Discovery of X-ray quasi-periodic eruptions in a second galactic nucleus

2020-04-10

Image of Coma Cluster (Abell 1656), a giant Galaxy cluster that hosts more than 1.000 galaxies. Credits: NASA, ESA, Hubble Heritage (STScI/AURA).


After the discovery, a few months ago, of the first X-ray quasi-periodic eruptions
the same researchers from the Centro de Astrobiología (CSIC-INTA) has detected
QPEs again in another active galaxy, RX J1301.9+2747. The discovery of these
eruptions in a second galaxy confirms that QPEs are an extragalactic phenomenon. Its
study will help to better understand the physics of supermassive black holes accretion
in the nuclei of galaxies.



Quasi Periodic Eruptions, or QPEs, are sudden, sharp and recurring increases in X-ray intensity over a stable emission level. The discovery of QPEs from a second galaxy, made by a scientific team led by the Centro de Astrobiología (CAB, CSIC-INTA) and recently published in the journal Astronomy & Astrophysics, came after an observation by ESA's space X-ray telescope XMM-Newton. The galaxy is named RX J1301.9+2747 and is located in the periphery of the famous cluster of galaxies, Coma.

During the observations, made on May 30 and 31, 2019, three intense QPEs, with a duration of approximately half an hour each, were detected in the X-ray light curves obtained from RX J1301.9+2747. The recurrence time, or temporal separation, of the first two QPEs was longer, around 20 ks, compared to that of the second and third, around 13 ks. This temporal pattern is consistent with the alternate long-short recurrence times of the first QPEs discovered in the galaxy GSN 069, although the difference between consecutive recurrence times is significantly smaller in GSN 069 than in RX J1301.9+2747.

According to Margherita Giustini, CAB researcher and lead author of the study: “What has most impressed us is that the physical characteristics of these QPEs are similar to those of the QPEs that we detected in GSN 069, but with notable differences: the eruptions of RX J1301.9+2747 are shorter, lasting only half an hour, and are repeated more frequently, although their pattern of recurrence is not so clear, with repetitions after 5h30m and after 3h45m. New observations have been scheduled to try to elucidate the exact pattern of recurrence”.

Future, longer X-ray observations will help clarify the temporal pattern of QPEs in RX J1301.9+2747 and will allow for a detailed comparison with the QPEs of GSN 069. The X-ray spectral properties of the QPEs in the two sources are remarkably similar, representing rapid transitions from a relatively cold state, likely dominated by emission from an accretion disk, to a state characterized by a warmer emission, similar to the socalled "soft X-ray excess", a component seen almost ubiquitously in the X-ray spectra of active galaxies. Previous X-ray observations of RX J1301.9+2747 made in 2000 and 2009 strongly suggest that QPEs have been occurring in this source for at least the past 18.5 years.

As Giovanni Miniutti, CAB researcher and co-author of the study points out, “detection of QPEs in a second galactic nucleus after GSN 069 rules out contamination by a galactic source in both cases, so that QPEs should be considered a genuinely extra-galactic novel phenomenon associated with supermassive black hole accretion”.

 

Fuente: UCC-CAB

Fecha: 2020-04-10

 

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