Long-term photopolarimetric variability of DD Ser
We present some results of UBVRI-photopolarimetric observations of DD Ser, a poorly studied and understood Ae-star. The long-term component of light variation is detected, with the period of about fifteen years. Variability of the degree and positional angle of linear polarization is observed as wel...
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irk-123456789-1196152017-06-08T03:07:03Z Long-term photopolarimetric variability of DD Ser Belan, S.P. Shakhovskoy, D.N. We present some results of UBVRI-photopolarimetric observations of DD Ser, a poorly studied and understood Ae-star. The long-term component of light variation is detected, with the period of about fifteen years. Variability of the degree and positional angle of linear polarization is observed as well. Analysis of correlation between photometric and polarimetric data shows that observed light minima are likely caused by variability of circumstellar extinction produced by dust. 2013 Article Long-term photopolarimetric variability of DD Ser / S.P. Belan, D.N. Shakhovskoy // Advances in Astronomy and Space Physics. — 2013. — Т. 3., вип. 2. — С. 81-83. — Бібліогр.: 10 назв. — англ. 2227-1481 http://dspace.nbuv.gov.ua/handle/123456789/119615 en Advances in Astronomy and Space Physics Головна астрономічна обсерваторія НАН України |
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We present some results of UBVRI-photopolarimetric observations of DD Ser, a poorly studied and understood Ae-star. The long-term component of light variation is detected, with the period of about fifteen years. Variability of the degree and positional angle of linear polarization is observed as well. Analysis of correlation between photometric and polarimetric data shows that observed light minima are likely caused by variability of circumstellar extinction produced by dust. |
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Belan, S.P. Shakhovskoy, D.N. |
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Belan, S.P. Shakhovskoy, D.N. Long-term photopolarimetric variability of DD Ser Advances in Astronomy and Space Physics |
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Belan, S.P. Shakhovskoy, D.N. |
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Belan, S.P. |
| title |
Long-term photopolarimetric variability of DD Ser |
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Long-term photopolarimetric variability of DD Ser |
| title_full |
Long-term photopolarimetric variability of DD Ser |
| title_fullStr |
Long-term photopolarimetric variability of DD Ser |
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Long-term photopolarimetric variability of DD Ser |
| title_sort |
long-term photopolarimetric variability of dd ser |
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Головна астрономічна обсерваторія НАН України |
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2013 |
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Long-term photopolarimetric variability of DD Ser / S.P. Belan, D.N. Shakhovskoy // Advances in Astronomy and Space Physics. — 2013. — Т. 3., вип. 2. — С. 81-83. — Бібліогр.: 10 назв. — англ. |
| series |
Advances in Astronomy and Space Physics |
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AT belansp longtermphotopolarimetricvariabilityofddser AT shakhovskoydn longtermphotopolarimetricvariabilityofddser |
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2025-07-08T16:16:25Z |
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2025-07-08T16:16:25Z |
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1837096120291950592 |
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Long-term photopolarimetric variability of DD Ser
S. P.Belan∗, D.N. Shakhovskoy
Advances in Astronomy and Space Physics, 3, 81-83 (2013)
© S. P.Belan, D.N. Shakhovskoy, 2013
Crimean Astrophysical Observatory, Nauchny, Ukraine
We present some results of UBVRI-photopolarimetric observations of DDSer, a poorly studied and understood
Ae-star. The long-term component of light variation is detected, with the period of about �fteen years. Variability
of the degree and positional angle of linear polarization is observed as well. Analysis of correlation between pho-
tometric and polarimetric data shows that observed light minima are likely caused by variability of circumstellar
extinction produced by dust.
Key words: stars: variables: T Tauri, Herbig Ae/Be: individual: DD Ser � stars: pre-main sequence
introduction
The class of Herbig Ae/Be (HAeBe) stars was
established by Herbig [4] as stars which are sur-
rounded by nebulosities and the optical spectra of
which show emission lines. Further investigations re-
vealed that these sources are young stars (1�10Myr)
with masses 2�10M� in the later stages of their pre-
main sequence evolution. Existence of infrared emis-
sion is another characteristic of these stars. The
infrared excess emission arises from a protoplane-
tary disk [10] and in many cases from an envelope
as well [5]. HAeBe stars are, therefore, frequently
regarded as the higher mass counterparts of the low-
mass TTauri stars. There is a class of objects, named
UXORs, including Herbig Ae/Be and TTauri-type
stars, which is characterized by a pronounced pho-
tometric activity. The variability of these stars is
caused by changes of circumstellar extinction on the
line of sight [1].
Planet formation theories suggest that this evolu-
tionary stage (1�10Myr) is exactly where the forma-
tion of planetary embryos is likely to occur. Thus,
Herbig Ae/Be stars are natural candidates for study-
ing the physical processes playing an important role
in planet formation.
DDSer is a poorly studied and understood Ae
star that shows unpredictable light fading lasting
from a few days to several years with V-amplitude
near 1m [6, 9]. The star spectral classi�cation is
A5 III and absolute luminosity is Mv = −0m.2 [8].
There is a variable emission in Hα-line [7]. Existence
of emission and the type of photometric variability
of DDSer make it similar to Herbig Ae stars, but
it was not classi�ed so due to the lack of observed
infra-red excess.
observations and results
Observations of DDSer were carried out in 1988�
2013 at the Crimean Astrophysical Observatory as a
part of the program of long-term photopolarimetric
monitoring of young stars. All data were obtained
at 1.25m telescope with UBVRI-polarimeter. In our
photometric observations a long-term component of
variability is evident. It is apparently periodic, with
the period of about 5500 days and amplitude about
0m.3 in V-band (see Fig. 1).
A correlation between polarization parameters
and brightness is found in four bands (U, B, V, R)
(see Figs. 3�6 and Tab. 1). Pearson correlation coef-
�cients (R) for all bands are presented in Table 1,
where the third and fourth columns are the least
square �t slope and the false alarm probability of
the correlation, respectively.
The character of this dependence is rather linear,
unlike one typical for UXORs [1]:
P = Pis +P0 · 2.5m−m0 ,
where P is the pseudo-vector of observed polariza-
tion, having Px and Py normalized Stokes parameters
as components, Pis is interstellar (constant) compo-
nent of polarization, P0 is polarization in a certain
state of brightness m0.
Cyclic photometric activity with periods of ten-
�fteen years is typical for UXORs [3]. Correlation
of photometric and polarimetric data supports the
idea that observed light minima are likely caused by
variability of circumstellar extinction produced by
dust, like in UXORs. Linear dependence of polar-
ization on magnitude could be explained as predom-
inance of polarization mechanism caused by absorp-
tion by aligned non-spherical dust particles over the
∗sbelan17@gmail.com
81
Advances in Astronomy and Space Physics S. P. Belan, D.N. Shakhovskoy
mechanism associated with scattering. Abrupt non-
linear increase of polarization with light weakening
is observed in UXOri-type stars at the moments of
deep minima (> 2m). Such minima have not been
observed in DDSer, that is probably why scatter-
ing component of polarized radiation is never strong
enough to dominate in observed light.
Table 1: Pearson correlation coe�cients between photo-
metric and polarimetric data for all bands.
band R Se σ
U −0.28 0.05 4.71 · 10−5
B −0.27 0.06 8.73 · 10−5
V −0.33 0.08 2.87 · 10−6
R −0.29 0.1 4.06 · 10−5
I −0.08 0.26
Based on the whole pattern of photometric
and polarimetric variability one might suggest that
DDSer is a more massive analogue of RZPsc, a tran-
sitional object slightly older than typical UXORs,
with low-mass residual circumstellar dust disk [2].
Speci�c features common for DDSer and RZPsc are
the absence of observable IR-excess, sharp light min-
ima seldom (or never in case of DDSer) reaching 1m
depth, long-term cyclic photometric variability. The
best interpretation of this is a well-evolved disk with
dust-free inner lobe, where compact dust clouds spo-
radically appear presumably as a result of destruc-
tion of solid bodies similar to comets and asteroids.
This class of rare objects with disks almost dis-
sipated but still observable in the line-of-sight dust
absorption is very important for better understand-
ing of disk evolution and planetary system forma-
tion. That is why DDSer deserves further thorough
investigation.
references
[1] GrininV.P., KiselevN.N., ChernovaG.P., Miniku-
lovN.Kh. & VoshchinnikovN.V. 1991, Ap&SS, 186, 283
[2] GrininV.P., Potravnov I. S. & MusaevF.A. 2010, A&A,
524, A8
[3] GrininV.P., RostopchinaA.N. & ShakhovskoiD.N.
1998, Astron. Lett., 24, 802
[4] HerbigG.H. 1960, ApJS, 4, 337
[5] LeinertCh., HaasM., ÁbrahámP. & RichichiA. 2001,
A&A, 375, 927
[6] Meinunger L. 1965, Mitt. Veränderl. Sterne 3, 9
[7] PugachA. F. & KovalchukG.U. 1999, A&A, 347, 937
[8] TimoshenkoL.V. 1984, Astro�zika, 21, 314
[9] TsesevichV.P., DragomiretskayaB.A. & Bogorod-
skij A. F. 1973, Naukova Dumka, Kyiv
[10] Waters L. B. F.M. & WaelkensC. 1998, ARA&A, 36, 233
Fig. 1: The lightcurve of DDSer (gray line is the least
square �t of 5500 days period).
Fig. 2: Variability of Px component of polarization.
82
Advances in Astronomy and Space Physics S. P. Belan, D.N. Shakhovskoy
Fig. 3: Dependence of polarization on brightness (V). Fig. 4: Dependence of polarization on brightness (R).
Fig. 5: Dependence of polarization on brightness (B). Fig. 6: Dependence of polarization on brightness (U).
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