J/ApJS/255/7 X-ray monitoring of 1ES 1927+654 (Ricci+, 2021)
The 450 day X-ray monitoring of the changing-look AGN 1ES 1927+654.
Ricci C., Loewenstein M., Kara E., Remillard R., Trakhtenbrot B.,
Arcavi I., Gendreau K.C., Arzoumanian Z., Fabian A.C., Li R., Ho L.C.,
Macleod C.L., Cackett E., Altamirano D., Gandhi P., Kosec P., Pasham D.,
Steiner J., Chan C.-H.
<Astrophys. J. Suppl. Ser., 255, 7-7 (2021)>
=2021ApJS..255....7R 2021ApJS..255....7R (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei; X-ray sources
Keywords: Astrophysical black holes; X-ray quasars; Active galactic nuclei
Supermassive black holes
Abstract:
1ES 1927+654 is a nearby active galactic nucleus (AGN) that underwent
a changing-look event in early 2018, developing prominent broad Balmer
lines that were absent in previous observations. We have followed up
this object in the X-rays with an ongoing campaign that started in
2018 May and that includes 265 NICER (for a total of 678ks) and
14 Swift/XRT (26ks) observations, as well as three simultaneous
XMM-Newton/NuSTAR (158/169ks) exposures. In the X-rays, 1ES 1927+654
shows a behavior unlike any previously known AGN. The source is
extremely variable both in spectral shape and flux and does not show
any correlation between X-ray and UV flux on timescales of hours or
weeks/months. After the outburst, the power-law component almost
completely disappeared, and the source showed an extremely soft
continuum dominated by a blackbody component. The temperature of the
blackbody increases with the luminosity, going from kT∼80eV (for a
0.3-2keV luminosity of L0.3-2∼1041.5erg/s) to ∼200eV (for
L0.3-2∼1044erg/s). The spectra show evidence of ionized outflows
and of a prominent feature at ∼1keV, which can be reproduced by a
broad emission line. The unique characteristics of 1ES 1927+654 in the
X-ray band suggest that it belongs to a new type of changing-look AGN.
Future X-ray surveys might detect several more objects with similar
properties.
Description:
Our ongoing X-ray monitoring campaign started in 2018 May, after the
detection of broad optical lines in 1ES1927+654, and consists of three
joint XMM-Newton/NuSTAR observations (158/169ks in total) carried out
in June (PI: N. Schartel/C. Ricci), 2018 December (PI: N. Schartel /
E. Kara), and on 2019 May (PI: C. Ricci) and 14 Swift/XRT observations
(PI: I. Arcavi, C. Ricci, 26ks) and 265 Neutron Star Interior
Composition Explorer (NICER) observations (678ks; see
Kara+ 2018ATel12169....1K 2018ATel12169....1K for a summary of the first set of
observations). The observation log is reported in Table A1.
Objects:
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RA (ICRS) DE Designation(s)
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19 27 19.54 +65 33 54.3 1ES 1927+654 = RX J1927.3+6533
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 49 286 X-ray observation log
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See also:
B/swift : Swift Master Catalog (HEASARC, 2004-)
B/xmm : XMM-Newton Obs. Log (XMM-Newton Science Operation Center, 2012)
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005)
J/ApJS/129/547 : RBSC-NVSS sample. I. (Bauer+, 2000)
J/MNRAS/397/1177 : Swift-XRT observations of GRBs (Evans+, 2009)
J/ApJ/705/1336 : X-ray measurements of ChaMP-SDSS gal. (Constantin+, 2009)
J/MNRAS/423/600 : Type-1 low-z AGN emission properties (Stern+, 2012)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/A+A/588/A70 : Hard X-ray view of the soft excess in AGN (Boissay+, 2016)
J/MNRAS/466/3309 : X-ray flux variability of AGN (Rani+, 2017)
J/ApJ/836/99 : NuSTAR serendipitous survey: 40-month cat. (Lansbury+, 2017)
J/ApJ/850/74 : Swift/BAT AGN Spectroscopic Survey. I. (Koss+, 2017)
J/ApJS/233/17 : Swift/BAT AGN spectroscopic survey. V. X-ray (Ricci+, 2017)
J/ApJ/854/160 : SDSS and DES long-term extreme var. QSOs (Rumbaugh+, 2018)
J/ApJ/874/8 : Follow-up spec. of SDSS changing-look QSOs (Macleod+, 2019)
J/ApJ/883/94 : Opt. and UV follow-up of 1ES 1927+654 (Trakhtenbrot+, 2019)
J/MNRAS/498/4033 : Extreme quasar X-ray variability (Timlin+, 2020)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Tel X-ray telescope (1)
12- 21 A10 "Y/M/D" Obs.date Date of observation, ISO 8601
23- 30 A8 "h:m:s" Obs.time Time of observation, ISO 8601
32- 42 I11 --- ObsId Observation ID on Tel
44- 49 I6 s Exp Exposure time
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Note (1): Telescope as follows:
NICER = Neutron Star Interior Composition Explorer (265 occurrences)
Swift/XRT = Swift/XRT observations (PI: I. Arcavi, C. Ricci, 26ks;
14 occurrences)
XMM-Newton = 4 occurrences
NuSTAR = The Nuclear Spectroscopic Telescope Array (3 occurrences)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 25-Oct-2021