoidal}

\maketitle

\section{Accuracy of Hvar observations}
As mentioned in the paper, we took care to adapt the integration times of
observations in individual passbands to obtain comparable $S/N$ ratio
fo all of them. This is important for the non-linear tranformation
formul\ae, which we used since the resulting accuracy of the standard magnitudes
in each passband is affected by the precision of all three passbands.
In Figure~\ref{arms} we show the plots of the rms errors of one observation
of unit weight versus each magnitude, for the all-sky archive. Similar
plots forthe differential archive are in Fig.~\ref{drms}. Plotted are only
objects, for which at least 10 individual observations
are available in the respective archive. For a~better clarity, we also
excluded most of the variable stars, restricting the plots to a~maximum rms
of 0\m032.


\begin{figure}
\resizebox{\hsize}{!}{\includegraphics[angle=0]{ahv-v.pdf}}
\resizebox{\hsize}{!}{\includegraphics[angle=0]{ahv-b.pdf}}
\resizebox{\hsize}{!}{\includegraphics[angle=0]{ahv-u.pdf}}
\caption{The rms of one observation of unit weight as a function
of a standard magnitude for the stars from the Hvar all-sky archive.}
\label{arms}
\end{figure}

\begin{figure}
\resizebox{\hsize}{!}{\includegraphics[angle=0]{dhv-v.pdf}}
\resizebox{\hsize}{!}{\includegraphics[angle=0]{dhv-b.pdf}}
\resizebox{\hsize}{!}{\includegraphics[angle=0]{dhv-u.pdf}}
\caption{The rms of one observation of unit weight as a function
of a standard magnitude for the stars from the Hvar archive
of differential observations.}
\label{drms}
\end{figure}

\section{Monitoring the atmospheric extinction at Hvar}
Determination of linear extiction coefficients for every night
of observations, in which the observed standard stars
span a~sufficient range of air masses (at least 0.2),
was a natural part of the data reduction.

 It was deemed useful to present these data, relevant to air pollution
at Hvar. Their value exceeds the astronomical interest and can be
valuable for broader community, ecology studies in particular.

The seasonal variations, plotted in Fig~\ref{extph} and
already noted by \citet{koupav82}, are clearly seen. During the winter seasons,
atmospheric extinction is usually lower as the sea does not evaporate
too much. During the summer seasons, the values of the extinction coefficients
exhibit a large scatter due to local weather changes but on an average
they are much higher then in the winter. Another thing worth noting is
that the minimum values of the seasonal changes do not show any annual
modulation. Such a behavior has also been found at some other sites,
for instance at La~Silla \citep{rufener86} or Grosschwabhausen
observing station \citep{reimann92}). We note that in Fig~\ref{extph} there are some
values of extiction coefficients lying below the general slope of the
minimum extinction, especially for the $U$ band. These extinction
coefficients were usually determined on poor photometric nights or the nights
where only few extinction standard stars had been measured. Of course, such
nights were never used for all-sky photometry.

In Figure~\ref{extjd} we present a time plot of all extinction
coefficients in $U$, $B$ and $V$ passbands, recorded at Hvar Observatory
over the past fifty years. The scatter of the values is mainly caused by
seasonal changes discussed above. Nevertheless, a mild growth of
the extinction can be seen in 1975 and 1982. Such increases are often
related to large volcanic eruptions anywhere in the world.
The first maximum, seen in 1975 may be due to eruption of
the El Fuego volcano in Guatemala (October 1974). We warn, however,
that during the first observing seasons at Hvar, only a limited number
of nights and standard stars suitable for accurate determination of
the extinction were available.

 The next increase of the extinction appeared at the time of eruption
of the El Chiichon volcano (March 1982). The growth of extinction coefficients
after this eruption was also recorded at other observatories
like La Silla \citep{rufener86, burki95}, Jena University Observatory
\citep{reimann92}, or Lowell Observatory \citep{loctho86}. However, the effect
of the powerful eruption of the St. Helens volcano (March 1980) was not
obviously felt at extinction at Hvar. Needless to say, a very small number
of observations was made at that time, however. Also the La~Silla
observations \citep{rufener86} and observations at the Jena University
Observatory \citep{reimann92} did not detected this eruption while at
the Lowell Observatory \citep{loctho86}, the effect was only marginal.
The strong Pinatubo eruption (April 1991) was not covered by Hvar observations
because of the intermission due to war in Yugoslavia.

  A more detailed analysis of the extinction variations at Hvar
and their nature will be published elsewhere. Here we only note that
already \citet{pavlovski79} pointed out that the influence of the
molecular absorption (mainly by $O_3$) is of little effect in the
$UBV$ region. The Rayleigh scattering on air molecules that
depends on wavelength and the air pressure shows a small range
of variability. The most variable component of the extinction
is scattering by aerosols. The Hvar Observatory is a low-altitude
station and in the vicinity of the sea
and is a subject to significant weather changes even within one night.
Obviously the sea spray plays a major role in the large variations
of extinction during the summer seasons. Also occasional forest fires,
quite frequent on the Adriatic coast, may have significant influence on the
measured extinction.


\begin{figure}
\resizebox{\hsize}{!}{\includegraphics[angle=0]{extph.pdf}}
\caption{The seasonal variations of the extinction coefficients at Hvar Observatory.}
\label{extph}
\end{figure}


\begin{figure}
\resizebox{\hsize}{!}{\includegraphics[angle=0]{extjd.pdf}}
\caption{The long-time behaviour of the extinction coefficients at Hvar Observatory
over the past fifty years.}
\label{extjd}
\end{figure}

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