Browsing by Author "Leloudas, G."
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- ItemA young stellar environment for the superluminous supernova PTF12dam(OXFORD UNIV PRESS, 2015) Thoene, C. C.; Postigo, A. de Ugarte; Garcia Benito, R.; Leloudas, G.; Schulze, S.; Amorin, R.The progenitors of superluminous supernovae (SLSNe) are still a mystery. Hydrogen-poor SLSN hosts are young, highly star-forming dwarf galaxies and the majority belongs to the class of 'extreme emission line galaxies'. Here we present a resolved long-slit study of the host of the hydrogen-poor SLSN PTF12dam probing the kiloparsec environment of the SN site to determine the age of the progenitor. The SN occurred in a star-forming region in the head of a 'tadpole' galaxy with largely uniform properties. The galaxy experienced a recent starburst superimposed on an underlying old stellar population (SP). We determine a very young SP at the SN site of similar to 3 Myr and a metallicity of 12+log(O/H)=8.0 but do not observe any Wolf-Rayet features. The progenitor of PTF12dam was likely a massive star of >60 M-circle dot and one of the first stars exploding as an SN in the most recent starburst episode.
- ItemCosmic evolution and metal aversion in superluminous supernova host galaxies(2018) Schulze, Steve; Krühler, T.; Leloudas, G.; Gorosabel, J.; Mehner, A.; Buchner, J.; Kim, Sam; Ibar, Edo; Amorín, Ricardo; Herrero Illana, Rubén; Anderson, Joseph; Bauer, Franz Erik
- ItemDelayed appearance and evolution of coronal lines in the TDE AT2019qiz(Oxford University Press, 2023) Short, P.; Lawrence, A.; Nicholl, M.; Ward, M.; Reynolds, T. M.; Mattila, S.; Yin, C.; Arcavi, I; Carnall, A.; Charalampopoulos, P.; Gromadzki, M.; Jonker, P. G.; Kim, Sam; Leloudas, G.; Mandel, I; Onori, F.; Pursiainen, M.; Schulze, S.; Villforth, C.; Wevers, T.Tidal disruption events (TDEs) occur when a star gets torn apart by a supermassive black hole as it crosses its tidal radius. We present late-time optical and X-ray observations of the nuclear transient AT2019qiz, which showed the typical signs of an optical-UV transient class commonly believed to be TDEs. Optical spectra were obtained 428, 481, and 828 rest-frame days after optical light-curve peak, and a UV/X-ray observation coincided with the later spectrum. The optical spectra show strong coronal emission lines, including [Fe vii], [Fe x], [Fe xi], and [Fe xiv]. The Fe lines rise and then fall, except [Fe xiv] that appears late and rises. We observe increasing flux of narrow H & alpha; and H & beta; and a decrease in broad H & alpha; flux. The coronal lines have full width at half-maximum ranging from & SIM;150-300 km s(-1), suggesting they originate from a region between the broad- and narrow-line emitting gas. Between the optical flare and late-time observation, the X-ray spectrum softens dramatically. The 0.3-1 keV X-ray flux increases by a factor of & SIM;50, while the hard X-ray flux decreases by a factor of & SIM;6. Wide-field Infrared Survey Explorer fluxes also rose over the same period, indicating the presence of an infrared echo. With AT2017gge, AT2019qiz is one of two examples of a spectroscopically confirmed optical-UV TDE showing delayed coronal line emission, supporting speculations that Extreme Coronal Line Emitters in quiescent galaxies can be echos of unobserved past TDEs. We argue that the coronal lines, narrow lines, and infrared emission arise from the illumination of pre-existing material likely related to either a previous TDE or active galactic nucleus activity.
- ItemGRB 120422A/SN 2012bz : Bridging the gap between low- and high-luminosity gamma-ray bursts(2014) Schulze, S.; Malesani, D.; Cucchiara, A.; Tanvir, N.; Kruhler, T.; De Ugarte Postigo, A.; Leloudas, G.; Lyman, J.; Bersier, D.; Bauer, Franz Erik
- ItemPESSTO : survey description and products from the first data release by the Public ESO Spectroscopic Survey of Transient Objects(2015) Smartt, S. J.; Valenti, S.; Fraser, M.; Inserra, C.; Young, D. R.; Sullivan, M.; Bauer, Franz Erik; Clocchiatti, Alejandro; Romero Cañizales, Cristina; Schulze, S.; Pastorello, A.; Benetti, S.; Gal-Yam, A.; Knapic, C.; Molinaro, M.; Smareglia, R.; Smith, K. W.; Taubenberger, S.; Yaron, O.; Anderson, J. P.; Ashall, C.; Balland, C.; Baltay, C.; Barbarino, C.; Baumont, S.; Bersier, D.; Blagorodnova, N.; Bongard, S.; Botticella, M. T.; Bufano, F.; Bulla, M.; Cappellaro, E.; Campbell, H.; Cellier-Holzem, F.; Chen, T. W.; Childress, M. J.; Contreras, C.; Dall’Ora, M.; Danziger, J.; de Jaeger, T.; De Cia, A.; Della Valle, M.; Dennefeld, M.; Elias Rosa, N.; Elman, N.; Feindt, U.; Fleury, M.; Gall, E.; González Gaitan, S.; Galbany, L.; Morales Garoffolo, A.; Greggio, L.; Guillou, L. L.; Hachinger, S.; Hadjiyska, E.; Hage, P. E.; Hillebrandt, W.; Hodgkin, S.; Hsiao, E. Y.; James, P. A.; Jerkstrand, A.; Kangas, T.; Kankare, E.; Kotak, R.; Kromer, M.; Kuncarayakti, H.; Leloudas, G.; Lundqvist, P.; Lyman, J. D.; Hook, I. M.; Maguire, K.; Manulis, I.; Margheim, S. J.; Mattila, S.; Maund, J. R.; Mazzali, P. A.; McCrum, M.; McKinnon, R.; Moreno Raya, M. E.; Nicholl, M.; Nugent, P.; Pain, R.; Pignata, Giuliano; Phillips, M. M.; Polshaw, J.; Pumo, M. L.; Rabinowitz, D.; Reilly, E.; Scalzo, R.; Schmidt, B.; Sim, S.; Sollerman, J.; Taddia, F.; Tartaglia, L.; Terreran, G.; Tomasella, L.; Turatto, M.; Walker, E.; Walton, N. A.; Wyrzykowski, L.; Yuan, F.; Zampieri, L.
- ItemSN2015bh: NGC2770's 4th supernova or a luminous blue variable on its way to a Wolf-Rayet star?(2017) Thöne, C. C.; De Ugarte Postigo, A.; Leloudas, G.; Gall, C.; Cano, Z.; Maeda, K.; Schulze, S.; Campana, S.; Wiersema, K.; Bauer, Franz Erik; Groh, J.; De La Rosa, J.; Bauer, Franz Erik; Malesani, D.; Maund, J.; Morrell, N.; Beletsky, Y.
- ItemSpectroscopy of superluminous supernova host galaxies : A preference of hydrogen-poor events for extreme emission line galaxies(2015) Leloudas, G.; Schulze, S.; Kruhler, T.; Gorosabel, J.; Christensen, L.; Mehner, A.; De Ugarte Postigo, A.; Amorin, R.; Thone, C.; Bauer, Franz Erik
- ItemSupernova 2011ke(2013) Drake, A. J.; Djorgovski, S. G.; Mahabal, A. A.; Graham, M. J.; Williams, R.; Donalek, C.; Prieto, J.; Catelan, Marcio; Larson, S. M.; Christensen, E.; Inserra, C.; Smartt, S. J.; Fraser, M.; Young, D.; Smith, K.; Wright, D.; Kotak, R.; McCrum, M.; Magill, L.; Chen, T. -W.; Pastorello, A.; Benetti, S.; Valenti, S.; Bresolin, F.; Kudritzki, R.; Tonry, J.; Magnier, E.; Huber, M.; Chambers, K.; Kaiser, N.; Morgan, J.; Burgett, W.; Heasley, J.; Sweeney, W.; Waters, C.; Flewelling, H.; Stubbs, C.; Price, P. A.; Sollerman, J.; Taddia, F.; Ergon, M.; Leloudas, G.; Taubenberger, S.Report the Catalina Real-time Transient Survey discovery of an apparent supernova in V-band Catalina Sky Survey (CSS) images: SN 2011 UT R.A. (2000.0) Decl. Mag. 2011ke Apr. 25.4 13 50 57.78 +26 16 42.4 17.6 Nothing is visible at this position on a CSS image from 2011 Mar. 16 UT (limiting mag 19.5). C. Inserra, S. J. Smartt, M. Fraser, D. Young, K. Smith, D. Wright, R. Kotak, M. McCrum, L. Magill, and T.-W. Chen, Queen's University, Belfast; A. Pastorello and S. Benetti, Osservatorio Astronomico di Padova, Istituto Nazionale di Astrofisica; S. Valenti, Las Cumbres Observatory Global Telescope and University of California at Santa Barbara; F. Bresolin, R. Kudritzki, J. Tonry, E. Magnier, M. Huber, K. Chambers, N. Kaiser, J. Morgan, W. Burgett, J. Heasley, W. Sweeney, C. Waters, and H. Flewelling, University of Hawaii; C. Stubbs, Harvard University; P. A. Price, Princeton University; J. Sollerman, F. Taddia, and M. Ergon, Oscar Klein Centre, Stockholm; G. Leloudas, Dark Cosmology Centre, Copenhagen; and S. Taubenberger, Max-Planck-Institut fuer Astrophysik, Garching, report that they obtained a spectrogram of 2011ke on 2011 May 21 UT with the Telescopio Nazionale Galileo (+ DOLORES). The spectrum shows the clear presence of emission from the host galaxy of [O II], [O III], H-beta, and H-alpha. (The host galaxy is also clearly seen in images obtained via the Canada-France-Hawaii Telescope and the Sloan Digital Sky Survey.) A good match is obtained with the spectrum of SN 2010gx (cf. CBET 2413), a super-luminous type-Ic supernova, at a week after maximum light....
- ItemThe optical/NIR afterglow of GRB 111209A: Complex yet not unprecedented(2018) Kann, D. A.; Schady, P.; Olivares, E. F.; Klose, S.; Rossi, A.; Perley, D. A.; Zhang, B.; Kruehler, T.; Greiner, J.; Guelbenzu, A. Nicuesa; Elliott, J.; Knust, F.; Cano, Z.; Filgas, R.; Pian, E.; Mazzali, P.; Fynbo, J. P. U.; Leloudas, G.; Afonso, P. M. J.; Delvaux, C.; Graham, J. F.; Rau, A.; Schmidl, S.; Schulze, S.; Tanga, M.; Updike, A. C.; Varela, K.
- ItemThe superluminous transient ASASSN-15lh as a tidal disruption event from a Kerr black hole.(2016) Leloudas, G.; Kim, Sam; Fraser, M.; Stone, N. C.; Velzen, S. van; Jonker, P. G.; Arcavi, I.; Fremling, C.; Maund, J. R.; Smartt, S. J.; Krühler, Thomas
- ItemThe supermassive black hole coincident with the luminous transient ASASSN-15lh.(2017) Krühler, Thomas; Kim, Sam; Fraser, M.; Leloudas, G.; Schulze, Steve.; Stone, N. C.; Velzen, S. van; Amorin, R.; Hjorth, J.; Jonker, P. G.; Kann, D. A.
- ItemVLT/X-Shooter emission-line spectroscopy of 96 gamma-ray-burst-selected galaxies at 0.1 < z < 3.6(EDP SCIENCES S A, 2015) Kruehler, T.; Malesani, D.; Fynbo, J. P. U.; Hartoog, O. E.; Hjorth, J.; Jakobsson, P.; Perley, D. A.; Rossi, A.; Schady, P.; Schulze, S.; Tanvir, N. R.; Vergani, S. D.; Wiersema, K.; Afonso, P. M. J.; Bolmer, J.; Cano, Z.; Covino, S.; D'Elia, V.; de Ugarte Postigo, A.; Filgas, R.; Friis, M.; Graham, J. F.; Greiner, J.; Goldoni, P.; Gomboc, A.; Hammer, F.; Japelj, J.; Kann, D. A.; Kaper, L.; Klose, S.; Levan, A. J.; Leloudas, G.; Milvang Jensen, B.; Guelbenzu, A. Nicuesa; Palazzi, E.; Pian, E.; Piranomonte, S.; Sanchez Ramirez, R.; Savaglio, S.; Selsing, J.; Tagliaferri, G.; Vreeswijk, P. M.; Watson, D. J.; Xu, D.We present data and initial results from VLT/X-Shooter emission-line spectroscopy of 96 galaxies selected by long gamma-ray bursts (GRBs) at 0.1 < z < 3.6, the largest sample of GRB host spectra available to date. Most of our GRBs were detected by Swift and 76% are at 0.5 < z < 2.5 with a median z(med) similar to 1.6. Based on Balmer and/or forbidden lines of oxygen, nitrogen, and neon, we measure systemic redshifts, star formation rates (SFR), visual attenuations (A(V)), oxygen abundances (12 + log(O/H)), and emission-line widths (sigma). We study GRB hosts up to z similar to 3.5 and find a strong change in their typical physical properties with redshift. The median SFR of our GRB hosts increases from SFRmed similar to 0.6 M circle dot yr(-1) at z similar to 0.6 up to SFRmed similar to 15 M circle dot yr(-1) at z similar to 2. A higher ratio of [O III]/[O II] at higher redshifts leads to an increasing distance of GRB-selected galaxies to the locus of local galaxies in the Baldwin-Phillips-Terlevich diagram. There is weak evidence for a redshift evolution in A(V) and similar to, with the highest values seen at z similar to 1.5 (A(V)) or z similar to 2 (sigma). Oxygen abundances of the galaxies are distributed between 12 + log(O/H) = 7.9 and 12 + log(O/H) = 9.0 with a median 12 + log(O/H)(med) similar to 8.5. The fraction of GRB-selected galaxies with super-solar metallicities is similar to 20% at z < 1 in the adopted metallicity scale. This is significantly less than the fraction of total star formation in similar galaxies, illustrating that GRBs are scarce in high metallicity environments. At z similar to 3, sensitivity limits us to probing only the most luminous GRB hosts for which we derive metallicities of Z less than or similar to 0.5 Z circle dot. Together with a high incidence of Z similar to 0.5 Z circle dot galaxies at z similar to 1.5, this indicates that a metallicity dependence at low redshift will not be dominant at z similar to 3. Significant correlations exist between the hosts' physical properties. Oxygen abundance, for example, relates to A(V) (12 + log(O/H) proportional to 0.17 A(V)), line width (12 + log(O/H) proportional to sigma(0.6)), and SFR (12 + log(O/H) proportional to SFR0.2). In the last two cases, the normalization of the relations shift to lower metallicities at z > 2 by similar to 0.4 dex. These properties of GRB hosts and their evolution with redshift can be understood in a cosmological context of star-forming galaxies and a picture in which the hosts' properties at low redshift are influenced by the tendency of GRBs to avoid the most metal-rich environments.