Number4840
KonkolyObservatory
Budapest
29January2000
HUISSN0374{0676
CCD MINIMA OF SELECTED ECLIPSING BINARIES IN 1999
NELSON,ROBERTH.
CollegeofNewCaledonia,333022ndAvenue,PrineGeorge,BC,Canada,V2N1P8,e-mail:nelsonn.b.a
Thirty-two new times of minima for seleted elipsing binarieshave been determined
using a CCDamera atthe Prine George Astronomial Observatoryin 1999.
All observationswere madeusing anunltered SBIG ST6CCD amera(hip: TI
TC-241, 375241 pixels eah 2327 m, with an anti-blooming gate { not the author's
hoie) ooledto 40 Æ
Cand mounted atthe Cassegrainfous ofa 61-mtelesope. The
amera was equipped with a teleompressorlens that redued the foal ratio from f=12
to f=7. Field of view was then 5: 0
357: 0
00;eah pixel overed 1: 00
111: 00
30. Images were
taken, inmostases, everytwoorthree minutesthroughouttheelipsefor atimespanof
2to4hours. Finderhartswere madeusingthe programGuide7;the databases therein
provedinvaluable.
All dataredutionwasperformedwithMIRAAPversion5.04 (andlaterversion6.01)
by Axiom Researh In. Between exposures, frames wereat-elded in bath mode and
aperture photometry (using a single omparison star) performed. The aperture sizes
(pinholefor the star and annular regionfor the sky bakground)wereadjustedto gather
ountsfromthestar inthe mosteÆientmanner, and toavoidontaminationfromother
stars in the annular region. For eah elipse, a omparison magnitude, lose to the best
availablevalue, wasadopted and used throughoutthe elipse.
Times wereadjustedtothe mid-point ofthe exposure ineahase. Forallofthe data
sets (depending on the stars' brightnesses, exposure times and other fators), signal to
noise values for the variableor omparisonvaried from81to 1355.
In order to determine the time of minimum, several methods were used. First of all,
unless the minimum was learly at-bottomed, a parabola was tted by the method of
least squares to that part of the entral part of the minimum that appeared to t a
parabolawell. Toestimatethe error,the timeof minimum wasadjusted untilanobvious
badtwasseen;thediereneintimesofminimumwastakenastheerrorbythismethod.
In the majority of ases, there were signiant desending and asending portions of
theurve. Thetraingpapermethod(wheretheasendinganddesendingportionsofthe
urve are made to overlap { but now done on a spreadsheet) was used to determine the
timeofminimumapproximatelyandtodeterminethesymmetriregionsofthedesending
and asending branhes. The bisetorof hords method,and the method of Kwee&van
1999-10-19 ZZ Cyg GSC 3576-0964 51470.67204 0.00008 I
1999-05-11 BR Cyg GSC 3556-3310 51309.8253 0.0002 I 2
1999-09-12 BR Cyg GSC 3556-3310 51443.75421 0.00007 I 2
1999-09-21 CG Cyg GSC 2696-2622 51442.71870 0.00008 I
1999-12-08 Z Dra GSC 4396-1221 51520.81684 0.00001 I
1999-10-23 UZ Dra GSC 4444-0836 51474.86051 0.00016 I
1999-10-04 SW La GSC 3215-0906 51455.7416 0.0003 I
1999-12-03 SW La GSC 3215-1586 51515.8613 0.0001 I
1999-10-27 VX La GSC 3214-1065 51478.7423 0.0001 I
1999-08-14 FL Lyr GSC 3542-1400 51404.833 0.002 II 3
1999-09-19 FL Lyr GSC 3542-1400 51440.770 0.002 I 3
1999-11-29 RW Mon GSC 0733-0826 51511.92103 0.00005 I
1999-11-21 RV Per GSC 2366-1081 51503.8915 0.0002 I
1999-11-27 ST Per GSC 2847-1270 51509.8531 0.0001 I
1999-10-18 XZ Per GSC 3328-2029 51469.82784 0.00003 I
1999-11-27 RW Tau GSC 1826-0015 51509.68687 0.00003 I
1999-10-11 V Tri GSC 2293-1382 51462.8213 0.0002 I
1999-12-31 X Tri GSC 1763-2015 51543.790 0.001 I
1999-10-26 RV Tri GSC 2321-1715 51477.7786 0.0001 I
1999-12-07 VV UMa GSC 3810-0988 51519.84743 0.00006 I
1999-04-28 AW UMa GSC 1984-0145 51296.829 0.003 II 4
1999-04-13 AGVir GSC 0871-0330 51281.8693 0.0006 I 5
1999-05-09 AGVir GSC 0871-0330 51307.8597 0.0005 II 5
1999-11-01 BUVul GSC 2182-0483 51483.71885 0.00005 I
Notes:
I =primary,II =seondary.
1 Ephemeris foridentifyingtypeofminimumis fromBush(1985).
2 Comparison star GSC 3556-3310 was later disovered to be NSV 12304. However, light urves
of omparison versus hek star (GSC 3556-3166) revealed no signiant variation over the 0.1
magnitude level that ould not be attributed (based on other data) to varying extintion from
louds.
3 Ephemeris foridentifyingtypeofminimumis fromKeskin&Pohl(1989).
4 Ephemeris foridentifyingtypeofminimumis fromPribullaetal.(1999).
Figure 1. Primaryminimumofthe1.36-daysemidetahed Algol-typebinaryZDraonis.
The light urve for ST Per is shown in Figure 2. Absorption by thin louds was less
than (oronstantto) 0.06 magnitudes.
The light urvefor VX Lais shown inFigure3. Herethe sky wasphotometriup to
JD 0.72;the absorptionby loudsinreasedby2magnitudesinthe intervalfromJD 0.72
toabout 0.74;itremained onstant(withutuations)thereafter. In solvingforthe time
of minimum, one of the methods was to tthe reeted (smooth) desending portion of
theurvetothenoisyasending partbyleastsquares; theJDofthe reetionaxisagreed
with mean of times of minimum obtained by other methodsto 0.0001 days.
Thisombinationofa61-mtelesopeandamoderatelypriedunlteredCCDamera
has yielded some good to exellent light urves around times of minima, some taken in
marginalonditions. With lessthan photometri skies,the method is learly superior to
single-hannel photometry (see Nelson, 1998) where no results would be possible at all.
In the aseof photometriskies, very auratetimesof minimum(toa preisionof afew
seonds)an and havebeen determined.
It is a pleasure to aknowledge the assistane of the AAVSO Elipsing Binary
Ephe-meris, (prepared eah year by Gerald Samolyk) whih greatly helped the author plan
observing sessions. Thanks are also due to Dr. Mihael Newberry who has developed
a ne CCD data redution and analysis tool in MIRA and has responded promptly to
problems and suggestions for improvement. The author is also a Guest User, Canadian
Astronomy Data Centre, whih is operated by the Dominion Astrophysial Observatory
for the National Researh Counilof Canada's Herzberg Institute of Astrophysis.
Referenes:
Bell, S.A., et al., 1990, MNRAS, 247, 632
Bush, H., 1985, IBVS,No. 2788
Henden, A.A., & Kaithuk, R.H., 1982, Astronomial Photometry, VanNostrand
Rein-hold: New York
Keskin, V. &Pohl, E., 1989,IBVS, No. 3355
Kwee,K.K., & vanWoerden, H.,1956, B.A.N., 12,(464), 327
Nelson, R.H., 1998,IBVS, No. 4621
Pribulla,T., Chohol, D., &Parimuha, S., 1999, IBVS, No.4751
ERRATUM FOR IBVS 4840
In IBVS4840,the orrettime ofminimum forAGVirshouldbe51281:82820:0006
(the originalvalue reported wasout by one hour).
