FIRST DETERMINATION OF ABSOLUTE MAGNITUDES FOR RED CLUMP STARS WITH WISE PHOTOMETRY

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1 Dig Sites of Stellar Archeology: Giant Stars in the Milky Way Ege Uni. J. of Faculty of Sci., Special Issue, 2014, FIRST DETERMINATION OF ABSOLUTE MAGNITUDES FOR RED CLUMP STARS WITH WISE PHOTOMETRY Yaz Gökçe, E. 1, *, Bilir, S. 1, Öztürkmen, N. D 1, Duran, Ş. 1, Ak, T. 1, Ak, S. 1, Karaali, S. 1 1 Istanbul University, Faculty of Science, Department of Astronomy and Space Sciences, University, Istanbul, Tūrkiye Abstract: We present the first identification of absolute magnitudes for red clump (RC) stars with the Wide-field Infrared Survey Explorer (WISE) in the solar neighbourhood. The absolute magnitude of the RC stars is important due to use as a standard candle. We used the recent reduced Hipparcos parallaxes for determining distances and identified 3889 RC stars with WISE. We obtained mode values of the absolute magnitudes and colour index which are M W1 =-1.635±0.026, M W3 =-1.606±0.024 and (W1- W3) 0 =-0.028±0.001 mag. Mode values of M W1 and M W3 absolute magnitudes were tested by distance values which are determined by two different methods: a) using transformation equations from 2MASS to WISE data, b) using recent spectrophotometric data. Furthermore, the modes of 2MASS absolute magnitudes and colours of the RC stars are found to be M J = ±0.016, M H = ±0.014, M Ks = ±0.025, (J-H) 0 = 0.485±0.002, (H-K s ) 0 = 0.130±0.002 and (H-K s ) 0 = 0.612±0.003 mag. The values in this study are consistent with others in the literature. Keywords: distances; red clump; Solar neighbourhood 1. INTRODUCTION The RC stars occupy a very small region in the WISE colour-magnitude diagrams of the stars in the Solar neighbourhood and open clusters ([1], [2]). as expected from the general properties of these stars in other photometric systems. One of the most important features of the RC stars is their very limited luminosity distribution in all photometric systems. This suggests that they can be used as standard candles for estimating astronomical distances both in Galactic and extra-galactic scales. Thus RCs are useful tools to determine the distances using mean absolute magnitudes [3], [4], [5], [6], [7], [8]. * Corresponding Author: Tel: Fax: esmayaz@istanbul.edu.tr 12

2 2. DATA We used the newly-reduced Hipparcos catalogue [5] as the main sample for calculating precise distances of stars in the Solar neighbourhood. We collected 2MASS (Two Micron All-Sky Survey, [9]) and WISE (Wide-field Infrared Survey Explorer, [10]) data of the Hipparcos stars. The number of matched stars is The Hipparcos parallaxes include systematic biases [11]. We corrected the trigonometric parallaxes of stars using the method in [12]. Our sample was limited with 0 < σ π /π 0.15 relative parallax error to obtain more accurate absolute magnitudes. The colours and magnitudes were reduced by using [13] E(B-V) colour excess as described in [14]. WISE and 2MASS photometric magnitudes and colours of the stars were dereddened using the reduced colour E d (B-V) ([15], [16], [17], [18]). The E d (B-V) median value is 0.03 mag. 3. IDENTIFICATION OF RC STARS FOR WISE AND 2MASS We plotted colour- magnitude diagrams for 2MASS and WISE to identify RC stars by an eye inspection (Fig.1 and Fig.2, left panel) and determined the borders and modes for them using Gaussian distributions of colour and absolute magnitudes (Fig.3). We also checked the locations of WISE RCs by assigning the same borders of 2MASS data in order to see if they overlap (Fig.2, right panel). Firstly, we compared our values (Table 1, second column) to calculate the absolute magnitudes using transformation equations for 2MASS to WISE data in [16] (Table 1, third column). Differences of mode values between second and third columns are 0, 0.070, mag for both methods, respectively. Secondly, we compared the distances that were obtained by the mode values of M W1 and M W3, to spectrophotometric distances of 222 RC stars [19] (Fig.4). Solid lines, dashed lines and red plus signs represent the one-to-one lines, 1σ limits (69% of the sample) and error bars, respectively. In the bottom panels of Fig. 4, the distributions of residuals are shown. The mean of the differences between both distances and their standard deviations are <Δd> = 9.2 pc and σ =3 0.8 pc for Fig. 4a and <Δd> = 9.6 pc and σ = 30.7 pc for Fig. 4c. It is clear in the figure that the distances of [18] and ours for WISE are compatible. 13

3 E. YAZ GÖKÇE et al. / Ege Uni. J. of Faculty of Sci., Special Issue, 2014, Figure 1. MKs - (J - Ks)0 absolute magnitude- colour diagram. Mode Values WISE Value from TE Mode Values for 2MASS MW ± ±0.024 MJ ±0.016 MW ± ±0.028 MH ±0.014 (W1-W3) ± ±0.037 MKs ±0.025 (J-H) ±0.002 (H-Ks) ±0.002 (J- Ks) ±0.003 Table 1. Modes for WISE (second column) and 2MASS (last column). Values calculated from the transformation equation are given in the third column. 14

4 E. YAZ GÖKÇE et al. / Ege Uni. J. of Faculty of Sci., Special Issue, 2014, Figure 2. MW1 - (W1 - W3)0 absolute magnitude- colour diagrams for stars (left). Figure 3. Gaussian distributions of colour and magnitudes for the WISE photometry. 15

5 Figure 4. Comparison of distances from [18] and our distances determined from our mode values for 222 RC stars. 4. CONCLUSIONS The 2MASS absolute magnitudes and colours of RC stars are estimated and these values found compatible with the similar studies. The values of WISE absolute magnitudes and a colour of the RC stars are estimated for the solar neighbourhood. Also, there is a good agreement between the absolute magnitudes and the both methods (Saguner s distances and Bilir s transformation equation) which are stated in Section 3. Our results represent the first determinations of absolute magnitudes and a colour for RC stars in WISE. ACKNOWLEDGMENT This work has been supported in part by the Scientific and Technological Research Council (TÜBİTAK) 112T120. This research has made use of the WISE, 2MASS, NASA/IPAC Infrared Science Archive ( and the NED (NASA/IPAC Extragalactic Database, and the SIMBAD, and NASA s Astrophysics Data System Bibliographic Services. 16

6 REFERENCES [1] R.D. Cannon, Red giants in old open clusters, Mon. Not. Roy. Astron. Soc., vol. 150, pp. 111, [2] D.J. Faulkner, R.D. Cannon, Models of population I clump giants, Astroph. J., vol. 180, pp. 435, [3] P.C. Keenan, C. Barnbaum, Revision and calibration of MK luminosity classes for cool giants by HIPPARCOS parallaxes, Astroph. J., vol. 518, pp. 859, [4] D.R. Alves, K-band calibration of the red clump luminosity, Astroph. J., vol. 539, pp. 732, [5] F. van Leeuwen, Validation of the new Hipparcos reduction, Astron. And Astroph., vol. 474, pp. 653, [6] M.A.T. Groenewegen, The red clump absolute magnitude based on revised Hipparcos parallaxes, Astron. And Astroph., vol. 488, pp. 935, [7] C.D. Laney, M.D. Joner, G. Pietrzynski, A new large Magellanic Cloud K-band distance from precision measurements of nearby red clump stars, Mon. Not. Roy. Astron. Soc., vol. 419, pp. 1637, [8] S. Bilir, Ö. Önal, S. Karaali, A. Cabrera-Lavers, H. Çakmak, Luminosity-colour relations for red clump stars, Astroph. and Space Sci., vol. 344, pp. 417, [9] R.M.,Cutri, et al., 2MASS all-sky catalog of point sources, VizieR Online Data Catalog, 2246, 0, [10] R.M. Cutri, et al., WISE all-sky data release, VizieR Online Data Catalog, 2311, 0, [11] T.E. Lutz, D.H. Kelker, On the use of trigonometric parallaxes for the calibration of luminosity systems: theory, PASP, vol. 85, pp. 573, [12] Jr.H. Smith, The calibration problem. IV - The Lutz-Kelker correction, Astron. And Astroph., vol. 188, pp. 233, [13] D.J. Schlegel, D.P. Finkbeiner, M. Davis, Maps of dust infrared emission for use in estimation of reddening and cosmic microwave background radiation foregrounds, Astroph. J., vol. 500, pp. 525, [14] S. Bilir, Ö. Önal, S. Karaali, A. Cabrera-Lavers, H. Çakmak, Luminosity-colour relations for red clump stars, Astroph. and Space Sci., vol. 344, pp. 417, [15] M. Fiorucci, U. Munari, The Asiago Database on Photometric Systems (ADPS). II. Band and reddening parameters, Astron. And Astroph., vol. 401, pp.781,

7 [16] S. Bilir, S. Karaali, S. Ak, E. Yaz, A. Cabrera-Lavers, K.B. Coşkunoğlu, Luminositycolour relations for thin-disc main-sequence stars, Mon. Not. Roy. Astron. Soc., vol. 390, pp. 1569, [17] S. Bilir, S. Karaali, S. Ak, N.D. Dağtekin, Ö. Önal, E. Yaz, B. Coşkunoğlu, A. Cabrera- Lavers, Transformations between the WISE, 2MASS, SDSS and BVRI photometric systems - I. Transformation equations for dwarfs, Mon. Not. Roy. Astron. Soc., vol. 417, pp. 2230, [18] S. Bilir, S. Karaali, N.D. Dağtekin, Ö. Önal, S. Ak, T. Ak, A. Cabrera-Lavers, Transformations from WISE to 2MASS, SDSS and BVI photometric systems: II. Transformation equations for red-clump stars, Publ. Astron. Soc. Aus., vol. 29, pp. 121, [19] T. Saguner, U. Munari, M. Fiorucci, A. Vallenari, A spectroscopic survey of faint, high-galactic-latitude red clump stars. II. The medium resolution sample, Astron. And Astroph., vol. 527, pp. 40,

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