J/A+A/712/A226 Refined reduction of UBV photometry at Hvar (Bozic+, 2026)
Refined reduction and standardisation of 53 years of UBV photometry at Hvar.
Bozic H., Harmanec P., Broz M., Oplistilova A., Koubsky P., Hadrava P.,
Ruzdjak D., Sudar D., Wolf M., Zasche P., Honsa J., Zdarsky F., Harmanec A.,
Jonak J., Piantschitsch I., Skokic I., Svrckova J., Vitovsky K., Vrsnak D.,
Zummer M.
<Astron. Astrophys. 712, A226 (2026)>
=2026A&A...712A.226B 2026A&A...712A.226B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, early-type ; Photometry, UBV
Keywords: binaries: eclipsing - binaries: general - binaries: spectroscopic -
binaries: visual - stars: early-type - stars: emission-line, Be
Abstract:
Emission-line stars classified as Be exhibit light and colour
variability on various timescales, ranging from days to decades. Their
evolution must be constrained by long-term observations that are
accurately calibrated and stable.
Here, we provide a new reduction of photoelectric UBV observations
obtained at the Hvar observatory, spanning more than 50 years
(1972-2025). This unique dataset is highly complementary to the
Transiting Exoplanet Survey Satellite, which has been conducting
observations since 2018, not only in terms of the time baseline, but
also in providing fundamental constraints in the U and B bands.
We used new, non-linear reduction equations, with temporally variable
extinction over the course of the night, which allowed us to achieve
long-term accuracy of 0.008-0.016mag (1-σ uncertainty), as
verified by the Johnson standards. We then classified 59 Be stars into
five classes, based on their variability patterns; namely, long-term
envelope (LTE), long-term cyclic (LTC), binarity (BIN), rapid
low-amplitude (RLA), and long-term quiescence (LTQ).
According to our observations, the percentages of stars in the
individual classes are 44%, 24%, 25%, 66%, and 19%, respectively. We
note that stars in the sample often exhibited more than one pattern.
At certain times, changes in the U and B bands were markedly different
from those in V (e.g. for BU Tau, V744 Her, V923 Aql, and V1294 Aql).
We confirm that the LTE-positive variability is more common than the
inverse (20 vs 6); in addition, two stars exhibited both types (ζ
Tau and V1294 Aql). According to our observations, the LTC variability
and the LTE-positive variability are almost mutually exclusive. Among
26 binary systems with previously known orbital solutions, circular
orbits are more common than eccentric ones (18 vs 8). As for the
brightness variations between different quiescent phases, an
increasing trend is less common than a decreasing one (4 vs 7);
spanning from -6.5 to +6.0mmag/yr.
Our observations provide well-calibrated UBV light curves spanning
several decades, offering a valuable dataset for investigations of
Be-star variability and tests of various models, including the viscous
decretion disc model. Continuous monitoring is important for the most
interesting objects, namely, β Lyr, EW Lac, δ Sco,
γ Cas, and V1294 Aql.
Description:
The refinement of the reduction and standardisation of 53 years of UBV
photometry at Hvar has enabled us to address questions related to
various types of variability and the short-term temporal evolution of
hot emission-line stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 35 106 List of studied stars
tablea3.dat 101 28986 Archive of all UBV observations of 106 stars
tablea4.dat 96 10 Mean values for primary Johnson standards
(corrected version, 27-Aug-2026)
tablea5.dat 96 7 Mean values for secondary Johnson standards
(corrected version, 27-Aug-2026)
tablea6.dat 96 223 UBV magnitudes of comparison, check and red stars
tablea7.dat 96 152 UBV magnitudes of comparison, check and red stars
phot.tar 21418 60195 Complete all-sky and differential archives of
Hvar observations from the years 1972-2024
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Star name
13- 14 I2 h RAh Simbad right ascension (J2000)
16- 17 I2 min RAm Simbad right ascension (J2000)
19- 23 F5.2 s RAs Simbad right ascension (J2000)
25 A1 --- DE- Simbad declination sign (J2000)
26- 27 I2 deg DEd Simbad declination (J2000)
29- 30 I2 arcmin DEm Simbad declination (J2000)
32- 35 F4.1 arcsec DEs Simbad declination (J2000)
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Star name
13- 22 F10.4 d HJD Heliocentric Julian date (HJD-2400000)
24- 28 F5.3 --- Phase [0] Phase (never available)
30- 33 F4.2 --- w Weight
35- 39 F5.3 mag Vmag V magnitude
41- 46 F6.3 mag Bmag B magnitude
48- 53 F6.3 mag Umag U magnitude
55- 60 F6.3 mag B-V B-V index
62- 67 F6.3 mag U-B U-B index
69- 73 F5.3 --- X Airmass
75- 80 F6.3 --- dX Airmass increment
82- 87 I6 --- HD HD number of comparison star
89 I1 --- Status [1] Status
91-101 A11 --- Observers List of observers (abbreviated)
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Byte-by-byte Description of file: tablea4.dat tablea5.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Star name
16- 21 I6 --- HD HD number
23- 28 F6.4 mag Vmag V magnitude
30- 35 F6.4 mag e_Vmag V magnitude rms
37- 39 I3 --- o_Vmag V magnitude number of observations
41- 47 F7.4 mag B-V B-V index
49- 54 F6.4 mag e_B-V B-V index rms
56- 58 I3 --- o_B-V B-V index number of observations
60- 66 F7.4 mag U-B U-B index
68- 73 F6.4 mag e_U-B U-B index rms
75- 77 I3 --- o_U-B U-B index number of observations
79- 85 F7.4 mag V-R V-R index
87- 92 F6.4 mag e_V-R V-R index rms
94- 96 I3 --- o_V-R V-R index number of observations
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Byte-by-byte Description of file: tablea6.dat tablea7.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name Star name
17- 22 I6 --- HD/BD ? HD or BD number
24- 30 F7.1 d JDmin Beginning of observations (JD-2400000)
32- 38 F7.1 d JDmax End of observations (JD-2400000)
40- 43 I4 --- N Number of observations
45- 50 F6.3 mag Vmag V magnitude
52- 56 F5.3 mag e_Vmag V magnitude rms
58- 63 F6.3 mag Bmag B magnitude
65- 69 F5.3 mag e_Bmag B magnitude rms
71- 76 F6.3 mag Umag U magnitude
78- 82 F5.3 mag e_Umag U magnitude rms
84- 89 F6.3 mag B-V B-V index
91- 96 F6.3 mag U-B U-B index
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Acknowledgements:
Miroslav Broz, mira(at)sirrah.troja.mff.cuni.cz
License: CC-BY-4.0
History:
25-Aug-2026: on-line version
27-Aug-2026: tablea A4 and A5 corrected
(End) Patricia Vannier [CDS] 01-Jul-2026