Multiyear photometry and orbit-resolved spectroscopy of the nova-like cataclysmic variable PG 1000+667 show behavior associated with the VY Sculptoris subclass of nova-like cataclysmic variables. Photometric observations over a 35 month interval from Indiana University\u27s robotic telescope Robo-Scope show two drops of 3 mag to a low state. Spectroscopy shows a periodic velocity variation in the HÎ² emission line with P = 3.47 hr. This places the star just above the 2-3 hour period gap, which supports the VY Sculptoris classification

Hillwig, T. C.

Honeycutt, R. K.

Robertson, Jeff W.

English

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Arkansas Tech University Online Research Commons @ ATU Faculty Publications - Physical Sciences Department of Physical Sciences 1-1-1998 Spectroscopic and Photometric Analysis of the Nova-Like Cataclysmic Variable PG 1000+667: A New VY Sculptoris Star T. C. Hillwig Jeff W. Robertson Arkansas Tech University R. K. Honeycutt Follow this and additional works at: https://orc.library.atu.edu/faculty_pub_phys  Part of the Physical Sciences and Mathematics Commons Recommended Citation Hillwig, T. C.; Robertson, Jeff W.; and Honeycutt, R. K., "Spectroscopic and Photometric Analysis of the Nova-Like Cataclysmic Variable PG 1000+667: A New VY Sculptoris Star" (1998). Faculty Publications - Physical Sciences. 16. https://orc.library.atu.edu/faculty_pub_phys/16 This Article is brought to you for free and open access by the Department of Physical Sciences at Online Research Commons @ ATU. It has been accepted for inclusion in Faculty Publications - Physical Sciences by an authorized administrator of Online Research Commons @ ATU. For more information, please contact cpark@atu.edu. THE ASTRONOMICAL JOURNAL, 115 :2044È2046, 1998 May1998. The American Astronomical Society. All rights reserved. Printed in U.S.A.(SPECTROSCOPIC AND PHOTOMETRIC ANALYSIS OF THE NOVA-LIKE CATACLYSMIC VARIABLEPG 1000]667 : A NEW VY SCULPTORIS START. C. J. W. AND R. K.HILLWIG, ROBERTSON,1 HONEYCUTTDepartment of Astronomy, Indiana University, Swain West 319, Bloomington, IN 47405 ;thillwig=astro.indiana.edu, psjr=atuvm.atu.edu, honey=astro.indiana.eduReceived 1998 January 22ABSTRACTMultiyear photometry and orbit-resolved spectroscopy of the nova-like cataclysmic variable PG1000]667 show behavior associated with the VY Sculptoris subclass of nova-like cataclysmic variables.Photometric observations over a 35 month interval from Indiana UniversityÏs robotic telescope Robo-Scope show two drops of 3 mag to a low state. Spectroscopy shows a periodic velocity variation in theHb emission line with P\ 3.47 hr. This places the star just above the 2È3 hour period gap, which sup-ports the VY Sculptoris classiÐcation.Key words : binaries : close È novae, cataclysmic variables È stars : individual (PG 1000]667)1. INTRODUCTIONThe nova-like cataclysmic variable (CV) PG 1000]667 isone of a number of poorly studied variables found in thePalomar-Green survey Schmidt, & Liebert A(Green, 1986).study by gives a preliminary period, but noRingwald (1993)mention is made of its photometric behavior. Spectroscopicand photometric observations are presented here and theresults of these observations discussed, including the deter-mination of a reÐned period.Nova-like CVs have a number of subclassiÐcations. Oneof these, the VY Sculptoris stars, exhibits high and low statebehavior in the long-term light curves, at times droppingseveral magnitudes into a low state for weeks, months, oreven years. These drops range from 1 to over 5 mag andshow no apparent periodicity. The VY Sculptoris starspopulate a fairly narrow region just above the 2È3 hr periodgap for CVs, from about 3 to 5 hr In the high(Warner 1995).state their spectra resemble nova-likes, and in their lowstate the spectra appear similar to detached binaries withsome chromospheric emission from the secondary starand references therein).(Warner 1995Of the 25 nova-like variables listed by Warner withorbital periods between 3 and 4 hr, 15 are classiÐed as VYSculptoris stars. Recent observations by &HoneycuttRobertson place V794 Aql in this period range as(1998)well, making 16 of these 26 nova-like variables VY Sculp-toris type stars. Therefore, the likelihood of an individualCV in the period range 3È4 hr with nova-like propertiesbeing of the VY Sculptoris type is high. Considering thepossibility that several of the 10 systems in this range notclassiÐed as VY Sculptoris stars are as yet not well studiedphotometrically, it is possible that others may belong to theVY Sculptoris subclass. In addition, some VY Sculptoristype stars have been seen to remain in either the high or thelow state for a long period of time. MV Lyr, for example,has been seen to remain in high or low state for as long as10 years Romano, & Marziani Therefore it(Rosino, 1993).is easily conceivable that some well-studied nova-like CVsmay be VY Sculptoris stars without such behavior havingyet been recorded.ÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈ1 Current address : Department of Physical Sciences, Arkansas TechUniversity, Russellville, AR 72801-2222.classiÐes PG 1000]667 as a nova-likeRingwald (1993)variable on the basis of his preliminary period of 4.06 hr andthe character of the spectrum, which shows narrow Ha andHb emission lines, no appearance of a red star, and a strongcontinuum. The data presented here agree with this identiÐ-cation and introduce an additional classiÐcation to the VYSculptoris subclass. The major support for this classi-Ðcation comes from photometric data and is supported bythe reÐned orbital period from time-resolved spectroscopy.2. OBSERVATIONS AND REDUCTIONSThe photometric data consist of V -band CCD photom-etry of PG 1000]667 obtained during the interval from1993 October to 1997 January with the Indiana AutomatedCCD Photometric Telescope, also known as RoboScopeet al. & Turner A total(Honeycutt 1990 ; Honeycutt 1992).of 210 usable 4 minute exposures were reduced byinhomogeneous-ensemble photometry (Honeycutt 1992)using 15 comparison stars. The errors range from D0.02mag, with good sky transparency and when the system isbright, to D0.15 mag when the system is faint and/or thesky is poor. The zero point is determined using four second-ary standard stars & Honeycutt(Henden 1997).The light curve for PG 1000]667 shows a 3 mag(Fig. 1)fall from 15th magnitude to a low state at V B 18 followedby an immediate rise back to the high state, as well as arecent fall back to an extended low state. The high state istypical of nova-like CVs, showing small variations with nooutbursts. The high-state/low-state behavior of VY Sculp-toris stars et al. is believed to be caused by(Robinson 1981)a decrease in mass transfer rate that is reÑected in diskluminosity. No other low states were noted in the 1400 dayscovered. The longest observing window without coverage isabout half of the D200 day duration of the initial low state.The average spacing of the data points is 4.7 days, excludingthe three seasonal gaps. Therefore, it is unlikely that otherlow states were missed.A total of 76 spectra of PG 1000]667 were obtained on1996 March 26È29 with the Hydra spectrographWIYN2using the blue Ðber cable and the Bench SpectrographÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈ2 The WIYN Observatory is a joint facility of the University ofWisconsinÈMadison, Indiana University, Yale University, and the Nation-al Optical Astronomy Observatories.2044PG 1000]667 2045FIG. 1.ÈPhotometry of PG 1000]667 over a 38 month intervalshowing two drops of 3 mag to a low state, as is typical of VY Sculptoristype stars. Downward-pointing arrows indicate limiting magnitudes. Theinset shows nights on which spectra were taken (dashed lines).Camera. An 860 line mm~1 grating with a blaze angle30¡.9was used. The central wavelength was 4600 covering theA ,range 4288È4901 with 0.7 resolution. shows aA A Figure 2representative spectrum and a mean spectrum. The meanspectrum is an average of all 76 individual spectra, eachcorrected for orbital motion. As is the case with some nova-like CVs Schlegel, & Kaitchuck(Honeycutt, 1986 ; Szkody& Piche there is no double-peaked structure appar-1990),ent in either the Hb or Hc emission lines in the mean spec-trum. Neither do the individual spectra show signiÐcantdouble-peaked structure.The Hb emission line of each spectrum was Ðtted with aGaussian proÐle of variable width and height to determinethe line center, and a radial velocity curve was constructed.FIG. 2.ÈA single and an average (with orbital variations removed)spectrum of PG 1000]667 showing strong Hb and weak Hc emissionlines.The heliocentric radial velocities obtained are listed inThe periodogram was produced using theTable 1. (Fig. 3)technique of as modiÐed by &Scargle (1982) HorneBaliunas The major peak occurs at a period of(1986).D3.47 hr. The Hc emission line in the individual spectra(see had a signal-to-noise ratio too low to yieldFig. 2)accurate results. The mean FWHM of the Hb line was490 ^ 10 km s~1.To obtain a better result for the period, the radial velocitydata were Ðtted with a sine curve of the formvr\ c] K1 sin [2n(T [ T0)/P] ,with the above period used as the initial value. This yieldedP\ 3.465^ 0.003 hr and a velocity semiamplitude ofTABLE 1Hb EMISSION-LINE HELIOCENTRIC RADIAL VELOCITIES FOR PG 1000]667vrvrvrvrHJD (km s~1) HJD (km s~1) HJD (km s~1) HJD (km s~1)2,450,169.7123 . . . . . . [169 2,450,169.8570 . . . . . . [123 2,450,170.8793 . . . . . . [120 2,450,172.7961 . . . . . . [22,450,169.7202 . . . . . . [109 2,450,169.8642 . . . . . . [151 2,450,170.8865 . . . . . . [59 2,450,172.8037 . . . . . . 322,450,169.7274 . . . . . . [126 2,450,169.8714 . . . . . . [170 2,450,170.8941 . . . . . . [83 2,450,172.8109 . . . . . . 92,450,169.7346 . . . . . . [112 2,450,169.8787 . . . . . . [120 2,450,170.9013 . . . . . . [45 2,450,172.8182 . . . . . . 422,450,169.7476 . . . . . . [25 2,450,169.8859 . . . . . . [66 2,450,170.9086 . . . . . . [28 2,450,172.8254 . . . . . . [132,450,169.7548 . . . . . . [8 2,450,170.7675 . . . . . . [11 2,450,170.9158 . . . . . . [13 2,450,172.8326 . . . . . . [202,450,169.7621 . . . . . . [16 2,450,170.7772 . . . . . . 23 2,450,170.9230 . . . . . . 27 2,450,172.8402 . . . . . . [522,450,169.7693 . . . . . . 4 2,450,170.7844 . . . . . . 42 2,450,171.7516 . . . . . . [108 2,450,172.8474 . . . . . . [752,450,169.7765 . . . . . . 17 2,450,170.7916 . . . . . . 52 2,450,171.7589 . . . . . . [90 2,450,172.8547 . . . . . . [972,450,169.7840 . . . . . . [5 2,450,170.7989 . . . . . . 2 2,450,171.7661 . . . . . . [85 2,450,172.8619 . . . . . . [922,450,169.7912 . . . . . . 25 2,450,170.8061 . . . . . . [3 2,450,172.7304 . . . . . . [136 2,450,172.8691 . . . . . . [892,450,169.7984 . . . . . . [10 2,450,170.8157 . . . . . . [69 2,450,172.7377 . . . . . . [115 2,450,172.8768 . . . . . . [1152,450,169.8057 . . . . . . [63 2,450,170.8230 . . . . . . [27 2,450,172.7449 . . . . . . [158 2,450,172.8840 . . . . . . [1372,450,169.8129 . . . . . . [46 2,450,170.8302 . . . . . . [84 2,450,172.7521 . . . . . . [175 2,450,172.8913 . . . . . . [1002,450,169.8206 . . . . . . [84 2,450,170.8374 . . . . . . [43 2,450,172.7594 . . . . . . [147 2,450,172.8985 . . . . . . [1202,450,169.8278 . . . . . . [93 2,450,170.8446 . . . . . . [112 2,450,172.7672 . . . . . . [109 2,450,172.9057 . . . . . . [1182,450,169.8350 . . . . . . [110 2,450,170.8576 . . . . . . [139 2,450,172.7744 . . . . . . [69 2,450,172.9146 . . . . . . [662,450,169.8423 . . . . . . [111 2,450,170.8649 . . . . . . [146 2,450,172.7816 . . . . . . [37 2,450,172.9218 . . . . . . [1132,450,169.8495 . . . . . . [145 2,450,170.8721 . . . . . . [111 2,450,172.7889 . . . . . . [13 2,450,172.9290 . . . . . . 332046 HILLWIG, ROBERTSON, & HONEYCUTTFIG. 3.ÈPeriodogram for the radial velocity data, with major peak at aperiod of D3.47 hr.K \ 80 ^ 4 km s~1. The sine Ðt to the folded data is shownin The ephemeris isFigure 4.HJD 2,450,169.8164^ 0.0017] (0.144384^ 0.00012)E ,where E is the number of phase cycles and phase zero corre-sponds to inferior conjunction of the secondary.The peaks in with the next highest powersFigure 3(which occurred at PD 0.169 and 0.126 days) yield s2values 1030 and 850 times larger, respectively, than the0.144 day peak. The folded data also highly favor themaximum power peak described above as the true orbitalperiod.The light curve of was folded on the orbitalFigure 1period above, with low-state data omitted. No structureFIG. 4.ÈPhase-folded radial velocity data for PG 1000]667was seen in the folded light curve apart from typical randomD0.5 mag Ñickering.3. SUMMARYconcluded that PG 1000]667 was aRingwald (1993)nova-like CV with a preliminary spectroscopic period of4.06 hr, just above the 2È3 hr period gap. We support hisnova-like classiÐcation and add PG 1000]667 to the list ofVY Sculptoris stars that occupy the 3È4 hr period range. Inaddition, a reÐned period of 3.465 ^ 0.003 hr has beenderived.This work was made possible through an NSF grant toIndiana University.REFERENCESR. F., Schmidt, M., & Liebert, J. 1986, ApJS, 61,Green, 305A. A., & Honeycutt, R. K. 1997, PASP, 109,Henden, 441R. K. 1992, PASP, 104,Honeycutt, 435R. K., & Robertson, J. W. 1998, AJ,Honeycutt, submittedR. K., Schlegel, E. M., & Kaitchuck, R. H. 1986, ApJ, 302,Honeycutt, 388R. K., & Turner, G. W. 1992, in ASP Conf. Ser. 34, RoboticHoneycutt,Telescopes in the 1990s, ed. A. V. Filippenko (San Francisco : ASP), 77R. K., Vesper, D., White, J., Turner, G. W., & Adams, B. 1990,Honeycutt,in CCDs in Astronomy II, ed. A. G. D. Philip, D. S. Hayes, & S. J.Adelman (Schenectady : L. Davis), 177J. H., & Baliunas, S. L. 1986, ApJ, 302,Horne, 757F. A. 1993, Ph.D. thesis, DartmouthRingwald, Coll.E. L., Barker, E. S., Cochran, A. L., Cochran, W. D., & Nather,Robinson,R. E. 1981, ApJ, 251, 611L., Romano, G., & Marziani, P. 1993, PASP, 105,Rosino, 51J. D. 1982, ApJ, 263,Scargle, 835P., & Piche , F. 1990, ApJ, 361,Szkody, 235B. 1995, Cataclysmic Variable Stars (Cambridge : CambridgeWarner,Univ. Press), chap. 4

Spectroscopic and Photometric Analysis of the Nova-Like Cataclysmic Variable PG 1000+667: A New VY Sculptoris Star

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Spectroscopic and Photometric Analysis of the Nova-Like Cataclysmic Variable PG 1000+667: A New VY Sculptoris Star

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