E. Karamehmetoglu
A5068884480- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Advanced Power Generation Technologies
- Calibration and Measurement Techniques
- Nuclear reactor physics and engineering
- Neutrino Physics Research
- Radiative Heat Transfer Studies
- Historical Astronomy and Related Studies
- Color Science and Applications
- Spectroscopy and Laser Applications
- Nuclear Physics and Applications
- Optical Systems and Laser Technology
- Astrophysics and Star Formation Studies
- Laser Design and Applications
- Geological and Geophysical Studies
- Advanced SAR Imaging Techniques
- Semiconductor Lasers and Optical Devices
- Spectroscopy Techniques in Biomedical and Chemical Research
- Laser-Plasma Interactions and Diagnostics
Stockholm University
2016-2023
AlbaNova
2016-2023
Aarhus University
2019-2023
Fraunhofer Chalmers Research Centre for Industrial Mathematics
2018
Columbia University
2016
Abstract The Astropy Project supports and fosters the development of open-source openly developed Python packages that provide commonly needed functionality to astronomical community. A key element is core package astropy , which serves as foundation for more specialized projects packages. In this article, we summarize features in recent major release, version 5.0, updates on Project. We then discuss supporting a broader ecosystem interoperable packages, including connections with several...
Abstract Narrow transient emission lines (flash-ionization features) in early supernova (SN) spectra trace the presence of circumstellar material (CSM) around massive progenitor stars core-collapse SNe. The disappear within days after SN explosion, suggesting that this is spatially confined, and originates from enhanced mass loss shortly (months to a few years) prior explosion. We performed systematic survey H-rich (Type II) SNe discovered less than 2 explosion during first phase Zwicky...
Context. We investigate two stripped-envelope supernovae (SNe) discovered in the nearby galaxy NGC 5806 by (intermediate) Palomar Transient Factory [(i)PTF]. These SNe, designated PTF12os/SN 2012P and iPTF13bvn, exploded within ~520 days of one another at a similar distance from host-galaxy center. classify PTF12os as Type IIb SN based on our spectral sequence; iPTF13bvn has previously been classified Ib having likely progenitor with zero age main sequence (ZAMS) mass below ~17 M⊙. Because...
We present observations and analysis of 18 stripped-envelope supernovae observed during 2013–2018. This sample consists five H/He-rich SNe, six H-poor/He-rich three narrow lined SNe Ic, four broad Ic. The peak luminosity characteristic time-scales the bolometric light curves are calculated, modelled to derive 56Ni ejecta masses (MNi Mej). Additionally, temperature evolution spectral line velocity each SN examined. Analysis [O i] in nebular phase eight suggests their progenitors had initial...
We present multi-wavelength observations of the tidal disruption event (TDE) iPTF15af, discovered by intermediate Palomar Transient Factory (iPTF) survey at redshift $z=0.07897$. The optical and ultraviolet (UV) light curves transient show a slow decay over five months, in agreement with previous optically TDEs. It also has comparable black-body peak luminosity $L_{\rm{peak}} \approx 1.5 \times 10^{44}$ erg/s. inferred temperature from UV data shows value (3$-$5) $\times 10^4$ K. is not...
Abstract We present JWST near-infrared (NIR) and mid-infrared (MIR) spectroscopic observations of the nearby normal Type Ia supernova (SN) SN 2021aefx in nebular phase at +255 days past maximum light. Our Near Infrared Spectrograph (NIRSpec) Mid Instrument observations, combined with ground-based optical data from South African Large Telescope, constitute first complete optical+NIR+MIR spectrum covering 0.3–14 μ m. This unveils previously unobserved 2.5−5 m region, revealing strong iron...
We present a sample of supernovae Type IIn (SNe IIn) from the untargeted, magnitude-limited surveys Palomar Transient Factory (PTF) and its successor, intermediate PTF (iPTF). The SNe found followed by PTF/iPTF were used to select 42 events with useful constraints on rise times as well available post-peak photometry. discovered in 2009-2016 have at least one low-resolution classification spectrum, photometry P48 P60 telescopes Observatory. study light-curve properties these using spline fits...
Type Ic supernovae (SNe Ic) arise from the core-collapse of H (and He) poor stars, which could be either single WR stars or lower-mass stripped their envelope by a companion. Their light curves are radioactively powered and usually show fast rise to peak ($\sim$10-15 d), without any early (first few days) emission bumps (with exception broad-lined SNe as sometimes seen for other types stripped-envelope (e.g., IIb SN 1993J Ib 2008D). We have studied iPTF15dtg, spectroscopically normal with an...
We present 75 near-infrared (NIR; 0.8$-$2.5 $\mu$m) spectra of 34 stripped-envelope core-collapse supernovae (SESNe) obtained by the Carnegie Supernova Project-II (CSP-II), encompassing optical spectroscopic Types IIb, Ib, Ic, and Ic-BL. The range in phase from pre-maximum to 80 days past maximum. This unique data set constitutes largest NIR sample SESNe date. spectroscopy provides observables with additional information that is not available optical. Specifically, contains resonance lines...
Abstract We present a JWST/MIRI low-resolution mid-infrared (MIR) spectroscopic observation of the normal Type Ia supernova (SN Ia) SN 2021aefx at +323 days past rest-frame B -band maximum light. The spectrum ranges from 4 to 14 μ m and shows many unique qualities, including flat-topped [Ar iii ] 8.991 profile, strongly tilted [Co 11.888 feature, multiple stable Ni lines. These features provide critical information about physics explosion. observations are compared synthetic spectra detailed...
We present a measurement of the Hubble constant ( H 0 ) using type Ia supernovae (SNe Ia) in near-infrared (NIR) from recently updated sample SNe nearby galaxies with distances measured via Cepheid period-luminosity relations by SH0ES project. collected public photometry up to 19 calibrator and 57 flow z > 0.01), directly their peak magnitudes J - -band Gaussian processes spline interpolation. Calibrator together Cepheid-based were used estimate average absolute magnitude each band, while...
Type Ibn supernovae (SNe) are a small yet intriguing class of explosions whose spectra characterized by low-velocity helium emission lines with little to no evidence for hydrogen. The prevailing theory has been that these the core-collapse very massive stars embedded in helium-rich circumstellar material (CSM). We report optical observations six new SNe Ibn: PTF11rfh, PTF12ldy, iPTF14aki, iPTF15ul, SN 2015G, and iPTF15akq. This brings sample size such objects literature 22. also data,...
Abstract The Type Ia supernova (SN Ia) LSQ14fmg exhibits exaggerated properties that may help to reveal the origin of “super-Chandrasekhar” (or 03fg-like) group. optical spectrum is typical a 03fg-like SN Ia, but light curves are unlike those any SNe observed. rise extremely slowly. At −23 rest-frame days relative B -band maximum, already brighter than <?CDATA ${M}_{V}=-19$?> mag before host extinction correction. observed color show flat evolution from earliest observation approximately 1...
Supernovae (SNe) Type Ibn are rapidly evolving and bright (M$_\text{R,peak}$ $\sim-19$) transients interacting with He-rich circumstellar material (CSM). SN 2018bcc, detected by the ZTF shortly after explosion, provides best constraints on shape of rising light curve (LC) a fast Ibn. Aims: We used high-quality data set 2018bcc to study observational signatures class. Additionally, powering mechanism offers insights into debated progenitor connection SNe. Methods: compared well-constrained LC...
Context. Type Ic supernovae represent the explosions of most stripped massive stars, but their progenitors and explosion mechanisms remain unclear. Larger samples observed can help characterize population these transients. Aims. We present an analysis 44 spectroscopically normal supernovae, with focus on light curves. The photometric data were obtained over 7 years Palomar Transient Factory its continuation, intermediate Factory. This is first homogeneous large sample SNe from untargeted...
We investigate the spectroscopic characteristics of intermediate-luminosity Red Transients (ILRTs), a class elusive objects with peak luminosity between that classical novae and standard supernovae. Our goal is to provide stepping stone in path unveiling physical origin these events based on analysis collected datasets. present extensive optical near-infrared (NIR) monitoring four ILRTs, namely NGC 300 2008OT-1, AT 2019abn, 2019ahd 2019udc. First we focus evolution most prominent spectral...
We investigate the photometric characteristics of a sample intermediate-luminosity red transients (ILRTs), class elusive objects with peak luminosity between that classical novae and standard supernovae. Our goal is to provide stepping stone in path reveal physical origin such events, thanks analysis datasets collected. present multi-wavelength follow-up four ILRTs, namely NGC 300 2008OT-1, AT 2019abn, 2019ahd, 2019udc. Through modelling their spectral energy distribution bolometric light...
Abstract Wide-field surveys are discovering a growing number of rare transients whose physical origin is not yet well understood. Here we present optical and UV data analysis intermediate Palomar Transient Factory (iPTF) 16asu, luminous, rapidly evolving, high-velocity, stripped-envelope supernova (SN). With rest-frame rise time just four days peak absolute magnitude mag, the light curve iPTF 16asu faster more luminous than that previous rapid transients. The spectra show featureless blue...
We study PTF11mnb, a He-poor supernova (SN) whose pre-peak light curves (LCs) resemble those of SN 2005bf, peculiar double-peaked stripped-envelope (SE) SN. LCs, colors and spectral properties are compared to 2005bf normal SE SNe. A bolometric LC is built modeled with the SNEC hydrodynamical code explosion MESA progenitor star, as well semi-analytic models. The PTF11mnb turns out be similar that until $\sim$50 d, when main (secondary) peaks occur at $-18.5$ mag. early peak occurs $\sim$20...
We present an analysis of 507 spectra 173 stripped-envelope (SE) supernovae (SNe) discovered by the untargeted Palomar Transient Factory (PTF) and intermediate PTF (iPTF) surveys. Our sample contains 55 Type IIb SNe (SNe IIb), 45 Ib Ib), 56 Ic Ic), 17 Ib/c Ib/c). have compared SE SN subtypes via measurements pseudo-equivalent widths (pEWs) velocities He I λλ 5876, 7065 O λ 7774 absorption lines. Consistent with previous work, we find that show higher pEWs in to Ib. The lines are similar...
Type Ibn supernovae (SNe Ibn) are thought to be the core-collapse explosions of massive stars whose ejecta interact with He-rich circumstellar material (CSM). We report discovery a SN Ibn, longest rise-time ever observed, OGLE-2014-SN-131. discuss potential powering mechanisms and progenitor nature this peculiar stripped-envelope (SE), circumstellar-interacting SN. Optical photometry spectroscopy were obtained multiple telescopes including VLT, NTT, GROND. compare light curves spectra those...
Context: Research on supernovae (SNe) over the past decade has confirmed that there is a distinct class of events which are much more luminous (by $\sim2$ mag) than canonical core-collapse SNe (CCSNe). These with visual peak magnitudes $\lesssim-21$ called superluminous (SLSNe). Aims: There few intermediate have luminosities between these two classes. Here we study one such object, SN 2012aa. Methods: The optical photometric and spectroscopic follow-up observations event were conducted time...
Abstract High-cadence transient surveys are able to capture supernovae closer their first light than ever before. Applying analytical models such early emission, we can constrain the progenitor stars’ properties. In this paper, present observations of SN 2018fif (ZTF 18abokyfk). The supernova was discovered close and monitored by Zwicky Transient Facility (ZTF) Neil Gehrels Swift Observatory. Early spectroscopic suggest that surrounded relatively small amounts circumstellar material compared...
We study 34 Type Ic supernovae that have broad spectral features (SNe Ic-BL). obtained our photometric data with the Palomar Transient Factory (PTF) and its continuation, intermediate (iPTF). This is first large, homogeneous sample of SNe Ic-BL from an untargeted survey. Furthermore, given high cadence (i)PTF, most these were discovered soon after explosion. present K-corrected $Bgriz$ light curves SNe, through photometry on template-subtracted images. analyzed shape $r$-band curves, finding...