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Nine-hour X-ray quasi-periodic eruptions from a low-mass black hole galactic nucleus

Nine-hour X-ray quasi-periodic eruptions from a low-mass black hole galactic nucleus
Nine-hour X-ray quasi-periodic eruptions from a low-mass black hole galactic nucleus
In the past two decades, high amplitude electromagnetic outbursts have been detected from dormant galaxies and often attributed to the tidal disruption of a star by the central black hole. X-ray emission from the Seyfert 2 galaxy GSN 069 (2MASX J01190869-3411305) at redshift z = 0.018 was first detected in 2010 July and implies an X-ray brightening of more than a factor of 240 over ROSAT observations performed 16 years earlier. The emission has smoothly decayed over time since 2010, possibly indicating a long-lived tidal disruption event. The X-ray spectrum is ultra-soft and can be described by accretion disc emission with luminosity proportional to the fourth power of the disc temperature during long-term evolution. Here we report observations of X-ray quasi-periodic eruptions from the nucleus of GSN 069 over the course of 54 days, 2018 December onwards. During these eruptions, the X-ray count rate increases by up to two orders of magnitude with event duration of just over 1 hour and recurrence time of about 9 hours. These eruptions are associated with fast spectral transitions between a cold and a warm phase in the accretion flow around a low-mass black hole (of approximately 4x10$^5$ solar masses) with peak X-ray luminosity of ~ 5x10$^{42}$ ergs per second. The warm phase has a temperature of about 120 eV, reminiscent of the typical soft X-ray excess, an almost universal thermal-like feature in the X-ray spectra of luminous active nuclei. If the observed properties are not unique to GSN 069, and assuming standard scaling of timescales with black hole mass and accretion properties, typical active galactic nuclei with more massive black holes can be expected to exhibit high-amplitude optical to X-ray variability on timescales as short as months or years.
astro-ph.HE, astro-ph.GA
0028-0836
381-384
Miniutti, G.
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Saxton, R. D.
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Giustini, M.
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Alexander, K. D.
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Fender, R. P.
c802ddfc-25a3-4c0e-899d-11c405c705d1
Heywood, I.
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Monageng, I.
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Coriat, M.
95ca0a09-4085-44fc-a1c4-7cdf3cf4ca24
Tzioumis, A. K.
d069871e-6e05-4f5a-a876-58fc583346c6
Read, A. M.
d0ae8124-6af2-483a-a84e-5e65686f9d8c
Knigge, C.
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Gandhi, P.
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Pretorius, M. L.
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Agís-González, B.
11fc7863-bfac-45a7-9ceb-4372f2bc2f16
Miniutti, G.
99a8888c-5809-4220-8a92-2c0d7ba0dd00
Saxton, R. D.
22797581-102e-4f89-9860-db8d86cabb23
Giustini, M.
95252c16-b214-4a63-bc56-1614149c2e38
Alexander, K. D.
016e8a95-77a4-4dd3-92fb-50b5cf476a12
Fender, R. P.
c802ddfc-25a3-4c0e-899d-11c405c705d1
Heywood, I.
40ca8042-c994-470b-96dd-34e1979ad84a
Monageng, I.
2f5f38a6-c1ba-4c91-8bc8-805f49946bd8
Coriat, M.
95ca0a09-4085-44fc-a1c4-7cdf3cf4ca24
Tzioumis, A. K.
d069871e-6e05-4f5a-a876-58fc583346c6
Read, A. M.
d0ae8124-6af2-483a-a84e-5e65686f9d8c
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Gandhi, P.
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Pretorius, M. L.
ce6e49d6-c48e-495f-94bf-96bb8388bd07
Agís-González, B.
11fc7863-bfac-45a7-9ceb-4372f2bc2f16

Miniutti, G., Saxton, R. D., Giustini, M., Alexander, K. D., Fender, R. P., Heywood, I., Monageng, I., Coriat, M., Tzioumis, A. K., Read, A. M., Knigge, C., Gandhi, P., Pretorius, M. L. and Agís-González, B. (2019) Nine-hour X-ray quasi-periodic eruptions from a low-mass black hole galactic nucleus. Nature, 573, 381-384. (doi:10.1038/s41586-019-1556-x).

Record type: Article

Abstract

In the past two decades, high amplitude electromagnetic outbursts have been detected from dormant galaxies and often attributed to the tidal disruption of a star by the central black hole. X-ray emission from the Seyfert 2 galaxy GSN 069 (2MASX J01190869-3411305) at redshift z = 0.018 was first detected in 2010 July and implies an X-ray brightening of more than a factor of 240 over ROSAT observations performed 16 years earlier. The emission has smoothly decayed over time since 2010, possibly indicating a long-lived tidal disruption event. The X-ray spectrum is ultra-soft and can be described by accretion disc emission with luminosity proportional to the fourth power of the disc temperature during long-term evolution. Here we report observations of X-ray quasi-periodic eruptions from the nucleus of GSN 069 over the course of 54 days, 2018 December onwards. During these eruptions, the X-ray count rate increases by up to two orders of magnitude with event duration of just over 1 hour and recurrence time of about 9 hours. These eruptions are associated with fast spectral transitions between a cold and a warm phase in the accretion flow around a low-mass black hole (of approximately 4x10$^5$ solar masses) with peak X-ray luminosity of ~ 5x10$^{42}$ ergs per second. The warm phase has a temperature of about 120 eV, reminiscent of the typical soft X-ray excess, an almost universal thermal-like feature in the X-ray spectra of luminous active nuclei. If the observed properties are not unique to GSN 069, and assuming standard scaling of timescales with black hole mass and accretion properties, typical active galactic nuclei with more massive black holes can be expected to exhibit high-amplitude optical to X-ray variability on timescales as short as months or years.

Text
1909.04693v1 - Accepted Manuscript
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More information

Accepted/In Press date: 30 July 2019
e-pub ahead of print date: 11 September 2019
Published date: 19 September 2019
Additional Information: Authors' version of a Letter published on-line in Nature on September 11, 2019. Includes Methods and Extended Data. 43 pages, 3 tables and 10 figures
Keywords: astro-ph.HE, astro-ph.GA

Identifiers

Local EPrints ID: 434295
URI: http://eprints.soton.ac.uk/id/eprint/434295
ISSN: 0028-0836
PURE UUID: 362707b5-d2f3-4d1c-bb7f-613a471adb39
ORCID for P. Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

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Date deposited: 18 Sep 2019 16:30
Last modified: 07 Oct 2020 05:25

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