Alis, S.

Esenoglu, H. H.

Fisek, S.

Saygac, A. T.

Information Bulletin on Variable Stars

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COMMISSIONS G1 AND G4 OF THE IAUINFORMATION BULLETIN ON VARIABLE STARSVolume 63 Number 6214 DOI: 10.22444/IBVS.6214Konkoly ObservatoryBudapest05 September 2017HU ISSN 0374 – 0676DISCOVERY OF A NEW δ SCUTI VARIABLEIN THE FIELD OF RW UMiALIS, S.1,2; SAYGAC, A. T.1,2; FISEK, S.1; ESENOGLU, H. H.1,21 Istanbul University, Department of Astronomy and Space Sciences, 34119 Beyazit, Istanbul, Turkeye-mail: salis@istanbul.edu.tr2 Istanbul University Observatory Research and Application Centre, 34119 Beyazit, Istanbul, TurkeyDuring observations of the old nova RW UMi a new variable has been identified inthe same field. RW UMi, new variable, and comparison stars are marked in the findingchart given in Fig. 1. Variability of this star noticed as it was being used as a comparisonstar of RW UMi. Light curves that can be seen in Fig. 2, reveal that the new star is ashort-period pulsator, likely a δ Scuti star.Figure 1. Identification chart of the field. New variable, RW UMi and comparison stars are marked.RW UMi has been observed several nights since August 2015 with the 1.5m RTT150telescope of the TUBITAK National Observatory (aka. TUG) (Antalya, Turkey) andTFOSC imaging spectrograph attached to the telescope’s Cassegrainian focus. TFOSChas a 2k×2k Fairchild 447 back-illuminated chip with a pixel size of 15 microns. Inorder to increase temporal resolution, the field was observed in the sub-frame mode whichyields an effective area of 1040×200 pixels. Processing of frames led to an identificationof a new variable. Five out of 13 nights observations could be used to construct thelight curves of the new variable. This is due to overexposure for the variable as theprogram object RW UMi is very faint (i ≃ 19 mag). All the data were reduced instandard way using appropriate IRAF1 packages. Photometry of objects was performedwith aperture photometry. Differential magnitudes of the new variable were computed1Image Reduction and Analysis Facility, http://iraf.noao.edu2 IBVS 6214against the comparison star C1. Other comparison stars were used to check C1 and werenot found any variability for all observing runs. Light curves of the variable are given inFig. 2.Table 1. Log of observations.Date JD Interval Duration Number Filter Exposure Time2457000+ (hours) of Frames (seconds)07.08.2015 242.2814 − 242.5742 7.02 245 Clear 4018.09.2015 284.3248 − 284.4500 3.00 235 Clear 3019.09.2015 285.3157 − 285.3818 1.59 82 Clear 6010.09.2016 642.3663 − 642.5736 4.98 64 Clear 4502.06.2017 907.3219 − 907.4308 2.61 155 Clear 45Figure 2. Light curves of the new variable. Differential magnitudes are computed using comparisonstar C1.New variable has no record in the SIMBAD Astronomical Database or in GeneralCatalogue of Variable Stars, either. However, the object is detected in the Sloan Dig-ital Sky Survey with i-band magnitude i = 14.55. Coordinates of the new variableIBVS 6214 3taken from SDSS are α = 16h48m8.s23 (J2000) and δ = +76◦58′02.′′53 (J2000) (SDSSJ164808.23+765802.5).In order to perform a Fourier analysis, all available data given in Table 1 are combined.Fourier analysis performed with Period04 (Lenz & Breger, 2005) revealed a frequency of7.62731 c/d which corresponds a period of 0.131 d (3.147 h). Power spectrum of theFourier transformation is given in Figure 3. Light curves of the first two runs are plottedwith the resulting model in Figure 4.Figure 3. Power spectrum of the Fourier transformation.Figure 4. Model curves overplotted on light curves of the 07.08.2015 (left) and 18.09.2015 (right) runs.4 IBVS 6214Based on the SDSS ugriz magnitudes, B − V colour of the new variable is computedusing Karaali, Bilir and Tuncel (2005) transformation equations which then yielded acolour index of B − V = 0.62. This colour index implies an effective temperature of Teff= 5800 K (Ramirez & Melendez, 2005). Thus, period determined from Fourier analysisand effective temperature indicate that this new variable is most probably a δ Scuti-typepulsating star.Acknowledgements: We thank to TUBITAK for a partial support in using RTT150(Russian-Turkish 1.5m telescope in Antalya) with project numbers 15BRTT150-864 and17AT100-1174.References:Karaali, S., Bilir, S., Tuncel, S., 2005, PASA, 22, 24 DOILenz, P. and Breger M., 2005, CoAst, 146, 53 DOIRamirez, I. and Melendez, J., 2005, ApJ, 626, 446 DOI

Discovery of a New delta Scuti Variable  in the Field of RW UMi

S. Alis

A. T. Saygac

S. Fisek

H. H. Esenoglu

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Discovery of a New {delta} Scuti Variable in the Field of RW UMi

ALİŞ, Sinan

ESENOĞLU, Hasan Hüseyin

SAYGAÇ, Ahmet Talat

FİŞEK, Süleyman

İstanbul Üniversitesi Açık Erişim Sistemi

Discovery of a new δ scuti variable in the field of RW UMi

https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85033392701&origin=inward

Discovery of a New delta Scuti Variable in the Field of RW UMi

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İstanbul Üniversitesi Açık Erişim Sistemi