| 1. |
- Scolnic, D., et al.
(författare)
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How Many Kilonovae Can Be Found in Past, Present, and Future Survey Data Sets?
- 2018
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 852:1
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Tidskriftsartikel (refereegranskat)abstract
- The discovery of a kilonova (KN) associated with the Advanced LIGO (aLIGO)/Virgo event GW170817 opens up new avenues of multi-messenger astrophysics. Here, using realistic simulations, we provide estimates of the number of KNe that could be found in data from past, present, and future surveys without a gravitational-wave trigger. For the simulation, we construct a spectral time-series model based on the DES-GW multi-band light curve from the single known KN event, and we use an average of BNS rates from past studies of 103Gpc(-3) yr(-1), consistent with the one event found so far. Examining past and current data sets from transient surveys, the number of KNe we expect to find for ASAS-SN, SDSS, PS1, SNLS, DES, and SMT is between 0 and 0.3. We predict the number of detections per future survey to be 8.3 from ATLAS, 10.6 from ZTF, 5.5/69 from LSST (the Deep Drilling/Wide Fast Deep), and 16.0 from WFIRST. The maximum redshift of KNe discovered for each survey is z = 0.8 for WFIRST, z = 0.25 for LSST, and z = 0.04 for ZTF and ATLAS. This maximum redshift for WFIRST is well beyond the sensitivity of aLIGO and some future GW missions. For the LSST survey, we also provide contamination estimates from Type Ia and core-collapse supernovae: after light curve and template-matching requirements, we estimate a background of just two events. More broadly, we stress that future transient surveys should consider how to optimize their search strategies to improve their detection efficiency and to consider similar analyses for GW follow-up programs.
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| 2. |
- Margutti, R., et al.
(författare)
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A PANCHROMATIC VIEW OF THE RESTLESS SN 2009ip REVEALS THE EXPLOSIVE EJECTION OF A MASSIVE STAR ENVELOPE
- 2014
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 780:1
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Tidskriftsartikel (refereegranskat)abstract
- The double explosion of SN 2009ip in 2012 raises questions about our understanding of the late stages of massive star evolution. Here we present a comprehensive study of SN 2009ip during its remarkable rebrightenings. High-cadence photometric and spectroscopic observations from the GeV to the radio band obtained from a variety of ground-based and space facilities (including the Very Large Array, Swift, Fermi, Hubble Space Telescope, and XMM) constrain SN 2009ip to be a low energy (E similar to 1050 erg for an ejecta mass similar to 0.5 M-circle dot) and asymmetric explosion in a complex medium shaped by multiple eruptions of the restless progenitor star. Most of the energy is radiated as a result of the shock breaking out through a dense shell of material located at similar to 5 x 10(14) cm with M similar to 0.1 M-circle dot, ejected by the precursor outburst similar to 40 days before the major explosion. We interpret the NIR excess of emission as signature of material located further out, the origin of which has to be connected with documented mass-loss episodes in the previous years. Our modeling predicts bright neutrino emission associated with the shock break-out if the cosmic-ray energy is comparable to the radiated energy. We connect this phenomenology with the explosive ejection of the outer layers of the massive progenitor star, which later interacted with material deposited in the surroundings by previous eruptions. Future observations will reveal if the massive luminous progenitor star survived. Irrespective of whether the explosion was terminal, SN 2009ip brought to light the existence of new channels for sustained episodic mass loss, the physical origin of which has yet to be identified.
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| 3. |
- Nicholl, M., et al.
(författare)
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Slowly fading super-luminous supernovae that are not pair-instability explosions
- 2013
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 502:7471, s. 346-
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Tidskriftsartikel (refereegranskat)abstract
- Super-luminous supernovae(1-4) that radiate more than 1044 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(5,6). 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 Ni-56 are synthesized; this isotope decays to Fe-56 via Co-56, powering bright light curves(7,8). Such massive progenitors are expected to have formed from metal-poor gas in the early Universe(9). 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(1,10). 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(2,11,12), which are not powered by radio-activity. Modelling our observations with 10-16 solar masses of magnetar-energized(13,14) 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 x 10(-6) times that of the core-collapse rate.
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| 4. |
- Lunnan, Ragnhild, et al.
(författare)
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Hydrogen-poor Superluminous Supernovae from the Pan-STARRS1 Medium Deep Survey
- 2018
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 852:2
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Tidskriftsartikel (refereegranskat)abstract
- We present light curves and classification spectra of 17 hydrogen-poor superluminous supernovae (SLSNe) from the Pan-STARRS1 Medium Deep Survey (PS1 MDS). Our sample contains all objects from the PS1. MDS sample with spectroscopic classification that are similar to either of the prototypes SN 2005ap or SN 2007bi, without an explicit limit on luminosity. With a redshift range 0.3 < z < 1.6, PS1. MDS is the first SLSN sample primarily probing the high-redshift population; our multifilter PS1 light curves probe the rest-frame UV emission, and hence the peak of the spectral energy distribution. We measure the temperature evolution and construct bolometric light curves, and find peak luminosities of (0.5-5) x 10(44) erg s(-1) and lower limits on the total radiated energies of (0.3-2) x 10(51) erg. The light curve shapes are diverse, with both rise and decline times spanning a factor of similar to 5 and several examples of double-peaked light curves. When correcting for the flux-limited nature of our survey, we find a median peak luminosity at 4000 angstrom of M-4000 = -21.1 mag and a spread of sigma = 0.7 mag.
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| 5. |
- Lunnan, R., et al.
(författare)
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PS1-14bj : A HYDROGEN-POOR SUPERLUMINOUS SUPERNOVA WITH A LONG RISE AND SLOW DECAY
- 2016
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 831:2
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Tidskriftsartikel (refereegranskat)abstract
- We present photometry and spectroscopy of PS1-14bj, a hydrogen-poor superluminous supernova (SLSN) at redshift z = 0.5215 discovered in the last months of the Pan-STARRS1 Medium Deep Survey. PS1-14bj stands out because of its extremely slow evolution, with an observed rise of greater than or similar to 125 rest-frame days, and exponential decline out to similar to 250 days past peak at a measured rate of 0.01 mag day(-1), consistent with fully trapped Co-56 decay. This is the longest rise time measured in an SLSN to date, and the first SLSN to show a rise time consistent with pair-instability supernova (PISN) models. Compared to other slowly evolving SLSNe, it is spectroscopically similar to the prototype SN 2007bi at maximum light, although lower in luminosity (L-peak similar or equal to 4.6 x 10(43) erg s(-1) ) and with a flatter peak than previous events. PS1-14bj shows a number of peculiar properties, including a near-constant color temperature for > 200 days past peak, and strong emission lines from [O III] lambda 5007 and [O III] lambda 4363 with a velocity width of similar to 3400 km s(-1) in its late-time spectra. These both suggest there is a sustained source of heating over very long timescales, and are incompatible with a simple Ni-56-powered/PISN interpretation. A modified magnetar model including emission leakage at late times can reproduce the light curve, in which case the blue continuum and [O III] features are interpreted as material heated and ionized by the inner pulsar wind nebula becoming visible at late times. Alternatively, the late-time heating could be due to interaction with a shell of H-poor circumstellar material.
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| 6. |
- Milisavljevic, D., et al.
(författare)
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METAMORPHOSIS OF SN 2014C : DELAYED INTERACTION BETWEEN A HYDROGEN POOR CORE-COLLAPSE SUPERNOVA AND A NEARBY CIRCUMSTELLAR SHELL
- 2015
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 815:2
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Tidskriftsartikel (refereegranskat)abstract
- We present optical observations of supernova SN 2014C, which underwent an unprecedented slow metamorphosis from H-poor type Ib to H-rich type IIn over the course of one year. The observed spectroscopic evolution is consistent with the supernova having exploded in a cavity before encountering a massive shell of the progenitor star's stripped hydrogen envelope. Possible origins for the circumstellar shell include a brief Wolf-Rayet fast wind phase that overtook a slower red supergiant wind, eruptive ejection, or confinement of circumstellar material by external influences of neighboring stars. An extended high velocity Ha absorption feature seen in near-maximum light spectra implies that the progenitor star was not completely stripped of hydrogen at the time of core collapse. Archival pre-explosion Subaru Telescope Suprime-Cam and Hubble Space Telescope Wide Field Planetary Camera. 2 images of the region obtained in 2009 show a coincident source that is most likely a compact massive star cluster in NGC 7331 that hosted the progenitor system. By comparing the emission properties of the source with stellar population models that incorporate interacting binary stars we estimate the age of the host cluster to be 30-300 Myr, and favor ages closer to 30 Myr in light of relatively strong Ha emission. SN 2014C is the best observed member of a class of core-collapse supernovae that fill the gap between events that interact strongly with dense, nearby environments immediately after explosion and those that never show signs of interaction. Better understanding of the frequency and nature of this intermediate population can contribute valuable information about the poorly understood final stages of stellar evolution.
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| 7. |
- Scolnic, D. M., et al.
(författare)
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The Complete Light-curve Sample of Spectroscopically Confirmed SNe Ia from Pan-STARRS1 and Cosmological Constraints from the Combined Pantheon Sample
- 2018
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 859:2
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Tidskriftsartikel (refereegranskat)abstract
- We present optical light curves, redshifts, and classifications for 365 spectroscopically confirmed Type Ia supernovae (SNe Ia) discovered by the Pan-STARRS1 (PS1) Medium Deep Survey. We detail improvements to the PS1 SN photometry, astrometry, and calibration that reduce the systematic uncertainties in the PS1 SN Ia distances. We combine the subset of 279 PS1 SNe Ia (0.03 < z < 0.68) with useful distance estimates of SNe Ia from the Sloan Digital Sky Survey (SDSS), SNLS, and various low-z and Hubble Space Telescope samples to form the largest combined sample of SNe Ia, consisting of a total of 1048 SNe Ia in the range of 0.01 < z < 2.3, which we call the Pantheon Sample. When combining Planck 2015 cosmic microwave background (CMB) measurements with the Pantheon SN sample, we find Omega(m) = 0.307 +/- 0.012 and w = -1.026 +/- 0.041 for the wCDM model. When the SN and CMB constraints are combined with constraints from BAO and local H-0 measurements, the analysis yields the most precise measurement of dark energy to date: w(0) = -1.007 +/- 0.089 and w(a) = -0.222 +/- 0.407 for the w(0)w(a) CDM model. Tension with a cosmological constant previously seen in an analysis of PS1 and low-z SNe has diminished after an increase of 2x in the statistics of the PS1 sample, improved calibration and photometry, and stricter light-curve quality cuts. We find that the systematic uncertainties in our measurements of dark energy are almost as large as the statistical uncertainties, primarily due to limitations of modeling the low-redshift sample. This must be addressed for future progress in using SNe Ia to measure dark energy.
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| 8. |
- Gezari, S., et al.
(författare)
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GALEX and Pan-STARRS1 Discovery of SN IIP 2010aq : The First Few Days After Shock Breakout in a Red Supergiant Star
- 2010
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 720, s. L77-L81
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Tidskriftsartikel (refereegranskat)abstract
- We present the early UV and optical light curve of Type IIP supernova (SN) 2010aq at z = 0.0862, and compare it to analytical models for thermal emission following SN shock breakout in a red supergiant star. SN 2010aq was discovered in joint monitoring between the Galaxy Evolution Explorer (GALEX) Time Domain Survey (TDS) in the NUV and the Pan-STARRS1 Medium Deep Survey (PS1 MDS) in the g, r, i, and z bands. The GALEX and Pan-STARRS1 observations detect the SN less than 1 day after the shock breakout, measure a diluted blackbody temperature of 31, 000 ± 6000 K 1 day later, and follow the rise in the UV/optical light curve over the next 2 days caused by the expansion and cooling of the SN ejecta. The high signal-to-noise ratio of the simultaneous UV and optical photometry allows us to fit for a progenitor star radius of 700 ± 200R sun, the size of a red supergiant star. An excess in UV emission two weeks after shock breakout compared with SNe well fitted by model atmosphere-code synthetic spectra with solar metallicity is best explained by suppressed line blanketing due to a lower metallicity progenitor star in SN 2010aq. Continued monitoring of PS1 MDS fields by the GALEX TDS will increase the sample of early UV detections of Type II SNe by an order of magnitude and probe the diversity of SN progenitor star properties.
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| 9. |
- Cowperthwaite, P. S., et al.
(författare)
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An Empirical Study of Contamination in Deep, Rapid, and Wide-field Optical Follow-up of Gravitational Wave Events
- 2018
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 858:1
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Tidskriftsartikel (refereegranskat)abstract
- We present an empirical study of contamination in wide-field optical follow-up searches of gravitational wave sources from Advanced LIGO/Virgo using dedicated observations with the Dark Energy Camera. Our search covered similar to 56 deg(2), with two visits per night, in the i and z bands, followed by an additional set of griz images three weeks later to serve as reference images for subtraction. We achieve 5 sigma point-source limiting magnitudes of i approximate to 23.5 and z approximate to 22.4 mag in the coadded single-epoch images. We conduct a search for transient objects that mimic the i - z color behavior of both red (i-z > 0.5 mag) and blue (i-z < 0 mag) kilonova emission, finding 11 and 10 contaminants, respectively. Independent of color, we identify 48 transients of interest. Additionally, we leverage the rapid cadence of our observations to search for sources with characteristic timescales of approximate to 1 day and approximate to 3 hr, finding no potential contaminants. We assess the efficiency of our search with injected point sources, finding that we are 90% (60%) efficient when searching for red (blue) kilonova-like sources to a limiting magnitude of i less than or similar to 22.5 mag. Using our efficiencies, we derive sky rates for kilonova contaminants of R-red approximate to 0.16 deg(-2) and R-blue approximate to 0.80 deg(-2). The total contamination rate is R-all approximate to 1.79 deg(-2). We compare our results to previous optical follow-up efforts and comment on the outlook for gravitational wave follow-up searches as additional detectors (e.g., KAGRA, LIGO India) come online in the next decade.
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| 10. |
- Foley, R. J., et al.
(författare)
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Spectroscopy of High-Redshift Supernovae from the Essence Project : The First Four Years
- 2009
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 137, s. 3731-3742
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of spectroscopic observations from the ESSENCE high-redshift supernova (SN) survey during its first four years of operation. This sample includes spectra of all SNe Ia whose light curves were presented by Miknaitis et al. and used in the cosmological analyses of Davis et al. and Wood-Vasey et al. The sample represents 273 hr of spectroscopic observations with 6.5-10 m class telescopes of objects detected and selected for spectroscopy by the ESSENCE team. We present 184 spectra of 156 objects. Combining this sample with that of Matheson et al., we have a total sample of 329 spectra of 274 objects. From this, we are able to spectroscopically classify 118 Type Ia SNe. As the survey has matured, the efficiency of classifying SNe Ia has remained constant while we have observed both higher-redshift SNe Ia and SNe Ia farther from maximum brightness. Examining the subsample of SNe Ia with host-galaxy redshifts shows that redshifts derived from only the SN Ia spectra are consistent with redshifts found from host-galaxy spectra. Moreover, the phases derived from only the SN Ia spectra are consistent with those derived from light-curve fits. By comparing our spectra to local templates, we find that the rate of objects similar to the overluminous SN 1991T and the underluminous SN 1991bg in our sample are consistent with that of the local sample. We do note, however, that we detect no object spectroscopically or photometrically similar to SN 1991bg. Although systematic effects could reduce the high-redshift rate we expect based on the low-redshift surveys, it is possible that SN 1991bg-like SNe Ia are less prevalent at high redshift.
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