GX 340+0 II: Insights from the Z-source Star System
Recent observations reveal unique behaviors of the neutron star GX 340+0 II.
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GX 340+0 II is a fascinating star system that falls under the category of Z-sources, a special type of neutron star. Neutron stars are incredibly dense remnants of supernova explosions, and Z-sources are known for their distinct behavior. They follow a unique Z-shaped path when their brightness is plotted on a graph, showcasing their changes over time.
In this article, we will explore the recent observations of GX 340+0 II, including its X-ray and Radio Emissions, and discuss what we learned from its unique dance through the universe.
What Makes Z-sources Unique?
Z-sources like GX 340+0 II are interesting because they reveal crucial information about the life cycle of neutron stars and how they interact with their surroundings. These stars are in a binary system, meaning they have a companion star, usually a normal star. The neutron star pulls material from its companion, creating a process called Accretion. This process can lead to changes in brightness and the way the stars behave in relation to each other.
The Recent Campaign Observations
In August 2024, a thorough observation campaign was conducted to study GX 340+0 II using various telescopes and instruments. These observations helped researchers measure X-ray Polarization, a property that can indicate the presence and behavior of magnetic fields near the star. The campaign lasted for several days and involved collecting data from different wavelengths, including radio waves and X-rays.
The main goal was to understand how the X-ray brightness changes as the neutron star moves along its Z-shaped path. This journey included different stages called branches, specifically the horizontal branch (HB), normal branch (NB), and flaring branch (FB).
X-ray Polarization Measurements
One of the exciting findings from the observations was the measurement of X-ray polarization in the normal branch (NB) of GX 340+0 II. During this phase, it was observed that the degree of polarization was lower than in the horizontal branch (HB). The polarization angle remained consistent, suggesting that the source of the X-rays was likely similar across both branches.
The difference in polarization levels offers insights into the dynamics of the material falling onto the neutron star, providing clues about how the accretion disk behaves as the star moves along its path.
The Dance of the Z-track
As GX 340+0 II danced along its Z-track, researchers noted how the system transitioned between branches. During the observations, the star spent most of its time in the NB. This behavior aligns with what astronomers observe in other Z-sources, indicating that there is a relationship between the star's brightness, position, and the way the jets of material are expelled.
The Role of Radio Emissions
In addition to X-ray observations, researchers also studied the radio emissions of GX 340+0 II. Radio emissions are associated with the jets produced by the neutron star, which can vary based on the star’s brightness. The data collected showed that when the star was in the HB, there was a significant increase in radio emissions, suggesting that a steady jet was in play.
However, during the NB, no radio emissions were detected initially. A later observation revealed a tentative detection of radio waves, indicating a change in the jet's behavior. These observations help to connect the dots between the X-ray emissions and the jet activity, providing a fuller picture of the star's behavior.
The Spectral Composition of GX 340+0 II
To understand what contributes to the emissions from GX 340+0 II, researchers analyzed the spectrum of the X-rays. They identified three main components: an accretion disk, a blackbody, and Comptonized emission. Each of these components plays a role in how the star emits its energy.
The accretion disk is the swirling mass of material falling onto the neutron star, while the blackbody represents emission from the star's surface. Comptonized emission arises from interactions between hot electrons and photons, creating high-energy emissions. Together, these components explain the diverse and dynamic X-ray emissions from the star.
Polarization Insights
The polarized emission from GX 340+0 II provides valuable insights. Researchers found that the polarization in the NB was lower than in the HB, indicating a change in the nature of the emissions as the star transitioned between branches. This finding is essential for understanding the behavior of accretion disks and jets around neutron stars.
By analyzing the polarization, scientists can infer information about the geometry and dynamics of the material surrounding the neutron star. Understanding these elements is crucial for piecing together the life cycle of these extreme astrophysical objects.
The Bigger Picture
The findings from GX 340+0 II offer a glimpse into the nature of Z-sources and their behavior in the universe. This research contributes to our broader understanding of neutron stars, their interactions with companions, and the dynamics of accretion disks.
By studying the relationship between X-ray and radio emissions, as well as polarization measurements, researchers can build a clearer picture of how these systems evolve over time. Observations like those of GX 340+0 II provide crucial data that enhances our knowledge of the extreme conditions present in the universe.
Conclusion
The study of GX 340+0 II showcases the fascinating and complex behavior of Z-sources. Through extensive observations, researchers have begun to unravel the secrets of neutron stars, their jets, and the material that surrounds them. These findings not only enrich our understanding of individual stars but also contribute to the larger narrative of stellar evolution in the cosmos.
By combining data from multiple wavelengths, scientists can connect the dots, revealing the intricate dance of life and death among the stars. So, the next time you look up at the night sky, remember that some of those twinkling points of light may have their own stories to tell-stories of violent explosions, swirling disks, and the relentless pull of gravity.
Title: X-ray and Radio Campaign of the Z-source GX 340+0 II: the X-ray polarization in the normal branch
Abstract: We present the first X-ray polarization measurement of the neutron star low-mass X-ray binary and Z-source, GX 340$+$0, in the normal branch (NB) using a 200 ks observation with the Imaging X-ray Polarimetric Explorer (IXPE). This observation was performed in 2024 August. Along with IXPE, we also conducted simultaneous observations with NICER, AstroSat, Insight-HXMT, ATCA, and GMRT to investigate the broadband spectral and timing properties in the X-ray and radio wavelengths. During the campaign, the source traced a complete Z-track during the IXPE observation but spent most of the time in the NB. We measure X-ray polarization degree (PD) of $1.22\pm0.25\%$ in the 2-8 keV energy band with a polarization angle (PA) of $38\pm6^\circ$. The PD in the NB is observed to be weaker than in the horizontal branch (HB) but aligned in the same direction. The PD of the source exhibits a marginal increase with energy while the PA shows no energy dependence. The joint spectro-polarimetric modeling is consistent with the observed X-ray polarization originating from a single spectral component from the blackbody, the Comptonized emission, or reflection feature, while the disk emission does not contribute towards the X-ray polarization. GMRT observations at 1.26 GHz during HB had a tentative detection at 4.5$\pm$0.7 mJy while ATCA observations a day later during the NB detected the source at 0.70$\pm$0.05 mJy and 0.59$\pm$0.05 mJy in the 5.5 & 9 GHz bands, respectively, suggesting an evolving jet structure depending on the Z-track position.
Authors: Yash Bhargava, Thomas D. Russell, Mason Ng, Arvind Balasubramanian, Liang Zhang, Swati Ravi, Vishal Jadoliya, Sudip Bhattacharyya, Mayukh Pahari, Jeroen Homan, Herman L. Marshall, Deepto Chakrabarty, Francesco Carotenuto, Aman Kaushik
Last Update: 2024-11-01 00:00:00
Language: English
Source URL: https://arxiv.org/abs/2411.00350
Source PDF: https://arxiv.org/pdf/2411.00350
Licence: https://creativecommons.org/licenses/by/4.0/
Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.
Thank you to arxiv for use of its open access interoperability.
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