Person: Lunnan, R
Loading...
Email Address
AA Acceptance Date
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
Lunnan
First Name
R
Name
Lunnan, R
14 results
Search Results
Now showing 1 - 10 of 14
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 Slowly Fading Super-Luminous Supernovae That Are Not Pair-Instability Explosions(Nature Publishing Group, 2013) Nicholl, M.; Smartt, S. J.; Jerkstrand, A.; Inserra, C.; McCrum, M.; Kotak, R.; Fraser, M.; Wright, D.; Chen, T.-W.; Smith, K.; Young, D. R.; Sim, S. A.; Valenti, S.; Howell, D. A.; Bresolin, F.; Kudritzki, R. P.; Tonry, J. L.; Huber, M. E.; Rest, A.; Pastorello, A.; Tomasella, L.; Cappellaro, E.; Benetti, S.; Mattila, S.; Kankare, E.; Kangas, T.; Leloudas, G.; Sollerman, J.; Taddia, F.; Berger, E.; Chornock, R; Narayan, Gautham; Stubbs, Christopher; Foley, R. J.; Lunnan, R; Soderberg, Alicia; Sanders, Nathan Edward; Milisavljevic, Danny; Margutti, Raffaella; Kirshner, Robert; Elias-Rosa, N.; Morales-Garoffolo, A.; Taubenberger, S.; Botticella, M. T.; Gezari, S.; Urata, Y.; Rodney, S.; Riess, A. G.; Scolnic, D.; Wood-Vasey, W. M.; Burgett, W. S.; Chambers, K.; Flewelling, H. A.; Magnier, E. A.; Kaiser, N.; Metcalfe, N.; Morgan, J.; Price, P. A.; Sweeney, W.; Waters, C.Super-luminous supernovae that radiate more than 10\(^{44}\) ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1–4. Some evolve slowly, resembling models of ‘pair-instability’ supernovae. Such models involve stars with original masses 140–260 times that of the Sun that now have carbon–oxygen cores of 65–130 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron–positron pairs, causing rapid contraction and thermonuclear explosions. Many solar masses of \(^{56}\)Ni are synthesized; this isotope decays to \(^{56}\)Fe via \(^{56}\)Co, powering bright light curves. Such massive progenitors are expected to have formed from metal-poor gas in the early Universe. Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a metallicity one-third that of the Sun was observed to look like a fading pair-instability supernova. Here we report observations of two slow-to-fade super-luminous supernovae that show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Their late-time light-curve and spectral similarities to supernova 2007bi call the nature of that event into question. Our early spectra closely resemble typical fast-declining super-luminous supernovae, which are not powered by radioactivity. Modelling our observations with 10–16 solar masses of magnetar-energized ejecta demonstrates the possibility of a common explosion mechanism. The lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6 × 10\(^{−6}\) times that of the core-collapse rate.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 Rapidly evolving and luminous transients from Pan-STARRS1(IOP Publishing, 2014) Drout, Maria Rebecca; Chornock, R; Soderberg, Alicia; Sanders, Nathan Edward; McKinnon, R.; Rest, Armin; Foley, R. J.; Milisavljevic, Danny; Margutti, Raffaella; Berger, Edo; Calkins, Michael; Fong, W; Gezari, S.; Huber, M. E.; Kankare, E.; Kirshner, Robert; Leibler, C.; Lunnan, R; Mattila, S.; Marion, G. H.; Narayan, Gautham; Riess, A. G.; Roth, K. C.; Scolnic, D.; Smartt, S. J.; Tonry, J. L.; Burgett, W. S.; Chambers, K. C.; Hodapp, K. W.; Jedicke, R.; Kaiser, N.; Magnier, E. A.; Metcalfe, N.; Morgan, J. S.; Price, P. A.; Waters, C.In the past decade, several rapidly evolving transients have been discovered whose timescales and luminosities are not easily explained by traditional supernovae (SNe) models. The sample size of these objects has remained small due, at least in part, to the challenges of detecting short timescale transients with traditional survey cadences. Here we present the results from a search within the Pan-STARRS1 Medium Deep Survey (PS1-MDS) for rapidly evolving and luminous transients. We identify 10 new transients with a time above half-maximum (t 1/2) of less than 12 days and –16.5 > M > –20 mag. This increases the number of known events in this region of SN phase space by roughly a factor of three. The median redshift of the PS1-MDS sample is z = 0.275 and they all exploded in star-forming galaxies. In general, the transients possess faster rise than decline timescale and blue colors at maximum light (g P1 – r P1 lesssim –0.2). Best-fit blackbodies reveal photospheric temperatures/radii that expand/cool with time and explosion spectra taken near maximum light are dominated by a blue continuum, consistent with a hot, optically thick, ejecta. We find it difficult to reconcile the short timescale, high peak luminosity (L > 1043 erg s–1), and lack of UV line blanketing observed in many of these transients with an explosion powered mainly by the radioactive decay of 56Ni. Rather, we find that many are consistent with either (1) cooling envelope emission from the explosion of a star with a low-mass extended envelope that ejected very little (<0.03 M ☉) radioactive material, or (2) a shock breakout within a dense, optically thick, wind surrounding the progenitor star. After calculating the detection efficiency for objects with rapid timescales in the PS1-MDS we find a volumetric rate of 4800-8000 events yr–1 Gpc–3 (4%-7% of the core-collapse SN rate at z = 0.2).Publication The Properties and Environments of Superluminous Supernovae(2015-05-16) Lunnan, R; Kirshner, Robert P.; Berger, Edo; Narayan, Ramesh; Di Stefano, Rosanne; Quimby, Robert M.Superluminous supernovae (SLSNe) are a rare class of stellar explosions discovered by wide-field optical transient surveys in the past decade. They are characterized by peak luminosities 10-100 times that of ordinary core-collapse and Type Ia SNe, and radiated energies of order 10^51 erg, comparable to the entire kinetic energy of a canonical supernova explosion. Proposed sources of these tremendous energies include interaction between the supernova ejecta and dense circumstellar material (CSM), energy injection from the spin-down of a rapidly rotating and highly magnetized neutron star, or the pair-instability explosion of a very massive star producing several solar masses of radioactive nickel. In this thesis, I present results from the Pan-STARRS1 Medium Deep Survey (PS1/MDS), which discovered 15 hydrogen-poor SLSNe out to redshift 1.6 over the four years of its operation. I address the nature of SLSNe from two different angles. First, I characterize the SNe themselves, and compare their observed properties to model predictions. The PS1/MDS SLSN sample exhibits a diversity of light curve properties, and a wider range of peak luminosities than previously reported, particularly when accounting for the flux-limited nature of the survey. The light curves can generally be fit with magnetar spin-down models, though our sample also contains one very slowly evolving event that could plausibly be powered by radioactive decay. Second, I present the first comprehensive study of SLSN host galaxy environments and the sub-galactic environments, demonstrating that H-poor SLSNe preferentially occur in low-luminosity, low-mass, low-metallicity galaxies with high specific star formation rates. Their host galaxies are statistically distinct from the hosts of core-collapse SNe, but share many similarities with the galaxies that host long gamma-ray bursts (LGRBs). This suggests that the environmental factors leading to a massive star forming either a SLSN or a LGRB are similar, with a possible common ingredient being a preference for low-metallicity environments through the need of a progenitor with high core angular momentum. In terms of their local environments, resolved Hubble Space Telescope imaging reveals that SLSN locations are correlated with the UV light, though not as strongly as LGRBs are. Although a larger sample size is needed to distinguish them statistically, this trend is also consistent with the interpretation that SLSN progenitors are lower-mass than those of LGRBs, collapsing to form a rapidly spinning neutron star rather than a black hole launching a relativistic jet.Publication Zooming in on the progenitors of superluminous supernovae with the HST(IOP Publishing, 2015) Lunnan, R; Chornock, R; Berger, Edo; Rest, A.; Fong, W; Scolnic, D.; Jones, D. O.; Soderberg, Alicia; Challis, Peter; Drout, Maria Rebecca; Foley, R. J.; Huber, M. E.; Kirshner, Robert; Leibler, C.; Marion, G. H.; McCrum, M.; Milisavljevic, Danny; Narayan, Gautham; Sanders, Nathan Edward; Smartt, S. J.; Smith, K. W.; Tonry, J. L.; Burgett, W. S.; Chambers, K. C.; Flewelling, H.; Kudritzki, R.-P.; Wainscoat, R. J.; Waters, C.We present Hubble Space Telescope (HST) rest-frame ultraviolet imaging of the host galaxies of 16 hydrogen-poor superluminous supernovae (SLSNe), including 11 events from the Pan-STARRS Medium Deep Survey. Taking advantage of the superb angular resolution of HST, we characterize the galaxies' morphological properties, sizes, and star formation rate (SFR) densities. We determine the supernova (SN) locations within the host galaxies through precise astrometric matching and measure physical and host-normalized offsets as well as the SN positions within the cumulative distribution of UV light pixel brightness. We find that the host galaxies of H-poor SLSNe are irregular, compact dwarf galaxies, with a median half-light radius of just 0.9 kpc. The UV-derived SFR densities are high ($\langle {{{\Sigma }}_{{\rm SFR}}}\rangle \simeq 0.1{{M}_{\odot }}\;{\rm y}{{{\rm r}}^{-1}}\;{\rm kp}{{{\rm c}}^{-2}}$), suggesting that SLSNe form in overdense environments. Their locations trace the UV light of their host galaxies, with a distribution intermediate between that of long-duration gamma-ray bursts (LGRBs; which are strongly clustered on the brightest regions of their hosts) and a uniform distribution (characteristic of normal core-collapse SNe), though cannot be statistically distinguished from either with the current sample size. Taken together, this strengthens the picture that SLSN progenitors require different conditions than those of ordinary core-collapse SNe to form and that they explode in broadly similar galaxies as do LGRBs. If the tendency for SLSNe to be less clustered on the brightest regions than are LGRBs is confirmed by a larger sample, this would indicate a different, potentially lower-mass progenitor for SLSNe than LRGBs.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 Toward Characterization of the Type IIP Supernova Progenitor Population: A Statistical Sample of Light Curves from Pan-STARRS1(IOP Publishing, 2015) Sanders, Nathan Edward; Soderberg, Alicia; Gezari, S.; Betancourt, M.; Chornock, R; Berger, Edo; Foley, R. J.; Challis, Peter; Drout, Maria Rebecca; Kirshner, Robert; Lunnan, R; Marion, G. H.; Margutti, Raffaella; McKinnon, R.; Milisavljevic, Danny; Narayan, G.; Rest, A.; Kankare, E.; Mattila, S.; Smartt, S. J.; Huber, M. E.; Burgett, W. S.; Draper, P.W.; Hodapp, K. W.; Kaiser, N.; Kudritzki, R. P.; Magnier, E. A.; Metcalfe, N.; Morgan, J. S.; Price, P. A.; Tonry, J. L.; Wainscoat, R. J.; Waters, C.In recent years, wide-field sky surveys providing deep multiband imaging have presented a new path for indirectly characterizing the progenitor populations of core-collapse supernovae (SNe): systematic light-curve studies. We assemble a set of 76 grizy-band Type IIP SN light curves from Pan-STARRS1, obtained over a constant survey program of 4 yr and classified using both spectroscopy and machine-learning-based photometric techniques. We develop and apply a new Bayesian model for the full multiband evolution of each light curve in the sample. We find no evidence of a subpopulation of fast-declining explosions (historically referred to as "Type IIL" SNe). However, we identify a highly significant relation between the plateau phase decay rate and peak luminosity among our SNe IIP. These results argue in favor of a single parameter, likely determined by initial stellar mass, predominantly controlling the explosions of red supergiants. This relation could also be applied for SN cosmology, offering a standardizable candle good to an intrinsic scatter of lesssim 0.2 mag. We compare each light curve to physical models from hydrodynamic simulations to estimate progenitor initial masses and other properties of the Pan-STARRS1 Type IIP SN sample. We show that correction of systematic discrepancies between modeled and observed SN IIP light-curve properties and an expanded grid of progenitor properties are needed to enable robust progenitor inferences from multiband light-curve samples of this kind. This work will serve as a pathfinder for photometric studies of core-collapse SNe to be conducted through future wide-field transient searches.Publication Host Galaxy Properties of the Subluminous GRB 120422A/SN 2012bz(IOP Publishing, 2012) Levesque, Emily M.; Chornock, R; Soderberg, Alicia; Berger, Edo; Lunnan, RGRB 120422A is a nearby (z = 0.283) long-duration GRB (LGRB) detected by Swift with Eγ,iso ∼ 4.5 × 1049 erg. It is also associated with the spectroscopically-confirmed broad-lined Type Ic SN 2012bz. These properties establish GRB 120422A/SN 2012bz as the sixth and newest member of the class of subluminous GRB/SNe. Observations also show that GRB 120422A/SN 2012bz occurred at an unusually large offset (∼8 kpc) from the host galaxy nucleus, setting it apart from other nearby LGRBs and leading to speculation that the host environment may have undergone prior interaction activity. Here we present spectroscopic observations using the 6.5m Magellan telescope at Las Campanas. We extract spectra at three specific locations within the GRB/SN host galaxy, including the host nucleus, the explosion site, and the “bridge” of diffuse emission connecting these two regions. We measure a metallicity of log(O/H) + 12 = 8.3 ± 0.1 and a star formation rate per unit area of 0.08 M⊙ yr−1 kpc−2 at the host nucleus. At the GRB/SN explosion site we measure a comparable metallicity of log(O/H) + 12 = 8.2 ± 0.1, but find a much lower star formation rate per unit area of 0.01 M⊙ yr−1 kpc−2. We also compare the host galaxy of this event to the hosts of other LGRBs, including samples of subluminous LGRBs and cosmological LGRBs, and find no systematic metallicity difference between the environments of these different subtypes.Publication Sn 2012au: A Golden Link Between Superluminous Supernovae and Their Lower-Luminosity Counterparts(IOP Publishing, 2013) Milisavljevic, Danny; Soderberg, Alicia; Margutti, Raffaella; Drout, Maria Rebecca; Marion, G. Howie; Sanders, Nathan Edward; Hsiao, Eric Y.; Lunnan, R; Chornock, R; Fesen, Robert A.; Parrent, Jerod T.; Levesque, Emily M.; Berger, Edo; Foley, Ryan J.; Challis, Pete; Kirshner, Robert P.; Dittmann, Jason Adam; Bieryla, Allyson; Kamble, Atish; Chakraborti, Sayan; De Rosa, Gisella; Fausnaugh, Michael; Hainline, Kevin N.; Chen, Chien-Ting; Hickox, Ryan C.; Morrell, Nidia; Phillips, Mark M.; Stritzinger, MaximilianWe present optical and near-infrared observations of SN 2012au, a slow-evolving supernova (SN) with properties that suggest a link between subsets of energetic and H-poor SNe and superluminous SNe. SN 2012au exhibited conspicuous SN Ib-like He I lines and other absorption features at velocities reaching ≈ 2×104 km s−1 in its early spectra, and a broad light curve that peaked at MB = −18.1 mag. Models of these data indicate a large explosion kinetic energy of ∼ 1052 erg and 56Ni mass ejection of MNi ≈ 0.3M⊙ on par with SN 1998bw. SN 2012au’s spectra almost one year after explosion show a blend of persistent Fe II P-Cyg absorptions and nebular emissions originating from two distinct velocity regions. These late-time emissions include strong [Fe II], [Ca II], [O I], Mg I], and Na I lines at velocities & 4500 km s−1, as well as O I and Mg I lines at noticeably smaller velocities . 2000 km s−1. Many of the late-time properties of SN 2012au are similar to the slow-evolving hypernovae SN 1997dq and SN 1997ef, and the superluminous SN 2007bi. Our observations suggest that a single explosion mechanism may unify all of these events that span −21 . MB . −17 mag. The aspherical and possibly jetted explosion was most likely initiated by the core collapse of a massive progenitor star and created substantial high-density, low-velocity Ni-rich material.