J/AJ/145/60 Light curves of GN Boo, BL Leo, and V1918 Cyg (Yang+, 2013) ================================================================================ Photometric studies of three neglected short-period contact binaries GN Bootis, BL Leonis, and V1918 Cygni. Yang Y.-G., Qian S.-B., Dai H.-F. =2013AJ....145...60Y ================================================================================ ADC_Keywords: Binaries, eclipsing ; Photometry, UBVRI Keywords: binaries: close - binaries: eclipsing - stars: individual (GN Boo,BL Leo,V1918 Cyg) Abstract: We present new photometry for three short-period contact binaries, GN Boo, BL Leo, and V1918 Cyg, observed from 2008 December to 2012 April using several small telescopes in China. Photometric models were deduced from new observations using the updated Wilson-Devinney Code. The results show that GN Boo and BL Leo are W-type contact binaries, while V1918 Cyg is an A-type one. The mass ratios and fill-out factors are q=0.320(+/-0.002) and f=5.8(+/-0.1)% for GN Boo, q=0.476(+/-0.005) and f=21.3(+/-1.1)% for BL Leo, q=0.264(+/-0.002), and f=49.7(+/-0.7)% for V1918 Cyg, respectively. From the (O-C) curves, it is discovered that the orbital periods of three binaries have varied in a complicated way, i.e., cyclic oscillation for GN Boo, long-term period decrease for BL Leo, and both for V1918 Cyg. The cyclic variations for GN Boo and V1918 Cyg may probably be attributed to the magnetic activity of the primary component or light-time effect due to the third body. Meanwhile, the secular period decreases for BL Leo and V1918 Cyg may result from mass transfer from the primary to the secondary, accompanying the mass and angular momentum loss from the central system. Finally, GN Boo, BL Leo, and V1918 Cyg will evolve into deep contact binaries. Additionally, a statistical study of 37 contact binaries with decreasing periods is given. We obtained the relations of q-f and q-dlnP/dt, and preliminarily determined the mass loss rate of dln M/dt from the binary system. Description: Photometric observations of GN Boo, BL Leo, and V1918 Cyg were carried out between 2008 December and 2012 April using two small telescopes at the Xinglong station (XLs) of the National Astronomical Observatories of China (NAOC). The telescopes were equipped with the standard Johnson-Cousin-Bessel UBVRI filters. New photometry of GN Boo was performed on 2012 March 16 and April 25, using the 85cm telescope. The integration times for VR measurements are 60s and 80s, respectively. We obtained 264 frames in the V band and 266 frames in the R band (table2a). BL Leo was observed on two consecutive nights of 2008 December using the 80cm telescope. Typical exposure times were set to 60s and 50s in the VR bands, respectively. In total, 192 useful images in the V band and 197 ones in the R band were obtained (table2b). BVR observations of V1918 Cyg were obtained on 2011 September 2, 4, and 5 using the 85cm telescope. The exposure times for the B, V, and R bands were 30s, 25s 15s, respectively. We obtained a total of 1199 individual observations: 406 in B, 402 in V, and 391 in R (table3). On 2011 March 3 and 7, and 2012 March 20 and 21, four eclipsing times of GN Boo and BL Leo were observed, using the 1.56m telescope at the Sheshan station of SHanghai Astronomical Observatory (SHAO). Using the 85cm telescope at XLs of NAOC and the 60cm and 1.0m telescopes at the Yunnan Astronomical Observatory (YNAO), eight light minimum times of V1918 Cyg were monitored from 2009 August to 2011 September. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file variable.dat 51 3 Information on the variable stars table3.dat 59 406 BVR photometric observations of V1918 Cyg in 2011 table2a.dat 59 266 VR photometric observations of GN Boo table2b.dat 59 197 VR photometric observations of BL Leo table4.dat 47 33 New eclipsing times of GN Boo, BL Leo, and V1918 Cyg table5.dat 49 63 Photoelectric and CCD light minimum times of GN Boo table6.dat 49 142 All compiled light minimum times of BL Leo table7.dat 49 66 All available light minimum times of V1918 Cyg refs.dat 79 127 References -------------------------------------------------------------------------------- See also: B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2014) B/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013) J/AJ/144/149 : Photometry of W UMa type TY Boo (Christopoulou+, 2012) J/other/NewA/17.347 : Eclipsing times of BE Cep (Dai+, 2012) J/other/RAA/11.181 : VR light curves of EI CVn (Yang, 2011) J/PASP/123/895 : EH Cnc RV light curves (Yang+, 2011) J/AJ/141/44 : V396 Mon BVRI light curves (Liu+, 2011) J/AJ/142/99 : BVRI observations of TZ Boo (Christopoulou+, 2011) J/AJ/137/236 : CC Com and BV Dra light curves (Yang+, 2009) J/AJ/136/594 : BS Cas BVR light curves (Yang+, 2008) J/A+A/446/785 : Catalogue of eclipsing variables (Malkov+, 2006) J/AcA/54/207 : Ephemerids of eclipsing binaries (Kreiner, 2004) J/other/IBVS/5296 : Extrema of pulsating stars (Agerer+, 2002) J/AJ/119/1901 : ROTSE all-sky surveys for variable stars (Akerlof+, 2000) J/A+A/311/523 : Photometry of W UMa (Maceroni+, 1996) Byte-by-byte Description of file: variable.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 9 A9 --- Name Star name 11- 12 I2 h RAh Hour of Right Ascension (J2000) 14- 15 I2 min RAm Minute of Right Ascension (J2000) 17- 21 F5.2 s RAs Second of Right Ascension (J2000) 23 A1 --- DE- Sign of the Declination (J2000) 24- 25 I2 deg DEd Degree of Declination (J2000) 27- 28 I2 arcmin DEm Arcminute of Declination (J2000) 30- 34 F5.2 arcsec DEs Arcsecond of Declination (J2000) 36- 40 F5.2 mag Vmag V-band magnitude 42- 51 F10.8 --- Per Period -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat table2a.dat table2b.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 12 F12.4 d HJD-B ? Heliocentric Julian Date of B band (1) 14- 19 F6.3 mag DBmag ? Differential B band magnitude (1) 21- 32 F12.4 d HJD-V ? Heliocentric Julian Date of V band 34- 39 F6.3 mag DVmag ? Differential V band magnitude 41- 52 F12.4 d HJD-R ? Heliocentric Julian Date of R band 54- 59 F6.3 mag DRmag ? Differential R band magnitude -------------------------------------------------------------------------------- Note (1): Only for V1918 Cyg (table3). -------------------------------------------------------------------------------- Byte-by-byte Description of file: table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 9 A9 --- Name Star name (GN Boo, BL Leo, or V1918 Cyg) 11- 23 F13.5 d HJD Heliocentric Julian Date 25- 31 F7.5 d e_HJD Error in HJD 33- 34 A2 --- Min Type of minimum (I or II) 36 A1 --- Flt [BVRI] Filter (B, V, R , or I) 38- 42 A5 --- Tel Telescope (1.0m, 1.56m, 60cm, 80cm, or 85cm) 44- 47 A4 --- Obs Observatory (SHAO, XLs, or YNAO) (1) -------------------------------------------------------------------------------- Note (1): Observatory as follows: SHAO = (Sheshan station of) SHanghai Astronomical Observatory; XLs = XingLong station (of the National Astronomical Observatories of China); YNAO = Yunnan Astronomical Observatory. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table[567].dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 12 F12.4 d HJD Heliocentric Julian Date 14- 21 F8.1 --- Epoch Epoch 23- 25 A3 --- Meth Observational method (CCD, pe, pg, or vi) (1) 27- 28 A2 --- Min [I II]Type of minimum (I or II) 30- 36 F7.4 d O-C1 Eclipse time residual (2) 38- 44 F7.4 d O-C2 ? Eclipse time residual (3) 45 A1 --- f_O-C2 [d] Discarded value due to a large residual 47- 49 I3 --- Ref Reference; in refs.dat file -------------------------------------------------------------------------------- Note (1): Observational method used: pe = photoelectric; pg = photographic; vi = visual. Note (2): Ephemeris are: * for GN Boo, calculated by Blattler & Diethelm (2001IBVS.5125....1B): Min.I=HJD2451996.4139+0.301601*E (Equation (1) in this paper). * for BL Leo, calculated by the Kreiner et al. (2001aocd.book.....K):` Min.I=HJD2437650.6710+0.28193068*E (Equation (3) in this paper). * for V1918 Cyg, calculated by the Kreiner (2004, cat. J/AcA/54/207): Min.I=HJD2452500.277+0.4131754*E (Equation (5) in this paper). Note (3): Ephemeris used: * for GN Bootis, calculated from the Equation (2) ephemeris: Min.I = HJD2451996.4156(2) + 0.30160220(3)*E + 0.0042(3)*sin[5.25(9)*10^-4^*E+5.73(7)] * for BL Leonis, calculated from the Equation (4) ephemeris: Min.I = HJD2437650.6612(7) + 0.28193148(4)*E - 1.78(6)*10^-11^*E^2^. * for V1918 Cyg, calculated from the Equation (6) ephemeris: Min.I = HJD2437650.266(2) + 0.4131769(2)*E. -------------------------------------------------------------------------------- Byte-by-byte Description of file: refs.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 3 I3 --- Ref Reference number 5- 23 A19 --- BibCode Bibliographic code 25- 44 A20 --- Aut Author's name 46- 79 A34 --- Com Comments -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 25-Mar-2014