An Unusually Powerful Water-Maser Flare in the Galactic Source W49N     

Volvach  L. N.  Volvach  A. E.  Larionov  M. G.  Wolak  P.  Kramer  B.  Menten  K.  Kraus  A.  Brand  J.  Zanichelli  A.  Poppi  S.  Rigini  S.  Ipatov  A. V.  Ivanov  D. V.  Mikhailov  A. G.  Mel’nikov  A. 《Astronomy Reports》2019,63(8):652-665

The most powerful flare ever registered in the Galactic water-maser source W49N has been detected in long-term monitoring data in the 6₁₆–5₂₃ transition with line frequency f = 22.235 GHz carried out on the 22-m Simeiz, 32-m Toruń, 100-m Effelsberg, and 32-m Medicina radio telescopes, beginning in September 2017 and continuing in 2018. Some stages of the flare were monitored daily. Detailed variations of the source spectral flux density with time have been obtained. At the flare maximum, the flux exceeded P ≈ 8 × 10⁴ Jy, and this was record highest flux registered over the entire history of observations of this source. Important conclusions related to details of the mechanism for the H₂O line emission have been drawn. An exponential increase in the flare flux density was detected during both the rise and decline of the flare. The data obtained indicate that the maser is unsaturated, and remained in this state up to the maximum observed flux densities. Additional support for the idea that the maser is unsaturated is the shape of the dependence of the line width on the flux. The characteristics of the variations of the spectral flux density are probably associated with a sharp increase in the density of the medium and the photon flux that led to an increase in the temperature from an initial level of 10–40 K to hundreds of Kelvins. Interferometric maps of the object during the increase in the spectral flux density of the flare have been obtained. A possible mechanism for the primary energy release in W49N is considered.

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Deep 1.4-GHz observations of diffuse polarized emission     

E. Carretti  S. Poppi  W. Reich  P. Reich  E. Fürst  G. Bernardi  S. Cortiglioni  C. Sbarra 《Monthly notices of the Royal Astronomical Society》2006,367(1):132-138

Polarized diffuse emission observations at 1.4 GHz in a high Galactic latitude area of the Northern celestial hemisphere are presented. The  3.2 × 3.2 deg²  field, centred at  RA = 10^h58^m, Dec. =+42°18' (B1950)  , has Galactic coordinates   l ∼ 172°, b ∼+63°  and is located in the region selected as northern target of the Balloon-borne Radiometers for Sky Polarization Observations experiment. Observations have been performed with the Effelsberg 100-m telescope. We find that the angular power spectra of the E and B modes have slopes of  β _E =−1.79 ± 0.13  and  β _B =−1.74 ± 0.12  , respectively. Because of the very high Galactic latitude and the smooth emission, a weak Faraday rotation action is expected, which allows both a fair extrapolation to cosmic microwave background polarization (CMBP) frequencies and an estimate of the contamination by the Galactic synchrotron emission. We extrapolate the E -mode spectrum up to 32 GHz and confirm the possibility to safely detect the CMBP E -mode signal in the Ka band found in another low-emission region. Extrapolated up to 90 GHz, the Galactic synchrotron B mode looks to compete with the cosmic signal only for models with a tensor-to-scalar perturbation power ratio   T / S < 0.001  , which is even lower than the T / S value of 0.01 found to be accessible in the only other high Galactic latitude area investigated to date. This suggests that values as low as   T / S = 0.01  might be accessed at high Galactic latitudes. Such low-emission values can allow a significant redshift of the best frequency to detect the CMBP B mode, also reducing the contamination by Galactic dust, and opening interesting perspectives to investigate inflation models.  相似文献   

The heat behaviour of the cation exchanged zeolites with heulandite structure     

Prof. A. Alietti  Prof. G. Gottardi  Dr. L. Poppi 《Mineralogy and Petrology》1974,21(3-4):291-298

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1.4-GHz polarimetric observations of the two fields imaged by the DASI experiment     

G. Bernardi  E. Carretti †  R. J. Sault  S. Cortiglioni  S. Poppi 《Monthly notices of the Royal Astronomical Society》2006,370(4):2064-2070

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High Galactic latitude polarized emission at 1.4 GHz and implications for cosmic microwave background observations     

E. Carretti  G. Bernardi  R. J. Sault  S. Cortiglioni  S. Poppi 《Monthly notices of the Royal Astronomical Society》2005,358(1):1-12

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A polarized synchrotron template for cosmic microwave background polarization experiments based on WMAP data     

G. Bernardi  E. Carretti  R. Fabbri  C. Sbarra  S. Poppi  S. Cortiglioni  J. L. Jonas 《Monthly notices of the Royal Astronomical Society》2004,351(2):436-446

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A new approach for a Galactic synchrotron polarized emission template in the microwave range     

G. Bernardi  E. Carretti  R. Fabbri  C. Sbarra  S. Poppi  S. Cortiglioni 《Monthly notices of the Royal Astronomical Society》2003,344(2):347-357

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Results of the first Italian planetary radar experiment     

M. Di Martino  S. Montebugnoli  S. Ostro  S. Righini  S. Poppi  A. Orlati  C. Bortolotti  Y. Gavrik 《Planetary and Space Science》2004,52(4):325-330

We describe the first intercontinental planetary radar initiative undertaken in Italy.We present the results of the observations of Near-Earth Asteroid (NEA) 33342 (1998 WT24), performed in December 2001 using the bistatic configurations Goldstone-Medicina and Evpatoria-Medicina, with the 32-m Medicina dish used to receive echoes in both cases.The experiment goal was to characterise the system for radar follow-up observations of NEA and artificial orbiting debris, in the framework of a feasibility study which aims at using the Sardinia Radio Telescope, at present under construction, also as a planetary radar facility.  相似文献