Examinando por Autor "Milisavljevic, Dan"
Mostrando 1 - 5 de 5
Resultados por página
Opciones de ordenación
Ítem A missing-link in the supernova-GRB connection: The case of SN 2012ap(Institute of Physics Publishing, 2015-06) Chakraborti, Sayan; Soderberg, Alicia; Chomiuk, Laura; Kamble, Atish; Yadav, Naveen; Ray, Alak; Hurley, Kevin; Margutti, Raffaella; Milisavljevic, Dan; Bietenholz, Michael; Brunthaler, Andreas; Pignata, Giuliano; Pian, Elena; Mazzali, Paolo; Fransson, Claes; Bartel, Norbert; Hamuy, Mario; Levesque, Emily; Macfadyen, Andrew; Dittmann, Jason; Krauss, Miriam; Briggs, M.S.; Connaughton, V.; Yamaoka, K.; Takahashi, T.; Ohno M., Fukazawa; Tashiro, M.; Terada, Y.; Murakami, T.; Goldsten, J.; Barthelmy, S.; Gehrels, N.; Cummings, J.; Krimm, H.; Palmer, D.; Golenetskii, S.; Aptekar, R.; Frederiks, D.; Svinkin, D.; Cline, T.; Mitrofanov, I.G.; Golovin, D.; Litvak, M.L.; Sanin, A.B.; Boynton, W.; Fellows, C.; Harshman, K.; Enos, H.; Kienlin, A. Von; Rau, A.; Zhang, X.; Savchenko, V.Gamma-ray bursts (GRBs) are characterized by ultra-relativistic outflows, while supernovae are generally characterized by non-relativistic ejecta. GRB afterglows decelerate rapidly, usually within days, because their low-mass ejecta rapidly sweep up a comparatively larger mass of circumstellar material. However, supernovae with heavy ejecta can be in nearly free expansion for centuries. Supernovae were thought to have non-relativistic outflows except for a few relativistic ones accompanied by GRBs. This clear division was blurred by SN 2009bb, the first supernova with a relativistic outflow without an observed GRB. However, the ejecta from SN 2009bb was baryon loaded and in nearly free expansion for a year, unlike GRBs. We report the first supernova discovered without a GRB but with rapidly decelerating mildly relativistic ejecta, SN 2012ap. We discovered a bright and rapidly evolving radio counterpart driven by the circumstellar interaction of the relativistic ejecta. However, we did not find any coincident GRB with an isotropic fluence of more than one-sixth of the fluence from GRB 980425. This shows for the first time that central engines in SNe Ic, even without an observed GRB, can produce both relativistic and rapidly decelerating outflows like GRBs. © 2015. The American Astronomical Society. All rights reserved.Ítem High-density circumstellar interaction in the luminous type IIn SN 2010jl: The first 1100 days(Institute of Physics Publishing, 2014) Fransson, Claes; Ergon, Mattias; Challis, Peter J.; Chevalier, Roger A.; France, Kevin; Kirshner, Robert P.; Marion G., H.; Milisavljevic, Dan; Smith, Nathan; Bufano, Filomena; Friedman, Andrew S.; Kangas, Tuomas; Larsson, Josefin; Mattila, Seppo; Benetti, Stefano; Chornock, Ryan; Czekala, Ian; Soderberg, Alicia; Sollerman, JesperHubble Space Telescope and ground-based observations of the Type IIn supernova (SN) 2010jl are analyzed, including photometry and spectroscopy in the ultraviolet, optical, and near-IR bands, 26-1128 days after first detection. At maximum, the bolometric luminosity was ∼ 3 × 1043 erg s-1 and even at 850 days exceeds 1042 erg s-1. A near-IR excess, dominating after 400 days, probably originates in dust in the circumstellar medium (CSM). The total radiated energy is ≳ 6.5 × 1050 erg, excluding the dust component. The spectral lines can be separated into one broad component that is due to electron scattering and one narrow with expansion velocity ∼ 100 km s-1 from the CSM. The broad component is initially symmetric around zero velocity but becomes blueshifted after ∼50 days, while remaining symmetric about a shifted centroid velocity. Dust absorption in the ejecta is unlikely to explain the line shifts, and we attribute the shift instead to acceleration by the SN radiation. From the optical lines and the X-ray and dust properties, there is strong evidence for large-scale asymmetries in the CSM. The ultraviolet lines indicate CNO processing in the progenitor, while the optical shows a number of narrow coronal lines excited by the X-rays. The bolometric light curve is consistent with a radiative shock in an r-2 CSM with a mass-loss rate of M ∼ 0.1 M⊙ yr-1. The total mass lost is ≳3 M⊙. These properties are consistent with the SN expanding into a CSM characteristic of a luminous blue variable progenitor with a bipolar geometry. The apparent absence of nuclear processing is attributed to a CSM that is still opaque to electron scattering. © 2014. The American Astronomical Society. All rights reserved.Ítem Multi-wavelength observations of supernova 2011ei: time-dependent classification of type iib and ib supernovae and implications for their progenitors(2012) Milisavljevic, Dan; Margutti, Raffaella; Soderberg, Alicia M.; Pignata, Giuliano; Chomiuk, Laura; Fesen, Robert A.; Bufano, Filomena; Sanders, Nathan E.; Parrent, Jerod T.; Parker, Stuart; Pickering, Timothy; Buckley, David A. H.; Crawford, Steven M.; Gulbis, Amanda A. S.; Hettlage, Christian; Hooper, Eric; Nordsieck, Kenneth H.; O'Donoghue, Darragh; Husser, Tim-Oliver; Potter, Stephen; Kniazev, Alexei; Kotze, Paul; Romero-Colmenero, Encarni; Vaisanen, Petri; Wolf, Marsha; Bartel, Norbert; Bietenholz, Michael F.; Fransson, Claes; Mazzali, Paolo; Brunthaler, Andreas; Chakraborti, Sayan; Levesque, Emily M.; MacFayden, Andrew; Drescher, Colin; Bock, Greg; Marples, Peter; Anderson, Joseph P.; Benetti, Stefano; Reichart, Daniel; Ivarsen, KevinWe present X-ray, UV/optical, and radio observations of the stripped-envelope, core-collapse supernova (SN) 2011ei, one of the least luminous SNe IIb or Ib observed to date. Our observations begin with a discovery within 1 day of explosion and span several months afterward. Early optical spectra exhibit broad, Type II-like hydrogen Balmer profiles that subside rapidly and are replaced by Type Ib-like He-rich features on the timescale of one week. High-cadence monitoring of this transition identifies an absorption feature around 6250 °A to be chiefly due to hydrogen, as opposed to C II, Ne I, or Si II. Similarities between this observed feature and several SNe Ib suggest that hydrogen absorption attributable to a high velocity (& 12, 000 km s−1) H-rich shell is not rare in Type Ib events. Radio observations imply a shock velocity of v 0.13c and a progenitor star mass-loss rate of ˙M 1.4 × 10−5 M⊙ yr−1 (assuming wind velocity vw = 103 km s−1). This is consistent with independent constraints estimated from deep X-ray observations with Swift -XRT and Chandra. We find the multi-wavelength properties of SN2011ei to be consistent with the explosion of a lower-mass (3−4 M⊙), compact (R∗ 1×1011 cm), He core star. The star retained a thin hydrogen envelope at the time of outburst, and was embedded in an inhomogeneous circumstellar wind suggestive of modest episodic mass-loss. We conclude that SN2011ei’s rapid spectral metamorphosis calls attention to time-dependent classifications that bias estimates of explosion rates for a subset of Type IIb and Ib objects. Further, that important information about a progenitor star’s evolutionary state and associated mass-loss in the days to years prior to SN outburst can be inferred from timely multi-wavelength observations.Ítem Optical Spectroscopic Observations of Gamma-Ray Blazar Candidates. XII. Follow-up Observations from SOAR, Blanco, NTT, and OAN-SPM(American Astronomical Society, 2023-03) García-Pérez, Abigail; Peña-Herazo, Harold A.; Massaro, Francesco; Chavushyan, Vahram; D’abrusco, Raffaele; Masetti, Nicola; Landoni, Marco; Franca, Fabio La; Patiño-Álvarez, Víctor M.; Amaya-Almazán, Raúl A.; Milisavljevic, Dan; Paggi, Alessandro; Ricci, Federica; Jiménez-Bailón, Elena; Smith, Howard A.Roughly one third of the sources in the Fermi-LAT catalogs are listed as unidentified/unassociated γ-ray sources (UGS), i.e., they lack a low-energy counterpart. In addition, there is a growing population of blazars of uncertain type (BCUs). Spectroscopic observations are crucial to confirm the blazar nature of the UGSs candidate counterparts and BCUs. Hence, in 2013 we started an optical spectroscopic campaign to carry out the identifications and classifications. In this paper, as a continuation of the campaign we report the spectra of 39 sources: the sample comprises 37 sources classified as BCUs, one source classified as a BL Lac in the Fourth Source Catalog of the Fermi-LAT (4FGL), and one source classified as UGS. We classify 19 of the sources in the sample as BL Lacs, 13 as blazars with nonnegligible host-galaxy emission, six as Flat Spectrum Radio Quasars, and one as a normal elliptical galaxy. The source listed as BL Lac in the 4FGL seems to be a blazar with nonnegligible host-galaxy emission in our observations, most likely due to an ongoing quiescent state. We classified the UGS source as a BL Lac. Six out of the 39 sources were previously reported in the campaign; in general, both the classifications and redshifts are in agreement, except for one of them with no redshift reported before. Altogether, we provided reliable redshift estimates to 21 out of the 39 sources. Finally, we describe the statistics of the data collected in our campaign so far. © 2023. The Author(s). Published by the American Astronomical Society.Ítem Two New Catalogs of Blazar Candidates in the WISE Infrared Sky(Astrophysical Journal, Supplement Series, 2019) D’Abrusco, Raffaele; Álvarez Crespo, Nuria; Massaro, Francesco; Campana, Riccardo; Chavushyan, Vahram; Landoni, Marco; La Franca, Fabio; Masetti, Nicola; Milisavljevic, Dan; Paggi, Alessandro; Ricci, Federica; Smith, Howard A.We present two catalogs of radio-loud candidate blazars whose Wide-Field Infrared Survey Explorer (WISE) mid-infrared colors are selected to be consistent with the colors of confirmed γ-ray-emitting blazars. The first catalog is the improved and expanded release of the WISE Blazar-like Radio-Loud Sources (WIBRaLS) catalog presented by D’Abrusco et al. It includes sources detected in all four WISE filters, spatially cross-matched with radio sources in one of three radio surveys and radio-loud based on their q22 spectral parameter. WIBRaLS2 includes 9541 sources classified as BL Lacs, flat-spectrum radio quasars, or mixed candidates based on their WISE colors. The second catalog, called KDEBLLACS, based on a new selection technique, contains 5579 candidate BL Lacs extracted from the population of WISE sources detected in the first three WISE passbands ([3.4], [4.6], and [12]) only, whose mid-infrared colors are similar to those of confirmed, γ-ray BL Lacs. Members of KDBLLACS are also required to have a radio counterpart and be radio-loud based on the parameter q12, defined similarly to the q22 used for the WIBRaLS2. We describe the properties of these catalogs and compare them with the largest samples of confirmed and candidate blazars in the literature. We cross-match the two new catalogs with the most recent catalogs of γ-ray sources detected by the Fermi Large Area Telescope. Since spectroscopic observations of candidate blazars from the first WIBRaLS catalog within the uncertainty regions of γ-ray unassociated sources confirmed that ∼90% of these candidates are blazars, we anticipate that these new catalogs will again play an important role in the identification of the γ-ray sky.