The HELLAS2<i>XMM</i>Survey. II. Multiwavelength Observations of P3: An X‐Ray–bright, Optically Inactive Galaxy

Comastri, A.; Mignoli, M.; Ciliegi, P.; Severgnini, P.; Maiolino, R.; Brusa, M.; Fiore, F.; Baldi, A.; Molendi, S.; Morganti, R.; Vignali, C.; Franca, F. La; Matt, Giorgio; Perola, G. C.

doi:10.1086/340016

Cited by 161 publications

(190 citation statements)

References 34 publications

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“…12, lower right panel): we therefore classify it as an X-ray bright, optically normal galaxy (XBONG; see Comastri et al 2002). The "normal galaxy" nature of this source is confirmed using the approach of Laurent-Muehleisen et al (1998).…”

Section: Agnsmentioning

confidence: 70%

Unveiling the nature ofINTEGRALobjects through optical spectroscopy

Masetti¹,

Parisi

Palazzi³

et al. 2010

A&A

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Hard X-ray surveys performed by the INTEGRAL satellite have discovered a conspicuous fraction (up to 30%) of unidentified objects among the detected sources. Here we continue our program of identification of these objects by (i) selecting probable optical candidates by means of positional cross-correlation of the INTEGRAL detections with soft X-ray, radio, and/or optical archives and (ii) performing optical spectroscopy on them. As a result, we pinpointed and identified, or more accurately characterized, 44 definite or likely counterparts of INTEGRAL sources. Among them, 32 are active galactic nuclei (AGNs; 18 with broad emission lines, 13 with narrow emission lines only, and one X-ray bright, optically normal galaxy) with redshift 0.019 < z < 0.6058, 6 cataclysmic variables (CVs), 5 high-mass X-ray binaries (2 of which in the Small Magellanic Cloud), and 1 low-mass X-ray binary. This was achieved by using 7 telescopes of various sizes and archival data from two online spectroscopic surveys. The main physical parameters of these hard X-ray sources were also determined using the multiwavelength information available in the literature. In general, AGNs are the most abundant population among hard X-ray objects, and our results confirm the tendency of finding AGNs more frequently than any other type of hard X-ray emitting object among unidentified INTEGRAL sources when optical spectroscopy is used as an identification tool. Moreover, the deeper sensitivity of the more recent INTEGRAL surveys enables one to begin detecting hard X-ray emission above 20 keV from sources such as LINER-type AGNs and non-magnetic CVs.

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Section: Agnsmentioning

confidence: 70%

Unveiling the nature ofINTEGRALobjects through optical spectroscopy

Masetti¹,

Parisi

Palazzi³

et al. 2010

A&A

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“…9). Using the approach of Laurent-Muehleisen et al (1998), we find that these sources do not show any suggestion of AGN activity: we thus classify them as X-ray bright, optically normal galaxies (XBONGs; see Comastri et al 2002). We also note that we identify IGR J10200−1436 as the farthest XBONG known up to now within the hard X-ray surveys made with INTEGRAL.…”

Section: Agnsmentioning

confidence: 71%

Unveiling the nature of INTEGRAL objects through optical spectroscopy

Chavushyan¹

2013

A&A

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Within the framework of our program (running since 2004) of identification of hard X-ray INTEGRAL sources through optical spectroscopy, we present the results concerning the nature of 33 high-energy objects. The data were acquired with the use of six telescopes of different sizes and from one on-line archive. The results indicate that the majority of these objects (23 out of 33) are active galactic nuclei (AGNs), whereas 10 are sources in the local Universe with eight of which in the Galaxy and two in the Small Magellanic Cloud (SMC). Among the identified AGNs, 13 are of Type 1 (i.e., with broad emission lines), eight are of Type 2 (with narrow emissions only), and two are X-ray bright, optically normal galaxies with no apparent nuclear activity in the optical. Six of these AGNs lie at high redshift (z > 0.5). Concerning local objects, we found that five of them are Galactic cataclysmic variables, three are high-mass X-ray binaries (two of which lying in the SMC), one is a low-mass X-ray binary, and one is classified as a flare star that is likely of RS CVn type. The main optical properties and inferred physical characteristics of these sources are presented and discussed.

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“…The optical normalcy of elusive AGNs and XBONGs may be caused by dilution from host-galaxy starlight (e.g., Moran et al 2002;Georgantopoulos & Georgakakis 2005;Caccianiga et al 2007;Civano et al 2007), attenuation by dust (e.g., Comastri et al 2002;Rigby et al 2006;Smith et al 2014), or perhaps radiatively inefficient accretion flows (Yuan & Narayan 2004), or more speculatively, the "switching-on" of the AGN, where the narrow-line region has yet to be photoionized .…”

Section: Optical Galaxiesmentioning

confidence: 99%

On R − W1 as a Diagnostic to Discover Obscured Active Galactic Nuclei in Wide-Area X-Ray Surveys

LaMassa

Civano

Brusa

et al. 2016

ApJ

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Capitalizing on the all-sky coverage of WISEand the 35% and 50% sky coverage from Sloan Digital Sky Survey and Pan-STARRS, respectively, we explore the efficacy of-, as a color diagnostic to identify obscured supermassive black hole accretion in wide-area X-ray surveys. We use the ∼16.5 deg 2 Stripe 82 X-ray survey data as a testbed to compare R W1 -with R−K, an oft-used obscured active galactic nucleus (AGN) selection criterion, and examine where different classes of objects lie in this parameter space. Most stars follow a well-defined path in R−K versus R W1space. We demonstrate that optically normal galaxies hosting X-ray AGNs at redshifts z 0.5 1 < < can be recovered with an R W1 4 -> colorcut, while they typically are not selected as AGNs based on their W W 1 2 -colors. Additionally, different observed X-ray luminosity bins favor different regions in R W1 -parameter space: moderate-luminosity AGNs > -erg s −1 ) have bluer colors; higher spectroscopic completeness of the Stripe 82X sample is needed to determine whether this is a selection effect or an intrinsic property. Finally, we parameterize X-ray obscuration of Stripe 82X AGNs by calculating their hardness ratios (HRs) and find no clear trends between HR and optical reddening. Our results will help inform best-effort practices in followingup obscured AGN candidates in current and future wide-area, shallow X-ray surveys, including the all-sky eROSITA mission.

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The HELLAS2XMMSurvey. II. Multiwavelength Observations of P3: An X‐Ray–bright, Optically Inactive Galaxy

Cited by 161 publications

References 34 publications

Unveiling the nature ofINTEGRALobjects through optical spectroscopy

Unveiling the nature ofINTEGRALobjects through optical spectroscopy

Unveiling the nature of INTEGRAL objects through optical spectroscopy

On R − W1 as a Diagnostic to Discover Obscured Active Galactic Nuclei in Wide-Area X-Ray Surveys

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