-
Planck Collaboration,
P. A. R. Ade,
N. Aghanim,
C. Armitage-Caplan,
M. Arnaud,
M. Ashdown,
F. Atrio-Barandela,
J. Aumont,
C. Baccigalupi,
A. J. Banday, [......],
J. Varis,
P. Vielva,
F. Villa,
N. Vittorio,
L. A. Wade,
B. D. Wandelt,
S. D. M. White,
D. Yvon,
A. Zacchei,
A. Zonca
03/2013;
-
Planck Collaboration,
P.A.R. Ade,
N. Aghanim,
M.I.R. Alves,
C. Armitage-Caplan,
M. Arnaud,
M. Ashdown,
F. Atrio-Barandela,
J. Aumont,
C. Baccigaluppi, [......],
P. Vielva,
F. Villa,
N. Vittorio,
L. A. Wade,
B. D. Wandelt,
I. K. Wehus,
H. Yamamoto T. Yoda,
D. Yvon,
A. Zacchei,
A. Zonca
03/2013;
-
Planck collaboration: P. A. R. Ade,
N. Aghanim,
C. Armitage-Caplan,
M. Arnaud,
M. Ashdown,
F. Atrio-Barandela,
J. Aumont,
C. Baccigalupi,
A. J. Banday,
R. B. Barreiro, [......],
F. Villa,
N. Vittorio,
L. A. Wade,
B. D. Wandelt,
I. K. Wehus,
M. White,
S. D. M. White,
D. Yvon,
A. Zacchei,
A. Zonca
03/2013;
-
Planck Collaboration: P. A. R. Ade,
N. Aghanim,
C. Armitage-Caplan,
M. Arnaud,
M. Ashdown,
F. Atrio-Barandela,
J. Aumont,
C. Baccigalupi,
A. J. Banday,
R. B. Barreiro, [......],
P. Vielva,
F. Villa,
N. Vittorio,
L. A. Wade,
B. D. Wandelt,
M. White,
A. Wilkinson,
D. Yvon,
A. Zacchei,
A. Zonca
03/2013;
-
Planck Collaboration: P. A. R. Ade,
N. Aghanim,
M. Arnaud,
M. Ashdown,
J. Aumont,
C. Baccigalupi,
A. Balbi,
A. J. Banday,
R. B. Barreiro,
E. Battaner, [......],
B. Van Tent,
P. Vielva,
F. Villa,
N. Vittorio,
L. A. Wade,
N. Welikala,
D. Yvon,
A. Zacchei,
J. P. Zibin,
A. Zonca
[show abstract]
[hide abstract]
ABSTRACT: Using Planck data combined with the Meta Catalogue of X-ray detected Clusters of galaxies (MCXC), we address the study of peculiar motions by searching for evidence of the kinetic Sunyaev-Zeldovich effect (kSZ). By implementing various filters designed to extract the kSZ generated at the positions of the clusters, we obtain consistent constraints on the radial peculiar velocity average, root mean square (rms), and local bulk flow
amplitude at different depths. For the whole cluster sample of average redshift 0.18, the measured average radial peculiar velocity with respect to the cosmic microwave background (CMB) radiation at that redshift, i.e., the kSZ monopole, amounts to 72 ± 60 kms−1. This constitutes less than 1% of the relative Hubble velocity of the cluster sample with respect to our local CMB frame. From a subset of this cluster sample Planck finds
the radial peculiar velocity rms to be below 800 kms−1 at the 95% confidence level, which is around three times the �CDM prediction for the typical cluster radial velocity rms at z = 0.15. Planck data also set strong constraints on the local bulk flow in volumes centred on the Local Group. There is no detection of bulk flow as measured in any comoving sphere extending to the maximum redshift covered by the cluster sample. A blind search for bulk flows in this sample has an upper limit of 254 kms−1 (95% confidence level) dominated by CMB confusion and instrumental noise, indicating that the Universe is largely homogeneous on Gpc scales. In this context, in conjunction with supernova observations, Planck is able to rule out a large class of inhomogeneous void models as alternatives to dark energy or modified gravity. The Planck constraints on peculiar velocities and bulk flows are thus consistent with the �CDM scenario.
03/2013;
-
L. Foschini,
E. Angelakis,
G. Bonnoli,
V. Braito,
A. Caccianiga,
L. Fuhrmann,
L. Gallo,
G. Ghirlanda,
G. Ghisellini,
D. Grupe, [......],
S. Mathur,
B. M. Peterson,
P. Romano,
P. Severgnini,
G. Tagliaferri,
J. Tammi,
F. Tavecchio,
O. Tibolla,
M. Tornikoski,
S. Vercellone
[show abstract]
[hide abstract]
ABSTRACT: We present the preliminary results of a survey performed with Swift to
observe a sample of radio-loud Narrow-Line Seyfert 1 Galaxies (RLNLS1s).
Optical-to-X-ray data from Swift are complemented with gamma-ray observations
from Fermi/LAT and radio measurements available in the literature. The
comparison with a sample of bright Fermi blazars indicates that RLNLS1s seem to
be the low-power tail of the distribution.
01/2013;
-
Astronomy Reports 01/2013; 57(1):46. · 0.73 Impact Factor
-
T. Arlen,
T. Aune,
M. Beilicke,
W. Benbow,
A. Bouvier,
J. H. Buckley,
V. Bugaev,
A. Cesarini,
L. Ciupik,
M. P. Connolly, [......],
W. Max-Moerbeck,
A. Readhead,
M. L. Lister,
Y. Y. Kovalev,
A. B. Pushkarev,
M. A. Gurwell, A. Lahteenmaki,
E. Nieppola,
M. Tornikoski,
E. Jarvela
[show abstract]
[hide abstract]
ABSTRACT: We report on the detection of a very rapid TeV gamma-ray flare from BL
Lacertae on 2011 June 28 with the Very Energetic Radiation Imaging Telescope
Array System (VERITAS). The flaring activity was observed during a 34.6-minute
exposure, when the integral flux above 200 GeV reached $(3.4\pm0.6) \times
10^{-6} \;\text{photons}\;\text{m}^{-2}\text{s}^{-1}$, roughly 125% of the Crab
Nebula flux measured by VERITAS. The light curve indicates that the
observations missed the rising phase of the flare but covered a significant
portion of the decaying phase. The exponential decay time was determined to be
$13\pm4$ minutes, making it one of the most rapid gamma-ray flares seen from a
TeV blazar. The gamma-ray spectrum of BL Lacertae during the flare was soft,
with a photon index of $3.6\pm 0.4$, which is in agreement with the measurement
made previously by MAGIC in a lower flaring state. Contemporaneous radio
observations of the source with the Very Long Baseline Array (VLBA) revealed
the emergence of a new, superluminal component from the core around the time of
the TeV gamma-ray flare, accompanied by changes in the optical polarization
angle. Changes in flux also appear to have occurred at optical, UV, and GeV
gamma-ray wavelengths at the time of the flare, although they are difficult to
quantify precisely due to sparse coverage. A strong flare was seen at radio
wavelengths roughly four months later, which might be related to the gamma-ray
flaring activities. We discuss the implications of these multiwavelength
results.
The Astrophysical Journal 11/2012; 762(2):92. · 6.02 Impact Factor
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L. Foschini,
E. Angelakis,
L. Fuhrmann,
G. Ghisellini,
T. Hovatta, A. Lahteenmaki,
M. L. Lister,
V. Braito,
L. Gallo,
T. S. Hamilton, [......],
J. Tammi,
M. Tornikoski,
H. Ungerechts,
J. A. Zensus,
A. Celotti,
G. Bonnoli,
A. Doi,
L. Maraschi,
G. Tagliaferri,
F. Tavecchio
[show abstract]
[hide abstract]
ABSTRACT: We present more than three years of observations at different frequencies,
from radio to high-energy gamma-rays, of the Narrow-Line Seyfert 1 (NLS1)
Galaxy PMN J0948+0022 (z=0.585). This source is the first NLS1 detected at
energies above 100 MeV and therefore can be considered the prototype of this
emerging new class of gamma-ray emitting active galactic nuclei (AGN). The
observations performed from 2008 August 1 to 2011 December 31 confirmed that
PMN J0948+0022 generates a powerful relativistic jet, able to develop an
isotropic luminosity at gamma-rays of the order of 10^48 erg s^-1, at the level
of powerful quasars. The evolution of the radiation emission of this source in
2009 and 2010 followed the canonical expectations of relativistic jets, with
correlated multiwavelength variability (gamma-rays followed by radio emission
after a few months), but it was difficult to retrieve a similar pattern in the
light curves of 2011. The comparison of gamma-ray spectra before and including
2011 data suggested that there was a softening of the high-energy spectral
slope. We selected five specific epochs to be studied by modelling the
broad-band spectrum, characterised by an outburst at gamma-rays or very
low/high flux at other wavelengths. The observed variability can largely be
explained either by changes in the injected power, the bulk Lorentz factor of
the jet or the electron spectrum. The characteristic time scale of
doubling/halving flux ranges from a few days to a few months, depending on the
frequency and the sampling rate. The shortest doubling time scale at gamma-rays
is 2.3+-0.5 days. These small values underline the need of highly-sampled
multiwavelength campaigns to better understand the physics of these sources.
09/2012;
-
M. Ackermann,
M. Ajello,
J. Ballet,
G. Barbiellini,
D. Bastieri,
R. Bellazzini,
R. D. Blandford,
E. D. Bloom,
E. Bonamente,
A. W. Borgland, [......],
M. Yoshida,
T. Belloni,
G. Tagliaferri,
E. W. Bonning,
J. Isler,
C. M. Urry,
E. Hoversten,
A. Falcone,
C. Pagani,
M. Stroh
[show abstract]
[hide abstract]
ABSTRACT: The blazar AO 0235+164 (z = 0.94) has been one of the most active objects
observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008.
In addition to the continuous coverage by Fermi, contemporaneous observations
were carried out from the radio to {\gamma} -ray bands between 2008 September
and 2009 February. In this paper, we summarize the rich multi-wavelength data
collected during the campaign (including F-GAMMA, GASP- WEBT, Kanata, OVRO,
RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation
between the light curves measured in the different energy bands, and interpret
the resulting spectral energy distributions in the context of well-known blazar
emission models. We find that the {\gamma} -ray activity is well correlated
with a series of near-IR/optical flares, accompanied by an increase in the
optical polarization degree. On the other hand, the X-ray light curve shows a
distinct 20 day high state of unusually soft spectrum, which does not match the
extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret
this feature as the bulk Compton emission by cold electrons contained in the
jet, which requires an accretion disk corona with an effective covering factor
of 19% at a distance of 100 Rg . We model the broadband spectra with a leptonic
model with external radiation dominated by the infrared emission from the dusty
torus.
07/2012;
-
A. E. Vol’vach,
L. N. Vol’vach,
A. M. Kut’kin,
M. G. Larionov,
M. Villata,
K. M. Panteri, A. Lahteenmaki,
M. Tornikoski,
P. Savolainen,
G. Tammi, [......],
V. T. Doroshenko,
Yu. S. Efimov,
S. A. Klimanov,
S. V. Nazarov,
G. V. Borman,
A. B. Pushkarev,
V. I. Zhdanov,
E. V. Fedorova,
I. B. Vavilova,
N. G. Chesnok
[show abstract]
[hide abstract]
ABSTRACT: Long-term monitoring data at five radio frequencies from 4.8 to 37 GHz obtained at the Crimean Astrophysical Observatory,
Metsahovi Radio Observatory of Aalto University, and the University of Michigan Radio Astronomy Observatory are used to analyze
variations of the flux of the Active Galactic Nucleus (AGN) 3C 454.3. The dynamical characteristics of the three latest powerful
flares from 2004 to 2010 are analyzed in detail. Observations in the gamma-ray (0.1–300 GeV), X-ray (2–10 kev, 15–50 keV),
and optical are also used. Delays in the development of flares at different frequencies are derived. An empirical frequency
dependence for the delays of flares from the gamma-ray to the radio is determined, which can be fit using a logarithmic low
and remains the same from flare to flare. The physical characteristics of the central region of the AGN 3C 454.3 are used
to estimate the size of its Strömgren sphere, taking into account the relevant mechanisms for heating and cooling the medium,
as well as the adopted laws for the variation of the density and temperature with distance from the source of ionization.
A model for the location of the radiation regions in the jet at various frequency ranges during the development of flares
is proposed.
Astronomy Reports 05/2012; 55(7):608-615. · 0.73 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The coexistence of Planck and Fermi satellites in orbit has enabled the
exploration of the connection between the (sub-)millimeter and gamma-ray
emission in a large sample of blazars. We find that the gamma-ray emission and
the (sub-)mm luminosities are correlated over five orders of magnitude.
However, this correlation is not significant at some frequency bands when
simultaneous observations are considered. The most significant statistical
correlations, on the other hand, arise when observations are quasi-simultaneous
within 2 months. Moreover, we find that sources with an approximate spectral
turnover in the middle of the mm-wave regime are more likely to be strong
gamma-ray emitters. These results suggest a physical relation between the newly
injected plasma components in the jet and the high levels of gamma-ray
emission.
04/2012;
-
I. Agudo,
S. G. Jorstad,
A. P. Marscher,
V. M. Larionov,
J. L. Gomez, A. Lahteenmaki,
M. A. Gurwell,
P. S. Smith,
H. Wiesemeyer,
C. Thum,
J. Heidt
[show abstract]
[hide abstract]
ABSTRACT: We combine the Fermi-LAT light curve of the BL Lacertae type blazar OJ287
with time-dependent multi-waveband flux and linear polarization observations
and submilliarcsecond-scale polarimetric images at lambda=7mm to locate the
gamma-ray emission in prominent flares in the jet of the source >14pc from the
central engine. We demonstrate a highly significant correlation between the
strongest gamma-ray and millimeter-wave flares through Monte Carlo simulations.
The two reported gamma-ray peaks occurred near the beginning of two major
millimeter-wave outbursts, each of which is associated with a linear
polarization maximum at millimeter wavelengths. Our very long baseline array
observations indicate that the two millimeter-wave flares originated in the
second of two features in the jet that are separated by >14pc. The simultaneity
of the peak of the higher-amplitude gamma-ray flare and the maximum in
polarization of the second jet feature implies that the gamma-ray and
millimeter-wave flares are cospatial and occur >14pc from the central engine.
We also associate two optical flares, accompanied by sharp polarization peaks,
with the two gamma-ray events. The multi-waveband behavior is most easily
explained if the gamma-rays arise from synchrotron self Compton scattering of
optical photons from the flares. We propose that flares are triggered by
interaction of moving plasma blobs with a standing shock.
10/2011;
-
P. Giommi,
G. Polenta, A. Lahteenmaki,
D. J. Thompson,
M. Capalbi,
S. Cutini,
D. Gasparrini,
J. Gonzalez-Nuevo,
J. Leon-Tavares,
M. Lopez-Caniego, [......],
M. Tornikoski,
C. Trigilio,
M. Turunen,
G. Umana,
H. Ungerechts,
F. Villa,
J. Wu,
A. Zacchei,
J. A. Zensus,
X. Zhou
[show abstract]
[hide abstract]
ABSTRACT: We present simultaneous Planck, Swift, Fermi, and ground-based data for 105
blazars belonging to three samples with flux limits in the soft X-ray, hard
X-ray, and gamma-ray bands. Our unique data set has allowed us to demonstrate
that the selection method strongly influences the results, producing biases
that cannot be ignored. Almost all the BL Lac objects have been detected by
Fermi-LAT, whereas ~40% of the flat-spectrum radio quasars (FSRQs) in the
radio, soft X-ray, and hard X-ray selected samples are still below the
gamma-ray detection limit even after integrating 27 months of Fermi-LAT data.
The radio to sub-mm spectral slope of blazars is quite flat up to ~70GHz, above
which it steepens to <\alpha>~-0.65. BL Lacs have significantly flatter spectra
than FSRQs at higher frequencies. The distribution of the rest-frame
synchrotron peak frequency (\nupS) in the SED of FSRQs is the same in all the
blazar samples with <\nupS>=10^13.1 Hz, while the mean inverse-Compton peak
frequency, <\nupIC>, ranges from 10^21 to 10^22 Hz. The distributions of \nupS
and of \nupIC of BL Lacs are much broader and are shifted to higher energies
than those of FSRQs and strongly depend on the selection method. The Compton
dominance of blazars ranges from ~0.2 to ~100, with only FSRQs reaching values
>3. Its distribution is broad and depends strongly on the selection method,
with gamma-ray selected blazars peaking at ~7 or more, and radio-selected
blazars at values ~1, thus implying that the assumption that the blazar power
is dominated by high-energy emission is a selection effect. Simple SSC models
cannot explain the SEDs of most of the gamma-ray detected blazars in all
samples. The SED of the blazars that were not detected by Fermi-LAT may instead
be consistent with SSC emission. Our data challenge the correlation between
bolometric luminosity and \nupS predicted by the blazar sequence.
08/2011;
-
V. A. Acciari,
E. Aliu,
T. Arlen,
T. Aune,
M. Beilicke,
W. Benbow,
D. Boltuch,
S. M. Bradbury,
J. H. Buckley,
V. Bugaev, [......],
L. O. Takalo,
C. Villforth,
T. Montaruli,
M Baker, A. Lahteenmaki,
M. Tornikoski,
T. Hovatta,
E. Nieppola,
H. D. Aller,
M. F. Aller
[show abstract]
[hide abstract]
ABSTRACT: We report on TeV gamma-ray observations of the blazar Mrk 421 (redshift of
0.031) with the VERITAS observatory and the Whipple 10m Cherenkov telescope.
The excellent sensitivity of VERITAS allowed us to sample the TeV gamma-ray
fluxes and energy spectra with unprecedented accuracy where Mrk 421 was
detected in each of the pointings. A total of 47.3 hrs of VERITAS and 96 hrs of
Whipple 10m data were acquired between January 2006 and June 2008. We present
the results of a study of the TeV gamma-ray energy spectra as a function of
time, and for different flux levels. On May 2nd and 3rd, 2008, bright TeV
gamma-ray flares were detected with fluxes reaching the level of 10 Crab. The
TeV gamma-ray data were complemented with radio, optical, and X-ray
observations, with flux variability found in all bands except for the radio
waveband. The combination of the RXTE and Swift X-ray data reveal spectral
hardening with increasing flux levels, often correlated with an increase of the
source activity in TeV gamma-rays. Contemporaneous spectral energy
distributions were generated for 18 nights, each of which are reasonably
described by a one-zone SSC model.
06/2011;
-
F. D'Ammando,
C. M. Raiteri,
M. Villata,
P. Romano,
G. Pucella,
H. A. Krimm,
S. Covino,
M. Orienti,
G. Giovannini,
S. Vercellone, [......],
C. Trigilio,
I. S. Troitsky,
G. Umana,
L. A. Antonelli,
S. Colafrancesco,
C. Pittori,
P. Santolamazza,
F. Verrecchia,
P. Giommi,
L. Salotti
[show abstract]
[hide abstract]
ABSTRACT: We report on the extreme gamma-ray activity from the FSRQ PKS 1510-089
observed by AGILE in March 2009. In the same period a radio-to-optical
monitoring of the source was provided by the GASP-WEBT and REM. Moreover,
several Swift ToO observations were triggered, adding important information on
the source behaviour from optical/UV to hard X-rays. We paid particular
attention to the calibration of the Swift/UVOT data to make it suitable to the
blazars spectra. Simultaneous observations from radio to gamma rays allowed us
to study in detail the correlation among the emission variability at different
frequencies and to investigate the mechanisms at work. In the period 9-30 March
2009, AGILE detected an average gamma-ray flux of (311+/-21)x10^-8 ph cm^-2
s^-1 for E>100 MeV, and a peak level of (702+/-131)x10^-8 ph cm^-2 s^-1 on
daily integration. The gamma-ray activity occurred during a period of
increasing activity from near-IR to UV, with a flaring episode detected on
26-27 March 2009, suggesting that a single mechanism is responsible for the
flux enhancement observed from near-IR to UV. By contrast, Swift/XRT
observations seem to show no clear correlation of the X-ray fluxes with the
optical and gamma-ray ones. However, the X-ray observations show a harder
photon index (1.3-1.6) with respect to most FSRQs and a hint of
harder-when-brighter behaviour, indicating the possible presence of a second
emission component at soft X-ray energies. Moreover, the broad band spectrum
from radio-to-UV confirmed the evidence of thermal features in the optical/UV
spectrum of PKS 1510-089 also during high gamma-ray state. On the other hand,
during 25-26 March 2009 a flat spectrum in the optical/UV energy band was
observed, suggesting an important contribution of the synchrotron emission in
this part of the spectrum during the brightest gamma-ray flare, therefore a
significant shift of the synchrotron peak.
03/2011;
-
[show abstract]
[hide abstract]
ABSTRACT: We compare the gamma-ray photon flux variability of northern blazars in the
Fermi/LAT First Source Catalog with 37 GHz radio flux density curves from the
Metsahovi quasar monitoring program. We find that the relationship between
simultaneous millimeter (mm) flux density and gamma-ray photon flux is
different for different types of blazars. The flux relation between the two
bands is positively correlated for quasars and does not exist for BLLacs.
Furthermore, we find that the levels of gamma-ray emission in high states
depend on the phase of the high frequency radio flare, with the brightest
gamma-ray events coinciding with the initial stages of a mm flare. The mean
observed delay from the beginning of a mm flare to the peak of the gamma-ray
emission is about 70 days, which places the average location of the gamma-ray
production at or downstream of the radio core. We discuss alternative scenarios
for the production of gamma-rays at distances of parsecs along the length the
jet.
02/2011;
-
Planck Collaboration,
A. Abergel,
P. A. R. Ade,
N. Aghanim,
M. Arnaud,
M. Ashdown,
J. Aumont,
C. Baccigalupi,
A. Balbi,
A. J. Banday, [......],
P. Vielva,
F. Villa,
N. Vittorio,
L. A. Wade,
B. D. Wandelt,
A Wilkinson,
N. Ysard,
D. Yvon,
A. Zacchei,
A. Zonca
[show abstract]
[hide abstract]
ABSTRACT: (abridged) Planck has observed the entire sky from 30 GHz to 857GHz. The
observed foreground emission contains contributions from different phases of
the interstellar medium (ISM). We have separated the observed Galactic emission
into the different gaseous components (atomic, molecular and ionised) in each
of a number of Galactocentric rings. Templates are created for various
Galactocentric radii using velocity information from atomic (neutral hydrogen)
and molecular (12CO) observations. The ionised template is assumed to be traced
by free-free emission as observed by WMAP, while 408 MHz emission is used to
trace the synchrotron component. Gas emission not traced by the above
templates, namely "ark gas", as evidenced using Planck data, is included as an
additional template, the first time such a component has been used in this way.
These templates are then correlated with each of the Planck frequency bands, as
well as other ancillary data. The emission per column density of the gas
templates allows us to create distinct spectral energy distributions (SEDs) per
Galactocentric ring and in each of the gaseous tracers from 1.4 GHz to 25 THz
(12\mu m). Apart from the thermal dust and free-free emission, we have probed
the Galaxy for anomalous (e.g., spinning) dust as well as synchrotron emission.
We show that anomalous dust emission is present in the atomic, molecular and
dark gas phases throughout the Galactic disk. The derived dust propeties
associated with the dark gas phase are derived but do not allow us to reveal
the nature of this phase. For all environments, the anomalous emission is
consistent with rotation from polycyclic aromatic hydrocarbons (PAHs) and,
according to our simple model, accounts for $(25\pm5)%$ (statistical) of the
total emission at 30 GHz.
01/2011;
-
A.E. Volvach,
L.N.Volvach,
A.M. Kut’kin,
M.G. Larionov,
M. Villata,
K.M. Panteri, A. Lahteenmaki,
M.Tornikoski,
P. Savolainen,
G. Tammi, [......],
V.T. Doroshenko,
Yu.S. Efimov,
S.A. Klimanov,
S.V. Nazarov,
G.V. Borman,
A.B. Pushkarev,
V.I. Zhdanov,
E.V. Fedorova,
I.B.Vavilova,
N. G. Chesnok
Astronomy Reports 01/2011; 55(7):608. · 0.73 Impact Factor
-
A.E. Volvach,
L.N.Volvach,
A.M. Kut’kin,
M.G. Larionov,
M. Villata,
K.M. Panteri, A. Lahteenmaki,
M.Tornikoski,
P. Savolainen,
G. Tammi, [......],
V.T. Doroshenko,
Yu.S. Efimov,
S.A. Klimanov,
S.V. Nazarov,
G.V. Borman,
A.B. Pushkarev,
V.I. Zhdanov,
E.V. Fedorova,
I.B.Vavilova,
N. G. Chesnok
Astronomy Report. 01/2011; 55(7):608.
