High resolution study reveals orbital alignment and atmospheric properties of planet WASP-13 b

Researchers have conducted the first high-resolution atmospheric study of the hot gas giant WASP-13 b. By observing four transits, the team refined the orbital geometry of this inflated planet and searched for chemical signatures in its atmosphere. While the study did not detect distinct molecular absorption, it provides important evidence that high-altitude clouds likely obscure the planet's atmospheric features.

Star system: WASP-13 | Distance from the Sun: 753 light years

WASP-13 b is an inflated, hot gas giant planet with a temperature of approximately 1500 Kelvin. Because of its large scale height, it serves as a primary target for understanding the atmospheres of planets outside our solar system. Researchers analyzed four transits of the planet to better understand its orbital behavior and to search for chemical signs such as helium, sodium, water, and carbon monoxide within its atmosphere.

The investigation utilized high-resolution spectroscopy, which involves spreading light from the system into a detailed spectrum to identify the chemical fingerprints of gases. The team also performed a Rossiter-McLaughlin analysis, a technique that measures how a planet passes in front of its star to determine the alignment between the planet's orbital path and the star's rotation. This work relied on data gathered by the GIARPS instrument, which allows for simultaneous observation in visible and near-infrared light.

While the study did not detect specific chemical absorption features, the findings provide a clearer picture of the planet's environment. The analysis suggests that high-altitude clouds are likely present in the upper atmosphere, which would mask the signals of deeper gases. These results help characterize WASP-13 b as a low-density hot Jupiter with a featureless transmission spectrum, setting the stage for more advanced observations in the future.

Key findings
The orbit of WASP-13 b is well-aligned with the rotation of its host star.
The stellar rotational velocity is measured at 4.5 kilometers per second.
No clear atmospheric absorption signals were detected in visible or near-infrared light.
High-altitude clouds are the most likely reason for the featureless transmission spectrum.
The data currently disfavor the possibility of a highly metal-enriched atmosphere.

Scientific study

The GAPS programme at TNG LXXXII. The first atmospheric investigation of the gas giant WASP-13b at high resolution with GIARPS (external link)