The first outburst of the new magnetar candidate SGR 0501+4516 (2009)
Rea, Nanda, Israel, GianLuca, Turolla, Roberto, Esposito, Paolo, Mereghetti, Sandro, Gotz, Diego, ...
We report here on the outburst onset and evolution of the new Soft Gamma Repeater SGR 0501+4516. We monitored the new SGR with XMM-Newton starting on 2008 August 23, one day after the source became...
How rapidly do neutron stars spin at birth? (2008)
Soria, Roberto, Perna, Rosalba, Pooley, David, Stella, Luigi
We have studied the X-ray properties of ageing historical core-collapse supernovae in nearby galaxies, using archival data from Chandra, XMM-Newton and Swift. We found possible evidence of a young...
Short Gamma-Ray Bursts and Gravitational Waves from Dynamically Formed Merging Binaries (2008)
Merging binary systems consisting of two collapsed objects are among the most promising sources of high frequency gravitational wave, GW, signals for ground based interferometers. Double neutron star...
Campana, Sergio, Stella, Luigi, Israel, Gianluca, D'Avanzo, Paolo
We present X-ray observations of the transient accretion-powered millisecond pulsar IGR J00291+5934 during quiescence. IGR J00291+5934 is the first source among accretion powered millisecond pulsars...
The general relativistic Poynting-Robertson effect (2008)
Bini, Donato, Jantzen, Robert T., Stella, Luigi
The general relativistic version is developed for Robertson's discussion of the Poynting-Robertson effect that he based on special relativity and Newtonian gravity for point radiation sources like...
Swift observations of SAX J1808.4-3658: monitoring the return to quiescence (2008)
Campana, Sergio, Stella, Luigi, Kennea, Jamie A.
The transient accreting millisecond pulsar SAX J1808.4-3658 has shown several outbursts to date but the transition from outburst to quiescence has never been investigated in detail. Thanks to the...
Perna, Rosalba, Soria, Roberto, Pooley, Dave, Stella, Luigi
Traditionally, studies aimed at inferring the distribution of birth periods of neutron stars are based on radio surveys. Here we propose an independent method to constrain the pulsar spin periods at...
Spectral modelling of the high energy emission of the magnetar 4U 0142+614 (2007)
Rea, Nanda, Turolla, Roberto, Zane, Silvia, Tramacere, Andrea, Stella, Luigi, Israel, Gianluca, ...
We present an empirical spectral modelling of the high energy emission of the anomalous X-ray pulsar 4U 0142+614, based on simultaneous Swift and INTEGRAL observations from X to gamma-ray energies....
Dall'Osso, Simone, Stella, Luigi
Soft Gamma Repeaters and the Anomalous X-ray Pulsars are believed to contain slowly spinning "magnetars". The enormous energy liberated in the 2004 Dece 27 giant flare from SGR 1806-20, together with...
On the spin-up/spin-down transitions in accreting X-ray binaries (2005)
Perna, Rosalba, Bozzo, Enrico, Stella, Luigi
Accreting X-Ray Binaries display a wide range of behaviours. Some of them are observed to spin up steadily, others to alternate between spin-up and spin-down states, sometimes superimposed on a...
Gravitational Radiation from Newborn Magnetars (2005)
Stella, Luigi, Dall'Osso, Simone, Israel, GianLuca, Vecchio, Alberto
There is growing evidence that two classes of high-energy sources, the Soft Gamma Repeaters and the Anomalous X-ray Pulsars contain slowly spinning ``magnetars'', i.e. neutron stars whose emission is...
A Compton reflection dominated spectrum in a peculiar accreting neutron star (2005)
Rea, Nanda, Stella, Luigi, Israel, Gian Luca, Matt, Giorgio, Zane, Silvia, Segreto, Alberto, ...
We report on a puzzling event occurred during a long BeppoSAX observation of the slow-rotating binary pulsar GX 1+4. During this event, lasting about 1 day, the source X-ray flux was over a factor 10...
Astrophysical Unipolar Inductors Powered by Gravitational Wave Emission (2005)
Dall'Osso, Simone, Israel, Gian Luca, Stella, Luigi
We consider the Unipolar Inductor Model (Goldreich & Lynden-Bell 1969) applied to Double Degenerate Binaries (DDBs) with ultrashort periods (Wu et al. 2002). In this model a magnetized primary white...
A continuous Flaring- to Normal-branch transition in Sco X-1 (2005)
Casella, Piergiorgio, Belloni, Tomaso, Stella, Luigi
We report the first resolved rapid transition from a Flaring Branch Oscillation to a Normal Branch Oscillation in the RXTE data of the Z source Sco X-1. The transition took place on a time scale of...
Israel, GianLuca, Covino, Stefano, Mignani, Roberto, Stella, Luigi, Marconi, Gianni, Testa, Vincenzo, ...
The sky region including the Chandra position of SGR 1806-20 was monitored in the IR band during 2004, following its increased high energy bursting activity. Observations were performed using...
Discovery of Rapid X-ray Oscillations in the Tail of the SGR 1806-20 Hyperflare (2005)
Israel, GianLuca, Belloni, Tomaso, Stella, Luigi, Rephaeli, Yoel, Gruber, Duane, Casella, Pier Giorgio, ...
We have discovered rapid Quasi Periodic Oscillations (QPOs) in RXTE/PCA measurements of the pulsating tail of the 27th December 2004 giant flare of SGR 1806-20. QPOs at about 92.5Hz are detected in a...
Swift XRT and VLT Observations of the Afterglow of GRB 041223 (2005)
Burrows, David N., Hill, Joanne E., Chincarini, Guido, Tagliaferri, Gianpiero, Campana, Sergio, Moretti, Alberto, ...
The Swift Gamma-Ray Burst Explorer, launched on 2004 November 20, is a multiwavelength, autonomous, rapid-slewing observatory for gamma-ray burst (GRB) astronomy. On 2004 December 23, during the...
Are all Gamma Ray Bursts like GRB 980425, GRB 030329 and GRB 031203? (2004)
Guetta, Dafne, Perna, Rosalba, Stella, Luigi, Vietri, Mario
We study the probability that three GRBs (980425, 030329, 031203) are found within z=0.17, given the luminosity functions consistent with the log N-log S relationship for classical cosmological...
A puzzling event during the X-ray emission of the binary system GX 1+4 (2004)
Rea, Nanda, Stella, Luigi, Israel, Gian Luca, Matt, Giorgio, Zane, Silvia, Segreto, Alberto, ...
We report on a long X-ray observation of the slow-rotating binary pulsar GX 1+4. BeppoSAX observed, in the 0.1-200 keV energy range, an event in which the source flux dropped for almost a day, and...
Casella, Piergiorgio, Belloni, Tomaso, Homan, Jeroen, Stella, Luigi
We present the results of an extensive timing analysis of the 1999 outburst of the soft X-ray transient and black hole candidate XTE J1859+226 as observed with the Rossi X-Ray Timing Explorer. Three...
Young Crab-like pulsars and luminous X-ray sources in starbursts and optically dull galaxies (2004)
Recent Chandra observations of nearby galaxies have revealed a number of ultraluminous X-ray sources (ULXs) with super-Eddington luminosities, away from the central regions of non-active galaxies....
A possible new dipping X-ray source in the field of M31 (2004)
Mangano, Vanessa, Israel, Gian Luca, Stella, Luigi
We report the discovery of the new dipping X-ray source, XMMU J004308.6+411247, in M31, during a systematic search for periodicities in XMM-Newton archival observations. During the 2002 January 6...
Unveiling the multi-wavelength phenomenology of Anomalous X-ray Pulsars (2003)
Israel, GianLuca, Stella, Luigi, Covino, Stefano, Campana, Sergio, Angelini, Lorella, Mignani, Roberto, ...
During 2002-2003 the number of IR-identified counterparts to the Anomalous X-ray Pulsars (AXPs) has grown to four (4U0142+614, 2E2259+584, 1E 1048-59 and 1RXS J170849-400910) out of the six assessed...
New results on neutron star low mass transients in the quiescence (2003)
Campana, Sergio, Stella, Luigi
We review the main observational properties of neutron star low mass transients in quiescence. We first survey the discoveries of BeppoSAX. We then focus on recent discoveries by Chandra and...
First evidence of a cyclotron feature in an anomalous X-ray pulsar (2003)
Rea, Nanda, Israel, Gian Luca, Stella, Luigi
We report on the results of the longest uninterrupted observation of the Anomalous X-ray Pulsar 1RXS J1708-4009 obtained with the BeppoSAX satellite in August 2001. In the phase-resolved spectrum,...
Campana, Sergio, Stella, Luigi
A moderate level of variability has been detected in the quiescent luminosity of several neutron star soft X-ray transients. Spectral variability was first revealed by Chandra observations of Aql X-1...
Bondi Accretion and the Problem of the Missing Isolated Neutron Stars (2003)
Perna, Rosalba, Narayan, Ramesh, Rybicki, George, Stella, Luigi, Treves, Aldo
A large number of neutron stars (NSs), ~10^9, populate the Galaxy, but only a tiny fraction of them is observable during the short radio pulsar lifetime. The majority of these isolated NSs, too cold...
Unveiling the nature of the 321s Orbital Period X-ray source RX J0806.3+1527 (2003)
Israel, GianLuca, Stella, Luigi, Covino, Stefano, Campana, Sergio, Marconi, Gianni, Mauche, Christopher W., ...
A nearly simultaneous X-ray/optical (Chandra and VLT) observational campaign of RX J0806.3+1527 has been carried out during November 2001. These observations allowed us to phase the X-ray and optical...
Rea, Nanda, Israel, Gian Luca, Stella, Luigi, Oosterbroek, Tim, Mereghetti, Sandro, Angelini, Lorella, ...
We report the results of a long observation of the anomalous X-ray pulsar 1RXS J170849-400910 obtained with the BeppoSAX satellite in August 2001. The best-fit phase-averaged spectrum was an absorbed...
Covino, Stefano, Negueruela, Ignacio, Campana, Sergio, Israel, Gianluca, Polcaro, Francesco, Stella, Luigi, ...
We report on the discovery and confirmation of the optical counterparts of the two transient X-ray pulsars, RXJ0052.1-7319 and XTEJ0111.2-7317. In the narrow (~3" radius) X-ray error circle of...
Israel, GianLuca, Negueruela, Ignacio, Campana, Sergio, Covino, Stefano, Di Paola, Andrea, Maxwell, Diana H., ...
We report on the identification of the optical/IR counterpart of the 29.5-s transient X-ray pulsar GS 1843+009. We re-analysed an archival ROSAT HRI observation of GS 1843+009, obtaining a new...
Illuminated, and enlightened, by GRB 991216 (2000)
Vietri, Mario, Ghisellini, Gabriele, Lazzati, Davide, Fiore, Fabrizio, Stella, Luigi
We consider models for the generation of the emission line recently discovered in the X-ray afterglow spectrum of several bursts, and especially of GRB 991216 observed by Chandra. These observations...
Campana, Sergio, Stella, Luigi
Low mass X-ray transients (LMXRTs) hosting black hole candidates (BHCs) display on average a factor of ~100 larger swing in the minimum (quiescent) to maximum (outburst) X-ray luminosity than neutron...
BeppoSAX observation of Cen X-4 in quiescence (2000)
Campana, Sergio, Stella, Luigi, Mereghetti, Sandro, Cremonesi, Davide
We report on a 61 ks BeppoSAX observation of the soft X-ray transient Cen X-4 during quiescence which allowed to study the source X-ray spectrum from ~ 0.3 keV to ~ 8 keV. A two-component spectral...
Evidence for an ~80 day periodicity in the X-ray transient pulsar XTE J1946+274 (1999)
Campana, Sergio, Israel, Gianluca, Stella, Luigi
We report evidence for an ~ 80 d periodicity in the X-ray flux of the hard transient pulsar XTE J1946+274. The 1.3-12 keV light curve obtained with the RossiXTE All Sky Monitor shows five regularly...
SupraNova Events from Spun-up Neutron Stars: an Explosion in Search of an Observation (1999)
We consider a formation scenario for supramassive neutron stars (SMNSs) taking place through mass and angular momentum transfer from a close companion during a Low Mass X-ray Binary (LMXB) phase,...
Stella, Luigi, Vietri, Mario, Morsink, Sharon
A remarkable correlation between the centroid frequencies of quasi periodic oscillations, QPOs, (or peaked noise components) from low mass X-ray binaries, has been recently discovered by Psaltis,...
Broad Band X-ray Spectra of M31 Sources with BeppoSAX (1999)
Trinchieri, Ginevra, Israel, Gian Luca, Chiappetti, Lucio, Belloni, Tomaso, Stella, Luigi, Primini, Frank, ...
We present the first spectral study of the X-ray emitting stellar sources in M31 in the energy band from 0.1 to 10 keV. We find that the globular cluster sources have spectral characteristics...
Further evidence that 1RXS J170849.0-400910 is an Anomalous X-ray pulsar (1999)
Israel, GianLuca, Covino, Stefano, Stella, Luigi, Campana, Sergio, Mereghetti, Sandro
We report the results of two ROSAT HRI observations of the recently discovered 11s X-ray pulsar 1RXS J170849.0-400910. A refined position with a smaller error radius (10" uncertainty) and a new spin...
We consider the interpretation of a pair of kHz Quasi Periodic Oscillations (QPOs) in the Fourier spectra of two Low Mass X-Ray Binaries, Sco X-1 and 4U1608-52, hosting an old accreting neutron star....
Morsink, Sharon M., Stella, Luigi
General relativity predicts that a rotating body produces a frame-dragging (or Lense-Thirring) effect: the orbital plane of a test particle in a non-equatorial orbit precesses about the body's...
A new instability of accretion disks around compact magnetic stars (1998)
Aperiodic variability and Quasi Periodic Oscillations (QPOs) are observed from accretion disks orbiting white dwarfs, neutron stars, and black holes, suggesting that the flow is universally broken up...
Lense-Thirring Precession and QPOs in Low Mass X-Ray Binaries (1997)
We show in this Letter that relativistic dragging of inertial frames around fast rotating collapsed stars is substantial and can give rise to observable effects. We apply this to the kHz quasi...
On the relationship between the periodic and aperiodic variability of accreting X-ray pulsars (1996)
Lazzati, Davide, Stella, Luigi
Besides the narrow peaks originating from the periodic signal, the power spectra of accreting X-ray pulsars display continuum components usually increasing towards low frequencies; these arise from...
Reverberation by a Relativistic Accretion Disk (1994)
Campana, Sergio, Stella, Luigi
We calculate the response of a line emitted from a relativistic accretion disk to a continuum variation of the central illuminating source. This model might be relevant to the very broad and...
The role of A3 adenosine receptors in central regulation of arterial blood pressure
Stella, Luigi, De Novellis, Vito, Marabese, Ida, Berrino, Liberato, Maione, Sabatino, Filippelli, Amelia, ...
Pharmacological studies have suggested that A3 receptors are present on central neurons. Recently this adenosine receptor subtype has been identified in the rat and its presence in the central...