J/AJ/158/104 LL Com BVR bands photometry & times of light minimum (Hu+, 2019)
LL Com: a near-contact total eclipsing binary at a key stage of evolution.
Hu K., Chen K., Xiang F.-Y., Yu Y.-X., Zhao E.-G.
<Astron. J., 158, 104 (2019)>
=2019AJ....158..104H 2019AJ....158..104H (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, eclipsing ; Photometry, UBVRI
Keywords: binaries: close - binaries: eclipsing - stars: evolution -
stars: individual (LL Com)
Abstract:
Despite the discovery of LL Com, a Lyrae-type eclipsing binary system,
approximately 60 yr ago, little has been found concerning its detailed
photometry and orbital-period change until now. In this paper, we present
the first multi-band charge-coupled-device photometric light curves, from
which a significant luminosity reduction around the primary eclipse is
revealed. Based on LAMOST data, we first determined LL Com's spectrum
as F1V and then analyzed the light curves with the 2015 version of the
Wilson-Devinney code. The fact that LL Com is a near-contact binary system
with a semi-detached configuration, where the secondary component only
fills its Roche lobe and the primary component fills more than 95% of
its Roche lobe, is suggested through the photometric solution. In addition,
according to archival photometry and previously published times of minima,
a secular period increase at a rate of P=2.62x10-7 day/yr was found,
which implies a continuous mass transfer from the secondary to the primary.
Utilizing the photometric solution and the simulations of single-particle
trajectories, we propose the existence of a cool spot on the surface
of the primary component. This cool spot can be naturally produced by
the impacts that occur during mass flow, and it also successfully
interprets the luminosity reduction in the light curves. Finally, with
the combination of thermal relaxation oscillation theory and the Roche-Lobe
model, we conclude that LL Com is transitioning from the semi-detached
to the detached phase.
Description:
New CCD photometric observations of the eclipsing binary LL Com were
made on three nights in 2017 December, using the 85 cm reflecting telescope
at the Xinglong Station of the National Astronomical Observatories of
China. The telescope was equipped with a Cassegrain-focus multi-color CCD
photometer. Johnson-Cousins BVR filters and an Andor DZ 936 PI2048 CCD
photometric system were attached to the telescope. Typical exposure times
of images were 80 s in the B band, 50 s in the V band, and 30 s in the
R band. We obtained 502 images for the B and V bands, and 501 images
for the R band.
To investigate orbital-period change of LL Com, we carefully searched
for all available light-minimum times. From the literature, 37 photographic
data items and 75 CCD items were collected. From our observations, three
light-minimum times were calculated with the Kwee-van Woerden method
(Kwee & van Woerden 1956BAN....12..327K 1956BAN....12..327K). We also searched for observations
of this binary in the public databases of some survey projects and found
that it has been observed on more than 100 nights by the WASP array of
robotic telescopes between 2004 and 2008 (Butters et al.
2010A&A...520L..10B 2010A&A...520L..10B). From the WASP data release, we obtained a total
of 6995 data points for LL Com, and we determined 109 light-minimum times
using the Kwee-van Woerden method (Kwee & van Woerden 1956BAN....12..327K 1956BAN....12..327K).
Objects:
------------------------------------------------
RA (ICRS) DE Designation(s)
------------------------------------------------
13 17 59.92 +30 08 01.7 LL Com = V* LL Com
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 95 502 BVR bands photometric data for the eclipsing binary
LL Com
table4.dat 29 224 Times of light minimum of LL Com
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See also:
J/other/IBVS/5296 : Extrema of pulsating stars (Agerer+, 2002)
J/other/IBVS/5438 : 162-nd list of minima of eclipsing binaries
(Diethelm, 2003)
J/AcA/54/207 : Ephemerids of eclipsing binaries (Kreiner, 2004)
J/other/IBVS/5543 : 163-nd list of minima of eclipsing binaries
(Diethelm+, 2004)
J/other/IBVS/5802 : Minima and maxima of 735 variables (Hubscher+, 2007)
J/AJ/136/1067 : New beta Lyrae and Algol candidates in NSVS
(Hoffman+, 2008)
J/other/IBVS/5918 : Minima and maxima of 452 variables (Hubscher+, 2010)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD-B Heliocentric Julian Date of B band observation
14- 18 F5.3 --- Phase-B [0.001/0.999] Corresponding phase for HJD
of B band
20- 25 F6.3 mag DBmag [-0.672/-0.078] Differential B band magnitude
27- 31 F5.3 mag e_DBmag [0.002/0.01] Photometric error in DBmag
33- 44 F12.4 d HJD-V Heliocentric Julian Date of V band observation
45- 50 F6.3 --- Phase-V [0/0.998] Corresponding phase for HJD of V band
52- 57 F6.3 mag DVmag [-0.604/-0.049] Differential V band magnitude
59- 63 F5.3 mag e_DVmag [0.002/0.007] Photometric error in DVmag
65- 76 F12.4 d HJD-R ? Heliocentric Julian Date of R band observation
78- 82 F5.3 --- Phase-R [0.001/0.999]? Corresponding phase for HJD
of R band
84- 89 F6.3 mag DRmag [-0.574/-0.043]? Differential R band magnitude
91- 95 F5.3 mag e_DRmag [0.002/0.006]? Photometric error in DRmag
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD-Min Heliocentric Julian Date of light-minimum time
14- 19 F6.4 d e_HJD-Min [0.0001/0.0047]? Corresponding error for HJD-Min
21- 22 A2 --- Type Type of light minimum (I=Primary; II=Secondary)
24- 26 A3 --- Meth [pg ccd] Method of observation (1)
28- 29 I2 --- Ref [1/44] Reference (2)
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Note (1): Method as follows:
pg = Photographic observation;
ccd = Charge-coupled-device observation.
Note (2): Reference as follows:
1 = Kurochkin (1959PZ.....12..409K 1959PZ.....12..409K);
2 = Frank et al. (1996IBVS.4386....1F 1996IBVS.4386....1F);
3 = Agerer & Huebscher (1999IBVS.4711....1A 1999IBVS.4711....1A);
5 = Agerer & Huebscher (1998IBVS.4562....1A 1998IBVS.4562....1A);
6 = Diethelm (1998BBSAG.118....7D 1998BBSAG.118....7D);
7 = Diethelm (2001IBVS.5038....1D 2001IBVS.5038....1D);
8 = Hoffman et al. (2008, J/AJ/136/1067);
9 = http://var.astro.cz/ocgate/;
10 = Diethelm (2001, http://www.astronomie.info/bbsag/bulletins/B125.pdf);
11 = Blaettler (2002, http://www.astronomie.info/bbsag/bulletins/B127.pdf);
12 = Agerer & Hubscher (2002, J/other/IBVS/5296);
13 = Agerer & Hubscher (2002IBVS.5484....1A 2002IBVS.5484....1A);
14 = Diethelm (2003, J/other/IBVS/5438);
15 = Zejda (2004IBVS.5583....1Z 2004IBVS.5583....1Z);
16 = Lewandowski et al. (2007IBVS.5784....1A 2007IBVS.5784....1A);
17 = Hubscher (2005IBVS.5642....1H 2005IBVS.5642....1H);
18 = Hubscher et al. (2005IBVS.5657....1H 2005IBVS.5657....1H);
19 = Diethelm (2004, J/other/IBVS/5543);
20 = Calculated times based on SWASP data;
21 = Zejda et al. (2006IBVS.5741....1Z 2006IBVS.5741....1Z);
22 = Nagai (2006, http://vsolj.cetus-net.org/no44.pdf);
23 = Diethelm (2006IBVS.5713....1D 2006IBVS.5713....1D);
24 = Nagai (2008, http://vsolj.cetus-net.org/no46rev.pdf);
25 = Hubscher (2007IBVS.5643....1H 2007IBVS.5643....1H);
26 = Diethelm (2007IBVS.5781....1D 2007IBVS.5781....1D);
27 = Diethelm (2009IBVS.5894....1D 2009IBVS.5894....1D);
28 = Hubscher et al. (2010, J/other/IBVS/5918);
29 = Hubscher (2014IBVS.6118....1H 2014IBVS.6118....1H);
30 = Nagai (2010, http://vsolj.cetus-net.org/vsoljno50.pdf);
31 = Honkova et al. (2013OEJV..160....1H 2013OEJV..160....1H);
32 = Honkova et al. (2014OEJV..165....1H 2014OEJV..165....1H);
33 = Hubscher et al. (2012IBVS.6026....1H 2012IBVS.6026....1H);
34 = Diethelm (2011IBVS.5992....1D 2011IBVS.5992....1D);
35 = Hubscher & Lehmann (2012IBVS.6026....1H 2012IBVS.6026....1H);
36 = Hubscher & Lehmann (2013IBVS.6070....1H 2013IBVS.6070....1H);
37 = Diethelm (2012IBVS.6029....1D 2012IBVS.6029....1D);
38 = Hubscher et al. (2013IBVS.6048....1H 2013IBVS.6048....1H);
39 = Honkova et al. (2015OEJV..168....1H 2015OEJV..168....1H);
40 = Hubscher (2017IBVS.6196....1H 2017IBVS.6196....1H);
41 = Hubscher (2015IBVS.6152....1H 2015IBVS.6152....1H);
42 = Jurysek et al. (2017OEJV..179....1J 2017OEJV..179....1J);
43 = This paper;
44 = http://var2.astro.cz/brno/.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 15-Oct-2019