Context.
The AGN bolometric correction is a key element for understanding black hole (BH) demographics and computing accurate BH accretion histories from AGN luminosities. However, current estimates ...still differ from each other by up to a factor of two to three, and rely on extrapolations at the lowest and highest luminosities.
Aims.
Here we revisit this fundamental question by presenting general hard X-ray (
K
X
) and optical (
K
O
) bolometric corrections, computed by combining several AGN samples spanning the widest (about 7 dex) luminosity range ever used for this type of studies.
Methods.
We analysed a total of ∼1000 type 1 and type 2 AGN for which we performed a dedicated SED-fitting.
Results.
We provide a bolometric correction separately for type 1 and type 2 AGN; the two bolometric corrections agree in the overlapping luminosity range. Based on this we computed for the first time a universal bolometric correction for the whole AGN sample (both type 1 and type 2). We found that
K
X
is fairly constant at log(
L
BOL
/
L
⊙
) < 11, while it increases up to about one order of magnitude at log(
L
BOL
/
L
⊙
) ∼ 14.5. A similar increasing trend has been observed when its dependence on either the Eddington ratio or the BH mass is considered, while no dependence on redshift up to
z
∼ 3.5 has been found. In contrast, the optical bolometric correction appears to be fairly constant (i.e.
K
O
∼ 5) regardless of the independent variable. We also verified that our bolometric corrections correctly predict the AGN bolometric luminosity functions. According to this analysis, our bolometric corrections can be applied to the whole AGN population in a wide range of luminosity and redshift.
We present X-shooter at Very Large Telescope observations of a sample of 10 luminous, X-ray obscured quasi-stellar objects (QSOs) at z ~ 1.5 from the XMM-COSMOS survey, expected to be caught in the ...transitioning phase from starburst to active galactic nucleus (AGN)-dominated systems. The main selection criterion is X-ray detection at bright fluxes (...) coupled to red optical-to-near-infrared-to-mid-infrared colours. Thanks to its large wavelength coverage, X-shooter allowed us to determine accurate redshifts from the presence of multiple emission lines for five out of six targets for which we had only a photometric redshift estimate, with an 80 per cent success rate, significantly larger than what is observed in similar programs of spectroscopic follow-up of red QSOs. We report the detection of broad and shifted components in the OIII ...5007, 4959 complexes for six out of eight sources with these lines observable in regions free from strong atmospheric absorptions. The full width at half-maximum (FWHM) associated with the broad components are in the range FWHM ~ 900-1600 km s..., larger than the average value observed in Sloan Digital Sky Survey type 2 AGN samples at similar observed OIII luminosity, but comparable to those observed for QSO/ultraluminous infrared galaxies systems for which the presence of kpc scale outflows has been revealed through integral field unit spectroscopy. Although the total outflow energetics (inferred under reasonable assumptions) may be consistent with winds accelerated by stellar processes, we favour an AGN origin for the outflows given the high outflow velocities observed (...) and the presence of strong winds also in objects undetected in the far-infrared. (ProQuest: ... denotes formulae/symbols omitted.)
ABSTRACT
At 66 Mpc, AT2019qiz is the closest optical tidal disruption event (TDE) to date, with a luminosity intermediate between the bulk of the population and the faint-and-fast event iPTF16fnl. ...Its proximity allowed a very early detection and triggering of multiwavelength and spectroscopic follow-up well before maximum light. The velocity dispersion of the host galaxy and fits to the TDE light curve indicate a black hole mass ≈106 M⊙, disrupting a star of ≈1 M⊙. By analysing our comprehensive UV, optical, and X-ray data, we show that the early optical emission is dominated by an outflow, with a luminosity evolution L ∝ t2, consistent with a photosphere expanding at constant velocity (≳2000 km s−1), and a line-forming region producing initially blueshifted H and He ii profiles with v = 3000–10 000 km s−1. The fastest optical ejecta approach the velocity inferred from radio detections (modelled in a forthcoming companion paper from K. D. Alexander et al.), thus the same outflow may be responsible for both the fast optical rise and the radio emission – the first time this connection has been observed in a TDE. The light-curve rise begins 29 ± 2 d before maximum light, peaking when the photosphere reaches the radius where optical photons can escape. The photosphere then undergoes a sudden transition, first cooling at constant radius then contracting at constant temperature. At the same time, the blueshifts disappear from the spectrum and Bowen fluorescence lines (N iii) become prominent, implying a source of far-UV photons, while the X-ray light curve peaks at ≈1041 erg s−1. Assuming that these X-rays are from prompt accretion, the size and mass of the outflow are consistent with the reprocessing layer needed to explain the large optical to X-ray ratio in this and other optical TDEs, possibly favouring accretion-powered over collision-powered outflow models.
Abstract
We report the virial measurements of the black hole (BH) mass of a sample of 17 type 2 active galactic nuclei (AGN), drawn from the Swift/BAT 70-month 14–195 keV hard X-ray catalogue, where ...a faint BLR component has been measured via deep NIR (0.8–2.5 μm) spectroscopy. We compared the type 2 AGN with a control sample of 33 type 1 AGN. We find that the type 2 AGN BH masses span the 5 < log(M
BH/M⊙) < 7.5 range, with an average log(M
BH/M⊙) = 6.7, which is ∼0.8 dex smaller than found for type 1 AGN. If type 1 and type 2 AGN of the same X-ray luminosity log(
$L_{\rm 14{\rm -}195}$
/erg s−1) ∼ 43.5 are compared, type 2 AGN have 0.5 dex smaller BH masses than type 1 AGN. Although based on few tens of objects, this result disagrees with the standard AGN unification scenarios in which type 1 and type 2 AGN are the same objects observed along different viewing angles with respect to a toroidal absorbing material.
We report on International Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the soft γ-ray repeater SGR 1935+2154 performed between 2020 April 28 and May 3. Several short bursts with ...fluence of erg cm−2 were detected by the Imager on-board INTEGRAL (IBIS) instrument in the 20-200 keV range. The burst with the hardest spectrum, discovered and localized in real time by the INTEGRAL Burst Alert System, was spatially and temporally coincident with a short and very bright radio burst detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and Survey for Transient Astronomical Radio Emission 2 (STARE2) radio telescopes at 400-800 MHz and 1.4 GHz, respectively. Its lightcurve shows three narrow peaks separated by ∼29 ms time intervals, superimposed on a broad pulse lasting ∼0.6 s. The brightest peak had a delay of 6.5 1.0 ms with respect to the 1.4 GHz radio pulse (that coincides with the second and brightest component seen at lower frequencies). The burst spectrum, an exponentially cutoff power law with photon index and peak energy , is harder than those of the bursts usually observed from this and other magnetars. By the analysis of an expanding dust-scattering ring seen in X-rays with the Neil Gehrels Swift Observatory X-ray Telescope (XRT) instrument, we derived a distance of kpc for SGR 1935+2154, independent of its possible association with the supernova remnant G57.2+0.8. At this distance, the burst 20-200 keV fluence of erg cm−2 corresponds to an isotropic emitted energy of erg. This is the first burst with a radio counterpart observed from a soft γ-ray repeater and it strongly supports models based on magnetars that have been proposed for extragalactic fast radio bursts.
Abstract
The microquasar MAXI J1820+070 went into outburst from 2018 mid-March until mid-July, with several faint rebrightenings afterward. With a peak flux of approximately 4 Crab in the 20–50 keV ...energy range, the source was monitored across the electromagnetic spectrum with detections from radio to hard X-ray frequencies. Using these multiwavelength observations, we analyzed quasi-simultaneous observations from April 12, near the peak of the outburst (∼March 23). Analysis of the X-ray spectrum found it indicative of an accreting black hole binary in the hard state, consistent with the flat/inverted radio spectrum and the accretion disk winds seen at optical wavelengths. Then, we constructed a spectral energy distribution spanning ∼12 orders of magnitude using modeling in
JetSeT
. The model is composed of an irradiated disk with a Compton hump and a leptonic jet with an acceleration region and a synchrotron-dominated cooling region.
JetSeT
finds that the spectrum is dominated by jet emission up to approximately 10
14
Hz, after which disk and coronal emission dominates. The acceleration region has a magnetic field of
B
∼ 1.6 × 10
4
G, a cross section of
R
∼ 2.8 × 10
9
cm, and a flat radio spectral shape naturally obtained from the synchroton cooling of the accelerated electrons. The jet luminosity is >8 × 10
37
erg s
−1
(>0.15
L
Edd
), compared to an accretion luminosity of ∼6 × 10
37
erg s
−1
, assuming a distance of 3 kpc. Because these two values are comparable, it is possible that the jet is powered predominately via accretion with only a small contribution needed from the Blanford–Znajek mechanism from the reportedly slowly spinning black hole.
ABSTRACT
We present results from spectroscopic observations of AT 2018hyz, a transient discovered by the All-Sky Automated Survey for Supernova survey at an absolute magnitude of MV ∼ −20.2 mag, in ...the nucleus of a quiescent galaxy with strong Balmer absorption lines. AT 2018hyz shows a blue spectral continuum and broad emission lines, consistent with previous TDE candidates. High cadence follow-up spectra show broad Balmer lines and He i in early spectra, with He ii making an appearance after ∼70–100 d. The Balmer lines evolve from a smooth broad profile, through a boxy, asymmetric double-peaked phase consistent with accretion disc emission, and back to smooth at late times. The Balmer lines are unlike typical active galactic nucleus in that they show a flat Balmer decrement (Hα/Hβ ∼ 1.5), suggesting the lines are collisionally excited rather than being produced via photoionization. The flat Balmer decrement together with the complex profiles suggests that the emission lines originate in a disc chromosphere, analogous to those seen in cataclysmic variables. The low optical depth of material due to a possible partial disruption may be what allows us to observe these double-peaked, collisionally excited lines. The late appearance of He ii may be due to an expanding photosphere or outflow, or late-time shocks in debris collisions.
ABSTRACT
We present optical spectroscopic and Swift UVOT/XRT observations of the X-ray and UV/optical bright tidal disruption event (TDE) candidate AT 2018fyk/ASASSN–18ul discovered by ASAS–SN. The ...Swift light curve is atypical for a TDE, entering a plateau after ∼40 d of decline from peak. After 80 d the UV/optical light curve breaks again to decline further, while the X-ray emission becomes brighter and harder. In addition to broad H, He, and potentially O/Fe lines, narrow emission lines emerge in the optical spectra during the plateau phase. We identify both high-ionization (O iii) and low-ionization (Fe ii) lines, which are visible for ∼45 d. We similarly identify Fe ii lines in optical spectra of ASASSN–15oi 330 d after discovery, indicating that a class of Fe-rich TDEs exists. The spectral similarity between AT 2018fyk, narrow-line Seyfert 1 galaxies, and some extreme coronal line emitters suggests that TDEs are capable of creating similar physical conditions in the nuclei of galaxies. The Fe ii lines can be associated with the formation of a compact accretion disc, as the emergence of low-ionization emission lines requires optically thick, high-density gas. Taken together with the plateau in X-ray and UV/optical luminosity this indicates that emission from the central source is efficiently reprocessed into UV/optical wavelengths. Such a two-component light curve is very similar to that seen in the TDE candidate ASASSN–15lh, and is a natural consequence of a relativistic orbital pericentre.
Context. It is currently only possible to accurately weigh, through reverberation mapping (RM), the masses of super massive black holes (BHs) in active galactic nuclei (AGN) for a small group of ...local and bright broad line AGN. Statistical demographic studies can be carried out considering the empirical scaling relation between the size of the broad line region (BLR) and the AGN optical continuum luminosity. There are still biases, however, against low-luminosity or reddened AGN, in which the rest-frame optical radiation can be severely absorbed or diluted by the host galaxy and the BLR emission lines can be hard to detect. Aims. Our purpose is to widen the applicability of virial-based single-epoch (SE) relations to measure reliably the BH masses for low-luminosity or intermediate and type 2 AGN, which the current methodology misses. We achieve this goal by calibrating virial relations based on unbiased quantities: the hard X-ray luminosities in the 2–10 keV and 14–195 keV bands that are less sensitive to galaxy contamination, and the full width at half maximum (FWHM) of the most important rest-frame near-infrared (NIR) and optical BLR emission lines. Methods. We built a sample of RM AGN with both X-ray luminosity, broad optical and NIR FWHM measurements available to calibrate new virial BH mass estimators. Results. We found that the FWHM of the Hα, Hβ, and NIR lines (i.e. Paα, Paβ, and He iλ10830) all correlate with each other with negligible or small offsets. This result allowed us to derive virial BH mass estimators based on either the 2–10 keV or 14–195 keV luminosity. We also took into account the recent determination of the different virial coefficients, f, for pseudo- and classical bulges. By splitting the sample according to the bulge type and adopting separate f factors, we found that our virial relations predict BH masses of AGN hosted in pseudo-bulges ~0.5 dex smaller than in classical bulges. Assuming the same average f factor for both populations, a difference of ~0.2 dex is still found.
We present medium resolution near-infrared spectroscopic observations of 41 obscured and intermediate class active galactic nuclei (AGN; type 2, 1.9 and 1.8; AGN2) with redshift z ... 0.1, selected ...from the Swift/Burst Alert Telescope 70-month catalogue. The observations have been carried out in the framework of a systematic study of the AGN2 near-infrared spectral properties and have been executed using Infrared Spectrometer And Array Camera/VLT, X-shooter/VLT and LUCI/LBT, reaching an average S/N ratio of ~30 per resolution element. For those objects observed with X-shooter, we also obtained simultaneous optical and UV spectroscopy. We have identified a component from the broad line region in 13 out of 41 AGN2, with full width at half-maximum (FWHM) > 800 km s super( -1). We have verified that the detection of the broad line region components does not significantly depend on selection effects due to the quality of the spectra, the X-ray or near-infrared fluxes, the orientation angle of the host galaxy or the hydrogen column density measured in the X-ray band. The average broad line region components found in AGN2 has a significantly (a factor 2) smaller FWHM if compared with a control sample of type 1 AGN. (ProQuest: ... denotes formulae/symbols omitted.)
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