Radial velocity analysis characterizes planetary systems around DMPP-7 HD 67200 and HD 2134

Star system: HD 67200 | Distance from the Sun: 178 light years

Recent observations have analyzed the environments around three stars - DMPP-7, HD 67200, and HD 2134 — to search for evidence of orbiting planets. By studying radial velocity, which measures the tiny wobbles in a star’s position caused by the gravitational tug of an orbiting planet, the project examined these systems to distinguish between genuine planetary signals and the natural activity of the stars themselves.

The researchers used a Bayesian framework, a statistical method for evaluating how well different models fit observed data. They compared purely gravitational models with those that include stellar noise, such as sunspots or magnetic cycles, modeled as a quasi-periodic Gaussian Process. This approach helps determine if a signal is likely a planet or just the star pulsing or rotating.

DMPP-7 was confirmed to host a giant planet with about 72 percent of the mass of Saturn, completing an orbit every 4.93 days. For HD 67200 and HD 2134, the data suggests potential small-mass planets with very short orbital periods of approximately 2.7 days, though these signals remain ambiguous as they could potentially be caused by stellar surface activity.

Despite the targets being chosen because their orbits were expected to be seen edge-on from Earth, which would typically result in the planet passing in front of the star and causing a dip in brightness, no such transits were found in TESS space telescope data. Future observations are needed to confirm the nature of the signals for HD 67200 and HD 2134.

Key findings
- DMPP-7 hosts a giant planet with an orbital period of 4.93 days and a mass 69 times that of Earth.
- HD 67200 shows moderate evidence for a planet with a 2.67-day orbit.
- HD 2134 shows moderate evidence for a planet with a 2.78-day orbit.
- No transit signals were detected for any of the three systems using TESS photometry.
- Stellar activity continues to complicate the detection of small-mass planets around active stars.

Scientific study

Three new exoplanet systems from the Dispersed Matter Planet Project (external link)