Journal of The Korean Astronomical Society (천문학회지)

The Korean Astronomical Society (한국천문학회)
권호 표지
DOI QR코드

DOI QR Code

SEARCH FOR EXOPLANETS AROUND NORTHERN CIRCUMPOLAR STARS III. LONG-PERIOD RADIAL VELOCITY VARIATIONS IN HD 18438 AND HD 158996

  • Bang, Tae-Yang (Department of Astronomy and Atmospheric Sciences, Kyungpook National University) ;
  • Lee, Byeong-Cheol (Korea Astronomy and Space Science Institute) ;
  • Jeong, Gwang-Hui (Korea Astronomy and Space Science Institute) ;
  • Han, Inwoo (Korea Astronomy and Space Science Institute) ;
  • Park, Myeong-Gu (Department of Astronomy and Atmospheric Sciences, Kyungpook National University)
  • Received : 2017.06.26
  • Accepted : 2018.02.06
  • Published : 2018.02.28
Download PDF
⟨ Previous Next ⟩

Abstract

Detecting exoplanets around giant stars sheds light on the later-stage evolution of planetary systems. We observed the M giant HD 18438 and the K giant HD 158996 as part of a Search for Exoplanets around Northern circumpolar Stars (SENS) and obtained 38 and 24 spectra from 2010 to 2017 using the high-resolution Bohyunsan Observatory Echelle Spectrograph (BOES) at the 1.8m telescope of Bohyunsan Optical Astronomy Observatory in Korea. We obtained precise RV measurements from the spectra and found long-period radial velocity (RV) variations with period 719.0 days for HD 18438 and 820.2 days for HD 158996. We checked the chromospheric activities using Ca $\text\tiny{II}$ H and $H{\alpha}$ lines, HIPPARCOS photometry and line bisectors to identify the origin of the observed RV variations. In the case of HD 18438, we conclude that the observed RV variations with period 719.0 days are likely to be caused by the pulsations because the periods of HIPPARCOS photometric and $H{\alpha}$ EW variations for HD 18438 are similar to that of RV variations in Lomb-Scargle periodogram, and there are no correlations between bisectors and RV measurements. In the case of HD 158996, on the other hand, we did not find any similarity in the respective periodograms nor any correlation between RV variations and line bisector variations. In addition, the probability that the real rotational period can be as longer than the RV period for HD 158996 is only about 4.3%. Thus we conclude that observed RV variations with a period of 820.2 days of HD 158996 are caused by a planetary companion, which has the minimum mass of 14.0 $M_{Jup}$, the semi-major axis of 2.1 AU, and eccentricity of 0.13 assuming the stellar mass of $1.8 M_{\odot}$. HD 158996 is so far one of the brightest and largest stars to harbor an exoplanet candidate.

Keywords

References

  1. Anderson, E., & Francis, C. 2012, XHIP: An extended hipparcos compilation, Astronomy Letters, 38, 331 https://doi.org/10.1134/S1063773712050015
  2. Baliunas, S. L., Donahue, R. A., Soon, W. H., Horne, J. H., Frazer, J., Woodard-Eklund, L., Bradford, M., Rao, L. M., Wilson, O. C., Zhang, Q., Bennett, W., Briggs, J., Carroll, S. M., Duncan, D. K., Figueroa, D., Lanning, H. H., Misch, T., Mueller, J., Noyes, R. W., Poppe, D., Porter, A. C., Robinson, C. R., Russell, J., Shelton, J. C., Soyumer, T., Vaughan, A. H., & Whitney, J. H. 1995, Chromospheric Variations in Main-Sequence Stars, ApJ, 438, 269 https://doi.org/10.1086/175072
  3. da Silva, L., Girardi, L., Pasquini, L., Setiawan, J., von der Lhe, O., de Medeiros, J. R., Hatzes, A., Dllinger, M. P., & Weiss, A. 2006, Basic Physical Parameters of a Selected Sample Of Evolved Stars, A&A, 458, 609 https://doi.org/10.1051/0004-6361:20065105
  4. de Medeiros, J. R., & Mayor, M. 1999, A Catalog of Rotational and Radial Velocities for Evolved Stars, A&AS, 139, 433 https://doi.org/10.1051/aas:1999401
  5. Dollinger, M. P., Hatzes, A. P., Pasquini, L., Guenther, E. W., Hartmann, M., Girardi, L., & Esposito, M. 2007, Discovery of a Planet around the K Giant Star 4 Ursae Majoris, A&A, 472, 649 https://doi.org/10.1051/0004-6361:20066987
  6. Eberhard, G., & Schwarzschild, K. 1913, On the Reversal of the Calcium Lines H and K in Stellar Spectra, ApJ, 38, 292
  7. ESA. 1997, VizieR Online Data Catalog: The Hipparcos and Tycho Catalogues (ESA 1997), VizieR Online Data Catalog, 1239, 0
  8. Fressin, F., Torres, G., Charbonneau, D., Bryson, S. T., Christiansen, J., Dressing, C. D., Jenkins, J. M., Walkowicz, L. M., & Batalha, N. M. 2013, The False Positive Rate of Kepler and the Occurrence of Planets, ApJ, 766, 81 https://doi.org/10.1088/0004-637X/766/2/81
  9. Frink, S., Mitchell, D. S., Quirrenbach, A., Fischer, Debra A., Marcy, Geoffrey W., & Butler, R. P. 2002, Discovery of a Substellar Companion to the K2 III Giant Draconis, ApJ, 576, 478 https://doi.org/10.1086/341629
  10. Gaia collaboration (Brown, A. G. A., et al.), 2016, Gaia Data Release 1. Summary of the Astrometric, Photometric, and Survey Properties, A&A, 595, A2 https://doi.org/10.1051/0004-6361/201629512
  11. Galazutdinov, G. A. 1992, Echelle Spectra Processing Program Package, Special Astrophysical Observatory Preprint 92 (Nizhnij Arkhyz: SAO)
  12. Gontcharov, G. A. 2006, Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos Stars in a Common System, ASTL, 32, 759
  13. Han, I., Kim, K.-M., Lee, B.-C., & Valyavin, G. 2007, Development of RVI2CELL - A Precise Radial Velocity Estimation Program with BOES Data, PKAS, 22, 75
  14. Han, I., Lee, B. C., Kim, K. M., Mkrtichian, D. E., Hatzes, A. P., & Valyavin, G. 2010, Detection of a Planetary Companion around the Giant Star y1 Leonis, A&A, 509, A24 https://doi.org/10.1051/0004-6361/200912536
  15. Hatzes, A. P., Cochran, W. D., & Bakker, E. J. 1998, Further Evidence for the Planet around 51 Pegasi, Nature, 391, 154 https://doi.org/10.1038/34369
  16. Hatzes, A. P., Guenther, E. W., Endl, M., Cochran, W. D., Dollinger, M. P., & Bedalov, A. 2005, A Giant Planet around the Massive Giant Star HD 13189, A&A, 437, 743 https://doi.org/10.1051/0004-6361:20052850
  17. Hatzes, A. P., Cochran, W. D., Endl, M., Guenther, E. W., MacQueen, P., Hartmann, M., Zechmeister, M., Han, I., Lee, B.-C., Walker, G. A. H., Yang, S., Larson, A. M.,, Kim, K.-M., Mkrtichian, , D. E., Dollinger, M., Simon, A. E., & Girardi, L. 2015, Long-Lived, Long-Period Radial Velocity Variations in Aldebaran: A Planetary Companion and Stellar Activity, A&A, 580, A31 https://doi.org/10.1051/0004-6361/201425519
  18. Howard, A. W. Marcy, G. W., Bryson, S. T., et al. 2012, Planet Occurrence within 0.25 AU of Solar-Type Stars from Kepler, ApJS, 201, 15 https://doi.org/10.1088/0067-0049/201/2/15
  19. Johnson, J. A., Butler, R. P., Marcy, G. W., Fischer, D. A., Vogt, S. S., Wright, J. T., & Peek, K. M. G. 2007, A New Planet around an M Dwarf: Revealing a Correlation between Exoplanets and Stellar Mass, ApJ, 670, 833 https://doi.org/10.1086/521720
  20. Kim, K.-M., Han, I., Valyavin, G. G., Plachinda, S., Jang, Jang, J.-G., Seong, B.-Ho., Lee, H.-C., Lee, B.-C. Kang, D.-I., Park, B.-G., Yoon, T.-S., & Vogt, Steven S. 2007, The BOES Spectropolarimeter for Zeeman Measurements of Stellar Magnetic Fields, PASP, 119, 1052 https://doi.org/10.1086/521959
  21. Kraus, A. L., Ireland, M. J., Martinache, F., & Lloyd, J. P. 2008, Mapping the Shores of the Brown Dwarf Desert. I. Upper Scorpius, ApJ, 679, 762 https://doi.org/10.1086/587435
  22. Kurster, M., Endl, M., Rouesnel, F., Els, S., Kaufer, A., Brillant, S., Hatzes, A. P., Saar, S. H., & Cochran, W. D. 2003, The Low-Level Radial Velocity Variability in Barnard's Star (= GJ 699). Secular Acceleration, Indications for Convective Redshift, and Planet Mass Limits, A&A, 403, 1077 https://doi.org/10.1051/0004-6361:20030396
  23. Lee, B.-C., Han, I., Park, M.-G., & Mkrtichian, D. E. 2012, Detection of the 128-Day Radial Velocity Variations in the Supergiant Persei. Rotational Modulations, Pulsations, or a Planet?, A&A, 543, A37 https://doi.org/10.1051/0004-6361/201118539
  24. Lee, B.-C., Park, M.-G., Lee, S.-M., Jeong, G., Oh, H.-I., Han, I., Lee, J. W., Lee, C.-U., Kim, S.-L., & Kim, K.-M. 2015, Search for Exoplanet around Northern Circumpolar Stars. Four Planets around HD 11755, HD 12648, HD 24064, and 8 Ursae Minoris, A&A, 584, A79
  25. Lee, B.-C., Jeong, G., Park, M.-G., Han, I., Mkrtichian, D. E., Hatzes, A. P., Gu, S.-H., Bai, J.-M., Lee, S.-M., Oh, H.-I., & Kim, L.-M., 2017, Search for Exoplanets around Northern Circumpolar Stars. II. The Detection of Radial Velocity Variations in M Giant Stars HD 36384, HD 52030, and HD 208742, ApJ, 844, 36 https://doi.org/10.3847/1538-4357/aa7577
  26. McDonald, I., Zijlstra, A. A., & Boyer, M. L. 2012, Fundamental Parameters and Infrared Excesses of Hipparcos Stars, MNRAS, 427, 343 https://doi.org/10.1111/j.1365-2966.2012.21873.x
  27. Massarotti, A., Latham, D. W., Stefanik, R. P., & Fogel, J. 2008, Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity, AJ, 135, 209 https://doi.org/10.1088/0004-6256/135/1/209
  28. Mayor, M., & Queloz, D. 2014, A Jupiter-Mass Companion to a Solar-Type Star, Nature, 378, 355
  29. Meschiari, S., Wolf, A. S., Rivera, E., Laughlin, G., Vogt, S., & Butler, P. 2009, Systemic: A Testbed for Characterizing the Detection of Extrasolar Planets. I. The Systemic Console Package, PASP, 121, 1016 https://doi.org/10.1086/605730
  30. Montes, D., de Castro, E., Fernandez-Figueroa, M. J., & Cornide, M. 1995, Application of the Spectral Subtraction Technique to the Ca ii H & K and H Lines in a Sample of Chromospherically Active Binaries, A&AS, 114, 287
  31. Mustil, A. 2014, The Stability of Multiplanet Systems on the Main Sequence and Post-Main Sequence, Habitable Worlds Across Time and Space, Proceedings of a Conference Held April 28 - May 1, 2014 at the Space Telescope Science Institute, id.35
  32. Queloz, D., Henry, G. W., Sivan, J. P., Baliunas, S. L., Beuzit, J. L., Donahue, R. A., Mayor, M., Naef, D., Perrier, C., & Udry, S. 2001, No Planet for HD 166435, A&A, 379, 279 https://doi.org/10.1051/0004-6361:20011308
  33. Sato, B., Izumiura, H., Toyota, E., Kambe, E., Takeda, Y., Masuda, S., Omiya, M., Murata, D., Itoh, Y., Ando, H., Yoshida, M., Ikoma, M., Kokubo, E., & Ida, S., 2007, A Planetary Companion to the Hyades Giant Tauri, ApJ, 661, 527 https://doi.org/10.1086/513503
  34. Sato, B., Omiya, M., Liu, Y., Harakawa, H., Izumiura, H., Kambe, E., Toyota, E., Murata, D., Lee, B.-C., Masuda, S., Takeda, Y., Yoshida, M., Itoh, Y., Ando, H., Kokubo, E., Ida, S., Zhao, G., & Han, I. 2010, Substellar Companions to Evolved Intermediate-Mass Stars: HD 145457 and HD 180314, PASJ, 62, 1063 https://doi.org/10.1093/pasj/62.4.1063
  35. Scargle, J. D. 1982, Studies in Astronomical Time Series Analysis. II - Statistical Aspects of Spectral Analysis of Unevenly Spaced Data, ApJ, 263, 835 https://doi.org/10.1086/160554
  36. Takeda, Y., Ohkubo, M., Sato, B., Kambe, E., & Sadakane, K. 2005, Spectroscopic Study on the Atmospheric Parameters of Nearby F-K Dwarfs and Subgiants, PASJ, 57, 27 https://doi.org/10.1093/pasj/57.1.27
  37. Takeda, Y., Sato, B., & Murata, D. 2008, Stellar Parameters and Elemental Abundances of Late-G Giants, PASJ, 60, 781 https://doi.org/10.1093/pasj/60.4.781
  38. van Leeuwen, F. 2007, Validation of the New Hipparcos Reduction, A&A, 474, 653 https://doi.org/10.1051/0004-6361:20078357
  39. Villaver, E., & Livio, M. 2007, Can Planets Survive Stellar Evolution?, ApJ, 661, 1192 https://doi.org/10.1086/516746
  40. Wilson R. E. 1953, General Catalogue of Stellar Radial Velocities, Carnegie Institution of Washington
  41. Wood, P. R., Olivier, E. A., & Kawaler, S. D. 2004, Long Secondary Periods in Pulsating Asymptotic Giant Branch Stars: An Investigation of Their Origin, ApJ, 604, 800 https://doi.org/10.1086/382123