175 research outputs found
Analisi carpologiche per la Vasca dello Specchio (Ferrara, XIV-XV sec. d.C.): metodologie dâindagine e risultati
Lo scavo condotto tra Corso Porta Reno e Via Vaspergolo, nel centro storico di Ferrara, ha portato alla luce un vano sotterraneo rettangolare denominato âVasca dello Specchioâ, utilizzato per lo smaltimento dei rifiuti tra XIV e XV secolo. Il riempimento, in parte giĂ analizzato e pubblicato, Ăš stato oggetto di nuove analisi carpologiche. I semi e i frutti, conservati prevalentemente per sommersione e in ottimo stato, sono complessivamente oltre 400.000 e la lista floristica comprende 168 taxa. La maggior parte dei reperti appartiene a piante coltivate/coltivabili o spontanee correlate allâuomo, che forniscono nuove informazioni sulla dieta vegetale e sullâambiente urbano della Ferrara basso-medievale/rinascimentale. I reperti evidenziano anche pratiche domestiche e culinarie talora curiose
The 1998 outburst of the X-ray transient XTE J2012+381 as observed with BeppoSAX
We report on the results of a series of X-ray observations of the transient
black hole candidate XTE J2012+381 during the 1998 outburst performed with the
BeppoSAX satellite. The observed broad-band energy spectrum can be described
with the superposition of an absorbed disk black body, an iron line plus a high
energy component, modelled with either a power law or a Comptonisation tail.
The source showed pronounced spectral variability between our five
observations. While the soft component in the spectrum remained almost
unchanged throughout our campaign, we detected a hard spectral tail which
extended to 200 keV in the first two observations, but became barely detectable
up to 50 keV in the following two. A further re-hardening is observed in the
final observation. The transition from a hard to a soft and then back to a hard
state occurred around an unabsorbed 0.1-200 keV luminosity of 10^38 erg/s (at
10 kpc). This indicates that state transitions in XTE 2012+281 are probably not
driven only by mass accretion rate, but additional physical parameters must
play a role in the evolution of the outburst.Comment: Paper accepted for publication on A&A (macro included, 9 pages, 5
figures
BeppoSAX observations of the black hole candidates LMC X-1 and LMC X-3
We describe BeppoSAX observations of the black hole candidates LMC X--1 and
LMC X--3 performed in Oct. 1997. Both sources can be modelled by a multicolor
accretion disk spectrum, with temperature keV. However, there is some
evidence that a thin emitting component coexists with the thick disk at these
temperatures. In the direction of LMC X--1, we detected a significant emission
above 10 keV, which we suspect originates from the nearby source PSR 0540-69.
For LMC X--1, we estimate an absorbing column density of cm, which is almost ten times larger than that found for LMC
X--3. In both sources, we find no indication of emission or absorption features
whatsoever.Comment: 4 pages, 2 figures. Accepted for pubblication in the Proc. of 32nd
Cospar scientific assembly, Nagoya, 13-15 July 199
BeppoSAX observation of the X-ray binary pulsar Vela X-1
We report on the spectral (pulse averaged) and timing analysis of the ~ 20
ksec observation of the X-ray binary pulsar Vela X-1 performed during the
BeppoSAX Science Verification Phase. The source was observed in two different
intensity states: the low state is probably due to an erratic intensity dip and
shows a decrease of a factor ~ 2 in intensity, and a factor 10 in Nh. We have
not been able to fit the 2-100 keV continuum spectrum with the standard (for an
X--ray pulsar) power law modified by a high energy cutoff because of the
flattening of the spectrum in ~ 10-30 keV. The timing analysis confirms
previous results: the pulse profile changes from a five-peak structure for
energies less than 15 keV, to a simpler two-peak shape at higher energies. The
Fourier analysis shows a very complex harmonic component: up to 23 harmonics
are clearly visible in the power spectrum, with a dominant first harmonic for
low energy data, and a second one as the more prominent for energies greater
than 15 keV. The aperiodic component in the Vela X-1 power spectrum presents a
knee at about 1 Hz. The pulse period, corrected for binary motion, is 283.206
+/- 0.001 sec.Comment: 5 pages, 4 PostScript figure, uses aipproc.sty, to appear in
Proceedings of Fourth Compton Symposiu
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