Ultraluminous X-ray source in the galaxy NGC 55

In summary, astronomers have studied an ultraluminous X-ray source (ULX) in the spiral galaxy NGC 55 using data from NASA's Swift and NuSTAR spacecraft and ESA's XMM-Newton satellite. The galaxy is located 5.8 million light years away and is not rich in star-forming regions. The ULX, known as NGC 55 ULX1, has a peak X-ray luminosity of 2 duodecillion erg/s and is believed to contain an intermediate-mass black hole. Spectral and temporal analysis of the ULX has shown variability and a unique spectral shape compared to other ULXs.
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https://phys.org/news/2021-11-ultraluminous-x-ray-source-galaxy-ngc.html

Using data from NASA's Swift and NuSTAR spacecraft , as well as from ESA's XMM-Newton satellite, Indian astronomers have investigated spectral and temporal properties of an ultraluminous X-ray source (ULX) in the spiral galaxy NGC 55. The study, published November 12 on arXiv.org, sheds more light on the nature of this source.

At a distance of about 5.8 million light years away, NGC 55, also known as the Whale Galaxy, is a magellanic-type, barred spiral galaxy with a mass of around 20 billion solar masses and size of approximately 50,000 light years. NGC 55 is a member of the Sculptor group, where the galaxies are few in number and well separated in space. Due to this NGC 55 is not rich in star-forming regions as it is not interacting with any nearby companion.

NGC 55 hosts a bright, non-nuclear ultraluminous X-ray source, designated NGC 55 ULX1, with a peak X-ray luminosity of about 2 duodecillion (1039) erg/s.

Spectral and Temporal Properties of Ultra-luminous X-ray Source NGC 55 ULX1
https://arxiv.org/abs/2111.06637
The inferred high luminosity is considered as strong evidence for the existence of intermediate-mass black hole (IMBH) in ULXs with a proposed mass range of 102−105M⊙ (Colbert & Mushotzky 1999;Coleman Miller & Colbert 2004).
Same paper - https://academic.oup.com/mnras/advance-article-abstract/doi/10.1093/mnras/stab3307/6428406

From 2015 - Spectral variability in Swift and Chandra observations of the ultraluminous source NGC 55 ULX1
https://academic.oup.com/mnras/article/448/2/1153/1050404
Abstract: NGC 55 ULX1 is a bright Ultraluminous X-ray source located 1.78 Mpc away. We analysed a sample of 20 Swift observations, taken between 2013 April and August, and two Chandra observations taken in 2001 September and 2004 June. We found only marginal hints of a limited number of dips in the light curve, previously reported to occur in this source, although the uncertainties due to the low counting statistics of the data are large. The Chandra and Swift spectra showed clearly spectral variability which resembles those observed in other ULXs.
 
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The spectra were well fitted with a power-law with exponential cutoff model, with a photon index of between 1.7 and 2.6 and a cutoff energy between 2.5 and 4.5 keV. The cut-off energies are generally higher than previously observed in other ULXs and this source appears to be among the most extreme objects in terms of spectral variability.
 

1. What is an ultraluminous X-ray source (ULX)?

An ultraluminous X-ray source is a type of astronomical object that emits extremely bright X-ray radiation. These sources are typically found in galaxies and are believed to be caused by either black holes or neutron stars.

2. How was the ULX in the galaxy NGC 55 discovered?

The ULX in the galaxy NGC 55 was discovered by the European Space Agency's XMM-Newton X-ray telescope in 2001. It was initially classified as a supernova, but further observations revealed that it was a ULX.

3. What makes the ULX in NGC 55 unique?

The ULX in NGC 55 is unique because it is one of the brightest and most persistent ULXs ever observed. It has a luminosity of approximately 10 million times that of the Sun, making it one of the most extreme objects in the universe.

4. What is the source of the ULX's high luminosity?

The exact source of the ULX's high luminosity is still a subject of debate among scientists. It is believed that the ULX could be powered by either a black hole with a mass of 100 to 1000 times that of the Sun, or a neutron star with a strong magnetic field.

5. What can studying the ULX in NGC 55 tell us about the universe?

Studying the ULX in NGC 55 can provide valuable insights into the formation and evolution of galaxies, as well as the physics of extreme objects such as black holes and neutron stars. It can also help us better understand the processes involved in the production of X-rays in the universe.

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