J. Spyromilio
A5037626921- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- Adaptive optics and wavefront sensing
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Astrophysics and Star Formation Studies
- Non-Destructive Testing Techniques
- Astronomical Observations and Instrumentation
- History and Developments in Astronomy
- Advanced optical system design
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Superconducting Materials and Applications
- Galaxies: Formation, Evolution, Phenomena
- Nuclear Physics and Applications
- Neutrino Physics Research
- Cosmology and Gravitation Theories
- Electrical Fault Detection and Protection
- Nuclear physics research studies
- Liver Disease Diagnosis and Treatment
- Radio Astronomy Observations and Technology
- Atomic and Molecular Physics
European Southern Observatory
2015-2024
KTH Royal Institute of Technology
2019
Max Planck Society
2018
AlbaNova
2007
Stockholm University
2007
European Southern Observatory
2003-2007
Australian Astronomical Observatory
1989-1996
Universitätsmedizin Göttingen
1991
University of California, Santa Cruz
1991
Imperial College London
1988-1990
We present spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 ≤ z 0.62. The luminosity distances these objects are determined by methods that employ relations between SN light curve shape. Combined with previous data from our High-z Supernova Search Team recent results Riess et al., this expanded set 16 high-redshift a 34 nearby used to place constraints on following cosmological parameters: Hubble constant (H0), mass density (ΩM), (i.e.,...
The High-z Supernova Search Team has discovered and observed 8 new supernovae in the redshift interval z=0.3-1.2. These independent observations, confirm result of Riess et al. (1998a) Perlmutter (1999) that supernova luminosity distances imply an accelerating universe. More importantly, they extend range consistently SN Ia to z~1, where signature cosmological effects opposite sign some plausible systematic effects. Consequently, these measurements not only provide another quantitative...
The High-Z Supernova Search is an international collaboration to discover and monitor Type Ia supernovae (SNe Ia) at z > 0.2 with the aim of measuring cosmic deceleration global curvature. Our has pursued a basic understanding in nearby universe, discovering observing large sample objects developing methods measure accurate distances SNe Ia. This paper describes extension this program ≥ 0.2, outlining our search techniques follow-up program. We have devised high-throughput filters that...
We present constraints on the dark energy equation-of-state parameter, w=P/(rho c^2), using 60 Type Ia supernovae (SNe Ia) from ESSENCE supernova survey. derive a set of nature assuming flat Universe. By including (Omega_M, w) baryon acoustic oscillations, we obtain value for static parameter w=-1.05^{+0.13}_{-0.12} (stat; 1 sigma) +- 0.11 (sys) and Omega_M=0.274^{+0.033}_{-0.020} with best-fit chi^2/DoF 0.96. These results are consistent those reported by SuperNova Legacy Survey in similar...
The highly elliptical, 16-year-period orbit of the star S2 around massive black hole candidate Sgr A ✻ is a sensitive probe gravitational field in Galactic centre. Near pericentre at 120 AU ≈ 1400 Schwarzschild radii, has an orbital speed ≈7650 km s −1 , such that first-order effects Special and General Relativity have now become detectable with current capabilities. Over past 26 years, we monitored radial velocity motion on sky S2, mainly SINFONI NACO adaptive optics instruments ESO Very...
We use Type Ia supernovae studied by the High-z Supernova Search Team to constrain properties of an energy component that may have contributed accelerating cosmic expansion. find for a flat geometry equation-of-state parameter unknown component, αx = Px/ρx, must be less than -0.55 (95% confidence) any value Ωm, and it is further limited < -0.60 if Ωm assumed greater 0.1. These values are inconsistent with being topological defects such as domain walls, strings, or textures. The supernova...
We have coordinated Hubble Space Telescope (HST) photometry with ground-based discovery for three supernovae: Type Ia supernovae near z ≈ 0.5 (SN 1997ce, SN 1997cj) and a third event at = 0.97 1997ck). The superb spatial resolution of HST separates each supernova from its host galaxy leads to good precision in the light curves. use these curves relations between luminosity, light-curve shape, color calibrated low-z samples derive relative luminosity distances that are accurate 10% 20% 1....
The first cosmological results from the ESSENCE supernova survey (Wood-Vasey and coworkers) are extended to a wider range of models including dynamical dark energy nonstandard models. We fold in greater number external data sets such as recent Higher-z release high-redshift supernovae (Riess coworkers), well several complementary probes. Model comparison statistics Bayesian Akaike information criteria applied gauge worth These favor that give good fit with fewer parameters. Based on this...
We present photometric and spectroscopic observations of 23 high-redshift supernovae (SNe) spanning a range z = 0.34-1.03, nine which are unambiguously classified as Type Ia. These SNe were discovered during the IfA Deep Survey, began in 2001 September observed total 2.5 deg2 to depth approximately m ≈ 25-26 RIZ over 9-17 visits, typically every 1-3 weeks for nearly 5 months, with additional continuing until 2002 April. give brief description survey motivations, observational strategy,...
We present and discuss the photometric spectroscopic evolution of peculiar SN 1998bw, associated with GRB 980425, through an analysis optical near-IR data collected at ESO-La Silla. The data, spanning period from day -9 to +376 (relative B maximum), have shown that this supernova (SN) was unprecedented, although somewhat similar 1997ef. Maximum expansion velocities as high 3 × 104 km s-1 some extent mask its resemblance other Type Ic SNe. At intermediate phases, between photospheric fully...
We describe the implementation and optimization of ESSENCE supernova survey, which we have undertaken to measure equation state parameter dark energy. present a method for optimizing survey exposure times cadence maximize our sensitivity energy w=P/rho c^2 given fixed amount telescope time. For on CTIO 4m telescope, measuring luminosity distances redshifts supernovae at modest (z~0.5 +- 0.2) is optimal determining w. data analysis pipeline based using reliable robust image subtraction find...
We present observations of the Type Ia supernovae (SNe) 1999M, 1999N, 1999Q, 1999S, and 1999U, at redshift z ≈ 0.5. They were discovered in early 1999 with 4.0 m Blanco telescope Cerro Tololo Inter-American Observatory by High-z Supernova Search Team (HZT) subsequently followed many ground-based telescopes. SNe 1999Q 1999U also observed Hubble Space Telescope. computed luminosity distances to new using two methods added them high-z diagram that HZT has been constructing since 1995. The...
SN 2004et is one of the nearest and best-observed Type IIP supernovae, with a progenitor detection as well good photometric spectroscopic observational coverage into nebular phase. Based on nucleosynthesis from stellar evolution/explosion models we apply spectral modeling to analyze its 140-700 day evolution ultraviolet mid-infrared. We find M_ZAMS= 15 Msun star (with an oxygen mass 0.8 Msun) satisfactorily reproduce [O I] 6300, 6364 {\AA} other emission lines carbon, sodium, magnesium,...
We present new data for five under-luminous type II-plateau supernovae (SNe IIP), namely SN 1999gn, 2002gd, 2003Z, 2004eg and 2006ov. This sample of low-luminosity SNe IIP (LL IIP) is analyzed together with similar objects studied in the past. All them show a flat light curve plateau lasting about 100 days, an under luminous late-time exponential tail, intrinsic colours that are unusually red, spectra showing prominent narrow P-Cygni lines. A velocity ejected material below 10^3 km/s...
We present high angular resolution (~80 mas) ALMA continuum images of the SN 1987A system, together with CO $J$=2 $\!\rightarrow\!$ 1, $J$=6 5, and SiO $J$=5 4 to $J$=7 6 images, which clearly resolve ejecta (dust molecules) ring (synchrotron continuum) components. Dust in is asymmetric clumpy, overall dust fills spatial void seen H$\alpha$ filling that region material from heavier elements. The clumps generally fill space where 5 fainter, tentatively indicating these are locationally...
We have measured the rest-frame B,V, and I-band light curves of a high-redshift type Ia supernova (SN Ia), SN 1999Q (z=0.46), using HST ground-based near-infrared detectors. A goal this study is measurement color excess, E_{B-I}, which sensitive indicator interstellar or intergalactic dust could affect recent cosmological measurements from SNe Ia. Our observations disfavor 30% opacity visual by as an alternative to accelerating Universe. This statement applies both Galactic-type (rejected at...
We investigate line formation processes in Type IIb supernovae (SNe) from 100 to 500 days post-explosion using spectral synthesis calculations. The modeling identifies the nuclear burning layers and physical mechanisms that produce major emission lines, diagnostic potential of these. compare model calculations with data on three best observed SNe to-date - SN 1993J, 2008ax, 2011dh. Oxygen nucleosynthesis depends sensitively main-sequence mass star [O I] 6300, 6364 lines constrains...
The light curves of Type Ia supernovae (SNe Ia) are powered by the radioactive decay $^{56}$Ni to $^{56}$Co at early times, and $^{56}$Fe from ~60 days after explosion. We examine evolution [Co III] 5892 A emission complex during nebular phase for SNe with multiple spectra show that line flux follows square mass as a function time. This result indicates both efficient local energy deposition positrons produced in decay, long-term stability ionization state nebula. compile 77 25 SN literature...
We investigate the light-curve properties of a sample 26 spectroscopically confirmed hydrogen-poor superluminous supernovae (SLSNe-I) in Palomar Transient Factory (PTF) survey. These events are brighter than SNe Ib/c and Ic-BL, on average, by about 4 2~mag, respectively. The peak absolute magnitudes SLSNe-I rest-frame $g$ band span $-22\lesssim M_g \lesssim-20$~mag, these peaks not powered radioactive $^{56}$Ni, unless strong asymmetries at play. rise timescales longer for SLSNe normal Ib/c,...
The late-time spectra of Type Ia supernovae (SNe Ia) are powerful probes the underlying physics their explosions. We investigate optical and near-infrared seven SNe obtained at VLT with XShooter $>$200 d after explosion. At these epochs, inner Fe-rich ejecta can be studied. use a line-fitting analysis to determine relative line fluxes, velocity shifts, widths prominent features contributing ([Fe II], [Ni [Co III]). By focussing on [Fe II] emission lines in ~7000-7500 Å region spectrum, we...
Aims. The aim of this paper is twofold: 1) to investigate the properties extragalactic dust and compare them what seen in Galaxy; 2) address an independent way problem anomalous extinction curves reported for reddened Type Ia Supernovae (SN) connection environments which they explode.
We present optical and near-infrared photometry spectroscopy of the type Ia SN 1998bu in Leo I Group galaxy M96 (NGC 3368). The data set consists 356 photometric measurements 29 spectra between UT 1998 May 11 July 15. well-sampled light curve indicates supernova reached maximum B on 19.3 (JD 2450952.8 +/- 0.8) with = 12.22 0.03 V 11.88 0.02. Application a revised version Multicolor Light Curve Shape (MLCS) method yields an extinction toward A_V 0.94 0.15 mag, was average luminosity compared...