[Paper Review] The CORALIE survey for southern extra-solar planets XI. The return of the giant planet orbiting HD192263

N. C. Santos, S. Udry+7 more|ArXiv.org|May 22, 2003

Stellar, planetary, and galactic studies32 references60 citations

TL;DR

This study confirms the presence of a giant planet around HD 192263, resolving earlier controversy over a photometric signal with the same period as the radial-velocity variation. Using simultaneous radial-velocity, photometry, and bisector measurements, the authors show the radial-velocity signal is stable and planet-induced, while the photometric variations are sporadic and likely due to planet-star interactions, not stellar activity or false positives.

ABSTRACT

The presence of a planet around the K dwarf HD192263 was recently called into question by the detection of a periodic photometric signal with the same period as the one observed in radial velocity. In this paper, we investigate this possibility, using a combination of radial-velocity, photometry, and bisector measurements obtained simultaneously. The results show that while the observed radial-velocity variation is always very stable in phase, period, and amplitude, the photometric signal changes with time. The combined information strongly suggests that the observed radial-velocity variation is being produced by the presence of a planet, as firstly proposed. The photometric variations are either not connected to the planetary companion, or can eventually be induced by the interaction between the planet and the star. Finally, the radial-velocity data further show the presence of a long term trend, whose origin, still not clear, might be related to the presence of another companion to the system.

Motivation & Objective

• To resolve conflicting interpretations of radial-velocity and photometric signals in the HD 192263 system, where a planet was questioned due to a coincident photometric period.
• To determine whether the radial-velocity variations are caused by a planetary companion or stellar activity such as spots or pulsations.
• To investigate the origin of the photometric variations and their potential link to planetary interactions.
• To examine the long-term radial-velocity trend for evidence of a second companion or long-term activity.
• To assess the reliability of photometry as a diagnostic tool for confirming planetary companions detected via radial-velocity methods.

Proposed method

• Conducted simultaneous radial-velocity, photometric, and bisector (BIS) measurements using the CORALIE spectrograph at the 1.2-m Euler telescope and the P7 photometer at the 1.2-m MERCATOR telescope.
• Analyzed long-term radial-velocity data spanning multiple years to assess stability in period, phase, and amplitude.
• Compared photometric light curves with radial-velocity and BIS measurements to detect correlations or phase offsets.
• Evaluated the possibility of stellar activity (e.g., spots, pulsations) or planetary-induced effects (magnetic or tidal) as the source of photometric variations.
• Used cross-correlation of the stellar spectral lines to derive BIS values, which serve as a diagnostic for stellar activity.
• Investigated phase relationships between radial-velocity and photometric signals to test for tidal or magnetic coupling between planet and star.

Experimental results

Research questions

• RQ1 Is the radial-velocity variation in HD 192263 caused by a planetary companion or by stellar activity such as spots or pulsations?
• RQ2 Why do photometric variations with the same period as the radial-velocity signal appear intermittently, and what is their physical origin?
• RQ3 Do the radial-velocity and photometric signals share a common cause, or are they independent phenomena?
• RQ4 What explains the observed phase offset between the radial-velocity maximum and the photometric modulation?
• RQ5 What is the origin of the long-term radial-velocity trend observed in the data?

Key findings

• The radial-velocity signal of HD 192263 is highly stable in period (24.4 days), phase, and amplitude over multiple years, strongly indicating a planetary origin.
• Photometric variations are sporadic and not correlated with radial-velocity or BIS measurements, indicating they are not caused by stellar activity like spots.
• The phase offset of ~90 degrees between the radial-velocity maximum and photometric modulation suggests a delayed response, possibly due to tidal or magnetic interactions.
• The detection of a period half the orbital period in the Mount Wilson S index supports a tidal or magnetic origin for the photometric variability.
• A long-term radial-velocity trend is present, suggesting the possible existence of a second companion or long-term stellar activity cycle.
• The combined data strongly support the initial interpretation that a Jupiter-mass planet orbits HD 192263, with photometric variations likely due to planet-star interaction rather than false positives.