@article {2014ApJ...792...38P, title = {{Constraints on the Progenitor System and the Environs of SN 2014J from Deep Radio Observations}}, journal = {The Astrophysical Journal}, volume = {792}, year = {2014}, pages = {38}, abstract = {We report deep EVN and eMERLIN observations of the Type Ia SN 2014J in the nearby galaxy M82. Our observations represent, together with JVLA observations of SNe 2011fe and 2014J, the most sensitive radio studies of Type Ia SNe ever. By combining data and a proper modeling of the radio emission, we constrain the mass-loss rate from the progenitor system of SN 2014J to $\backslash$dot$\{$M$\}$ $\backslash$lesssim 7.0$\backslash$times 10\^{}$\{$-10$\}$ $\{$$\backslash$,$\{$M\_$\{$$\backslash$odot $\}$ $\backslash$,yr\^{}$\{$-1$\}$$\}$$\}$ (for a wind speed of 100 km s$^{-1}$). If the medium around the supernova is uniform, then n $_{ISM}$ {\l}t}\~{} 1.3 cm$^{-3}$, which is the most stringent limit for the (uniform) density around a Type Ia SN. Our deep upper limits favor a double-degenerate (DD) scenario{\mdash}involving two WD stars{\mdash}for the progenitor system of SN 2014J, as such systems have less circumstellar gas than our upper limits. By contrast, most single-degenerate (SD) scenarios, i.e., the wide family of progenitor systems where a red giant, main-sequence, or sub-giant star donates mass to an exploding WD, are ruled out by our observations. (While completing our work, we noticed that a paper by Margutti et al. was submitted to The Astrophysical Journal. From a non-detection of X-ray emission from SN 2014J, the authors obtain limits of $\backslash$dot$\{$M$\}$ $\backslash$lesssim 1.2 $\backslash$times 10\^{}$\{$-9$\}$ M $_{\&sun;}$ yr$^{-1}$ (for a wind speed of 100 km s$^{-1}$) and n $_{ISM}$ {\l}t}\~{} 3.5 cm$^{-3}$, for the {$\rho$}vpropr $^{-2}$ wind and constant density cases, respectively. As these limits are less constraining than ours, the findings by Margutti et al. do not alter our conclusions. The X-ray results are, however, important to rule out free-free and synchrotron self-absorption as a reason for the radio non-detections.) Our estimates on the limits on the gas density surrounding SN2011fe, using the flux density limits from Chomiuk et al., agree well with their results. Although we discuss the possibilities of an SD scenario passing observational tests, as well as uncertainties in the modeling of the radio emission, the evidence from SNe 2011fe and 2014J points in the direction of a DD scenario for both.}, keywords = {stars: mass-loss, supernovae: individual: SN2011fe SN2014J}, doi = {10.1088/0004-637X/792/1/38}, url = {http://adsabs.harvard.edu/abs/2014ApJ...792...38P}, author = {M. A. P{\'e}rez-Torres and Lundqvist, P. and Beswick, R.~J. and Bj{\"o}rnsson, C.~I. and Muxlow, T.~W.~B. and Paragi, Z. and Ryder, S. and Alberdi, A. and Fransson, C. and Marcaide, J.~M. and Mart{\'\i}-Vidal, I. and Ros, E. and Argo, M.~K. and Guirado, J.~C.} } @article {2012A\&A...541A..99A, title = {{Constraining cosmic rays and magnetic fields in the Perseus galaxy cluster with TeV observations by the MAGIC telescopes}}, journal = {Astronomy and Astrophysics}, volume = {541}, year = {2012}, month = {may}, pages = {A99}, abstract = {Galaxy clusters are being assembled today in the most energetic phase of hierarchical structure formation which manifests itself in powerful shocks that contribute to a substantial energy density of cosmic rays (CRs). Hence, clusters are expected to be luminous gamma-ray emitters since they also act as energy reservoirs for additional CR sources, such as active galactic nuclei and supernova-driven galactic winds. To detect the gamma-ray emission from CR interactions with the ambient cluster gas, we conducted the deepest to date observational campaign targeting a galaxy cluster at very high-energy gamma-rays and observed the Perseus cluster with the MAGIC Cherenkov telescopes for a total of \~{}85 h of effective observing time. This campaign resulted in the detection of the central radio galaxy NGC 1275 at energies E {\gt} 100 GeV with a very steep energy spectrum. Here, we restrict our analysis to energies E {\gt} 630 GeV and detect no significant gamma-ray excess. This constrains the average CR-to-thermal pressure ratio to be {\l}sim}1-2\%, depending on assumptions and the model for CR emission. Comparing these gamma-ray upper limits to models inferred from cosmological cluster simulations that include CRs constrains the maximum CR acceleration efficiency at structure formation shocks to be {\l}t}50\%.Alternatively, this may argue for non-negligible CR transport processes such as CR streaming and diffusion into the outer cluster regions. Finally, we derive lower limits on the magnetic field distribution assuming that the Perseus radio mini-halo is generated by secondary electrons/positrons that are created in hadronic CR interactions: assuming a spectrum of E$^{-2.2}$ around TeV energies as implied by cluster simulations, we limit the central magnetic field to be {\gt}4-9 {$μ$}G, depending on the rate of decline of the magnetic field strength toward larger radii. This range is well below field strengths inferred from Faraday rotation measurements in cool cores. Hence, the hadronic model remains a plausible explanation of the Perseus radio mini-halo.}, keywords = {acceleration of particles, galaxies: clusters: individual: Perseus, gamma rays: galaxies: clusters}, doi = {10.1051/0004-6361/201118502}, url = {http://adsabs.harvard.edu/abs/2012A\%26A...541A..99A}, author = {Aleksi{\'c}, J. and Alvarez, E.~A. and Antonelli, L.~A. and Antoranz, P. and Asensio, M. and Backes, M. and Barres de Almeida, U. and Barrio, J.~A. and Bastieri, D. and Becerra Gonz{\'a}lez, J. and Bednarek, W. and Berdyugin, A. and Berger, K. and Bernardini, E. and Biland, A. and Blanch, O. and Bock, R.~K. and Boller, A. and Bonnoli, G. and Borla Tridon, D. and Braun, I. and Bretz, T. and Ca{\~n}ellas, A. and Carmona, E. and Carosi, A. and Colin, P. and Colombo, E. and Contreras, J.~L. and Cortina, J. and Cossio, L. and Covino, S. and Dazzi, F. and De Angelis, A. and De Caneva, G. and De Cea del Pozo, E. and De Lotto, B. and Delgado Mendez, C. and Diago Ortega, A. and Doert, M. and Dom{\'\i}nguez, A. and Dominis Prester, D. and Dorner, D. and Doro, M. and Eisenacher, D. and Elsaesser, D. and Ferenc, D. and Fonseca, M.~V. and Font, L. and Fruck, C. and Garc{\'\i}a L{\'o}pez, R.~J. and Garczarczyk, M. and Garrido, D. and Giavitto, G. and Godinovi{\'c}, N. and Gozzini, S.~R. and Hadasch, D. and H{\"a}fner, D. and Herrero, A. and Hildebrand, D. and H{\"o}hne-M{\"o}nch, D. and Hose, J. and Hrupec, D. and Jogler, T. and Kellermann, H. and Klepser, S. and Kr{\"a}henb{\"u}hl, T. and Krause, J. and Kushida, J. and La Barbera, A. and Lelas, D. and Leonardo, E. and Lewandowska, N. and Lindfors, E. and Lombardi, S. and L{\'o}pez, M. and L{\'o}pez, R. and L{\'o}pez-Oramas, A. and Lorenz, E. and Makariev, M. and Maneva, G. and Mankuzhiyil, N. and Mannheim, K. and Maraschi, L. and Mariotti, M. and Mart{\'\i}nez, M. and Mazin, D. and Meucci, M. and Miranda, J.~M. and Mirzoyan, R. and Mold{\'o}n, J. and Moralejo, A. and Munar-Adrover, P. and Niedzwiecki, A. and Nieto, D. and Nilsson, K. and Nowak, N. and Orito, R. and Paiano, S. and Paneque, D. and Paoletti, R. and Pardo, S. and Paredes, J.~M. and Partini, S. and M. A. P{\'e}rez-Torres and Persic, M. and Peruzzo, L. and Pilia, M. and Pochon, J. and Prada, F. and Prada Moroni, P.~G. and Prandini, E. and Puerto Gimenez, I. and Puljak, I. and Reichardt, I. and Reinthal, R. and Rhode, W. and Rib{\'o}, M. and Rico, J. and R{\"u}gamer, S. and Saggion, A. and Saito, K. and Saito, T.~Y. and Salvati, M. and Satalecka, K. and Scalzotto, V. and Scapin, V. and Schultz, C. and Schweizer, T. and Shayduk, M. and Shore, S.~N. and Sillanp{\"a}{\"a}, A. and Sitarek, J. and Snidaric, I. and Sobczynska, D. and Spanier, F. and Spiro, S. and Stamatescu, V. and Stamerra, A. and Steinke, B. and Storz, J. and Strah, N. and Sun, S. and Suri{\'c}, T. and Takalo, L. and Takami, H. and Tavecchio, F. and Temnikov, P. and Terzi{\'c}, T. and Tescaro, D. and Teshima, M. and Tibolla, O. and Torres, D.~F. and Treves, A. and Uellenbeck, M. and Vankov, H. and Vogler, P. and Wagner, R.~M. and Weitzel, Q. and Zabalza, V. and Zandanel, F. and Zanin, R. and MAGIC Collaboration and Pfrommer, C. and Pinzke, A.} } @article {2012ApJ...756..111M, title = {{Core-collapse Supernovae Missed by Optical Surveys}}, journal = {The Astrophysical Journal}, volume = {756}, year = {2012}, month = {sep}, pages = {111}, abstract = {We estimate the fraction of core-collapse supernovae (CCSNe) that remain undetected by optical SN searches due to obscuration by large amounts of dust in their host galaxies. This effect is especially important in luminous and ultraluminous infrared galaxies, which are locally rare but dominate the star formation at redshifts of z \~{} 1-2. We perform a detailed investigation of the SN activity in the nearby luminous infrared galaxy Arp 299 and estimate that up to 83\% of the SNe in Arp 299 and in similar galaxies in the local universe are missed by observations at optical wavelengths. For rest-frame optical surveys we find the fraction of SNe missed due to high dust extinction to increase from the average local value of \~{}19\% to \~{}38\% at z \~{} 1.2 and then remain roughly constant up to z \~{} 2. It is therefore crucial to take into account the effects of obscuration by dust when determining SN rates at high redshift and when predicting the number of CCSNe detectable by future high-z surveys such as LSST, JWST, and Euclid. For a sample of nearby CCSNe (distances 6-15 Mpc) detected during the last 12 yr, we find a lower limit for the local CCSN rate of 1.5$^{+0.4}$ $_{- 0.3}$ {\times} 10$^{-4}$ yr$^{-1}$ Mpc$^{-3}$, consistent with that expected from the star formation rate. Even closer, at distances less than \~{}6 Mpc, we find a significant increase in the CCSN rate, indicating a local overdensity of star formation caused by a small number of galaxies that have each hosted multiple SNe.}, keywords = {galaxies: individual: Arp 299, galaxies: starburst, infrared: galaxies, supernovae: general, supernovae: individual: SN 2005at SN 2010P}, doi = {10.1088/0004-637X/756/2/111}, url = {http://adsabs.harvard.edu/abs/2012ApJ...756..111M}, author = {Mattila, S. and Dahlen, T. and Efstathiou, A. and Kankare, E. and Melinder, J. and Alonso-Herrero, A. and M. A. P{\'e}rez-Torres and Ryder, S. and V{\"a}is{\"a}nen, P. and {\"O}stlin, G.} } @article {2011A\&A...533C...1M, title = {{Coherence loss in phase-referenced VLBI observations (Corrigendum)}}, journal = {Astronomy and Astrophysics}, volume = {533}, year = {2011}, month = {sep}, pages = {C1}, abstract = {We report an erratum in an equation that models the relation of the limiting dynamic range to the angular distance between target and calibrator.}, keywords = {addenda, atmospheric effects, errata, instrumentation: interferometers, techniques: interferometric}, doi = {10.1051/0004-6361/201014203e}, url = {http://adsabs.harvard.edu/abs/2011A\%26A...533C...1M}, author = {Mart{\'\i}-Vidal, I. and Ros, E. and M. A. P{\'e}rez-Torres and Guirado, J.~C. and Jim{\'e}nez-Monferrer, S. and Marcaide, J.~M.} } @article {2011MNRAS.415.2688R, title = {{The core-collapse supernova rate in Arp 299 revisited}}, journal = {Monthly Notices of the Royal Astronomical Society}, volume = {415}, year = {2011}, pages = {2688-2698}, abstract = {We present a study of the core-collapse supernova (CCSN) rate in nuclei A and B1, of the luminous infrared galaxy (LIRG) Arp 299, based on {\tilde}11 yr of Very Large Array (VLA) monitoring of their radio emission at 8.4 GHz. Significant variations in the nuclear radio flux density can be used to identify the CCSN activity in the absence of high-resolution very long baseline interferometry (VLBI) observations. In the case of the B1-nucleus, the small variations in its measured diffuse (synchrotron plus free-free) radio emission are below the fluxes expected from radio supernovae (RSNe), thus making it well-suited to detect RSNe through flux density variability. In fact, we find strong evidence for at least three RSNe this way, which results in a lower limit for the CCSN rate ({$ν$}$_{SN}$) of {\gt}0.28$^{+0.27}$$_{-0.15}$ yr$^{-1}$. This value agrees within the uncertainties with the infrared (IR) luminosity based SN rate estimate, and with previously reported radio estimates. In the A-nucleus, we did not detect any significant variability and found a SN detection threshold luminosity of {\ap}3.1 {\times} 10$^{28}$ erg s$^{-1}$ Hz$^{-1}$, allowing only the detection of the most luminous RSNe known. Our method is basically blind to normal CCSN explosions occurring within the A-nucleus, which result in too small variations in the nuclear flux density, remaining diluted by the strong diffuse emission of the nucleus itself. Additionally, we have attempted to find near-IR (NIR) counterparts for the earlier reported RSNe in the Arp 299 nucleus A, by comparing NIR adaptive optics images from the Gemini-N Telescope with contemporaneous observations from the European VLBI Network (EVN). However, we were not able to detect NIR counterparts for the reported radio SNe within the innermost regions of nucleus A. While our NIR observations were sensitive to typical CCSNe at {\tilde}300 mas (or 70 pc projected distance) from the centre of the nucleus A, suffering from extinction up to A$_{V}${\tilde} 15 mag, they were not sensitive to such highly obscured SNe within the innermost nuclear regions where most of the EVN sources were detected.}, keywords = {galaxies: individual: NGC 3690:IC 694, galaxies: starburst, supernovae: general}, doi = {10.1111/j.1365-2966.2011.18886.x}, url = {http://adsabs.harvard.edu/abs/2011MNRAS.415.2688R}, author = {Romero-Ca{\~n}izales, C. and Mattila, S. and Alberdi, A. and M. A. P{\'e}rez-Torres and Kankare, E. and Ryder, S.~D.} } @article {2010A\&A...515A..53M, title = {{Coherence loss in phase-referenced VLBI observations}}, journal = {Astronomy and Astrophysics}, volume = {515}, year = {2010}, month = {jun}, pages = {A53}, abstract = {Context. Phase-referencing is a standard calibration technique in radio interferometry, particularly suited for the detection of weak sources close to the sensitivity limits of the interferometers. However, effects from a changing atmosphere and inaccuracies in the correlator model may affect the phase-referenced images, and lead to wrong estimates of source flux densities and positions. A systematic observational study of signal decoherence in phase-referencing and its effects in the image plane has not been performed yet.
Aims: We systematically studied how the signal coherence in Very-Long-Baseline-Interferometry (VLBI) observations is affected by a phase-reference calibration at different frequencies and for different calibrator-to-target separations. The results obtained should be of interest for a correct interpretation of many phase-referenced observations with VLBI.
Methods: We observed a set of 13 strong sources (the S5 polar cap sample) at 8.4 and 15 GHz in phase-reference mode with 32 different calibrator/target combinations spanning angular separations between 1.5 and 20.5 degrees. We obtained phase-referenced images and studied how the dynamic range and peak flux-density depend on observing frequency and source separation.
Results: We obtained dynamic ranges and peak flux densities of the phase-referenced images as a function of frequency and separation from the calibrator. We compared our results with models and phenomenological equations previously reported.
Conclusions: The dynamic range of the phase-referenced images is strongly limited by the atmosphere at all frequencies and for all source separations. The limiting dynamic range is inversely proportional to the sine of the calibrator-to-target separation. Not surpriseingly, we also find that the peak flux densities decrease with source separation, relative to those obtained from the self-calibrated images.}, keywords = {atmospheric effects, instrumentation: interferometers, techniques: interferometric}, doi = {10.1051/0004-6361/201014203}, url = {http://adsabs.harvard.edu/abs/2010A\%26A...515A..53M}, author = {Mart{\'\i}-Vidal, I. and Ros, E. and M. A. P{\'e}rez-Torres and Guirado, J.~C. and Jim{\'e}nez-Monferrer, S. and Marcaide, J.~M.} }