G. Dimitriadis
A5007177823- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Pulsars and Gravitational Waves Research
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Advanced Power Generation Technologies
- Neutrino Physics Research
- Galaxies: Formation, Evolution, Phenomena
- Geophysics and Gravity Measurements
- Spectroscopy and Laser Applications
- Silicon and Solar Cell Technologies
- Global Political and Economic Relations
- Nuclear reactor physics and engineering
- Spectroscopy Techniques in Biomedical and Chemical Research
- Particle Accelerators and Free-Electron Lasers
- Astrophysics and Star Formation Studies
- Non-Destructive Testing Techniques
- Radiation Detection and Scintillator Technologies
- Solar and Space Plasma Dynamics
- CCD and CMOS Imaging Sensors
- Optical Network Technologies
- Calibration and Measurement Techniques
Lancaster University
2025
Trinity College Dublin
2021-2024
University of California, Santa Cruz
2018-2023
National Technical University of Athens
2022
University of Southampton
2014-2020
University of Amsterdam
2014
We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift $z=0.001$ to 2.26. This work features an increased sample size, span, and improved treatment systematic uncertainties comparison original Pantheon results a factor two improvement constraining power. For Flat$\Lambda$CDM model, we find $\Omega_M=0.334\pm0.018$ SNe alone. Flat$w_0$CDM measure $w_0=-0.90\pm0.14$ alone, H$_0=73.5\pm1.1$...
Here we present 1701 light curves of 1550 spectroscopically confirmed Type Ia supernovae (SNe Ia) that will be used to infer cosmological parameters as part the Pantheon+ SN analysis and SH0ES (Supernovae H0 for Equation State dark energy) distance-ladder analysis. This effort is one a series works perform an extensive review redshifts, peculiar velocities, photometric calibration, intrinsic-scatter models SNe Ia. The total number curves, which are compiled across 18 different surveys,...
We present panchromatic observations and modeling of supernova (SN) 2020tlf, the first normal type II-P/L SN with confirmed precursor emission, as detected by Young Supernova Experiment transient survey Pan-STARRS1 telescope. Pre-explosion emission was in $riz-$bands at 130 days prior to 2020tlf persisted relatively constant flux until light. Soon after discovery, "flash" spectroscopy revealed prominent narrow symmetric lines ($v_w < 300$ km s$^{-1}$) that resulted from photo-ionization...
Context. As type Ia supernova cosmology transitions from a statistics-dominated to systematics-dominated era, it is crucial understand the remaining unexplained uncertainties that affect their luminosity, such as those stemming astrophysical biases. Type supernovae are standardisable candles whose absolute magnitude reaches scatter of typically 0.15 mag when empirical correlations with light-curve stretch and colour environmental properties accounted for. Aims. We investigate dependence...
Context. Type Ia supernova (SN Ia) cosmology studies will soon be dominated by systematic, uncertainties, rather than statistical ones. Thus, it is crucial to understand the unknown phenomena potentially affecting their luminosity that may remain, such as astrophysical biases. For accurate application in studies, SN magnitudes need standardised; namely, they must corrected for correlation with light-curve width and colour. Aims. Here, we investigate how standardisation procedure used reduce...
Context. The unprecedented statistics of detected Type Ia supernovae (SNe Ia) brought by the Zwicky Transient Facility (ZTF) enable us to probe impact large-scale structure (LSS) on properties these objects. Aims. goal this paper is explore possible under-dense part LSS intrinsic SALT2 light-curve SNe and uncover biases in SN analyses. Methods. With a volume-limited selection ZTF-Cosmo-DR2 overlapping with SDSS-DR7 survey footprint, we investigated distribution their regard voids galaxy...
Objective . The COVID-19 epidemic has shown a more benign course in Greece possibly due to the early lockdown measures. Mental health consequences of however are unknown. In addition, illness perceptions and relevant strategies cope with stress may have played role complying restrictions. We conducted survey Greek population aim investigate prevalence anxiety depression during lockdown, emotional impact epidemic, effect coping mental health. Methods Adult persons were invited peak period...
A spectral-energy distribution (SED) model for Type Ia supernovae (SNe Ia) is a critical tool measuring precise and accurate distances across large redshift range constraining cosmological parameters. We present an improved framework, SALT3, which has several advantages over current models including the leading SALT2 (SALT2.4). While SALT3 similar philosophy, it differs from by having estimation of uncertainties, better separation color light-curve stretch, publicly available training code....
ABSTRACT We present observations of ASASSN-19dj, a nearby tidal disruption event (TDE) discovered in the post-starburst galaxy KUG 0810+227 by All-Sky Automated Survey for Supernovae (ASAS-SN) at distance d ≃ 98 Mpc. observed ASASSN-19dj from −21 to 392 relative peak ultraviolet (UV)/optical emission using high-cadence, multiwavelength spectroscopy and photometry. From ASAS-SN g-band data, we determine that TDE began brighten on 2019 February 6.8 first 16 rise was consistent with flux ∝t2...
Time domain science has undergone a revolution over the past decade, with tens of thousands new supernovae (SNe) discovered each year. However, several observational domains, including SNe within days or hours explosion and faint, red transients, are just beginning to be explored. Here, we present Young Supernova Experiment (YSE), novel optical time-domain survey on Pan-STARRS telescopes. Our is designed obtain well-sampled $griz$ light curves for transient events up $z \approx 0.2$. This...
We present Hubble Space Telescope imaging of a pre-explosion counterpart to SN 2019yvr obtained 2.6 years before its explosion as type Ib supernova (SN Ib). Aligning post-explosion Gemini-S/GSAOI image, we demonstrate that there is single source consistent with being the progenitor system, second candidate after iPTF13bvn. also analyzed Spitzer/IRAC imaging, but do not detect any counterparts at location. was highly reddened, and comparing spectra photometry those other, less extinguished...
We present multiwavelength observations of the Type II SN 2020pni. Classified at $\sim 1.3$ days after explosion, object showed narrow (FWHM $<250\,\textrm{km}\,\textrm{s}^{-1}$) recombination lines ionized helium, nitrogen, and carbon, as typically seen in flash-spectroscopy events. Using non-LTE radiative transfer code CMFGEN to model our first high resolution spectrum, we infer a progenitor mass-loss rate $\dot{M}=(3.5-5.3)\times10^{-3}$ M$_{\odot}$ yr$^{-1}$ (assuming wind velocity...
We present the Young Supernova Experiment Data Release 1 (YSE DR1), comprised of processed multi-color Pan-STARRS1 (PS1) griz and Zwicky Transient Facility (ZTF) gr photometry 1975 transients with host-galaxy associations, redshifts, spectroscopic/photometric classifications, additional data products from 2019 November 24 to 2021 December 20. YSE DR1 spans discoveries observations young fast-rising supernovae (SNe) that persist for over a year, redshift distribution reaching z~0.5. relative...
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...
Abstract Supernova (SN) 2018oh (ASASSN-18bt) is the first spectroscopically confirmed Type Ia supernova (SN Ia) observed in Kepler field. The data revealed an excess emission its early light curve, allowing us to place interesting constraints on progenitor system. Here we present extensive optical, ultraviolet, and near-infrared photometry, as well dense sampling of optical spectra, for this object. SN relatively normal photometric evolution, with a rise time 18.3 ± 0.3 days Δ m 15 ( B ) =...
Abstract We present panchromatic observations and modeling of the Calcium-rich supernova (SN) 2019ehk in star-forming galaxy M100 ( d ≈ 16.2 Mpc) starting 10 hr after explosion continuing for ∼300 days. SN shows a double-peaked optical light curve peaking at t = 3 15 The first peak is coincident with luminous, rapidly decaying Swift-XRT–discovered X-ray emission <?CDATA ${L}_{{\rm{x}}}\approx {10}^{41}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$?> days; L x ∝ −3 ), Shane/Kast spectral detection narrow H...
Abstract We present photometric and spectroscopic observations of Supernova 2020oi (SN 2020oi), a nearby (∼17 Mpc) type-Ic supernova Ic) within the grand-design spiral M100. undertake comprehensive analysis to characterize evolution SN constrain its progenitor system. detect flux in excess fireball rise model δ t ≈ 2.5 days from date explosion multiband optical UV photometry Las Cumbres Observatory Neil Gehrels Swift Observatory, respectively. The derived bolometric luminosity is consistent...
Abstract We present observations and analysis of the hostless luminous Type Ia supernova 2022ilv, illustrating it is part 2003fg-like family, often referred to as super-Chandrasekhar (Ia-SC) explosions. The Asteroid Terrestrial-impact Last Alert System light curve shows evidence a short-lived, pulse-like early excess, similar that detected in another (SN 2020hvf). broad, spectra are remarkably those SN 2009dc. Adopting redshift z = 0.026 ± 0.005 for 2022ilv based on spectral matching, our...
ABSTRACT We present a photometric and spectroscopic analysis of the ultraluminous slowly evolving 03fg-like Type Ia SN 2021zny. Our observational campaign starts from ∼5.3 h after explosion (making 2021zny one earliest observed members its class), with dense multiwavelength coverage variety ground- space-based telescopes, is concluded nebular spectrum ∼10 months peak brightness. displayed several characteristics class, such as brightness (MB = −19.95 mag), slow decline (Δm15(B) 0.62 blue...
Abstract We present high-cadence ultraviolet through near-infrared observations of the Type Ia supernova (SN Ia) 2023bee at D = 32 ± 3 Mpc, finding excess flux in first days after explosion, particularly our 10 minutes cadence TESS light curve and Swift UV data. Compared to a few other normal SNe with early flux, SN is redder less luminous. optical spectra 2023bee, including two during period where dominant. At this time, are similar those but weaker Si ii , C ii, Ca absorption lines,...
Abstract We present an analysis of ground-based and JWST observations SN 2022pul, a peculiar “03fg-like” (or “super-Chandrasekhar”) Type Ia supernova (SN Ia), in the nebular phase at 338 days postexplosion. Our combined spectrum continuously covers 0.4–14 μ m includes first mid-infrared 03fg-like Ia. Compared to normal 2021aefx, 2022pul exhibits lower mean ionization state, asymmetric emission-line profiles, stronger emission from intermediate-mass elements (IMEs) argon calcium, weaker...