An optical spectroscopic survey of the 3CR sample of radio galaxies with z (2009)
Buttiglione, Sara, Capetti, Alessandro, Celotti, Annalisa, Axon, David J., Chiaberge, Marco, Macchetto, F. Duccio, ...
We use the emission line measurements of 3CR radio sources with redshift < 0.3, to explore their spectroscopic properties. The 3CR sources show a bimodal distribution of Excitation Index, a new...
An optical spectroscopic survey of the 3CR sample of radio galaxies with z (2009)
Buttiglione, Sara, Capetti, Alessandro, Celotti, Annalisa, Axon, David J., Chiaberge, Marco, Macchetto, F. Duccio, ...
We present a homogeneous and 92 % complete dataset of optical nuclear spectra for the 113 3CR radio sources with redshifts < 0.3, obtained with the Telescopio Nazionale Galileo. For these sources we...
A unifying view of gamma-ray burst afterglows (2009)
Ghisellini, Gabriele, Nardini, Marco, Ghirlanda, Giancarlo, Celotti, Annalisa
We selected a sample of 33 Gamma Ray Bursts (GRBs) detected by Swift, with known redshift and optical extinction at the host frame. For these, we constructed the de-absorbed and K-corrected X-ray and...
Short versus long gamma-ray bursts: spectra, energetics, and luminosities (2009)
Ghirlanda, Giancarlo, Nava, Lara, Ghisellini, Gabriele, Celotti, Annalisa, Firmani, Claudio
We compare the spectral properties of 79 short and 79 long Gamma-Ray Bursts (GRBs) detected by BATSE and selected with the same limiting peak flux. Short GRBs have a low-energy spectral component...
An optical spectroscopic survey of the 3CR sample of radio galaxies with z (2009)
Buttiglione, Sara, Capetti, Alessandro, Celotti, Annalisa, Axon, David J., Chiaberge, Marco, Macchetto, F. Duccio, ...
We present a homogeneous and 92 % complete dataset of optical nuclear spectra for the 113 3CR radio sources with redshifts < 0.3, obtained with the Telescopio Nazionale Galileo. For these sources we...
TeV variability in blazars: how fast can it be? (2008)
Ghisellini, Gabriele, Tavecchio, Fabrizio, Bodo, Gianluigi, Celotti, Annalisa
Recent Cerenkov observations of the two BL Lac objects PKS 2155-304 and Mkn 501 revealed TeV flux variability by a factor ~2 in just 3-5 minutes. Even accounting for the effects of relativistic...
gamma-ray polarization constraints on Planck scale violations of special relativity (2008)
Maccione, Luca, Liberati, Stefano, Celotti, Annalisa, Kirk, John G., Ubertini, Pietro
Using recent polarimetric observations of the Crab Nebula in the hard X-ray band by INTEGRAL, we show that the absence of vacuum birefringence effects constrains O(E/M) Lorentz violation in QED to...
Precursors in Swift Gamma Ray Bursts with Redshift (2008)
Burlon, Davide, Ghirlanda, Giancarlo, Ghisellini, Gabriele, Lazzati, Davide, Nava, Lara, Nardini, Marco, ...
We study a sample of Gamma-Ray Bursts detected by the Swift satellite with known redshift which show a precursor in the Swift-BAT light curve. We analyze the spectra of the precursors and compare...
Gamma-ray polarization constraints on Planck scale violations of special relativity (2008)
Maccione, Luca, Liberati, Stefano, Celotti, Annalisa, Kirk, John G., Ubertini, Pietro
Using recent polarimetric observations of the Crab Nebula in the hard X-ray band by INTEGRAL, we show that the absence of vacuum birefringence effects constrains O(E/M) Lorentz violation in QED to...
Long gamma-ray bursts and their host galaxies at high redshift (2008)
Lapi, Andrea, Kawakatu, Nozomu, Bosnjak, Zeljka Marija, Celotti, Annalisa, Bressan, Alessandro, Granato, Gian Luigi, ...
Motivated by the recent observational and theoretical evidence that long Gamma-Ray Bursts (GRBs) are likely associated with low metallicity, rapidly rotating massive stars, we examine the...
Optical spectroscopy of 3CR sample of radio sources at z (2008)
Buttiglione, Sara, Capetti, Alessandro, Celotti, Annalisa
We are carrying out a program of optical spectroscopy of the complete subsample of the 3CR catalog of radio sources at redshift z < 0.3. The sample consists of 113 3CR sources, comprising FR I, FR II...
The power of blazar jets (2008)
Celotti, Annalisa, Ghisellini, Gabriele
We estimate the power of relativistic, extragalactic jets by modelling the spectral energy distribution of a large number of blazars. We adopt a simple one-zone, homogeneous, leptonic synchrotron and...
Energetics–spectral correlations versus the BATSE gamma-ray bursts population (2008)
Bosnjak, Zeljka Marija, Celotti, Annalisa, Longo, Francesco, Barbiellini, Guido
Recently proposed correlations between the energetics of Gamma-Ray Bursts (GRB) and their spectral properties, namely the peak energy of their prompt emission, are found to account for the observed...
Gamma-ray polarization constraints on Planck scale violations of special relativity (2008)
Maccione, Luca, Liberati, Stefano, Celotti, Annalisa, Kirk, John G., Ubertini, Pietro
New constraints on Planck-scale Lorentz violation in QED from the Crab Nebula (2007)
Maccione, Luca, Liberati, Stefano, Celotti, Annalisa, Kirk, John G.
We set constraints on O(E/M) Lorentz Violation in QED in an effective field theory framework. A major consequence of such assumptions is the modification of the dispersion relations for...
Extended inverse-Compton emission from distant, powerful radio galaxies (2007)
Erlund, Mary C., Fabian, Andrew C., Blundell, Katherine M., Celotti, Annalisa, Crawford, Carolin S.
We present Chandra observations of two relatively high redshift FRII radio galaxies, 3C 432 and 3C 191 (z=1.785 and z=1.956 respectively), both of which show extended X-ray emission along the axis of...
Using radio bubbles to constrain the matter content of AGN jets (2007)
Dunn, Robert J.H., Fabian, Andrew C., Celotti, Annalisa
We revisit a method to obtain upper limits on the jet matter content combining synchrotron self-absorption constraints and the large scale bubble energy. We use both X-ray observations, which give...
Radiative pressure feedback by a quasar in a galactic bulge (2007)
Fabian, Andrew C., Celotti, Annalisa, Erlund, Mary C.
We show that Eddington-limited black hole luminosities can be sufficient to deplete a galaxy bulge of gas through radiation pressure, when the ionization state of the gas and the presence of dust are...
Discovery of the low-energy cutoff in a powerful giant radio galaxy (2007)
Blundell, Katherine M., Fabian, Andrew C., Crawford, Carolin S., Erlund, Mary C., Celotti, Annalisa
The lobes of radio galaxies and quasars, fed by jets and hotspots, represent a significant, and currently ill-constrained, source of energy input into the inter-galactic medium (IGM). How much energy...
Multiwavelength Observations of the BL Lacertae Object PKS 2155-304 with XMM-Newton (2007)
Zhang, You-Hong, Bai, J.M., Zhang, S.N., Treves, Aldo, Maraschi, L., Celotti, Annalisa
The optical-UV and X-ray instruments on-board XMM-Ndewton provide an excellent opportunity to perform simultaneous observations of violently variable objects over a broad wavelength range. The UV and...
Gamma-ray bursts associated with supernovae: a systematic analysis of BATSE GRB candidates (2007)
Bosnjak, Zeljka Marija, Celotti, Annalisa, Ghirlanda, Giancarlo, Della Valle, Massimo, Pian, Elena
We examined the properties of a sample of BATSE Gamma--Ray Bursts (GRBs) comprising events which have indications of association with a supernova (SN), some on the basis of indications of...
GRB 990413: insight into the thermal phase evolution (2007)
Bosnjak, Zeljka Marija, Celotti, Annalisa, Ghirlanda, Giancarlo
GRB 990413 shows a very hard spectrum (with a low energy spectral component F(E) \propto E^{2.49}) which is well represented by a black body model with characteristic temperature ~70 keV. It thus...
Stochastic wake field particle acceleration in Gamma-Ray Bursts (2007)
Barbiellini, Guido, Longo, Francesco, Omodei, Nicola, Giulietti, D., Celotti, Annalisa, Tavani, Marco
Gamma-Ray Burst (GRB) prompt emission can, for specific conditions, be so powerful and short-pulsed to strongly influence any surrounding plasma. In this paper, we briefly discuss the possibility...
Re-born fireballs in gamma-ray bursts (2007)
Ghisellini, Gabriele, Celotti, Annalisa, Ghirlanda, Giancarlo, Firmani, Claudio, Nava, Lara
We consider the interaction between a relativistic fireball and material assumed to be still located just outside the progenitor star. Only a small fraction of the expected mass is sufficient to...
On the radio properties of the highest redshift quasars (2007)
Cirasuolo, Michele, Magliocchetti, Manuela, Gentile, Gianfranco, Celotti, Annalisa, Cristiani, Stefano, Danese, Luigi
We present deep radio observations of the most distant complete quasar sample drawn from the Sloan Digital Sky Survey. Combining our new data with those from literature we obtain a sample which is...
On the nature of optical nuclei in FR I radio-galaxies from ACS/HST imaging polarimetry (2007)
Capetti, Alessandro, Axon, David J., Chiaberge, Marco, Sparks, William B., Macchetto, F. Duccio, Cracraft, Misty, ...
We obtained optical imaging polarimetry with the ACS/HRC aboard the HST of the 9 closest radio-galaxies in the 3C catalogue with an FR I morphology. The nuclear sources seen in direct HST images in...
Bulk Comptonization spectra in blazars (2007)
Celotti, Annalisa, Ghisellini, Gabriele, Fabian, Andrew C.
We study the time dependent spectra produced via the bulk Compton process by a cold, relativistic shell of plasma moving (and accelerating) along the jet of a blazar, scattering on external photons...
On the nature of optical nuclei in FR I radio-galaxies from ACS/HST imaging polarimetry (2007)
Capetti, Alessandro, Axon, David, Chiaberge, Marco, Sparks, William, Macchetto, Ferdinando, Cracraft, Misty, ...
Also archived in: arXiv:0706.1944 v1 Jun 13 2007
New constraints on Planck-scale Lorentz Violation in QED from the Crab Nebula (2007)
Maccione, Luca, Liberati, Stefano, Celotti, Annalisa, Kirk, John G.
We set constraints on O(E/M) Lorentz Violation in QED in an effective field theory framework. A major consequence of such assumptions is the modification of the dispersion relations for...
Low–intermediate luminosity AGNs: from their X-ray emission to their SMBHs (2007)
Cristiani, Stefano, Danese, Luigi, Celotti, Annalisa, Ballo, Lucia
Bulk Comptonization spectra in blazars (2006)
Celotti, Annalisa, Ghisellini, Gabriele, Fabian, Andrew C.
We study the time dependent spectra produced via the bulk Compton process by a cold, relativistic shell of plasma moving (and accelerating) along the jet of a blazar, scattering on external photons...
The demography of the youngest radio sources (2005)
De Zotti, Gianfranco, Celotti, Annalisa, Dallacasa, Daniele, Tinti, Sara
Gamma Ray Bursts: clues from the spectra and variability of the prompt phase (2005)
Celotti, Annalisa, Ghirlanda, Giancarlo, Bošnjak, Željka Marija
Probing the nuclear obscuration in radio-galaxies with near infrared imaging (2005)
Marchesini, Danilo, Capetti, Alessandro, Celotti, Annalisa
We present the first near-infrared (K'-band) homogeneous observations of a complete sub-sample of the 3CR radio catalogue comprising all High Excitation Galaxies (HEGs) at z
Internal shocks and the blazar sequence. Low and intermediate power BL Lac objects (2004)
Guetta, Dafne, Ghisellini, Gabriele, Lazzati, Davide, Celotti, Annalisa
We consider internal shocks as the main dissipation mechanism responsible for the emission in blazars and show that it can satisfactorily account for the properties of all blazars. In particular, we...
The spectra of short gamma-ray bursts (2004)
Ghirlanda, Giancarlo, Ghisellini, Gabriele, Celotti, Annalisa
We present the results of the spectral analysis of a sample of short bright $\gamma$-ray bursts (GRB) detected by BATSE and compare them with the average and time resolved spectral properties of long...
Extremely hard GRB spectra prune down the forest of emission models (2003)
Ghirlanda, Giancarlo, Celotti, Annalisa, Ghisellini, Gabriele
We consider the evidence for very hard low energy spectra during the prompt phase of Gamma-Ray Bursts (GRB). In particular we examine the spectral evolution of GRB 980306 together with the detailed...
A multi-wavelength test of the FR I-BL Lac unifying model (2003)
Trussoni, E., Capetti, Alessandro, Celotti, Annalisa, Chiaberge, Marco, Feretti, L.
We collect multi-wavelength measurements of the nuclear emission of 20 low luminosity FR I radio-galaxies to test the viability of the FR I - BL Lac unifying model. Although poorly sampled, the...
Clumps in large scale relativistic jets (2003)
Tavecchio, Fabrizio, Ghisellini, Gabriele, Celotti, Annalisa
Tagliaferri, Gianpiero, Ravasio, M., Ghisellini, Gabriele, Giommi, Paolo, Massaro, E., Nesci, R., ...
We present the results of the BeppoSAX observations of two BL Lacs, OQ 530 and S5 0716+714, as part of a ToO program for the simultaneous observation at radio, optical, X-ray and TeV energies. Both...
Ghisellini, Gabriele, Celotti, Annalisa, Costamante, Luigi
The spectral properties of blazars seem to follow a phenomenological sequence according to the source luminosity. By inferring the source physical parameters through (necessarily) modeling the blazar...
Time resolved spectral analysis of bright gamma ray bursts (2002)
Ghirlanda, Giancarlo, Celotti, Annalisa, Ghisellini, Gabriele
We present the time integrated and time resolved spectral analysis of a sample of bright bursts selected with F_{peak}>20 phot cm^{-2} sec^{-1} from the BATSE archive. We fitted four different...
Understanding the nature of FR II optical nuclei: A new diagnostic plane for radio galaxies (2002)
Chiaberge, Marco, Capetti, Alessandro, Celotti, Annalisa
We extend our study of the nuclei of 3CR FR II radio galaxies through HST optical images up to z=0.3. In the majority of them an unresolved nucleus (central compact core, CCC) is found. We analyze...
Blank field X-ray sources (2001)
Cagnoni, Ilaria, Celotti, Annalisa, Elvis, Martin, Dong-Woo Kim, Nicastro, Fabrizio
The X-ray sky is not as well known as is sometimes thought. We report on our search of minority populations (Kim & Elvis 1999). One of the most intriguing is that of `blank field sources', i.e....
An X-ray selected sample of radio-loud quasars (2001)
Wolter, Anna, Celotti, Annalisa
We construct the first X-ray selected sample of broad line radio-loud AGN from the EMSS survey. In order to test unifying schemes for radio-loud objects, their spectral and statistical properties...
The dividing line between FR I and FR II radio-galaxies (2001)
Ghisellini, Gabriele, Celotti, Annalisa
In the radio - host galaxy optical luminosity plane FR I and FR II radio-galaxies are clearly divided. Since the optical luminosity of an elliptical galaxy is an indication of the mass of its central...
Testing the FR I/BL Lac unifying model with HST observations (1999)
Capetti, Alessandro, Celotti, Annalisa
Hubble Space Telescope (HST) observations provide a novel way of testing unified models for FR I radio sources and BL Lac objects. The detection of extended dust discs in some radio galaxies provides...
Astrophysical evidence for the existence of black holes (1999)
Celotti, Annalisa, Miller, John C., Sciama, Dennis W.
Following a short account of the history of the idea of black holes, we present a review of the current status of the search for observational evidence of their existence aimed at an audience of...
Reprocessing of radiation by multi-phase gas in low-luminosity accretion flows (1999)
We discuss the role that magnetic fields in low luminosity accretion flows can play in creating and maintaining a multi-phase medium, and show that small magnetically-confined clouds or filaments of...
The HST view of FR I radio galaxies: evidence for non-thermal nuclear sources (1999)
Chiaberge, Marco, Capetti, Alessandro, Celotti, Annalisa
Unresolved nuclear sources are detected by the Hubble Space Telescope in the great majority of a complete sample of 33 FR I radio galaxies belonging to the 3CR catalogue. The optical flux of these...
Spectral evolution of PKS 2155-304 observed with BeppoSAX during an active gamma-ray phase (1999)
Chiappetti, Lucio, Maraschi, L., Tavecchio, Fabrizio, Celotti, Annalisa
We present the results of BeppoSAX observations of PKS 2155-304 during an intense gamma-ray flare. The source was in a high X-ray state. A temporal analysis of the data reveals a tendency of the...
Di Matteo, Tiziana, Celotti, Annalisa, Fabian, Andrew C.
We present a model for the different X-ray spectral states displayed by Galactic Black Hole Candidates (GBHC). We discuss the physical and spectral implications for a magnetically structured corona...
Variability of the extreme z=4.72 blazar, GB 1428+4217 (1999)
Fabian, Andrew C., Celotti, Annalisa, Pooley, G., Iwasawa, K., Brandt, W. Niel
We report X-ray and radio variability of GB 1428+4217 which confirm its blazar nature. IR observations reveal a powerful optical-UV component, not obscured by dust, which is suggestive of the...
Constraints on the bulk Lorentz factor in the internal shock scenario for gamma-ray bursts (1999)
Lazzati, Davide, Ghisellini, Gabriele, Celotti, Annalisa
We investigate, independently of specific emission models, the constraints on the value of the bulk Lorentz factor Gamma of a fireball. We assume that the burst emission comes from internal shocks in...
Correlated variability of Mkn 421 at X-ray and TeV wavelengths on time scales of hours (1999)
Maraschi, L., Fossati, G., Tavecchio, Fabrizio, Celotti, Annalisa
Mkn 421 was observed for about two days with BeppoSAX, prior to and partly overlapping the start of a 1 week continuous exposure with ASCA in April 1998, as part of a world-wide multiwavelength...
A theoretical unifying scheme for gamma-ray bright blazars (1998)
Ghisellini, Gabriele, Celotti, Annalisa, Fossati, G., Maraschi, L., Comastri, A.
The phenomenology of gamma-ray bright blazars can be accounted for by a sequence in the source power and intensity of the diffuse radiation field surrounding the relativistic jet. Correspondingly,...