Search Publications
Scaling laws for magnetic fields on the quiet Sun
Stenflo, J. O.
The Sun's magnetic field is structured over a range of scales that span approximately seven orders of magnitudes, four of which lie beyond the resolving power of current telescopes. Here we have used a Hinode SOT/SP deep mode data set for the quiet-Sun disk center in combination with constraints from the Hanle effect to derive scaling laws that de…
Efficient deconvolution methods for astronomical imaging: algorithms and IDL-GPU codes
Prato, M.; Cavicchioli, R.; Zanni, L. +2 more
Context. The Richardson-Lucy method is the most popular deconvolution method in astronomy because it preserves the number of counts and the non-negativity of the original object. Regularization is, in general, obtained by an early stopping of Richardson-Lucy iterations. In the case of point-wise objects such as binaries or open star clusters, iter…
HS 1700+6416: the first high-redshift unlensed narrow absorption line-QSO showing variable high-velocity outflows
Cappi, M.; Vignali, C.; Dadina, M. +4 more
We present a detailed analysis of the X-ray emission of HS 1700+6416, a high-redshift (z = 2.7348) luminous quasar classified as a narrow absorption line (NAL) quasar on the basis of its SDSS spectrum. The source has been observed nine times by Chandra and once by XMM-Newton from 2000 to 2007. Long-term variability is clearly detected between the …
Herschel/SPIRE observations of the dusty disk of NGC 4244
Bianchi, S.; Dalcanton, J. J.; Baes, M. +7 more
We present Herschel/SPIRE images at 250, 350, and 500 µm of NGC 4244, a typical low-mass, disk-only and edge-on spiral galaxy. The dust disk is clumpy and shows signs of truncation at the break radius of the stellar disk. This disk coincides with the densest part of the Hi disk. We compare the spectral energy distribution (SED), including th…
A Chandra view of the z = 1.62 galaxy cluster IRC-0218A
Papovich, C.; Pierre, M.; Clerc, N. +3 more
Context. Very few z > 1.5 clusters of galaxies are currently known. It is important to study the properties of galaxies in these clusters and the intra-cluster medium and, furthermore, to cross-check the reliability of the various mass estimates. This will help to clarify the process of structure formation and how distant clusters may be used t…
The quasi-biennial periodicity (QBP) in velocity and intensity helioseismic observations. The seismic QBP over solar cycle 23
García, R. A.; Roth, M.; Finsterle, W. +4 more
Aims: We looked for signatures of quasi-biennial periodicity (QBP) over different phases of solar cycle by means of acoustic modes of oscillation. Low-degree p-mode frequencies are shown to be sensitive to changes in magnetic activity due to the global dynamo. Recently there has been reported evidence of two-year variations in p-mode frequenc…
An inhomogeneous lepto-hadronic model for the radiation of relativistic jets. Application to XTE J1118+480
Romero, G. E.; Vila, G. S.; Casco, N. A.
Context. Conceptually reconstructing the physical conditions in relativistic jets, given the observed electromagnetic spectrum, is a complex inverse problem.
Aims: We aim to improve our understanding of the mechanisms operating in relativistic jets by modeling their broadband electromagnetic spectrum.
Methods: We develop an inhomogeneous…
The Penn State-Toruń Centre for Astronomy Planet Search stars. I. Spectroscopic analysis of 348 red giants
Nowak, G.; Zieliński, P.; Adamów, M. +2 more
Aims: We present basic atmospheric parameters (Teff, log g, vt, and [Fe/H]) as well as luminosities, masses, radii, and absolute radial velocities for 348 stars, presumably giants, from the ~1000 star sample observed within the Penn State-Toruń Centre for Astronomy Planet Search with the High Resolution Spectrograph of t…
Near- and mid-infrared colors of evolved stars in the Galactic plane. The Q1 and Q2 parameters
Menten, K. M.; Habing, H.; Churchwell, E. +1 more
Context. Mass-loss from evolved stars chemically enriches the interstellar medium (ISM). Stellar winds from massive stars and their explosions as supernovae shape the ISM and trigger star formation. Studying evolved stars is fundamental for understanding galaxy formation and evolution at any redshift.
Aims: We aim to establish a photometric c…
Constraints on cosmic-ray efficiency in the supernova remnant RCW 86 using multi-wavelength observations
Giordano, F.; Lemoine-Goumard, M.; Uchiyama, Y. +4 more
Context. Several young supernova remnants (SNRs) have recently been detected in the high-energy (HE; 0.1 < E < 100 GeV) and very-high-energy (VHE; E > 100 GeV) gamma-ray domains. As exemplified by RX J1713.7-3946, the nature of this emission has been hotly debated, and direct evidence for the efficient acceleration of cosmic-ray protons a…