NGTS-1b: A hot Jupiter transiting an M-dwarf (1710.11099v1)

Abstract: We present the discovery of NGTS-1b, a hot-Jupiter transiting an early M-dwarf host ($T_{eff}=3916^{+71}_{-63}~K$) in a P=2.674d orbit discovered as part of the Next Generation Transit Survey (NGTS). The planet has a mass of $0.812^{+0.066}{-0.075}~M{J}$, making it the most massive planet ever discovered transiting an M-dwarf. The radius of the planet is $1.33^{+0.61}{-0.33}~R{J}$. Since the transit is grazing, we determine this radius by modelling the data and placing a prior on the density from the population of known gas giant planets. NGTS-1b is the third transiting giant planet found around an M-dwarf, reinforcing the notion that close-in gas giants can form and migrate similar to the known population of hot Jupiters around solar type stars. The host star shows no signs of activity, and the kinematics hint at the star being from the thick disk population. With a deep (2.5%) transit around a $K=11.9$ host, NGTS-1b will be a strong candidate to probe giant planet composition around M-dwarfs via JWST transmission spectroscopy.

• The paper presents the discovery of NGTS-1b, a hot Jupiter with 0.812 MJ mass and 1.33 RJ radius transiting its host M-dwarf every 2.647 days.
• The analysis uses detailed transit modeling of its grazing transit to challenge existing theories on giant planet formation around low-mass stars.
• The discovery paves the way for atmospheric studies using advanced telescopes like JWST and enhances our understanding of exoplanets orbiting M-dwarfs.

NGTS-1b: A Hot Jupiter Transiting an M-dwarf

The publication presents the identification and analysis of NGTS-1b, a noteworthy astronomical discovery detected by the Next Generation Transit Survey (NGTS). NGTS-1b is a hot-Jupiter class exoplanet transiting an early M-dwarf star, identified as NGTS-1, at an orbital period of approximately 2.647 days. This detection contributes significantly to our understanding of planetary formation around M-dwarf stars, which are among the most populous in the galaxy.

Key Findings

1. Exoplanet Characteristics: NGTS-1b is one of the most substantial gas giant planets detected around an M-dwarf, with a mass of 0.812 M$_J$ and a radius of 1.33 R$_J$. Its discovery is noteworthy due to its grazing transit, which requires modeling constraints and extrapolations using known populations of gas giants to estimate its radius accurately.
2. Transiting Hot Jupiters Around M-dwarfs: Reinforcing the understanding that close-in gas giants can develop and migrate similarly in M-dwarf systems as they do around solar-type stars. This paper records NGTS-1b as only the third example within this category, supporting the hypothesis that massive planet formation can occur in the early stages of the galaxy.
3. Astrophysical Context: The discovery of such a substantial planet around an M-dwarf challenges preconceived ideas about the rarity of giant planets in such systems due to the limited raw materials for planet formation in low-mass disks. It also emphasizes the need to understand better the correlation between stellar metallicity and giant planet frequency around these stars.

Implications and Future Prospects

The NGTS-1b discovery has several implications for both theoretical understanding and observational astrophysics. Theoretical models predicting planet formation challenges in M-dwarf systems may need reassessment to account for higher incidences of gas giants than currently expected. It suggests the necessity for larger surveys focused on M-dwarfs to establish more robust statistics on planet frequency and distribution.

Practically, NGTS-1b provides an opportunity for detailed atmospheric studies using transmission spectroscopy. Its deep transit makes it an adept candidate for investigating planet composition, potentially utilizing advanced platforms such as the James Webb Space Telescope (JWST) for further characterization.

Future studies may focus on improving measurement precision by leveraging upcoming surveys and missions like TESS, which, despite its limited sensitivity compared to NGTS, can offer longer continuous observations, critical for further understanding such short-period exoplanets.

Conclusion

The discovery of NGTS-1b signposts a remarkable advance in our investigation of exoplanets orbiting M-dwarfs. The data presented serve as valuable inputs for refining models of planetary formation and evolution within these widely dispersed stellar systems. With continued observational efforts, the understanding of planetary types and frequencies across stellar classes will deepen, contributing substantially to the field of exoplanetary science.