M. Marelli

Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano

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Papers

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Co-Authors

A. De Luca

Laboratoire de Physique Théorique

103

P. A. Caraveo

Mylan (South Africa)

P. M. Saz Parkinson

University of California, Santa Cruz

A. Belfiore

Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano

D. Salvetti

Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano

M. Razzano

Istituto Nazionale di Fisica Nucleare

A. K. Harding

Los Alamos National Laboratory

A. Morselli

Istituto Nazionale di Fisica Nucleare, Sezione di Roma I

D. F. Torres

Institute of Space Sciences

S. Ciprini

Istituto Nazionale di Fisica Nucleare

Cooperative Institutions

California Institute of Technology

495

Centre National de la Recherche Scientifique

406

Goddard Space Flight Center

381

National Institute for Astrophysics

286

Max Planck Society

261

Stanford University

235

Kavli Institute for Particle Astrophysics and Cosmology

222

Cardiff University

210

SLAC National Accelerator Laboratory

208

LIGO Scientific Collaboration

187

Author Statistics

Papers

Citation

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Modulated High-Energy Gamma-Ray Emission from the Microquasar Cygnus X-3

Science (2009)

A. A. Abdo M. Ackermann M. Ajello M. Axelsson L. Baldini

Microquasar Spotted Microquasars are binary star systems where a normal star sheds matter onto a neutron star or a black hole, generating x-ray radiation and jets of material moving at relativistic speeds. Microquasars have proved difficult to detect in high-energy gamma rays (> 100 megaelectron volts). Using the Fermi Large Area Telescope, Abdo et al. (p. 1512 , published online 26 November; see the Perspective by Bignami ) now report the detection of variable gamma-ray emission from the microquasar Cygnus X-3. The gamma-ray flux is modulated at the orbital period of Cygnus X-3, and its variation is correlated with the radio emission originating from the microquasar's relativistic jets.

Black hole (networking)

X-ray binary

Astrophysical jet

Star (game theory)

10.1126/science.1182174

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Citations (231)

SEARCH FOR GAMMA-RAY EMISSION FROM MAGNETARS WITH THE FERMI LARGE AREA TELESCOPE

The Astrophysical Journal Letters (2010)

A. A. Abdo M. Ackermann M. Ajello A. Allafort L. Baldini

We report on the search for 0.1-10 GeV emission from magnetars in 17 months of Fermi Large Area Telescope (LAT) observations. No significant evidence for gamma-ray emission from any of the currently-known magnetars is found. The most stringent upper limits to date on their persistent emission in the Fermi-LAT energy range are estimated between ~10^{-12}-10^{-10} erg/s/cm2, depending on the source. We also searched for gamma-ray pulsations and possible outbursts, also with no significant detection. The upper limits derived support the presence of a cut-off at an energy below a few MeV in the persistent emission of magnetars. They also show the likely need for a revision of current models of outer gap emission from strongly magnetized pulsars, which, in some realizations, predict detectable GeV emission from magnetars at flux levels exceeding the upper limits identified here using the Fermi-LAT observations.

Magnetar

10.1088/2041-8205/725/1/l73

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Citations (43)

THE VELA PULSAR: RESULTS FROM THE FIRST YEAR OFFERMILAT OBSERVATIONS

The Astrophysical Journal (2010)

A. A. Abdo M. Ackermann M. Ajello A. Allafort W. B. Atwood

We report on analysis of timing and spectroscopy of the Vela pulsar using 11 months of observations with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope.The intrinsic brightness of Vela at GeV energies combined with the angular resolution and sensitivity of the LAT allows us to make the most detailed study to date of the energy-dependent light curves and phase-resolved spectra, using a LAT-derived timing model.The light curve consists of two peaks (P1 and P2) connected by bridge emission containing a third peak (P3).We have confirmed the strong decrease of the P1/P2 ratio with increasing energy seen with EGRET and previous Fermi LAT data, and observe that P1 disappears above 20 GeV.The increase with energy of the mean phase of the P3 component can be followed with much greater detail, showing that P3 and P2 are present up to the highest energies of pulsation.We find significant pulsed emission at phases outside the main profile, indicating that magnetospheric emission exists over 80% of the pulsar period.With increased high-energy counts the phase-averaged spectrum is seen to depart from a power law with simple exponential cutoff, and is better fit with a more gradual cutoff.The spectra in fixed-count phase bins are well fit with power laws with exponential cutoffs, revealing a strong and complex phase dependence of the cutoff energy, especially in the peaks.By combining these results with predictions of the outer magnetosphere models that map emission characteristics to phase, it will be possible to probe the particle acceleration and the structure of the pulsar magnetosphere with unprecedented detail.

Vela

Cut-off

10.1088/0004-637x/713/1/154

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Citations (104)

ULX-1 in NGC5907: how bright can an accreting pulsar shine?

arXiv (Cornell University) (2016)

G. L. Israel A. Belfiore L. Stella P. Esposito P. Casella

Ultraluminous x-ray sources (ULXs) in nearby galaxies shine brighter than any X-ray source in our Galaxy. ULXs are usually modeled as stellar-mass black holes (BHs) accreting at very high rates or intermediate-mass BHs. We present observations showing that NGC5907 ULX is instead an x-ray accreting neutron star (NS) with a spin period evolving from 1.43~s in 2003 to 1.13~s in 2014. It has an isotropic peak luminosity of about 1000 times the Eddington limit for a NS at 17.1~Mpc. Standard accretion models fail to explain its luminosity, even assuming beamed emission, but a strong multipolar magnetic field can describe its properties. These findings suggest that other extreme ULXs (x-ray luminosity > 10^{41} erg/s) might harbor NSs.

Eddington luminosity

Black hole (networking)

Stellar mass

Source

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Citations (2)

X-RAY PULSATIONS FROM THE RADIO-QUIET GAMMA-RAY PULSAR IN CTA 1

The Astrophysical Journal Letters (2010)

P. A. Caraveo A. De Luca M. Marelli G. F. Bignami Paul S. Ray

Prompted by the Fermi-LAT discovery of a radio-quiet gamma-ray pulsar inside the CTA 1 supernova remnant, we obtained a 130 ks XMM-Newton observation to assess the timing behavior of this pulsar. Exploiting both the unprecedented photon harvest and the contemporary Fermi-LAT timing measurements, a 4.7σ single-peak pulsation is detected, making PSR J0007+7303 the second example, after Geminga, of a radio-quiet gamma-ray pulsar also seen to pulsate in X-rays. Phase-resolved spectroscopy shows that the off-pulse portion of the light curve is dominated by a power-law, non-thermal spectrum, while the X-ray peak emission appears to be mainly of thermal origin, probably from a polar cap heated by magnetospheric return currents, pointing to a hot spot varying throughout the pulsar rotation.

QUIET

10.1088/2041-8205/725/1/l6

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Citations (31)

X- AND γ-RAY PULSATIONS OF THE NEARBY RADIO-FAINT PSR J1741–2054

The Astrophysical Journal (2014)

M. Marelli A. Belfiore P. M. Saz Parkinson P. A. Caraveo A. De Luca

We report the results of a deep XMM-Newton observation of the radio-faint γ-ray pulsar J1741−2054 and its nebula together with the analysis of five years of Fermi Large Area Telescope (LAT) data. The X-ray spectrum of the pulsar is consistent with an absorbed power law plus a blackbody, originating at least partly from the neutron star cooling. The nebular emission is consistent with that of a synchrotron pulsar wind nebula, with hints of spatial spectral variation. We extended the available Fermi LAT ephemeris and folded the γ-ray and X-ray data. We detected X-ray pulsations from the neutron star: both the thermal and non-thermal components are ∼35%–40% pulsed, with phase-aligned maxima. A sinusoid fits the thermal-folded profile well. A 10 bin phase-resolved analysis of the X-ray emission shows softening of the non-thermal spectrum during the on-pulse phases. The radio, X-ray, and γ-ray light curves are single-peaked, not phase-aligned, with the X-ray peak trailing the γ-ray peak by more than half a rotation. Spectral considerations suggest that the most probable pulsar distance is in the 0.3–1.0 kpc range, in agreement with the radio dispersion measure.

Pulsar wind nebula

Black-body radiation

X-ray pulsar

10.1088/0004-637x/790/1/51

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Citations (13)

FERMI-LAT OBSERVATIONS OF THE LIGO EVENT GW150914

The Astrophysical Journal Letters (2016)

M. Ackermann M. Ajello A. Albert B. Anderson M. Arimoto

The Fermi Large Area Telescope (LAT) has an instantaneous field of view covering $\sim 1/5$ of the sky and completes a survey of the full sky every ~3 hours. It provides a continuous, all-sky survey of high-energy gamma-rays, enabling searches for transient phenomena over timescales from milliseconds to years. Among these phenomena could be electromagnetic counterparts to gravitational wave sources. In this paper, we present a detailed study of the LAT observations relevant to Laser Interferometer Gravitational-wave Observatory (LIGO) event GW150904 (Abbott et al. 2016), which is the first direct detection of gravitational waves and has been interpreted as due to coalescence of two stellar-mass black holes. The localization region for GW150904 was outside the LAT field of view at the time of the gravitational wave signal. However, as part of routine survey observations, the LAT observed the entire LIGO localization region within ~70 minutes of the trigger, and thus enabled a comprehensive search for a gamma-ray counterpart to GW150904. The study of the LAT data presented here did not find any potential counterparts to GW150904, but it did provide limits on the presence of a transient counterpart above 100 MeV on timescales of hours to days over the entire GW150904 localization region.

10.3847/2041-8205/823/1/l2

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Citations (67)

PSR J0357+3205: A FAST-MOVING PULSAR WITH A VERY UNUSUAL X-RAY TRAIL

The Astrophysical Journal Letters (2013)

A. De Luca R. Mignani M. Marelli D. Salvetti N. Sartore

The middle-aged PSR J0357+3205 is a nearby, radio-quiet, bright γ-ray pulsar discovered by the Fermi mission. Our previous Chandra observation revealed a huge, very peculiar structure of diffuse X-ray emission originating at the pulsar position and extending for >9' on the plane of the sky. To better understand the nature of such a nebula, we have studied the proper motion of the parent pulsar. We performed relative astrometry on Chandra images of the field spanning a time baseline of 2.2 yr, unveiling a significant angular displacement of the pulsar counterpart, corresponding to a proper motion of 0165 ± 0030 yr−1 at a position angle (P.A.) of 314° ± 8°. At a distance of ∼500 pc, the space velocity of the pulsar would be of ∼390 km s−1 assuming no inclination with respect to the plane of the sky. The direction of the pulsar proper motion is aligned very well with the main axis of the X-ray nebula (P.A. = 3155 ± 15), pointing to a physical, yet elusive, link between the nebula and the pulsar space velocity. No optical emission in the Hα line is seen in a deep image collected at the Gemini telescope, which implies that the interstellar medium into which the pulsar is moving is fully ionized.

Proper motion

Galactic plane

Pulsar wind nebula

Pulsar planet

X-ray pulsar

Astrometry

10.1088/2041-8205/765/1/l19

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Citations (25)

EXTraS unveils a supernova shock break-out candidate in XMM-Newton archival data

xru (2017)

A. Tiengo G. Novara Gianni Lisini A. De Luca R. Salvaterra

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CONSTRAINTS ON THE GALACTIC POPULATION OF TeV PULSAR WIND NEBULAE USINGFERMILARGE AREA TELESCOPE OBSERVATIONS

The Astrophysical Journal (2013)

F. Acero M. Ackermann M. Ajello A. Allafort L. Baldini

Pulsar wind nebulae (PWNe) have been established as the most populous class of TeV gamma-ray emitters. Since launch, the Fermi Large Area Telescope (LAT)identified five high-energy (100MeV

Galactic plane

10.1088/0004-637x/773/1/77

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Citations (109)