Unveiling the nature of INTEGRAL objects through optical spectroscopy. VIII. Identification of 44 newly detected hard X-ray sources

Abstract

(abridged) 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 identification program by selecting probable optical candidates using positional cross-correlation with soft X-ray, radio, and/or optical archives, and performing optical spectroscopy on them. As a result, we identified or more accurately characterized 44 counterparts of INTEGRAL sources: 32 active galactic nuclei, 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 available multiwavelength information. AGNs are the most abundant population among hard X-ray objects, and our results confirm this tendency when optical spectroscopy is used as an identification tool. The deeper sensitivity of 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. Comment: 22 pages, 14 figures, 6 tables, accepted for publication on A&A, main journal

Full text

Page 1

arXiv:1006.4513v1 [astro-ph.HE] 21 Jun 2010
Astronomy & Astrophysics manuscript no. aa14852
June 24, 2010
c ? ESO 2010
Unveiling the nature of INTEGRAL objects through optical
spectroscopy⋆
VIII. Identification of 44 newly detected hard X–ray sources
N. Masetti1, P. Parisi1,2, E. Palazzi1, E. Jim´ enez-Bail´ on3, V. Chavushyan4, L. Bassani1, A. Bazzano5, A.J.
Bird6, A.J. Dean6, P.A. Charles6,7, G. Galaz8, R. Landi1, A. Malizia1, E. Mason9, V.A. McBride6, D.
Minniti8,10, L. Morelli11, F. Schiavone1, J.B. Stephen1and P. Ubertini5
1INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, Via Gobetti 101, I-40129 Bologna, Italy
2Dipartimento di Astronomia, Universit` a di Bologna, Via Ranzani 1, I-40127 Bologna, Italy
3Instituto de Astronom´ ıa, Universidad Nacional Aut´ onoma de M´ exico, Apartado Postal 70-264, 04510 M´ exico D.F.,
M´ exico
4Instituto Nacional de Astrof´ ısica,´Optica y Electr´ onica, Apartado Postal 51-216, 72000 Puebla, M´ exico
5INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Roma, Via Fosso del Cavaliere 100, I-00133 Rome, Italy
6School of Physics & Astronomy, University of Southampton, Southampton, Hampshire, SO17 1BJ, United Kingdom
7South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
8Departamento de Astronom´ ıa y Astrof´ ısica, Pontificia Universidad Cat´ olica de Chile, Casilla 306, Santiago 22, Chile
9European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
10Specola Vaticana, V-00120 Citt` a del Vaticano
11Dipartimento di Astronomia, Universit` a di Padova, Vicolo dell’Osservatorio 3, I-35122 Padua, Italy
Received 23 April 2010; accepted 20 May 2010
ABSTRACT
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.
Key words. Galaxies: Seyfert — quasars: emission lines — X–rays: binaries — Stars: novae, cataclysmic variables —
Techniques: spectroscopic — X–rays: individuals
Send
(masetti@iasfbo.inaf.it)
⋆Based on observations collected at the following obser-
vatories: Cerro Tololo Interamerican Observatory (Chile);
Observatorio del Roque de los Muchachos of the Instituto
de Astrof´ ısica de Canarias (Canary Islands, Spain); ESO (La
Silla, Chile) under programme 083.D-0110(A); Astronomical
Observatory ofBolognain
Observatory of Asiago(Italy); Observatorio Astron´ omico
Nacional(San PedroM´ artir,
Astronomical Observatory (Sutherland, South Africa); Anglo-
Australian Observatory (Siding Spring, Australia); Apache
Point Observatory (New Mexico, USA).
offprintrequeststo: N. Masetti
Loiano (Italy); Astronomical
M´ exico);South African
1. Introduction
The fourth survey (Bird et al. 2010) performed by the IBIS
instrument (Ubertini et al. 2003) onboard the INTEGRAL
satellite (Winkler et al. 2003) has allowed the detection of
more than 700 hard X–ray sources over the whole sky in the
20–100 keV band down to an average flux level of about 1
mCrab and with positional accuracies ranging between 0.2
and ∼5 arcmin.
In this survey, IBIS found mostly active galactic nu-
clei (AGNs, 35% of the total number of detected objects)
followed by known Galactic X–ray binaries (26%) and cata-
clysmic variables (CVs, 5%). A large number of the remain-
ing objects (29% of all detections) has no obvious counter-

Page 2

2N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources
Fig.1. Optical images of the fields of 9 of the INTEGRAL hard X–ray sources selected in this paper for optical spec-
troscopic follow-up (see Table 1). The object name is indicated in each panel. The proposed optical counterparts are
indicated with tick marks. Field sizes are 5′×5′and are extracted from the DSS-II-Red survey with the exception of IGR
J04451−0445, which is extracted from the DSS-I survey. In all cases, north is up and east to the left.
part at other wavelengths and therefore cannot be associ-
ated with any known class of high-energy emitting objects.
Therefore, a multiwavelength observational campaign on
these unidentified sources is crucial to determine their na-
ture, and is especially important given that they constitute
one third of the whole set of IBIS detections.
X–ray analysis methods have helped in identifying the
nature of new INTEGRAL sources, such as for example
X–ray timing (by the detection of pulsations or orbital pe-
riods, e.g., Walter et al. 2006; Corbet et al. 2010; La Parola
et al. 2010) or, in general, X–ray spectroscopy and imaging
(Tomsick et al. 2009 and references therein). Alternatively,
and also quite effectively, cross-correlation with soft X–ray
catalogs and optical spectroscopy on thereby selected can-
didates allows the determination of the nature and main
multiwavelength characteristics of unidentified or poorly
studied hard X–ray objects.
We thuscontinue the
INTEGRAL sources started in 2004, which has allowed us
to identify up to now more than 100 sources by means of
optical spectroscopy (see Masetti et al. 2004, 2006a,b,c,d,
2008a, 2009 — hereafter Papers I-VII, respectively —
and Masetti et al. 2007, 2008b), by presenting optical
spectra of the firm or likely counterparts of 42 unidentified,
unclassified or poorly studied sources belonging to the 4th
IBIS catalog (Bird et al. 2010) or the online INTEGRAL
All-Sky Survey Source Catalog (Krivonos et al. 20101); we
moreover included two additional sources in our sample,
identification workon
1A preliminary version of this catalog can be found at
http://hea.iki.rssi.ru/rsdc/catalog/index.php

Page 3

N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources3
Fig.2. As Fig. 1, but for 9 more INTEGRAL sources of our sample (see Table 1).
that is, IGR J01054−7253 (Bozzo et al. 2009; Coe et
al. 2010) and Swift J0208.4−7428 (McBride et al. 2010)
observed in the Small Magellanic Cloud (SMC), thus
reaching a total of 44 objects. Optical spectroscopy for all
of them was acquired using 7 different telescopes and 2
public spectroscopic archives.
The paper is structured as follows: in Sect. 2, we explain
the criteria used to select the sample of INTEGRAL and
optical objects considered in this work. In Sect. 3, a brief
description of the observations is given. Section 4 reports
and discusses the results, divided into three broad classes of
sources (CVs, X–ray binaries, and AGNs), and an update of
the statistical outline of the identifications of INTEGRAL
sources obtained until now. Conclusions are drawn in Sect.
5.
The main results of this paper, along with the informa-
tion about the INTEGRAL sources that have been iden-
tified (by us or by other groups) using optical or near-
infrared (NIR) observations, are also collected in a web
page2that we maintain as a service to the scientific com-
munity (Masetti & Schiavone 2008). In this work, if not
otherwise stated, errors and limits are reported at 1σ and
3σ confidence levels, respectively. We also note that this
work supersedes the results presented in the preliminary
analysis of Masetti et al. (2010) in which the identifications
for a subsample of 25 sources were reported.
2. Sample selection
In a similar way to Papers I-VII, and this time using the two
largest and most recently available IBIS surveys (Bird et al.
2010; Krivonos et al. 2010), we selected unidentified or un-
classified hard X–ray sources that contain, within the IBIS
90% confidence level error box, a single bright soft X–ray
object detected either in the ROSAT all-sky surveys (Voges
et al. 1999, 2000), or with Swift/XRT (from Baumgartner
2http://www.iasfbo.inaf.it/extras/IGR/main.html

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4N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources
Fig.3. As Fig. 1, but for 9 more INTEGRAL sources of our sample (see Table 1).
et al. 2008, Landi et al. 2009, 2010, Mescheryakov et al.
2009, Krivonos et al. 2009, Coe et al. 2009, Kniazev et al.
2010, McBride et al. 2010, and — in some cases indepen-
dently — from the XRT archive3), or in the XMM-Newton
Slew Survey (Saxton et al. 2008), or with Chandra (Tomsick
et al. 2009). This approach was proven by Stephen et al.
(2006) to be very effective in associating, with a high degree
of probability, IBIS sources with a softer X–ray counterpart
and in turn drastically reducing their positional error cir-
cles to a few arcsec in radius, thus shrinking the search area
by a factor of ∼104.
After this first selection, we chose among these objects
those that had, within their refined 90% confidence level
soft X–ray error boxes4, a single or a few (3 at most) pos-
3XRT archival data are freely available at
http://www.asdc.asi.it/
4When needed, for the cases in which the soft X–ray posi-
tional error is given at 1σ confidence level (basically, the ROSAT
sible optical counterparts with magnitudes R<∼19 in the
DSS-II-Red survey5, for which optical spectroscopy could
be obtained with reasonable signal-to-noise ratio (S/N) at
telescopes with diameter smaller than 4 metres.
This allowed us to pinpoint 31 sources, to which we
added two hard X–ray objects detected with INTEGRAL
in the SMC, as mentioned above (Bozzo et al. 2009; Coe et
al. 2009, 2010; McBride et al. 2010).
To enlarge the sample, we performed a similar pro-
cedure by cross-correlating the above IBIS surveys with
radio catalogs such as the NVSS (Condon et al. 1998),
SUMSS (Mauch et al. 2003), and MGPS (Murphy et al.
2007) surveys when a soft X–ray observation of the hard
X–ray source field was not available. This step provided
and XMM-Newton Slew Survey sources) we rescaled it to the
corresponding 90% confidence level assuming a Gaussian prob-
ability distribution.
5Available at http://archive.eso.org/dss/dss

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N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources5
Fig.4. As Fig. 1, but for 9 more INTEGRAL sources of our sample (see Table 1).
5 more INTEGRAL sources with likely optical counter-
parts. Finally, we also considered IBIS objects that contain
within their error box a conspicuous galaxy belonging to the
2MASX archive (Skrutskie et al. 2006), or an emission-line
object present in the SIMBAD database6. This identified 6
additional IBIS sources to be included in our sample.
Although selected by means of cross-correlation with
optical catalogs only, the position of the possible counter-
part to IGR J08262−3736 is within the 2σ error circle of
a ROSAT all-sky faint survey source (Voges et al. 2000);
however, given the large extent of its ROSAT error circle
(31′′in radius at 1σ confidence level), we consider the as-
sociation between the optical and the ROSAT sources too
loose to be assumed as firm.
Thus, in total we gathered a sample of 44 INTEGRAL
objects with possible optical counterparts, which we ex-
plored by means of optical spectroscopy. Their names and
6Available at http://simbad.u-strasbg.fr
accurate coordinates (to 1′′or less) are reported in Table
1, while their optical finding charts are shown in Figs.
1-5, with the corresponding putative counterparts indi-
cated with tick marks. The finding chart for source IGR
J22292+6647 is not reported here as it was already pub-
lished in Landi et al. (2009).
For the source naming in Table 1, we simply adopted
the names as they appear in the relevant catalogs (Bird et
al. 2010; Krivonos 2010) or papers (Bozzo et al. 2009; Coe
et al. 2010; McBride et al. 2010), and the “IGR” alias when
available. However, we note that for one of the hard X–ray
objects selected by means of cross-correlation with soft X–
ray catalogs, i.e., 1RXS J191928.5−295808, we chose to use
its ROSAT name (thus associated with its soft X–ray emis-
sion) rather than the denomination reported in the 4thIBIS
Survey (PKS 1916−300; Bird et al. 2010) because the latter
refers to a radio source that is slightly but significantly off-
set from the optical and soft X–ray positions of the possible
counterpart to this INTEGRAL hard X–ray object.

Page 6

6 N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources
Fig.5. As Fig. 1, but for 7 more INTEGRAL sources of our sample (see
Table 1).
In any case, we wish to point out that the 11 sources
with no associated soft X–ray counterpart should be con-
sidered to have only a tentative, albeit likely, counterpart:
this is indicated with an asterisk in Table 1. This caution,
although to a much lesser extent, should also be applied to
those IBIS sources (IGR J03344+1506, IGR J09094+2735,
and 1RXS J211336.1+542226) associated only with an ob-
ject belonging to the ROSAT all-sky faint survey (Voges
et al. 2000) as pointed out by Stephen et al. (2006). The
reader is nevertheless referred to Paper III for the caveats
and the shortcomings of choosing, within an IBIS error box,
“peculiar” sources that are not straightforwardly linked to
an arcsec-sized soft X–ray position.
We also note that, for the high-energy sources in our
sample with more than one optical candidate in the cor-
responding arcsec-sized error box, all objects with R<∼19
were spectroscopically observed. However, we only indicate
their firm or likely optical counterpart, identified on the ba-
sis of peculiar spectral features (that is, emission lines). All
other candidates are considered no further because their
spectra do not exhibit any peculiarity.
To summarize, we emphasize that in our final sam-
ple there are 4 INTEGRAL sources (IGR J12107+3822,
Mescheryakov et al. 2009; IGR J13168−7157, Kniazev et
al. 2010; IGR J17009+3559, Krivonos et al. 2009; and IGR
J22292+6647, Butler et al. 2009) that, although already
identified by these authors, have incomplete information at
longer wavelengths or were independently observed by us
before their identification was published. Our observations
are thus presented here to confirm the nature of these ob-
jects and improve their classification and the amount of
information known about them.
3. Optical spectroscopy
Similarly to Papers VI and VII, the data presented in this
work were collected in the course of a campaign that lasted
one year and a half involving observations at the following
telescopes:

Page 7

N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources7
Table 1. Log of the spectroscopic observations presented in this paper (see text for details). If not indicated otherwise,
source coordinates were extracted from the 2MASS catalog and have an accuracy better than 0.′′1.
(1)(2)
RA
(3)
Dec
(J2000)
(4)(5)(6)
Disp.
(˚ A/pix)
(7)(8)
Object Telescope+instrument
λ range
(˚ A)
UT Date & Time
at mid-exposure
Exposure
time (s)(J2000)
IGR J00158+5605
IGR J00465−4005
IGR J01054−7253
IGR J01545+6437∗
Swift J0208.4−7428
IGR J02086−1742
IGR J03344+1506
IGR J04451−0445∗
IGR J04571+4527
IGR J05253+6447
IGR J06058−2755
IGR J06293−1359∗
1RXS J080114.6−462324
IGR J08262−3736∗
Swift J0845.0−3531
IGR J08557+6420
IGR J09094+2735
MCG +04−26−006
PKS 1143−696
IGR J12107+3822
IGR J12123−5802
IGR J1248.2−5828
IGR J13168−7157
IGR J13187+0322∗
IGR J14301−4158∗
Swift J1513.8−8125
IGR J15311−3737
IGR J15549−3740∗
IGR J16287−5021
IGR J16327−4940∗
1RXS J165443.5−191620
IGR J17009+3559
IGR J18078+1123
IGR J18308+0928
IGR J18311−3337∗
IGR J19077−3925
IGR J19113+1533∗
IGR J19118−1707∗
1RXS J191928.5−295808
IGR J19552+0044
1RXS J211336.1+542226
1RXS J211928.4+333259
1RXS J213944.3+595016
IGR J22292+6647
00:15:54.19
00:46:20.68
01:04:42.28
01:54:35.29
02:06:45.17
02:08:34.95
03:34:32.77
04:44:52.93
04:57:06.98
05:24:28.61
06:05:48.96
06:29:09.3‡
08:01:17.03
08:26:13.65
08:45:21.38
08:55:12.54
09:09:18.75
10:46:42.51
11:45:53.62
12:10:44.28
12:12:26.24
12:47:57.84
13:16:54.28
13:18:31.24
14:30:12.17
15:14:41.92
15:30:51.79
15:54:46.76
16:28:27.36
16:32:39.95
16:54:43.74
17:00:53.00
18:07:49.91
18:30:50.64
18:31:14.75
19:07:50.36
19:11:18.83
19:11:42.64
19:19:28.04
19:55:12.47
21:13:35.38†
21:19:29.13
21:39:45.1‡
22:29:13.84
+56:02:57.5
−40:05:49.1
−72:54:03.7
+64:37:57.5
−74:27:47.7
−17:39:34.8
+15:08:01.2
−04:46:39.5
+45:27:48.5
+64:44:43.7
−27:54:40.1
−14:04:49‡
−46:23:27.5
−37:37:11.9
−35:30:24.2
+64:23:45.5
+27:37:33.7
+25:55:53.9
−69:54:01.8
+38:20:10.2
−58:00:20.5
−58:30:00.2
−71:55:27.1
+03:19:48.9
−41:58:31.4
−81:23:38.0
−37:34:57.3
−37:38:19.1
−50:22:42.9
−49:42:13.8
−19:16:31.1
+35:59:56.2
+11:20:49.1
+09:28:41.7
−33:36:08.5
−39:23:31.9
+15:32:32.8
−17:10:05.1
−29:58:08.0
+00:45:36.6
+54:22:32.8†
+33:32:57.0
+59:50:14‡
+66:46:51.5
Cassini+BFOSC
CTIO 1.5m+RC Spec.
Radcliffe+Gr. Spec.
Copernicus+AFOSC
CTIO 1.5m+RC Spec.
SPM 2.1m+B&C Spec.
SPM 2.1m+B&C Spec.
SPM 2.1m+B&C Spec.
SPM 2.1m+B&C Spec.
Cassini+BFOSC
CTIO 1.5m+RC Spec.
SPM 2.1m+B&C Spec.
NTT+EFOSC2
CTIO 1.5m+RC Spec.
CTIO 1.5m+RC Spec.
SPM 2.1m+B&C Spec.
SDSS+CCD Spec.
SPM 2.1m+B&C Spec.
CTIO 1.5m+RC Spec.
SDSS+CCD Spec.
CTIO 1.5m+RC Spec.
Radcliffe+Gr. Spec.
CTIO 1.5m+RC Spec.
SDSS+CCD Spec.
AAT+6dF
Radcliffe+Gr. Spec.
Radcliffe+Gr. Spec.
AAT+6dF
NTT+EFOSC2
Radcliffe+Gr. Spec.
SPM 2.1m+B&C Spec.
Copernicus+AFOSC
SPM 2.1m+B&C Spec.
Cassini+BFOSC
AAT+6dF
AAT+6dF
SPM 2.1m+B&C Spec.
AAT+6dF
AAT+6dF
Cassini+BFOSC
SPM 2.1m+B&C Spec.
SPM 2.1m+B&C Spec.
SPM 2.1m+B&C Spec.
TNG+DOLoReS
3500-8700
3300-10500
3850-7200
3500-7800
3300-10500
3500-7800
3500-7800
3500-7800
3500-7800
3500-8700
3300-10500
3500-7800
3650-9300
3300-10500
3300-10500
3500-7800
3800-9200
3500-7800
3300-10500
3800-9200
3300-10500
3850-7200
3300-10500
3800-9200
3900-7600
3850-7200
3850-7200
3900-7600
3650-9300
3850-7200
3500-7800
3500-7800
3500-7800
3500-8700
3900-7600
3900-7600
3500-7800
3900-7600
3900-7600
3500-8700
3500-7800
3500-7800
3500-7800
3800-8000
4.0
5.7
2.3
4.2
5.7
4.0
4.0
4.0
4.0
4.0
5.7
4.0
5.5
5.7
5.7
4.0
1.0
4.0
5.7
1.0
5.7
2.3
5.7
1.0
1.6
2.3
2.3
1.6
5.5
2.3
4.0
4.2
4.0
4.0
1.6
1.6
4.0
1.6
1.6
4.0
4.0
4.0
4.0
2.5
16 Nov 2009, 19:46
12 Sep 2009, 04:22
16 Aug 2009, 03:17
07 Dec 2008, 22:51
27 Dec 2009, 01:13
03 Dec 2008, 06:28
19 Sep 2009, 10:31
19 Sep 2009, 11:49
29 Jan 2009, 07:01
09 Dec 2009, 22:35
30 Nov 2009, 02:51
05 Dec 2008, 05:38
01 Jun 2009, 00:31
30 Nov 2009, 08:18
19 Dec 2009, 06:10
30 Jan 2009, 07:17
17 Jan 2005, 06:22
03 Dec 2008, 11:51
31 Dec 2009, 06:19
13 Apr 2005, 07:12
31 Dec 2009, 07:22
13 Aug 2009, 17:56
28 Jan 2010, 05:15
22 Jan 2002, 13:07
29 Jun 2003, 12:00
13 Aug 2009, 20:37
15 Aug 2009, 19:36
12 May 2002, 15:38
31 May 2009, 01:41
10 Aug 2009, 20:44
21 Jun 2009, 06:13
16 Oct 2009, 18:04
21 Jun 2009, 18:49
18 May 2009, 23:24
27 Jul 2003, 12:48
26 Jun 2003, 15:25
04 Dec 2008, 02:06
21 Apr 2004, 18:34
10 Sep 2002, 10:10
19 May 2009, 01:58
22 Jun 2009, 10:21
04 Dec 2008, 03:12
24 Jun 2009, 10:44
13 Aug 2008, 01:27
2×1800
2×1800
2×1800
2×1800
2×1200
2×1800
2×1800
2×1800
2×1800
2×1800
2×1000
2×1800
1200
2×900
2×1800
2×1800
2700
2×1800
2×1800
2300
2×1800
1800
2×1200
4800
600+1200
2×1800
2×1800
1200+600
1200
2×1800
2×1800
2×1800
2×1800
2×1200
1200+600
1200+600
1200
1200+600
1200+600
2×1800
3×1800
2×1800
2×1800
1800
∗: tentative association (see text).
†: coordinates extracted from the USNO catalogs, having an accuracy of about 0.′′2 (Deutsch 1999; Assafin et al. 2001; Monet et al. 2003).
‡: coordinates extracted from the DSS-II-Red frames, having an accuracy of ∼1′′.
– the 1.5m at the Cerro Tololo Interamerican Observatory
(CTIO), Chile;
– the 1.52m “Cassini” telescope of the Astronomical
Observatory of Bologna, in Loiano, Italy;
– the 1.82m “Copernicus” telescope of the Astronomical
Observatory of Asiago, Italy;
– the 1.9m “Radcliffe” telescope of the South African
Astronomical Observatory (SAAO) in Sutherland,
South Africa;
– the 2.1m telescope of the Observatorio Astron´ omico
Nacional in San Pedro Martir (SPM), M´ exico;
– the 3.58m “Telescopio Nazionale Galileo” (TNG) at the
Roque de Los Muchachos Observatory in La Palma,
Spain;
– the 3.58m “New Technology Telescope” (NTT) at the
ESO-La Silla Observatory, Chile.
The spectroscopic data acquired at these telescopes
were optimally extracted (Horne 1986) and reduced follow-
ing standard procedures using IRAF7. Calibration frames
(flat fields and bias) were taken on the day preceeding
or following the observing night. The wavelength calibra-
tion was performed using lamp data acquired soon after
each on-target spectroscopic acquisiton; the uncertainty
in this calibration was ∼0.5˚ A in all cases according to
our checks made using the positions of background night
sky lines. Flux calibration was performed using catalogued
spectrophotometric standards.
Additional spectra were retrieved from two different as-
tronomical archives: the Sloan Digital Sky Survey8(SDSS,
Adelman-McCarthy et al. 2007) archive, and the Six-degree
7IRAF is the Image Reduction and Analysis Facility made
available to the astronomical community by the National
Optical Astronomy Observatories, which are operated by
AURA, Inc., under contract with the U.S. National Science
Foundation. It is available at http://iraf.noao.edu/
8http://www.sdss.org/

Page 8

8 N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources
Field Galaxy Survey9(6dFGS) archive (Jones et al. 2004).
Since the 6dFGS archive provides spectra that are not flux-
calibrated, we used the optical photometric information in
Jones et al. (2005) to calibrate the 6dFGS spectra presented
in this work.
We report in Table 1 the detailed log of all observations.
We list in Col. 1 the names of the observed INTEGRAL
sources. In Cols. 2 and 3, we indicate the possible optical
counterpart coordinates, extracted from the 2MASS cata-
log (with an accuracy of ≤0.′′1, according to Skrutskie et
al. 2006), from the USNO catalogs (with uncertainties of
about 0.′′2: Deutsch 1999; Assafin et al. 2001; Monet et al.
2003), or from the DSS-II-Red astrometry (which has a pre-
cision of ∼1′′). In Col. 4, we report the telescope and the
instrument used for the observations. The characteristics of
each spectrograph are presented in Cols. 5 and 6. Column
7 provides the observation date and the UT time at mid-
exposure, while Col. 8 reports the exposure times and the
number of observations for each source.
To provide additional information about the possible
counterpart to IGR J16287−5021, we also analyzed an op-
tical R-band frame acquired with the NTT plus EFOSC2 on
31 May 2009 (start time: 01:27 UT; duration: 20 s) in seeing
conditions of 1.′′8; the 2×2-rebinned CCD of EFOSC2 pro-
vides a plate scale of 0.′′24/pix and a useful field of 4.′1×4.′1.
This imaging frame was corrected for both bias and flat-
field using standard procedures and was calibrated using
nearby USNO-A2.010stars. Simple aperture photometry,
within the MIDAS11package, was then used to evaluate
the R-band magnitude of the possible optical counterpart
to IGR J16287−5021.
4. Results
We describe the identification and classification criteria for
the optical spectra of the 44 sources belonging to the sample
considered in this work. The optical magnitudes quoted be-
low, if not stated otherwise, are extracted from the USNO-
A2.0 catalog.
To determinate the reddening along the line of sight to
the Galactic sources of our sample, when possible and ap-
plicable, we considered an intrinsic Hα/Hβline ratio of 2.86
(Osterbrock 1989) and inferred the corresponding color ex-
cess by comparing the intrinsic line ratio with the measured
one by applying the Galactic extinction law of Cardelli et
al. (1989).
To determine the distances of the compact Galactic X–
ray sources of our sample, for CVs we assumed an ab-
solute magnitude MV ∼ 9 and an intrinsic color index
(V − R)0∼ 0 mag (Warner 1995), whereas for high-mass
X–ray binaries (HMXBs), when applicable, we used the
intrinsic stellar color indices and absolute magnitudes re-
ported in Lang (1992) and Wegner (1994). For the single
low-mass X–ray binary (LMXB) in our sample, we consid-
ered (V −R)0∼ 0 ∼ MR(e.g., van Paradijs & McClintock
1995). Although these methods basically provide an order-
of-magnitude value for the distance of Galactic sources, our
past experience (Papers I-VII) tells us that these estimates
9http://www.aao.gov.au/local/www/6df/
10Available at
http://archive.eso.org/skycat/servers/usnoa/
11http://www.eso.org/projects/esomidas
are in general correct to within 50% of the refined value
subsequently determined with more precise approaches.
For the emission-line AGN classification, we used the
criteria of Veilleux & Osterbrock (1987) and the line ratio
diagnostics of both Ho et al. (1993, 1997) and Kauffmann
et al. (2003); for the subclass assignation of Seyfert 1 nu-
clei, we used the Hβ/[O iii]λ5007 line flux ratio criterion
described in Winkler (1992), and the criteria of Osterbrock
& Pogge (1985) for the classification of narrow-line Seyfert
1 galaxies.
The spectra of the galaxies shown here were not cor-
rected for starlight contamination (see, e.g., Ho et al. 1993,
1997) because of the limited S/N and spectral resolution.
In this case, we also do not expect this to affect any of our
main results and conclusions.
In the following, we consider a cosmology with H0= 65
km s−1Mpc−1, ΩΛ = 0.7, and Ωm = 0.3; the luminosity
distances of the extragalactic objects reported in this paper
were computed for these parameters using the Cosmology
Calculator of Wright (2006). When not explicitly stated
otherwise, for our X–ray flux estimates we assume a Crab-
like spectrum except for the XMM-Newton sources, for
which we considered the fluxes reported in Saxton et al.
(2008).
In the following subsections, we consider the object
identifications by dividing them into three broad classes
(CVs, X–ray binaries, and AGNs) listed according to their
increasing distance from Earth.
4.1. CVs
We identify 6 objects of our sample (IGR J04571+4527,
1RXS J080114.6−462324,
J165443.5−191620,IGRJ19552+0044,
J211336.1+542226) as dwarf
the characteristics of their optical spectra (Fig. 6). All of
them show Balmer emission lines up to at least Hδ, as
well as helium lines in emission. All of the detected lines
are consistent with a redshift z = 0, indicating that these
sources are within our Galaxy.
The main spectral diagnostic lines of these objects, as
well as the main astrophysical parameters which can be
inferred from the available optical and X–ray observational
data, are reported in Table 2. The X–ray luminosities listed
in this table for the various objects were computed using
the fluxes reported in Voges et al. (1999, 2000), Bird et al.
(2010), Cusumano et al. (2010), Krivonos et al. (2010), and
Landi et al. (2010).
In the spectra of some of these sources (namely
1RXS J080114.6−462324, IGR J12123−5802, and 1RXS
J165443.5−191620), the He ii λ4686 / Hβequivalent width
(EW) ratio is>∼0.5 and the EWs of these emission lines are
around (or larger than) 10˚ A. This indicates that these
sources are likely magnetic CVs belonging to the inter-
mediate polar (IP) subclass (see Warner 1995 and refer-
ences therein). To a lesser extent, a tentative IP classifi-
cation can also be made for IGR J19552+0044 and 1RXS
J211336.1+542226 given the strength of their He ii emis-
sion, although their He ii/Hβ EW ratios are <0.5. The
spectral characteristics of IGR J04571+4527 (namely the
He ii/HβEW ratio and the He ii EW) instead imply that
it is a non-magnetic CV.
IGR J12123−5802, 1RXS
1RXS and
becausenovaCVs of

Page 9

N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources9
Fig.6. Spectra (not corrected for the intervening Galactic absorption) of the optical counterparts of the 6 CVs belonging
to the sample of INTEGRAL sources presented in this paper. For each spectrum, the main spectral features are labeled.
The symbol ⊕ indicates atmospheric telluric absorption bands.
These IP classifications however need confirmation by
the measurement of both the orbital period and the spin
period of the white dwarf (WD) harbored in these systems,
as optical spectroscopy is sometimes insufficient to firmly
establish the magnetic nature of CVs (see e.g., Pretorius
2009 and de Martino et al. 2010).
4.2. X–ray binaries
Six objects of our sample can be classified as X–ray bina-
ries, given their optical spectral shape and characteristics
(see Fig. 7), that is, Balmer emission lines at redshift 0
superimposed on an intrinsically blue continuum (in some
cases modified by interstellar reddening).
Table 3 collects the relevant optical spectral information
about these 6 sources, along with their main parameters
inferred from the available X–ray and optical data. X–ray
luminosities in Table 3 were calculated using the fluxes in
Saxton et al. (2008), Bozzo et al. (2009), Rodriguez et al.
(2009), Tomsick et al. (2009), Bird et al. (2010), Krivonos et
al. (2010), and McBride et al. (2010). In this table, we also
report the results of our R-band photometry of the coun-

Page 10

10 N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources
Table 2. Synoptic table containing the main results concerning the 6 CVs (see Fig. 6) identified in the present sample
of INTEGRAL sources.
ObjectHα
Hβ
He ii λ4686
RAV
dLX
EW FluxEW FluxEW Fluxmag (mag)(pc)
IGR J04571+452719.4±0.6 10.3±0.3 9.5±0.54.8±0.2 3.6±0.41.67±0.1717.5
∼0
∼5000.10 (0.1–2.4)
53 (17–60)
67 (14–150)
1RXS J080114.6−46232419.9±0.6 7.2±0.2 16.7±0.8 6.5±0.39.7±0.73.8±0.314.8
∼0
∼150 0.064 (0.1–2.4)
1.1 (0.2–12)
0.43–1.4 (2–10)
1.6 (20–100)
IGR J12123−580220.3±1.07.1±0.412.7±1.3 5.1±0.5 7.4±0.73.5±0.3 15.4
∼0
∼190 1.9 (2–10)
1.6 (20–40)
<1.6 (40–100)
1RXS J165443.5−19162038.7±1.260.9±1.8 18.5±0.9 33.2±1.7 7.5±0.5 13.4±0.9 15.6
∼0
∼2100.17 (0.1–2.4)
7.7 (20–100)
IGR J19552+0044271±8 164±5 264±8 168±5 39±2 60±3 16.0
∼0
∼250 0.66 (0.1–2.4)
4.2 (0.2–12)
6.2 (20–40)
<4.9 (40–100)
1RXS J211336.1+54222646±2 5.6±0.3 43±3 2.61±0.1810±2 5.0±1.0 18.8
∼0
∼910 1.3 (0.1–2.4)
99 (20–100)
Note: EWs are expressed in˚ A, line fluxes are in units of 10−15erg cm−2s−1, whereas X–ray luminosities are in units of 1031erg s−1and the
reference band (between round brackets) is expressed in keV.
Table 3. Synoptic table containing the main results concerning the 6 X–ray binaries (see Fig. 7) identified in the present
sample of INTEGRAL sources.
ObjectHα
Hβ
He ii λ4686 Optical
AV
d
Spectral
LX
EW FluxEW FluxEWFlux mag. (mag)(kpc) type
IGR J01054−7253 7.15±0.1516.8±0.30.47±0.12 2.0±0.5 in abs.in abs. 14.81a(V )
∼0.7 60b
B0 III 0.13 (0.1–2.4)
700c(3–10)
77 (20–100)
Swift J0208.4−74282.9±0.3 4.5±0.5in abs.in abs.
<0.5
<0.2 14.75d(V ) 0.18e
60b
B1 III19 (0.2–12)
6.5 (3–10)
108 (15–35)
IGR J08262−373665±2 1050±30 5.5±0.4 96±7in abs.? in abs.? 12.9f(V )
∼3.3e
∼6.1 OB V0.43 (20–100)
IGR J16327−494031.3±0.9370±11 7.6±0.73.8±0.4in abs.in abs.15.5 (R) 11.2
≈2 OB giant
<0.0072 (20–40)
0.018 (40–100)
IGR J19113+153322.5±1.1 159±8 3.6±0.75.9±1.2
<1.2
<1.513.3 (R) 7.0
∼9.1sgB[e]
<0.15 (20–40)
<0.28 (40–100)
IGR J16287−502152±3 1.75±0.09 19±6 0.23±0.07 15±5 0.16±0.0519.5g(R) 3.1
<19—
<1.3 (0.2–12)
<2.9 (0.3–10)
<2.8 (2–10)
<3.8 (17–60)
<2.3 (20–40)
<1.2 (40–100)
Note: EWs are expressed in˚ A, line fluxes are in units of 10−15erg cm−2s−1, whereas X–ray luminosities are in units of 1035erg s−1and the reference
band (between round brackets) is expressed in keV.
a: from Massey (2002);b: from Harries et al. (2003);c: from Coe et al. (2010);d: from Demers & Irwin (1991);
e: only the Galactic reddening along the line of sight was assumed;f: from Pettersson (1987);g: this work.
terpart of IGR J16287−5021, described in Sect. 3, which
infers a magnitude R = 19.5±0.1.
Fiveof the sources
J0208.4−7428, IGR J08262−3736, IGR J16327−4940, and
IGR J19113+1533)can be classified as HMXBs due to their
overall early-type star spectral appearance, which is typical
of this class of objects (see e.g. Papers II-VII).
The spectra of the last three sources appear substan-
tially reddened, which is indicative of interstellar dust along
(IGRJ01054−7253, Swift
their lines of sight. This is quite common in X–ray binaries
detected with INTEGRAL (e.g., Papers III-VII) and indi-
cates that these objects are relatively far from Earth. The
confirmation of reddening towards these sources comes from
either their Hα/Hβline ratio (see Table 3) or their optical
colors. For IGR J08262−3736 and IGR J16327−4940, we
find a reddening compatible with the Galactic one along
the line of sight of the object (Schlegel et al. 1998).

Page 11

N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources11
Fig.7. Spectra (not corrected for the intervening Galactic absorption) of the optical counterparts of the 6 X–ray binaries
belonging to the sample of INTEGRAL sources presented in this paper. For each spectrum, the main spectral features
are labeled. The symbol ⊕ indicates atmospheric telluric absorption bands.
The Balmer line ratio of KW97 36−14, the putative op-
tical counterpart of IGR J19113+1533, instead indicates
an absorption that is larger than the Galactic one, im-
plying that there is additional absorbing material local to
the source. The spectral appearance of this optical object
resembles that of IGR J16318−4848 (Filliatre & Chaty
2004), a heavily absorbed X–ray binary hosting a super-
giant B[e] star, albeit the source of our sample is much
less affected by reddening. Assuming these two sources to
be similar, and the distance to IGR J16318−4848 as re-
ported in Rahoui et al. (2008), the relevant parameters in
Table 3 for IGR J19113+1533 were computed. We note
that, if pointed soft X–ray observations confirm the associ-
ation of IGR J19113+1533 with KW97 36−14, this would
be the second supergiant B[e]/X–ray binary detected by
INTEGRAL at hard X–rays.
For the first 4 HMXBs of Table 3, we obtained the con-
straints for distance, reddening, spectral type, and X–ray
luminosity shown in the table by considering the absolute
magnitudes of early-type stars and by applying the method
described in Papers III and IV for the classification of this
type of X–ray sources. In particular, the optical counter-
parts of IGR J01054−7253 and Swift J0208.4−7428 are
consistent with being blue giant stars at the distance of
the SMC (60 kpc: see e.g. Harries et al. 2003) in terms
of line redshift, magnitude, and optical colors. This result

Page 12

12 N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources
for IGR J01054−7253 was independently confirmed by the
X–ray timing analysis of Townsend et al. (2009): these au-
thors indeed classify this source as a Be/X–ray binary on
the basis of its orbital and neutron star spin periodicities.
For Swift J0208.4−7428, the use of our spectroscopy with
the available optical photometry (Demers & Irwin 1991)
allowed us to state that this is a B-type star and thus
improve the preliminary classification given to the puta-
tive optical counterpart of this source by McBride et al.
(2010). The two remaining cases (IGR J08262−3736 and
IGR J16327−4940) are instead broadly classified as OB
stars due to the strength of their Hαemission lines, which
is much larger than the typical values seen in blue super-
giants (Leitherer 1988); the Galactic Arm model of Leitch
& Vasisht (1998) is then used to infer a likely distance
of these stars and hence their luminosity class. The lack
of further detailed photometric optical information and of
higher-resolution spectroscopy does not allow us to refine
our classification for the putative counterparts of these two
INTEGRAL sources.
The HMXB nature of IGR J16287−5021 can instead be
excluded because its spectral shape differs from those of
the HMXBs in the present sample (see Fig. 7, lower right
panel); it resembles instead those of reddened LMXBs de-
tected with INTEGRAL (see Papers V-VII). The presence
of Balmer and helium emission lines and no apparent ab-
sorption lines on top of a reddened (but intrinsically blue)
continuum are indicative of an accretion disk dominating
the total optical emission; the relative faintness of the op-
tical/NIR counterpart also indicates that the size of the
system (and thus of the donor star) is much smaller than
that of a HMXB. In addition, the reddening itself suggests
that this source lies far from Earth.
This is confirmed by the X–ray spectrum of this ob-
ject (Tomsick et al. 2009), which also reveals absorption
toward the source direction. A CV identification would in-
stead make the relatively large optical and X–ray absorp-
tion mentioned above incompatible with the relatively small
distance of the source (∼500 pc) derived from its R-band
magnitude. We thus conclude that this hard X–ray source
is a LMXB. Despite this classification, we are unable to pro-
vide meaningful constraints on the distance to this source:
the assumptions of Sect. 3 only allow us to determine a dis-
tance of 19 kpc (which can be considered as an upper limit
given its large value; see Table 3).
We finally note that none of these systems are associ-
ated with a radio source. This implies that they are X–ray
binaries that do not display collimated (jet-like) outflows,
that is, that no system is a microquasar.
4.3. AGNs
It is found that 32 objects of our sample have optical spec-
tra that allow us to classify them as AGNs (see Figs. 8-
13). Thirty-one of them exhibit strong, redshifted broad
and/or narrow emission lines typical of nuclear galactic ac-
tivity: 18 of them can be classified as Type 1 (broad-line)
and 13 as Type 2 (narrow-line) AGNs (see Tables 4 and 5,
respectively, for their breakdown in terms of subclasses).
In any case, we wish to draw the reader’s attention to
our identification, for the first time, of two definite low-
ionization nuclear emission-line regions (LINERs; Heckman
1980) among the unknown-nature hard X–ray sources de-
tected with INTEGRAL: they are MCG +04−26−006 and
IGR J19118−1707 (see Fig. 13).
In a single galaxy, IGR J17009+3559, the nuclear ac-
tivity was discovered only thanks to soft X–ray emission
detected with Swift (Krivonos et al. 2009), because no emis-
sion lines appear in its optical spectrum (Fig. 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). The as-
sociation of this galaxy with a NVSS radio source (Condon
et al. 1998) also points to an AGN nature. We note that,
as already mentioned and at variance with Krivonos et al.
(2009), we do not detect any emission line in the optical
spectrum of IGR J17009+3559.
The main observed and inferred parameters for each of
these two broad classes of AGNs are reported in Tables 4
and 5, respectively; those regarding the XBONG are shown
in Table 5. In these tables, X–ray luminosities were com-
puted from the fluxes reported in Voges et al. (1999, 2000),
Saxton et al. (2008), Krivonos et al. (2009), Bird et al.
(2010), Cusumano et al. (2010), Krivonos et al. (2010),
Landi et al. (2010), Rodriguez et al. (2010), and Tueller
et al. (2010).
For most of the AGNs in our sample (that is, 22 objects
out of 32), the redshift value was determined or explictly
published12in this work for the first time. The redshifts of
the remaining 10 sources are consistent with those reported
in the literature, i.e., in the Hyperleda archive (Prugniel
2005), Mescheryakov et al. (2009), Kniazev et al. (2010),
Krivonos et al. (2009), and Butler et al. (2009).
We were also able to give a more accurate classi-
fication of the three sources (IGR J12107+3822, IGR
J13168−7157, and IGR J22292+6647) independently iden-
tified by Mescheryakov et al. (2009), Kniazev et al. (2010),
and Butler et al. (2009), respectively: in detail, all of them
could be classified as Seyfert 1.5 galaxies.
In addition, we slightly corrected the classification of
Swift J1513.8−8125 from Seyfert 1.9 (as given in Tueller
et al. 2010) to Seyfert 1.2, based on the appearance of its
optical spectrum (Fig. 9, lower left panel). At this stage,
we are unable to say whether this classification mismatch
is caused by intrinsic spectral variability of the source in
the optical.
When we examined in detail the optical and X–ray
properties of the AGN sources of our sample, we found
the following noteworthy issues for some selected cases. We
note that IGR J00158+5605 could have been classified as
a narrow-line Seyfert 1 AGN, given the narrowness of the
full width at half maximum (FWHM) of its Hβ emission
(∼2000 km s−1); however, owing to the absence of the Fe ii
bumps around 4600˚ A and 5200˚ A, we opted for a Seyfert
1.5 galaxy classification.
It is also seen that, among all narrow-line AGNs (in
Table 5) for which an estimate of the local absorption can
be obtained, the LINER MCG +04−26−006 appears to
display no reddening local to the AGN host. This suggests
that this source may be a “naked” LINER. While “naked”
Seyfert 2 galaxies, i.e. AGNs that lack the broad-line region
12We here define as “explicitly published” the galaxy redshifts
that appeared in published papers, rather than simply in on-
line catalogs or databases (such as, for instance, the SIMBAD
database).

Page 13

N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources13
Table 4. Synoptic table containing the main results concerning the 18 broad emission-line AGNs (Figs. 8-10) identified
or observed in the present sample of INTEGRAL sources.
Object
FHα
FHβ
F[OIII]
Class
zDL (Mpc)
E(B − V )Gal
LX
IGR J00158+5605*
*
27.7±1.3
[88±4]
30.0±0.9
[94±3]
Sy1.5 0.169875.5 0.427 1.8 (0.1–2.4)
6.1 (0.2–2)
35 (20–40)
<26 (40–100)
IGR J02086−1742*
*
120±12
[126±13]
38.5±1.9
[42±2]
Sy1.20.129 651.80.028 1.1 (0.1–2.4)
33 (2–10)
140 (20–100)
IGR J06058−2755*
*
58±6
[64±6]
66±3
[72±4]
Sy1.50.090443.1 0.030 5.0 (0.1–2.4)
30 (0.2–12)
36 (17–60)
Swift J0845.0−3531*
*
26.3±1.3
[112±6]
5.4±0.3
[22.9±1.6]
Sy1.2 0.137695.7 0.531 5.9 (0.1–2.4)
78 (14–150)
50 (17–60)
IGR J09094+2735*
*
4.7±0.3
[4.8±0.3]
1.36±0.04
[1.51±0.05]
NLSy1 0.28441572.40.030 6.7 (0.1–2.4)
920 (17–60)
PKS 1143−696*
*
48±2
[134±7]
1.0±0.1
[2.4±0.2]
Sy1.2 0.2441320.20.385 23 (0.1–2.4)
120 (2–10)
230 (17–60)
280 (20–100)
IGR J12107+3822*
*
109±7
[115±7]
64.2±1.9
[68±2]
Sy1.5 0.0229107.50.021 0.31 (0.2–12)
1.8 (14–150)
1.6 (17–60)
IGR J1248.2−5828*
*
1.1±0.3
[5.8±1.6]
7.8±0.5
[54±4]
Sy1.90.028131.9 0.6240.85 (2–10)
1.6 (17–60)
2.1 (20–100)
IGR J13168−7157*
*
67±10
[160±20]
47.1±1.4
[103±3]
Sy1.5 0.070 339.90.255 0.60 (0.1–2.4)
11 (0.2–12)
13 (17–60)
IGR J13187+0322—
—
17.2±1.7
[17.2±1.7]
1.5±0.3
[1.5±0.3]
Type 1
QSO
0.6058 3846.20.031
<540 (20–40)
<1300 (40–100)
Swift J1513.8−8125*
*
103±5
[223±11]
37.3±1.1
[83±2]
Sy1.2 0.069334.80.272 20 (14–150)
34 (14–195)
15 (17–60)
IGR J15311−3737—
—
48±2
[120±4]
6.9±0.3
[16.6±0.5]
Sy1 0.127 640.80.320 2.3 (0.1–2.4)
12–16 (0.2–12)
44 (20–100)
IGR J18078+1123*
*
64±4
[90±6]
12.6±0.6
[18.6±0.9]
Sy1/1.20.078 380.9 0.1311.2 (0.1–2.4)
51 (17–60)
IGR J19077−3925*
*
4.8±0.7
[6.2±0.9]
20.1±1.2
[28.0±1.4]
Sy1.90.0760 370.60.107 1.3 (0.1–2.4)
24 (20–100)
1RXS J191928.5−295808*
*
42±8
[56±11]
122±6
[183±9]
Sy1.5/1.8 0.1669863.5 0.139 12 (0.1–2.4)
120 (17–60)
67 (20–40)
<42 (40–100)
1RXS J211928.4+333259*
*
10±2
[18±3]
15.2±0.8
[29.6±1.5]
Sy1.50.051 244.40.217 0.44 (0.1–2.4)
6.8 (0.2–12)
5.6 (14–150)
11 (14–195)
9.1 (17–60)
11 (20–100)
1RXS J213944.3+595016*
*
3.0±0.2
[112±8]
2.01±0.10
[72±4]
Sy1.50.114 570.4 1.2711.7 (0.1–2.4)
23 (2–10)
14 (14–150)
40 (20–100)
IGR J22292+6647*
*
2.25±0.11
[52±3]
1.24±0.06
[26.3±1.3]
Sy1.50.112559.6 1.089 0.63 (0.1–2.4)
12 (0.2–12)
25 (2–10)
55 (14–150)
100 (14–195)
42 (17–60)
42 (20–100)
Note: emission-line fluxes are reported both as observed and (between square brackets) corrected for the intervening Galactic
absorption E(B − V )Galalong the object line of sight (from Schlegel et al. 1998). Line fluxes are in units of 10−15erg cm−2s−1,
whereas X–ray luminosities are in units of 1043erg s−1and the reference band (between round brackets) is expressed in keV.
The typical error in the redshift measurement is ±0.001 but for the SDSS and 6dFGS spectra, for which an uncertainty
of ±0.0003 can be assumed.
∗: heavily blended with [N ii] lines

Page 14

14N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources
Table 5. Synoptic table containing the main results concerning the 13 narrow emission-line AGNs and of the single
XBONG (see Figs. 11-13) identified or observed in the present sample of INTEGRAL sources.
Object
FHα
FHβ
F[OIII]
Class
zDL
E(B − V )
LX
(Mpc)Gal.AGN
IGR J00465−40051.8±0.4
[2.1±0.6]
0.17±0.05
[0.21±0.07]
3.63±0.18
[3.71±0.19]
Sy20.201 1061.30.0111.26 16 (2–10)
480 (20–100)
IGR J01545+643727±3
[170±20]
2.6±0.3
[41±5]
17.0±0.9
[240±12]
Sy20.034 160.90.8660.38 1.4 (20–40)
<1.2 (40–100)
IGR J03344+150642±2
[87±4]
5.1±0.5
[14.0±1.4]
20.7±1.0
[54±3]
Sy2 0.02198.4 0.316 0.810.0095 (0.1–2.4)
<0.79 (20–40)
2.3 (40–100)
IGR J04451−04455.2±0.5
[5.6±0.3]
<0.5
[<0.7]
<0.7
[<0.9]
likely Sy2 0.076 370.60.048
>1.0547 (20–100)
IGR J05253+64474.5±0.5
[6.7±0.7]
in abs.
′′
6.0±0.3
[11.1±0.6]
likely Sy2 0.071345.00.190— 7.7 (0.2–2)
<8.6 (20–40)
19 (40–100)
IGR J06293−135934.8±1.7
[73±4]
3.3±0.2
[7.4±0.5]
19.0±0.6
[51.7±1.6]
Sy2 0.033156.0 0.323 1.28 4.8 (20–40)
<4.1 (40–100)
IGR J08557+6420 6.2±0.4
[7.9±0.6]
in abs.
′′
8.8±0.4
[12.3±0.6]
likely Sy2 0.037175.50.103— 7.4 (17–60)
MCG +04−26−00621±2
[22±2]
8.2±0.6
[8.6±0.6]
15.4±0.8
[17.0±0.9]
LINER0.020 93.70.0300 0.23 (2–10)
1.4 (14–150)
3.3 (20–100)
IGR J14301−415822.5±1.8
[29±2]
5.7±0.9
[7.6±1.2]
39.6±1.2
[56.1±1.7]
Sy20.0387 183.8 0.117 0.293.7 (20–100)
IGR J15549−374067.7±1.8
[200±6]
7.93±0.12
[36±5]
46±2
[195±10]
Sy20.0194 90.80.475 0.671.7 (20–100)
IGR J17009+3559—
—
in abs.
′′
<0.33
[<0.34]
XBONG 0.113565.00.018— 8.0 (1–10)
52 (17–60)
IGR J18308+092813.1±1.3
[26±3]
<2
<4
16.0±1.6
[33±3]
Sy2 0.01988.9 0.243
>0.83 1.5 (14–150)
3.7 (14–195)
0.081 (17–60)
IGR J18311−3337 40.2±1.8
[60±3]
6.0±0.6
[8.4±0.8]
82±2
[141±4]
Sy2 0.0687333.30.185 0.9422 (20–100)
IGR J19118−1707 132±4
[179±5]
32±2
49±3
83±4
[126±6]
LINER0.0234109.90.137 0.250.87 (20–40)
<0.82 (40–100)
Note: emission-line fluxes are reported both as observed and (between square brackets) corrected for the intervening Galactic
absorption E(B − V )Galalong the object line of sight (from Schlegel et al. 1998). Line fluxes are in units of 10−15erg cm−2s−1,
whereas X–ray luminosities are in units of 1043erg s−1and the reference band (between round brackets) is expressed in keV.
The typical error in the redshift measurement is ±0.001 but for the SDSS and 6dFGS spectra, for which an uncertainty
of ±0.0003 can be assumed.
(BLR) are not unheard of (see, e.g., Panessa & Bassani
2002, Bianchi et al. 2008 and Paper VI), the detection of
a similar situation in a LINER is quite peculiar, so it is
potentially interesting and deserves further study.
A reliable assessment of the Compton nature of the
narrow-line AGNs of our sample (see Table 5) can be ob-
tained using the diagnostic of Bassani et al. (1999), that is,
the ratio of the measured 2–10 keV X–ray flux to the un-
absorbed flux of the [O iii]λ5007 forbidden emission line.
Because of its definition, however, this diagnostic could be
explored only for the Seyfert 2 galaxy IGR J00465−4005
and the LINER MCG +04−26−006,which are the only two
sources of Table 5 for which the above fluxes are simulta-
neously known. After correcting the [O iii]λ5007 emission
line flux of these objects for the absorption local to the
AGN (see again Table 5), we found that the parameter T,
defined in Bassani et al. (1999), has values 5.7 and 130, re-
spectively, indicating that both sources are in the Compton
thin regime. This finding strengthens the result of Landi et
al. (2010) who classified these sources as Compton thin (al-
beit considerably absorbed) AGNs on the basis of their local
hydrogen column, determined by means of X–ray spectral
fitting and larger than 1023cm−2in both cases.
Following an independent method, we also verified this
result by applying the diagnostic of Malizia et al. (2007),
which uses the ratio of the flux measurement in the 2–10
keV band to that in the 20–100 keV band. Because of its
definition, among the objects listed in Table 5, this method
can be used with the presently available information only
for the two sources above, in addition to the XBONG IGR
J17009+3559. We found that this diagnostic yields values
0.033, 0.069, and 0.15, respectively, for the three sources
considered. We caution the reader that, despite the defini-
tion of the diagnostic of Malizia et al. (2007), at present

Page 15

N. Masetti et al.: The nature of 44 newly detected INTEGRAL sources15
Fig.8. Spectra (not corrected for the intervening Galactic absorption) of the optical counterparts of 6 broad emission-line
AGNs belonging to the sample of INTEGRAL sources presented in this paper. For each spectrum, the main spectral
features are labeled. The symbol ⊕ indicates atmospheric telluric absorption bands. The SDSS spectrum has been
smoothed using a Gaussian filter with σ = 5˚ A.
only the (1–10 keV)/(17–60 keV) flux ratio is available for
IGR J17009+3559 (see Table 5): this means that, for this
source, the value of this diagnostic should be considered as
a strict upper limit. Nevertheless, when comparing these
numbers with those of the sample of Malizia et al. (2007,
their Fig. 5), we found that none of these sources fall in the
locus in which possible Compton thick AGNs dwell. This
result therefore independently confirms that these three
AGNs are in the Compton thin regime.
Finally, we applied the prescriptions of Wu et al. (2004)
and Kaspi et al. (2000), which use the width and the
strength of the broad component of the Hβ emission as a
probe of the orbital velocity and the size of the BLR. With
them we calculated an estimate of the mass of the central
black hole in 16 of the 18 Type 1 AGNs of our sample (a
procedure that could not be applied to IGR J1248.2−5828
and IGR J19077−3925 as no broad Hβemission component
was detected in their spectra). The corresponding black
hole masses for these 16 cases are reported in Table 6. Here