TW Hydrae: Evidence of stellar spots instead of a hot Jupiter

N. Huélamo, P. Figueira, X. Bonfils, N. C. Santos, F. Pepe, M. Gillon, R. Azevedo, Travis S Barman, M. Fernández, E. Di Folco, E. W. Guenther, C. Lovis, C. H F Melo, D. Queloz, S. Udry

Research output: Contribution to journalArticle

140 Citations (Scopus)

Abstract

Context. TW Hya is a classical T Tauri star that shows significant radial-velocity variations in the optical regime. These variations have been attributed to a 10 planet orbiting the star at 0.04 AU. Aims. The aim of this letter is to confirm the presence of the giant planet around TW Hya by (i) testing whether the observed RV variations can be caused by stellar spots and (ii) analyzing new optical and infrared data to detect the signal of the planet companion. Methods. We fitted the RV variations of TW Hya using a cool spot model. In addition, we obtained new high-resolution optical & infrared spectra, together with optical photometry of TW Hya and compared them with previous data. Results. Our model shows that a cold spot covering 7% of the stellar surface and located at a latitude of 54°can reproduce the reported RV variations. The model also predicts a bisector semi-amplitude variation < 10 m s-1, which is less than the errors of the RV measurements discussed in Setiawan et al. (2008, Nature, 451, 38). The analysis of our new optical RV data, with typical errors of 10 m s-1, shows a larger RV amplitude that varies depending on the correlation mask used. A slight correlation between the RV variation and the bisector is also observed although not at a very significant level. The infrared -band RV curve is almost flat, showing a small variation (<35 m s-1) that is not consistent with the published optical orbit. All these results support the spot scenario rather than the presence of a hot Jupiter. Finally, the photometric data shows a 20% (peak to peak) variability, which is much larger than the 4% variation expected for the modeled cool spot. The fact that the optical data are correlated with the surface of the cross-correlation function points towards hot spots as being responsible for the photometric variability. Conclusions. We conclude that the best explanation for the RV signal observed in TW Hya is the presence of a cool stellar spot and not an orbiting hot Jupiter.

Original languageEnglish (US)
JournalAstronomy and Astrophysics
Volume489
Issue number2
DOIs
StatePublished - Oct 2008
Externally publishedYes

Fingerprint

Jupiter (planet)
Jupiter
planet
planets
T Tauri stars
radial velocity
cross correlation
photometry
coverings
infrared spectra
masks
orbits
stars
high resolution
curves

Keywords

  • Stars: individual: TW Hya
  • Stars: planetary systems
  • Stars: pre-main sequence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Huélamo, N., Figueira, P., Bonfils, X., Santos, N. C., Pepe, F., Gillon, M., ... Udry, S. (2008). TW Hydrae: Evidence of stellar spots instead of a hot Jupiter. Astronomy and Astrophysics, 489(2). https://doi.org/10.1051/0004-6361:200810596

TW Hydrae : Evidence of stellar spots instead of a hot Jupiter. / Huélamo, N.; Figueira, P.; Bonfils, X.; Santos, N. C.; Pepe, F.; Gillon, M.; Azevedo, R.; Barman, Travis S; Fernández, M.; Di Folco, E.; Guenther, E. W.; Lovis, C.; Melo, C. H F; Queloz, D.; Udry, S.

In: Astronomy and Astrophysics, Vol. 489, No. 2, 10.2008.

Research output: Contribution to journalArticle

Huélamo, N, Figueira, P, Bonfils, X, Santos, NC, Pepe, F, Gillon, M, Azevedo, R, Barman, TS, Fernández, M, Di Folco, E, Guenther, EW, Lovis, C, Melo, CHF, Queloz, D & Udry, S 2008, 'TW Hydrae: Evidence of stellar spots instead of a hot Jupiter', Astronomy and Astrophysics, vol. 489, no. 2. https://doi.org/10.1051/0004-6361:200810596
Huélamo N, Figueira P, Bonfils X, Santos NC, Pepe F, Gillon M et al. TW Hydrae: Evidence of stellar spots instead of a hot Jupiter. Astronomy and Astrophysics. 2008 Oct;489(2). https://doi.org/10.1051/0004-6361:200810596
Huélamo, N. ; Figueira, P. ; Bonfils, X. ; Santos, N. C. ; Pepe, F. ; Gillon, M. ; Azevedo, R. ; Barman, Travis S ; Fernández, M. ; Di Folco, E. ; Guenther, E. W. ; Lovis, C. ; Melo, C. H F ; Queloz, D. ; Udry, S. / TW Hydrae : Evidence of stellar spots instead of a hot Jupiter. In: Astronomy and Astrophysics. 2008 ; Vol. 489, No. 2.
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abstract = "Context. TW Hya is a classical T Tauri star that shows significant radial-velocity variations in the optical regime. These variations have been attributed to a 10 planet orbiting the star at 0.04 AU. Aims. The aim of this letter is to confirm the presence of the giant planet around TW Hya by (i) testing whether the observed RV variations can be caused by stellar spots and (ii) analyzing new optical and infrared data to detect the signal of the planet companion. Methods. We fitted the RV variations of TW Hya using a cool spot model. In addition, we obtained new high-resolution optical & infrared spectra, together with optical photometry of TW Hya and compared them with previous data. Results. Our model shows that a cold spot covering 7{\%} of the stellar surface and located at a latitude of 54°can reproduce the reported RV variations. The model also predicts a bisector semi-amplitude variation < 10 m s-1, which is less than the errors of the RV measurements discussed in Setiawan et al. (2008, Nature, 451, 38). The analysis of our new optical RV data, with typical errors of 10 m s-1, shows a larger RV amplitude that varies depending on the correlation mask used. A slight correlation between the RV variation and the bisector is also observed although not at a very significant level. The infrared -band RV curve is almost flat, showing a small variation (<35 m s-1) that is not consistent with the published optical orbit. All these results support the spot scenario rather than the presence of a hot Jupiter. Finally, the photometric data shows a 20{\%} (peak to peak) variability, which is much larger than the 4{\%} variation expected for the modeled cool spot. The fact that the optical data are correlated with the surface of the cross-correlation function points towards hot spots as being responsible for the photometric variability. Conclusions. We conclude that the best explanation for the RV signal observed in TW Hya is the presence of a cool stellar spot and not an orbiting hot Jupiter.",
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AU - Bonfils, X.

AU - Santos, N. C.

AU - Pepe, F.

AU - Gillon, M.

AU - Azevedo, R.

AU - Barman, Travis S

AU - Fernández, M.

AU - Di Folco, E.

AU - Guenther, E. W.

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AU - Udry, S.

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N2 - Context. TW Hya is a classical T Tauri star that shows significant radial-velocity variations in the optical regime. These variations have been attributed to a 10 planet orbiting the star at 0.04 AU. Aims. The aim of this letter is to confirm the presence of the giant planet around TW Hya by (i) testing whether the observed RV variations can be caused by stellar spots and (ii) analyzing new optical and infrared data to detect the signal of the planet companion. Methods. We fitted the RV variations of TW Hya using a cool spot model. In addition, we obtained new high-resolution optical & infrared spectra, together with optical photometry of TW Hya and compared them with previous data. Results. Our model shows that a cold spot covering 7% of the stellar surface and located at a latitude of 54°can reproduce the reported RV variations. The model also predicts a bisector semi-amplitude variation < 10 m s-1, which is less than the errors of the RV measurements discussed in Setiawan et al. (2008, Nature, 451, 38). The analysis of our new optical RV data, with typical errors of 10 m s-1, shows a larger RV amplitude that varies depending on the correlation mask used. A slight correlation between the RV variation and the bisector is also observed although not at a very significant level. The infrared -band RV curve is almost flat, showing a small variation (<35 m s-1) that is not consistent with the published optical orbit. All these results support the spot scenario rather than the presence of a hot Jupiter. Finally, the photometric data shows a 20% (peak to peak) variability, which is much larger than the 4% variation expected for the modeled cool spot. The fact that the optical data are correlated with the surface of the cross-correlation function points towards hot spots as being responsible for the photometric variability. Conclusions. We conclude that the best explanation for the RV signal observed in TW Hya is the presence of a cool stellar spot and not an orbiting hot Jupiter.

AB - Context. TW Hya is a classical T Tauri star that shows significant radial-velocity variations in the optical regime. These variations have been attributed to a 10 planet orbiting the star at 0.04 AU. Aims. The aim of this letter is to confirm the presence of the giant planet around TW Hya by (i) testing whether the observed RV variations can be caused by stellar spots and (ii) analyzing new optical and infrared data to detect the signal of the planet companion. Methods. We fitted the RV variations of TW Hya using a cool spot model. In addition, we obtained new high-resolution optical & infrared spectra, together with optical photometry of TW Hya and compared them with previous data. Results. Our model shows that a cold spot covering 7% of the stellar surface and located at a latitude of 54°can reproduce the reported RV variations. The model also predicts a bisector semi-amplitude variation < 10 m s-1, which is less than the errors of the RV measurements discussed in Setiawan et al. (2008, Nature, 451, 38). The analysis of our new optical RV data, with typical errors of 10 m s-1, shows a larger RV amplitude that varies depending on the correlation mask used. A slight correlation between the RV variation and the bisector is also observed although not at a very significant level. The infrared -band RV curve is almost flat, showing a small variation (<35 m s-1) that is not consistent with the published optical orbit. All these results support the spot scenario rather than the presence of a hot Jupiter. Finally, the photometric data shows a 20% (peak to peak) variability, which is much larger than the 4% variation expected for the modeled cool spot. The fact that the optical data are correlated with the surface of the cross-correlation function points towards hot spots as being responsible for the photometric variability. Conclusions. We conclude that the best explanation for the RV signal observed in TW Hya is the presence of a cool stellar spot and not an orbiting hot Jupiter.

KW - Stars: individual: TW Hya

KW - Stars: planetary systems

KW - Stars: pre-main sequence

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