Person: Czekala, Ian
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Czekala
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Ian
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Czekala, Ian
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Publication Cosmological Constraints from Measurements of Type Ia Supernovae Discovered during the First 1.5 yr of the Pan-STARRS1 Survey(IOP Publishing, 2014) Rest, Armin; Scolnic, D.; Foley, R. J.; Huber, M. E.; Chornock, R.; Narayan, Gautham; Tonry, J. L.; Berger, Edo; Soderberg, Alicia; Stubbs, Christopher; Riess, A.; Kirshner, Robert; Smartt, S. J.; Schlafly, E.; Rodney, S.; Botticella, M. T.; Brout, D.; Challis, P.; Czekala, Ian; Drout, Maria Rebecca; Hudson, M. J.; Kotak, R.; Leibler, C.; Lunnan, R; Marion, G. H.; McCrum, M.; Milisavljevic, D.; Pastorello, A.; Sanders, Nathan Edward; Smith, K.; Stafford, E.; Thilker, D.; Valenti, S.; Wood-Vasey, W. M.; Zheng, Z.; Burgett, W. S.; Chambers, K. C.; Denneau, L.; Draper, P. W.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E. A.; Metcalfe, N.; Price, P. A.; Sweeney, W.; Wainscoat, R.; Waters, C.We present griz P1 light curves of 146 spectroscopically confirmed Type Ia supernovae (SNe Ia; 0.03 < z < 0.65) discovered during the first 1.5 yr of the Pan-STARRS1 Medium Deep Survey. The Pan-STARRS1 natural photometric system is determined by a combination of on-site measurements of the instrument response function and observations of spectrophotometric standard stars. We find that the systematic uncertainties in the photometric system are currently 1.2% without accounting for the uncertainty in the Hubble Space Telescope Calspec definition of the AB system. A Hubble diagram is constructed with a subset of 113 out of 146 SNe Ia that pass our light curve quality cuts. The cosmological fit to 310 SNe Ia (113 PS1 SNe Ia + 222 light curves from 197 low-z SNe Ia), using only supernovae (SNe) and assuming a constant dark energy equation of state and flatness, yields $w=-1.120^{+0.360}_{-0.206}\hbox{(Stat)} ^{+0.269}_{-0.291}\hbox{(Sys)}$. When combined with BAO+CMB(Planck)+H 0, the analysis yields $\Omega _{\rm M}=0.280^{+0.013}_{-0.012}$ and $w=-1.166^{+0.072}_{-0.069}$ including all identified systematics. The value of w is inconsistent with the cosmological constant value of –1 at the 2.3σ level. Tension endures after removing either the baryon acoustic oscillation (BAO) or the H 0 constraint, though it is strongest when including the H 0 constraint. If we include WMAP9 cosmic microwave background (CMB) constraints instead of those from Planck, we find $w=-1.124^{+0.083}_{-0.065}$, which diminishes the discord to <2σ. We cannot conclude whether the tension with flat ΛCDM is a feature of dark energy, new physics, or a combination of chance and systematic errors. The full Pan-STARRS1 SN sample with ~three times as many SNe should provide more conclusive results.Publication PS1-10afx at z = 1.388: Pan-STARRS1 Discovery of a New Type of Superluminous Supernova(American Astronomical Society, 2013) Chornock, R; Berger, Edo; Rest, A.; Milisavljevic, Danny; Lunnan, R; Foley, R. J.; Soderberg, Alicia; Smartt, S. J.; Burgasser, A. J.; Challis, Peter; Chomiuk, L.; Czekala, Ian; Drout, Maria Rebecca; Fong, W; Huber, M. E.; Kirshner, Robert; Leibler, C.; McLeod, Brian; Marion, G. H.; Narayan, Gautham; Riess, A. G.; Roth, K. C.; Sanders, Nathan Edward; Scolnic, D.; Smith, K.; Stubbs, Christopher; Tonry, J. L.; Valenti, S.; Burgett, W. S.; Chambers, K. C.; Hodapp, K. W.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E. A.; Price, P. A.We present the Pan-STARRS1 discovery of PS1-10afx, a unique hydrogen-deficient superluminous supernova (SLSN) at redshift z = 1.388. The light curve peaked at z P1 = 21.7 mag, making PS1-10afx comparable to the most luminous known SNe, with Mu = –22.3 mag. Our extensive optical and near-infrared observations indicate that the bolometric light curve of PS1-10afx rose on the unusually fast timescale of ~12 days to the extraordinary peak luminosity of 4.1 × 1044 erg s–1 (M bol = –22.8 mag) and subsequently faded rapidly. Equally important, the spectral energy distribution is unusually red for an SLSN, with a color temperature of ~6800 K near maximum light, in contrast to previous hydrogen-poor SLSNe, which are bright in the ultraviolet (UV). The spectra more closely resemble those of a normal SN Ic than any known SLSN, with a photospheric velocity of ~11, 000 km s–1 and evidence for line blanketing in the rest-frame UV. Despite the fast rise, these parameters imply a very large emitting radius (gsim 5 × 1015 cm). We demonstrate that no existing theoretical model can satisfactorily explain this combination of properties: (1) a nickel-powered light curve cannot match the combination of high peak luminosity with the fast timescale; (2) models powered by the spindown energy of a rapidly rotating magnetar predict significantly hotter and faster ejecta; and (3) models invoking shock breakout through a dense circumstellar medium cannot explain the observed spectra or color evolution. The host galaxy is well detected in pre-explosion imaging with a luminosity near L*, a star formation rate of ~15 M ☉ yr–1, and is fairly massive (~2 × 1010 M ☉), with a stellar population age of ~108 yr, also in contrast to the young dwarf hosts of known hydrogen-poor SLSNe. PS1-10afx is distinct from known examples of SLSNe in its spectra, colors, light-curve shape, and host galaxy properties, suggesting that it resulted from a different channel than other hydrogen-poor SLSNe.Publication Pan-STARRS1 Discovery of Two Ultraluminous Supernovae at z ≈ 0.9(IOP Publishing, 2011) Chomiuk, Laura; Chornock, R; Soderberg, Alicia; Berger, Edo; Chevalier, R. A.; Foley, R. J.; Huber, M. E.; Narayan, Gautham; Rest, A.; Gezari, S.; Kirshner, Robert; Riess, A.; Rodney, S. A.; Smartt, S. J.; Stubbs, Christopher; Tonry, J. L.; Wood-Vasey, W. M.; Burgett, W. S.; Chambers, K. C.; Czekala, Ian; Flewelling, H.; Forster, K.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E. A.; Martin, D. C.; Morgan, J. S.; Neill, J. D.; Price, P. A.; Roth, K. C.; Sanders, Nathan Edward; Wainscoat, R. J.We present the discovery of two ultraluminous supernovae (SNe) at z ≈ 0.9 with the Pan-STARRS1 Medium Deep Survey. These SNe, PS1-10ky and PS1-10awh, are among the most luminous SNe ever discovered, comparable to the unusual transients SN 2005ap and SCP 06F6. Like SN 2005ap and SCP 06F6, they show characteristic high luminosities (M bol ≈ –22.5 mag), blue spectra with a few broad absorption lines, and no evidence for H or He. We have constructed a full multi-color light curve sensitive to the peak of the spectral energy distribution in the rest-frame ultraviolet, and we have obtained time series spectroscopy for these SNe. Given the similarities between the SNe, we combine their light curves to estimate a total radiated energy over the course of explosion of (0.9-1.4) × 1051 erg. We find photospheric velocities of 12,000-19,000 km s–1 with no evidence for deceleration measured across ~3 rest-frame weeks around light curve peak, consistent with the expansion of an optically thick massive shell of material. We show that, consistent with findings for other ultraluminous SNe in this class, radioactive decay is not sufficient to power PS1-10ky, and we discuss two plausible origins for these events: the initial spin-down of a newborn magnetar in a core-collapse SN, or SN shock breakout from the dense circumstellar wind surrounding a Wolf-Rayet star.Publication The Intermediate Luminosity Optical Transient Sn 2010da: The Progenitor, Eruption, and Aftermath of a Peculiar Supergiant High-Mass X-Ray Binary(American Astronomical Society, 2016) Villar, Ashley; Berger, Edo; Chornock, R.; Margutti, R.; Laskar, T.; Brown, P. J.; Blanchard, Peter; Czekala, Ian; Lunnan, R.; Reynolds, M. T.We present optical spectroscopy, ultraviolet-to-infrared imaging, and X-ray observations of the intermediate luminosity optical transient (ILOT) SN 2010da in NGC 300 (d = 1.86 Mpc) spanning from −6 to +6 years relative to the time of outburst in 2010. Based on the light-curve and multi-epoch spectral energy distributions of SN 2010da, we conclude that the progenitor of SN 2010da is a ≈10–12 M ⊙ yellow supergiant possibly transitioning into a blue-loop phase. During outburst, SN 2010da had a peak absolute magnitude of M bol lesssim −10.4 mag, dimmer than other ILOTs and supernova impostors. We detect multi-component hydrogen Balmer, Paschen, and Ca ii emission lines in our high-resolution spectra, which indicate a dusty and complex circumstellar environment. Since the 2010 eruption, the star has brightened by a factor of ≈5 and remains highly variable in the optical. Furthermore, we detect SN 2010da in archival Swift and Chandra observations as an ultraluminous X-ray source (L X ≈ 6 × 1039 erg s−1). We additionally attribute He ii 4686 Å and coronal Fe emission lines in addition to a steady X-ray luminosity of ≈1037 erg s−1 to the presence of a compact companion.Publication The Ultraviolet-Bright, Slowly Declining Transient PS1-11af as a Partial Tidal Disruption Event.(IOP Publishing, 2013) Chornock, R.; Berger, Edo; Gezari, S.; Zauderer, B; Rest, A.; Chomiuk, L.; Kamble, Atish; Soderberg, Alicia; Czekala, Ian; Dittmann, Jason Adam; Drout, Maria Rebecca; Foley, R. J.; Fong, W; Huber, M. E.; Kirshner, Robert; Lawrence, A.; Lunnan, R; Marion, G. H.; Narayan, Gautham; Riess, A. G.; Roth, K. C.; Sanders, Nathan Edward; Scolnic, D.; Smartt, S. J.; Smith, K.; Stubbs, Christopher; Tonry, J. L.; Burgett, W. S.; Chambers, K. C.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Magnier, E. A.; Martin, D. C.; Neill, J. D.; Price, P. A.; Wainscoat, R.We present the Pan-STARRS1 discovery of the long-lived and blue transient PS1-11af, which was also detected by Galaxy Evolution Explorer with coordinated observations in the near-ultraviolet (NUV) band. PS1-11af is associated with the nucleus of an early type galaxy at redshift z = 0.4046 that exhibits no evidence for star formation or active galactic nucleus activity. Four epochs of spectroscopy reveal a pair of transient broad absorption features in the UV on otherwise featureless spectra. Despite the superficial similarity of these features to P-Cygni absorptions of supernovae (SNe), we conclude that PS1-11af is not consistent with the properties of known types of SNe. Blackbody fits to the spectral energy distribution are inconsistent with the cooling, expanding ejecta of a SN, and the velocities of the absorption features are too high to represent material in homologous expansion near a SN photosphere. However, the constant blue colors and slow evolution of the luminosity are similar to previous optically selected tidal disruption events (TDEs). The shape of the optical light curve is consistent with models for TDEs, but the minimum accreted mass necessary to power the observed luminosity is only ∼0.002 M , which points to a partial disruption model. A full disruption model predicts higher bolometric luminosities, which would require most of the radiation to be emitted in a separate component at high energies where we lack observations. In addition, the observed temperature is lower than that predicted by pure accretion disk models for TDEs and requires reprocessing to a constant, lower temperature. Three deep non-detections in the radio with the Very Large Array over the first two years after the event set strict limits on the production of any relativistic outflow comparable to Swift J1644+57, even if off-axis.Publication A Jet Break in the X-Ray Light Curve of Short Grb 111020a: Implications for Energetics and Rates(IOP Publishing, 2012) Fong, W; Berger, Edo; Margutti, Raffaella; Zauderer, B; Troja, E.; Czekala, Ian; Chornock, R; Gehrels, N.; Sakamoto, T.; Fox, D. B.; Podsiadlowski, P.We present broad-band observations of the afterglow and environment of the short GRB 111020A. An extensive X-ray light curve from Swift/XRT, XMM-Newton and Chandra, spanning ∼ 100 seconds to 10 days after the burst, reveals a significant break at δt ≈2 days with pre- and post-break decline rates of αX,1 ≈ −0.78 and αX,2 . −1.7, respectively. Interpreted as a jet break, we infer a collimated outflow with an opening angle of θj ≈ 3 − 8◦. The resulting beaming-corrected γ-ray (10 − 1000 keV band) and blastwave kinetic energies are (2−3)×1048 erg and (0.3−2)×1049 erg, respectively, with the range depending on the unknown redshift of the burst. We report a radio afterglow limit of <39 µJy (3σ) from EVLA observations which, along with our finding that νc < νX , constrains the circumburst density to n0 ∼ 0.01 − 0.1 cm−3. Optical observations provide an afterglow limit of i & 24.4 mag at 18 hours after the burst, and reveal a potential host galaxy with i ≈ 24.3 mag. The sub-arcsecond localization from Chandra provides a precise offset of 0.80′′ ±0.11′′ (1σ) from this galaxy corresponding to an offset of 5−7 kpc for z = 0.5−1.5. We find a high excess neutral Hydrogen column density of (7.5 ± 2.0) × 1021 cm−2 (z = 0). Our observations demonstrate that a growing fraction of short GRBs are collimated which may lead to a true event rate of & 100 − 1000 Gpc−3 yr−1, in good agreement with the NS-NS merger rate of ≈ 200 − 3000 Gpc−3 yr−1. This consistency is promising for coincident short GRB-gravitational wave searches in the forthcoming era of Advanced LIGO/VIRGO.Publication Ultra-Luminous Supernovae as a New Probe of the Interstellar Medium in Distant Galaxies(IOP Publishing, 2012) Berger, Edo; Chornock, R; Lunnan, R.; Foley, R.; Czekala, Ian; Rest, A.; Leibler, C.; Soderberg, Alicia; Roth, K.; Narayan, G.; Huber, M. E.; Milisavljevic, Danny; Sanders, Nathan Edward; Drout, M.; Margutti, R.; Kirshner, Robert; Marion, G. H.; Challis, P. J.; Riess, A. G.; Smartt, S. J.; Burgett, W. S.; Hodapp, K. W.; Heasley, J. N.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E. A.; McCrum, M.; Price, P. A.; Smith, K.; Tonry, J. L.; Wainscoat, R. J.We present the Pan-STARRS1 discovery and light curves, and follow-up MMT and Gemini spectroscopy of an ultra-luminous supernova (ULSN; dubbed PS1-11bam) at a redshift of z = 1.566 with a peak brightness of MUV ≈ −22.3 mag. PS1-11bam is one of the highest redshift spectroscopically-confirmed SNe known to date. The spectrum is characterized by broad absorption features typical of previous ULSNe (e.g., C II, Si III), and by strong and narrow Mg II and Fe II absorption lines from the interstellar medium (ISM) of the host galaxy, confirmed by an [O II]λ3727 emission line at the same redshift. The equivalent widths of the Fe IIλ2600 and Mg IIλ2803 lines are in the top quartile of the quasar intervening absorption system distribution, but are weaker than those of gamma-ray burst intrinsic absorbers (i.e., GRB host galaxies). We also detect the host galaxy in pre-explosion Pan-STARRS1 data and find that its UV spectral energy distribution is best fit with a young stellar population age of τ∗ ≈ 15 − 45 Myr and a stellar mass of M∗ ≈ (1.1 − 2.6) × 109 M⊙ (for Z = 0.05 − 1 Z⊙). The star formation rate inferred from the UV continuum and [O II]λ3727 emission line is ≈ 10 M⊙ yr−1, higher than in any previous ULSN host. PS1-11bam provides the first direct demonstration that ULSNe can serve as probes of the interstellar medium in distant galaxies. At the present, the depth and red sensitivity of PS1 are uniquely suited to finding such events at cosmologically interesting redshifts (z ∼ 1 − 2); the future combination of LSST and 30-m class telescopes promises to extend this technique to z ∼ 4.Publication The Unusually Luminous Extragalactic Nova Sn 2010u(IOP Publishing, 2013) Czekala, Ian; Berger, Edo; Chornock, R; Pastorello, A.; Marion, G. H.; Margutti, R.; Botticella, M. T.; Challis, P.; Ergon, M.; Smartt, S.; Sollerman, J.; Vinkó, J.; Wheeler, J. C.We present observations of the unusual optical transient SN 2010U, including spectra taken 1.03 days to 15.3 days after maximum light that identify it as a fast and luminous Fe II type nova. Our multi-band light curve traces the fast decline (t2 = 3.5 ± 0.3 days) from maximum light (MV = −10.2 ± 0.1 mag), placing SN 2010U in the top 0.5% of the most luminous novae ever observed. We find typical ejecta velocities of ≈ 1100 km s−1 and that SN 2010U shares many spectral and photometric characteristics with two other fast and luminous Fe II type novae, including Nova LMC 1991 and M31N-2007-11d. For the extreme luminosity of this nova, the maximum magnitude vs. rate of decline relationship indicates a massive white dwarf progenitor with a low pre-outburst accretion rate. However, this prediction is in conflict with emerging theories of nova populations, which predict that luminous novae from massive white dwarfs should preferentially exhibit an alternate spectral type (He/N) near maximum light.Publication A Spectroscopic Study of Type Ibc Supernova Host Galaxies From Untargeted Surveys(IOP Publishing, 2012) Sanders, Nathan Edward; Soderberg, Alicia; Levesque, E. M.; Foley, R. J.; Chornock, R; Milisavljevic, Danny; Margutti, Raffaella; Berger, Edo; Drout, Maria Rebecca; Czekala, Ian; Dittmann, Jason AdamWe present the first spectroscopic study of the host environments of Type Ibc supernovae (SN Ibc) discovered exclusively by untargeted SN searches. Past studies of SN Ibc host environments have been biased towards high-mass, high-metallicity galaxies by focusing on SNe discovered in galaxytargeted SN searches. Our new observations more than double the total number of spectroscopic stellar population age and metallicity measurements published for untargeted SN Ibc host environments. For the 12 SNe Ib and 21 SNe Ic in our metallicity sample, we find median metallicities of 0.62 Z⊙ and 0.83 Z⊙, respectively, but determine that the discrepancy in the full distribution of metallicities is not statistically significant. This median difference would correspond to only a small difference in the mass loss via metal-line driven winds (. 30%), suggesting this does not play the dominant role in distinguishing SN Ib and Ic progenitors. However, the median metallicity of the 7 broad-lined SN Ic (SN Ic-BL) in our sample is significantly lower, 0.45 Z⊙. The age of the young stellar population of SN Ic-BL host environments also seems to be lower than for SN Ib and Ic, but our age sample is small. Combining all SN Ibc host environment spectroscopy from the literature to date does not reveal a significant difference in SN Ib and Ic metallicities, but reinforces the significance of the lower metallicities for SN Ic-BL. This combined sample demonstrates that galaxy-targeted SN searches introduce a significant bias for studies seeking to infer the metallicity distribution of SN progenitors, and we identify and discuss other systematic effects that play smaller roles. We discuss the path forward for making progress on SN Ibc progenitor studies in the LSST era. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.Publication The superluminous supernova PS1-11ap: bridging the gap between low and high redshift(Oxford University Press (OUP), 2013) McCrum, M.; Smartt, S. J.; Kotak, R.; Rest, A.; Jerkstrand, A.; Inserra, C.; Rodney, S. A.; Chen, T.- W.; Howell, D. A.; Huber, M. E.; Pastorello, A.; Tonry, J. L.; Bresolin, F.; Kudritzki, R.- P.; Chornock, R.; Berger, Edo; Smith, K.; Botticella, M. T.; Foley, R. J.; Fraser, M.; Milisavljevic, Danny; Nicholl, M.; Riess, A. G.; Stubbs, Christopher; Valenti, S.; Wood-Vasey, W. M.; Wright, D.; Young, D. R.; Drout, Maria Rebecca; Czekala, Ian; Burgett, W. S.; Chambers, K. C.; Draper, P.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Magnier, E. A.; Metcalfe, N.; Price, P. A.; Sweeney, W.; Wainscoat, R. J.We present optical photometric and spectroscopic coverage of the superluminous supernova (SLSN) PS1-11ap, discovered with the Pan-STARRS1 Medium Deep Survey at z = 0.524. This intrinsically blue transient rose slowly to reach a peak magnitude of Mu = −21.4 mag and bolometric luminosity of 8 × 1043 erg s−1 before settling on to a relatively shallow gradient of decline. The observed decline is significantly slower than those of the SLSNe-Ic which have been the focus of much recent attention. Spectroscopic similarities with the lower redshift SN2007bi and a decline rate similar to 56Co decay time-scale initially indicated that this transient could be a candidate for a pair instability supernova (PISN) explosion. Overall the transient appears quite similar to SN2007bi and the lower redshift object PTF12dam. The extensive data set, from 30 d before peak to 230 d after, allows a detailed and quantitative comparison with published models of PISN explosions. We find that the PS1-11ap data do not match these model explosion parameters well, supporting the recent claim that these SNe are not pair instability explosions. We show that PS1-11ap has many features in common with the faster declining SLSNe-Ic, and the light-curve evolution can also be quantitatively explained by the magnetar spin-down model. At a redshift of z = 0.524, the observer-frame optical coverage provides comprehensive rest-frame UV data and allows us to compare it with the SLSNe recently found at high redshifts between z = 2 and 4. While these high-z explosions are still plausible PISN candidates, they match the photometric evolution of PS1-11ap and hence could be counterparts to this lower redshift transient.