Photometric variability of the 1H1936+541 star in 2008-2014
We report the results of observations of the Be/X-ray binary system 1H1936+541. All of the data were obtained on the base of Lisnyky observational station (Astronomical Observatory of the Taras Shevchenko National University of Kyiv) and Southern Station of the Sternberg Astronomical Institute (Lomo...
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| Zitieren: | Photometric variability of the 1H1936+541 star in 2008-2014 / A.O. Simon, V.V. Vasylenko, N.V. Metlova // Advances in Astronomy and Space Physics. — 2014. — Т. 4., вип. 1-2. — С. 28-31. — Бібліогр.: 8 назв. — англ. |
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irk-123456789-1198072017-06-10T03:03:18Z Photometric variability of the 1H1936+541 star in 2008-2014 Simon, A.O. Vasylenko, V.V. Metlova, N.V. We report the results of observations of the Be/X-ray binary system 1H1936+541. All of the data were obtained on the base of Lisnyky observational station (Astronomical Observatory of the Taras Shevchenko National University of Kyiv) and Southern Station of the Sternberg Astronomical Institute (Lomonosov Moscow State University), giving us three different CCDs in U, B, V, R, and I filters, from 2008 till 2014. During this time, photometrical variability occurred in all bands, however the most significant changes were present in U and I bands. Variabilities in these bands anti-correlate with each other and are in a good agreement with the model of decretion disks around Be stars. Thus, photometric variability claims for changes in the decretion disc structure. Further photometric and spectral observations can help us develop a physical model of this system. 2014 Article Photometric variability of the 1H1936+541 star in 2008-2014 / A.O. Simon, V.V. Vasylenko, N.V. Metlova // Advances in Astronomy and Space Physics. — 2014. — Т. 4., вип. 1-2. — С. 28-31. — Бібліогр.: 8 назв. — англ. 2227-1481 DOI: 10.17721/2227-1481.4.28-31 http://dspace.nbuv.gov.ua/handle/123456789/119807 en Advances in Astronomy and Space Physics Головна астрономічна обсерваторія НАН України |
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We report the results of observations of the Be/X-ray binary system 1H1936+541. All of the data were obtained on the base of Lisnyky observational station (Astronomical Observatory of the Taras Shevchenko National University of Kyiv) and Southern Station of the Sternberg Astronomical Institute (Lomonosov Moscow State University), giving us three different CCDs in U, B, V, R, and I filters, from 2008 till 2014. During this time, photometrical variability occurred in all bands, however the most significant changes were present in U and I bands. Variabilities in these bands anti-correlate with each other and are in a good agreement with the model of decretion disks around Be stars. Thus, photometric variability claims for changes in the decretion disc structure. Further photometric and spectral observations can help us develop a physical model of this system. |
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Article |
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Simon, A.O. Vasylenko, V.V. Metlova, N.V. |
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Simon, A.O. Vasylenko, V.V. Metlova, N.V. Photometric variability of the 1H1936+541 star in 2008-2014 Advances in Astronomy and Space Physics |
| author_facet |
Simon, A.O. Vasylenko, V.V. Metlova, N.V. |
| author_sort |
Simon, A.O. |
| title |
Photometric variability of the 1H1936+541 star in 2008-2014 |
| title_short |
Photometric variability of the 1H1936+541 star in 2008-2014 |
| title_full |
Photometric variability of the 1H1936+541 star in 2008-2014 |
| title_fullStr |
Photometric variability of the 1H1936+541 star in 2008-2014 |
| title_full_unstemmed |
Photometric variability of the 1H1936+541 star in 2008-2014 |
| title_sort |
photometric variability of the 1h1936+541 star in 2008-2014 |
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Головна астрономічна обсерваторія НАН України |
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2014 |
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http://dspace.nbuv.gov.ua/handle/123456789/119807 |
| citation_txt |
Photometric variability of the 1H1936+541 star in 2008-2014 / A.O. Simon, V.V. Vasylenko, N.V. Metlova // Advances in Astronomy and Space Physics. — 2014. — Т. 4., вип. 1-2. — С. 28-31. — Бібліогр.: 8 назв. — англ. |
| series |
Advances in Astronomy and Space Physics |
| work_keys_str_mv |
AT simonao photometricvariabilityofthe1h1936541starin20082014 AT vasylenkovv photometricvariabilityofthe1h1936541starin20082014 AT metlovanv photometricvariabilityofthe1h1936541starin20082014 |
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2025-07-08T16:38:35Z |
| last_indexed |
2025-07-08T16:38:35Z |
| _version_ |
1837097514439802880 |
| fulltext |
Photometric variability of the 1H1936+541 star in 2008�2014
A.O. Simon1∗, V.V.Vasylenko1, N.V.Metlova2
Advances in Astronomy and Space Physics, 4, 28-31 (2014)
© A.O. Simon, V.V.Vasylenko, N.V.Metlova, 2014
1Taras Shevchenko National University of Kyiv, Glushkova ave., 4, 03127, Kyiv, Ukraine
2Sternberg Astronomical Institute, Universitetski ave., 13, 119992, Moscow, Russia
We report the results of observations of the Be/X-ray binary system 1H1936+541. All of the data were obtained
on the base of Lisnyky observational station (Astronomical Observatory of the Taras Shevchenko National Univer-
sity of Kyiv) and Southern Station of the Sternberg Astronomical Institute (Lomonosov Moscow State University),
giving us three di�erent CCDs in U, B, V, R, and I �lters, from 2008 till 2014. During this time, photometrical
variability occurred in all bands, however the most signi�cant changes were present in U and I bands. Variabilities
in these bands anti-correlate with each other and are in a good agreement with the model of decretion disks around
Be stars. Thus, photometric variability claims for changes in the decretion disc structure. Further photometric and
spectral observations can help us develop a physical model of this system.
Key words: stars: emission-line, Be, observations
introduction
1H1936+541 belongs to the Be/X-ray binaries �
a subgroup of high-mass X-ray binaries (HMXB). As
an X-ray source it was described �rst in �The HEAO
A-1 X-ray source catalog� [8] in 1984. Later, in 1988
it was supposed that the star DM+53◦2262 is an op-
tical component for the mentioned X-ray source [6]
because this star was listed as an emission-line star
with medium intensity, an Hα line in 1950 [2], and
then in 1970 in �a catalogue of early-type stars the
spectra of which have shown emission lines� [7], and
it is located within the positional error box of the
X-ray experiment HEAO A-1.
After detecting 1H1936+541 by HEAO A-1 it
has never been detected by any other X-ray mission
[5]. Furthermore, we have not found any data on
optical variability of its optical component � the
DM+53◦2262 star. So, we conclude that the photo-
metric investigation of this object is necessary, and
therefore we carry it out.
observations and data processing
All the data were obtained at the base of the
Lisnyky observational station (Astronomical Obser-
vatory of the Taras Shevchenko National University
of Kyiv) and Southern Station of the Sternberg As-
tronomical Institute (Lomonosov Moscow State Uni-
versity) using of three di�erent CCDs in U, B, V,
R, and I �lters from 2008 until 2014. At the Lis-
nyky observational station we used SBIG ST-8 CCD
(510× 340 pixels, which corresponds to the angular
size of the �eld matrix 19′18′′×12′52′′) and PL47-10
FLI CCD (1056× 1027 pixels, which corresponds to
the angular �eld size matrix 19′25′′ × 18′53′′). At
the Southern Station of the Sternberg Astronomical
Institute we used Ap-47P CCD (528 × 512 pixels,
which corresponds to the angular size of the �eld
matrix 7′34′′ × 7′20′′).
The photometric image processing was carried
out using standard methods of di�erential photom-
etry. The dark frames of the same CCD were sub-
tracted from the images, then the resulting image
was divided into a �at �eld of the telescope (from
which the dark frames were also subtracted). To
�nd the instrumental magnitude of the star the in-
tensity of sky background was subtracted from the
image total intensity [3]:
minst = −2.5 lg (Isum − Isky),
It is possible to transfer instrumental magnitudes
into standard ones using a comparison of magnitudes
of our object and those of the standard star:
m∗
inst = mst
syst +∆minst,
where ∆minst is the di�erence between the instru-
mental magnitude of the object and the standard
star. As a standard star we chose HD184658, which
according to the SIMBAD database is not a variable
star. Magnitudes of the HD184658 as a standard
were taken from the AAVSO Special Notice #2131
and are listed in Table 1.
∗andrew_simon@mail.ru
1http://www.aavso.org/aavso-special-notice-213
28
Advances in Astronomy and Space Physics A.O. Simon, V.V.Vasylenko, N.V.Metlova
To monitor and con�rm variability of the object
using di�erential photometry we used a few more
control stars. Control stars were chosen so that they
were present in all CCDs including the Ap-47P CCD,
the �eld of view of which is the smallest one (Fig. 5).
Table 1: Standard magnitudes for HD184658 from
AAVSO Special Notice, except U-magnitude which is
taken from [4] due to its absence there.
Name U∗ B V R I
HD184658 9.56 9.697 9.684 9.645 9.629
results
Following the image processing, we determined
magnitudes of the investigated object 1H1936+541
in the standard photometrical system, and plotted
lightcurves in all bands. In Fig. 1 all of these curves
are presented. In U and B �lters one can see increase
of brightness of the object from the beginning of ob-
servations until December 2010. After that during a
period of two years the small density of observational
data does not give us a possibility to do unequivo-
cal conclusions about the system state, however the
decrease of brightness during this time interval is ev-
ident. Since July 2013 one can see another increase
of the brightness in the U and B bands. In the R
and I bands the situation is opposite: the brightness
of the object �rstly decreases up to December 2010,
then it increases to its original values up until July
2013, after which it again begins to decrease. In V
band the magnitude does not change signi�cantly.
The amplitude of the magnitude changes in di�erent
�lters varies: in the U �lter ∆m is approximately
0.21; in the B �lter it is ∼ 0.23, in the R �lter it
is ∼ 0.12, and in the I �lter it is ∼ 0.28. The un-
certainty of stellar magnitude estimation for most of
the data does not exceed ±0.02m.
One of the important characteristics in photomet-
ric studies is the measure of colour � the di�erence
between magnitudes obtained in di�erent �lters. The
main ones are the colour indices (U−B) and (B−V ).
The (U − B) index is a good indicator of the tem-
perature of the O and B stars. These colour indices
are shown in Fig. 2, 3. Additionally, according to the
lightcurves (Fig. 1), the largest photometric changes
of the object occur in the U and I bands. Therefore,
we also present the (U − I) colour index in Fig. 2.
Throughout the entire series of observations, the
colour indices did not change much, except for one
case near the Julian date JD = 2455400, which cor-
responds to a period in December 2010 � January
2011. The signi�cance of these changes were con-
�rmed by Sign Test (see Table 2). In Fig. 4, where
di�erent symbols stand for data obtained with dif-
ferent CCDs:
a) all the points near JD = 2455400 were obtained
with the same instrument;
b) aside from �drop-down� points, all other data
from this camera are in a good agreement with the
whole light curve, so the �drop-down� points are not
camera artifacts.
2454600 2455200 2455800 2456400 2457000
10,6
10,5
10,4
10,3
10,6
10,5
10,4
10,3
10,6
10,5
10,4
10,3
10,6
10,5
10,4
10,3
10,6
10,5
10,4
10,3
2454600 2455200 2455800 2456400 2457000
U
JD
B
V
R
I
Fig. 1: Lightcurves of the 1H1936+541 in all bands.
2455200 2456000 2456800
-1,1
-1,0
-0,9
-0,8
-0,7
-0,2
-0,1
0,0
0,1
-1,0
-0,9
-0,8
-0,7
2455200 2456000 2456800
U
-B
JD
B
-V
U
-I
Fig. 2: Colour indices of the 1H1936+541.
29
Advances in Astronomy and Space Physics A.O. Simon, V.V.Vasylenko, N.V.Metlova
Thus, we can conclude that changes in colour in-
dex shown in this plot really occurred in the system.
Comparison of (U − B), (B − V ) plots and
lightcurves in U and I bands yields the following
results. The colour changes coincide in time with
changes in magnitudes. Namely, the magnitude in
the U-�lter decreases, i. e. the brightness increases,
and vice versa, for the I-�lter (Fig. 3). Also, the cor-
relation coe�cient for the I �lter and (B−V ) colour
index is −0.63316 ± 0.00006, and 0.517 ± 0.004 for
the U �lter and (B − V ) colour index.
2454600 2455200 2455800 2456400 2457000
10,6
10,5
10,4
10,3
9,7
9,6
9,5
9,4
9,3
-0,2
-0,1
0,0
-1,0
-0,9
-0,8
2454600 2455200 2455800 2456400 2457000
I
JD
U
B
-V
U
-B
Fig. 3: Lightcurves of the 1H1936+541 in U and I bands,
and (B − V and (U −B) colour indices.
2454600 2455200 2455800 2456400 2457000
-0,25
-0,20
-0,15
-0,10
-0,05
0,00
0,05
PL47-10 FLI
SBIG ST-8
Ap-47P
B
-V
JD
Fig. 4: Colour index (B − V ) from di�erent CCDs.
To con�rm that the observed changes are not just
�uctuations in a frame of similar distribution, the
Sign test were applied. This test function tests the
hypothesis that two sample populations X and Y
have the same mean of distribution against the hy-
pothesis that they di�er. For this purpose we have
divided our data into two equal parts and compared
them. The results of this test shows that these two
samples of data have di�erent means of distribution
(in Table 2, the maximum number of signed di�er-
ences between corresponding pairs of xi and yi, and
its one-tailed signi�cance).
Within the frame of the decretion disk model [1]
this observed fact can be interpreted as the destruc-
tion of the disk, or a signi�cant reduction in its size.
The decretion disk is a powerful source of infrared ra-
diation; hence its distruction should lead to decrease
in the intensity of infrared radiation. On the other
hand, in terms of geometry, a wide decretion disk can
cover a signi�cant portion of the surface of the star,
thus preventing the spread of its own radiation, the
main part of which is concentrated in the ultravio-
let region. The disappearance of the decretion disk
removes all obstacles, and the �ux of radiation from
the star increases.
Table 2: Results of the Sign Test.
Num. of Max. Num.
Filter points of di�. Signif.
U 40 17 0.001
I 33 13 0.013
U-B 33 13 0.025
B-V 41 17 0.004
U-I 33 14 0.006
Return of the system to the initial values of the
colour indicates the re-formation of the disk, or its
substantial growth. The lower brightness in the U
�lter and the greater one in I �lter, comparable with
the values from early observations, may indicate a
more powerful drive than that which existed in 2008.
Changing in magnitude in aforementioned bands and
minor �uctuations in colour may indicate changes in
the current system, which do not lead to catastrophic
changes in the structure of the disk. However, in the
near future the disk has to be disbanded again.
conclusions
We conducted a series of observations of the ob-
ject 1H1936+541 and got lightcurves in U, B, V,
R, and I bands and colour indices for it. Our re-
sults indicate a violent physical processes in the sys-
tem probably associated with the deformation and
the re-formation of the decretion disk around the
main component of Be/X-ray binary 1H1936+541.
These results can be a small claim for the version
of the Be/X-ray binary even without X-ray activity
30
Advances in Astronomy and Space Physics A.O. Simon, V.V.Vasylenko, N.V.Metlova
Fig. 5: The sky chart with the standard star HD184658 (Reference star), our object 1H1936+541
(Obj1) and the comparison stars (Obj2, Obj3, Obj4, Obj5).
throughout past thirty years. We expect the next
disbandment of the decretion disk in the nearest fu-
ture. Hence, a detailed study of the processes asso-
ciated with the conversion of the disk, and further
observations, are necessary.
acknowledgement
We would like to thank the sta� of the Astronom-
ical Observatory of the Taras Shevchenko National
University of Kyiv, and that of the Southern Station
of the Sternberg Astronomical Institute, for the pos-
sibility of the photometric studies with the help of
their telescopes and equipment. Special thanks to
Ganna Ivashchenko and Oleksiy Agapitov for useful
discussions.
references
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eskie osnovy fotometrii i spektrophotometrii zvezd', Phys-
MathLit, Moscow
[4] OfekE.O. 2008, PASP, 120, 1128
[5] Torrejón J.M. & OrrA. 2001, A&A, 377, 148
[6] Tuohy I. R., BuckleyD.A.H., RemillardR.A., BradtH.V.
& SchwartzD.A. 1988, International Symposium on the
Physics of Neutron Stars and Black Holes, 93
[7] Wackerling L.R. 1970, MmRAS, 73, 153
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