| 51. |
- Askebjer, P., et al.
(författare)
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UV and optical light transmission properties in deep ice at the South Pole
- 1997
-
Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 24:11, s. 1355-1358
-
Tidskriftsartikel (refereegranskat)abstract
- Both absorption and scattering of light at wavelengths 410 to 610 nanometers were measured in the South Pole ice at depths 0.8 to 1 kilometer with the laser calibration system of the Antarctic Muon And Neutrino Detector Array (AMANDA). At the shortest wavelengths the absorption lengths exceeded 200 meters - an order of magnitude longer than has been reported for laboratory ice. The absorption shows a strong wavelength dependence while the scattering length is found to be independent of the wavelength, consistent with the hypothesis of a residual density of air bubbles in the ice. The observed linear decrease of the inverse scattering length with depth is compatible with an earlier measurement by the AMANDA collaboration (at ∼515 nanometers).
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| 52. |
- Astier, P., et al.
(författare)
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Extending the supernova Hubble diagram to z similar to 1.5 with the Euclid space mission
- 2014
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 572, s. A80-
-
Tidskriftsartikel (refereegranskat)abstract
- We forecast dark energy constraints that could be obtained from a new large sample of Type Ia supernovae where those at high redshift are acquired with the Euclid space mission. We simulate a three-prong SN survey: a z < 0.35 nearby sample (8000 SNe), a 0.2 < z < 0.95 intermediate sample (8800 SNe), and a 0.75 < z < 1.55 high-z sample (1700 SNe). The nearby and intermediate surveys are assumed to be conducted from the ground, while the high-z is a joint ground-and space-based survey. This latter survey, the Dark Energy Supernova Infra-Red Experiment (DESIRE), is designed to fit within 6 months of Euclid observing time, with a dedicated observing programme. We simulate the SN events as they would be observed in rolling-search mode by the various instruments, and derive the quality of expected cosmological constraints. We account for known systematic uncertainties, in particular calibration uncertainties including their contribution through the training of the supernova model used to fit the supernovae light curves. Using conservative assumptions and a 1D geometric Planck prior, we find that the ensemble of surveys would yield competitive constraints: a constant equation of state parameter can be constrained to sigma(omega) = 0.022, and a Dark Energy Task Force figure of merit of 203 is found for a two-parameter equation of state. Our simulations thus indicate that Euclid can bring a significant contribution to a purely geometrical cosmology constraint by extending a high-quality SN Ia Hubble diagram to z similar to 1.5. We also present other science topics enabled by the DESIRE Euclid observations.
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| 53. |
- Barbary, K., et al.
(författare)
-
Discovery of an Unusual Optical Transient with the Hubble Space Telescope
- 2009
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 690, s. 1358-1362
-
Tidskriftsartikel (refereegranskat)abstract
- We present observations of SCP 06F6, an unusual optical transient discovered during the Hubble Space Telescope Cluster Supernova Survey. The transient brightened over a period of ~100 days, reached a peak magnitude of ~ 21.0 in both i 775 and z 850, and then declined over a similar timescale. There is no host galaxy or progenitor star detected at the location of the transient to a 3σ upper limit of i 775 >= 26.4 and z 850 >= 26.1, giving a corresponding lower limit on the flux increase of a factor of ~ 120. Multiple spectra show five broad absorption bands between 4100 Å and 6500 Å, and a mostly featureless continuum longward of 6500 Å. The shape of the light curve is inconsistent with microlensing. The transient's spectrum, in addition to being inconsistent with all known supernova types, does not match any spectrum in the Sloan Digital Sky Survey database. We suggest that the transient may be one of a new class. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute (STScI). STScI is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under the NASA contract NAS 5-26555. The observations are associated with program GO-10496. Based in part on observations obtained at the European Southern Observatory under ESO program 077.A-0110. Based in part on observations collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA.
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| 54. |
- Bergstrom, L., et al.
(författare)
-
The AMANDA experiment : Status and prospects for indirect dark matter detection
- 1996
-
Ingår i: The identification of dark matter. Proceedings, 1st International Workshop, Sheffield, UK, September 8-12, 1996. ; , s. 521-528
-
Konferensbidrag (refereegranskat)abstract
- At the AMANDA South Pole site, four new holes were drilled to depths 2050m to 2180 m and instrumented with 86 photomultipliers (PMTs) at depths1520-2000 m. Of these PMTs 79 are working, with 4-ns timing resolutionand noise rates 300 to 600 Hz. Various diagnostic devices were deployedand are working. An observed factor 60 increase in scattering length anda sharpening of the distribution of arrival times of laser pulses relative tomeasurements at 800-1000 m showed that bubbles are absent below 1500 m.Absorption lengths are 100 to 150 m at wavelengths in the blue and UV to337 nm. Muon coincidences are seen between the SPASE air shower arrayand the AMANDA PMTs at 800-1000 m and 1500-1900 m. The muon trackrate is 30 Hz for 8-fold triggers and 10 Hz for 10-fold triggers. The presentarray is the nucleus for a future expanded array. The potential of AMANDAfor SUSY dark matter search through the detection of high-energy neutrinosfrom the centre of the Sun or Earth is discussed.
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| 55. |
- Hulth, P. O., et al.
(författare)
-
The AMANDA experiment
- 1996
-
Ingår i: Neutrino '96. Proceedings, 17th International Conference on Neutrino Physics and Astrophysics, Helsinki, Finland, June 13-19, 1996. ; , s. 518-523
-
Konferensbidrag (refereegranskat)abstract
- At the AMANDA South Pole site, four new holes were drilled to depths 2050 m to 2180 m and instrumented with 86 photomultipliers (PMTs) at depths 1520-2000 m. Of these PMTs 79 are working, with 4-ns timing resolution and noise rates 300 to 600 Hz. Various diagnostic devices were deployed and are working. An observed factor 60 increase in scattering length and a sharpening of the distribution of arrival times of laser pulses relative to measurements at 800-1000 m showed that bubbles are absent below 1500 m. Absorption lengths are 100 to 150 m at wavelengths in the blue and UV to 337 nm. Muon coincidences are seen between the SPASE air shower array and the AMANDA PMTs at 800-1000 m and 1500-1900 m. The muon track rate is 30 Hz for 8-fold triggers and 10 Hz for 10-fold triggers. The present array is the nucleus for a future expanded array.
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| 56. |
- Johansson, Joel, et al.
(författare)
-
Spectroscopy of the first resolved strongly lensed Type Ia supernova iPTF16geu
- 2021
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 502:1, s. 510-520
-
Tidskriftsartikel (refereegranskat)abstract
- We report the results from spectroscopic observations of the multiple images of the strongly lensed Type Ia supernova (SN Ia), iPTF16geu, obtained with ground-based telescopes and the Hubble Space Telescope (HST). From a single epoch of slitless spectroscopy with HST, we resolve spectra of individual lensed supernova images for the first time. This allows us to perform an independent measurement of the time-delay between the two brightest images, Delta t = 1.4 +/- 5.0 d, which is consistent with the time-delay measured from the light curves. We also present measurements of narrow emission and absorption lines characterizing the interstellar medium in the SN Ia host galaxy at z = 0.4087, as well as in the foreground lensing galaxy at z = 0.2163. We detect strong Naid absorption in the host galaxy, indicating that iPTF16geu belongs to a subclass of SNe Ia displaying 'anomalously' large Naid column densities compared to dust extinction derived from light curves. For the lens galaxy, we refine the measurement of the velocity dispersion, sigma = 129 +/- 4 kms(-1), which significantly constrains the lens model. We use ground-based spectroscopy, boosted by a factor similar to 70 from lensing magnification, to study the properties of a high-z SN Ia with unprecedented signal-to-noise ratio. The spectral properties of the supernova, such as pseudo-Equivalent widths of several absorption features and velocities of the Si II-line, indicate that iPTF16geu is a normal SN Ia. We do not detect any significant deviations of the SN spectral energy distribution from microlensing of the SN photosphere by stars and compact objects in the lensing galaxy.
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| 57. |
- Kasliwal, Mansi M., et al.
(författare)
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Kilonova Luminosity Function Constraints Based on Zwicky Transient Facility Searches for 13 Neutron Star Merger Triggers during O3
- 2020
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 905:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present a systematic search for optical counterparts to 13 gravitational wave (GW) triggers involving at least one neutron star during LIGO/Virgo's third observing run (O3). We searched binary neutron star (BNS) and neutron star black hole (NSBH) merger localizations with the Zwicky Transient Facility (ZTF) and undertook follow-up with the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration. The GW triggers had a median localization area of 4480 deg(2), a median distance of 267 Mpc, and false-alarm rates ranging from 1.5 to 10(-25) yr(-1). The ZTF coverage in the g and r bands had a median enclosed probability of 39%, median depth of 20.8 mag, and median time lag between merger and the start of observations of 1.5 hr. The O3 follow-up by the GROWTH team comprised 340 UltraViolet/Optical/InfraRed (UVOIR) photometric points, 64 OIR spectra, and three radio images using 17 different telescopes. We find no promising kilonovae (radioactivity-powered counterparts), and we show how to convert the upper limits to constrain the underlying kilonova luminosity function. Initially, we assume that all GW triggers are bona fide astrophysical events regardless of false-alarm rate and that kilonovae accompanying BNS and NSBH mergers are drawn from a common population; later, we relax these assumptions. Assuming that all kilonovae are at least as luminous as the discovery magnitude of GW170817 (-16.1 mag), we calculate that our joint probability of detecting zero kilonovae is only 4.2%. If we assume that all kilonovae are brighter than -16.6 mag (the extrapolated peak magnitude of GW170817) and fade at a rate of 1 mag day(-1) (similar to GW170817), the joint probability of zero detections is 7%. If we separate the NSBH and BNS populations based on the online classifications, the joint probability of zero detections, assuming all kilonovae are brighter than -16.6 mag, is 9.7% for NSBH and 7.9% for BNS mergers. Moreover, no more than <57% (<89%) of putative kilonovae could be brighter than -16.6 mag assuming flat evolution (fading by 1 mag day(-1)) at the 90% confidence level. If we further take into account the online terrestrial probability for each GW trigger, we find that no more than <68% of putative kilonovae could be brighter than -16.6 mag. Comparing to model grids, we find that some kilonovae must have M-ej M, X-lan > 10(-4), or > 30 degrees to be consistent with our limits. We look forward to searches in the fourth GW observing run; even 17 neutron star mergers with only 50% coverage to a depth of -16 mag would constrain the maximum fraction of bright kilonovae to <25%.
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| 58. |
- Kromer, Markus, et al.
(författare)
-
The peculiar Type Ia supernova iPTF14atg : Chandrasekhar-mass explosion or violent merger?
- 2016
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 459:4, s. 4428-4439
-
Tidskriftsartikel (refereegranskat)abstract
- iPTF14atg, a subluminous peculiar Type Ia supernova (SN Ia) similar to SN 2002es, is the first SN Ia for which a strong UV flash was observed in the early-time light curves. This has been interpreted as evidence for a single-degenerate (SD) progenitor system, where such a signal is expected from interactions between the SN ejecta and the non-degenerate companion star. Here, we compare synthetic observables of multidimensional state-of-the-art explosion models for different progenitor scenarios to the light curves and spectra of iPTF14atg. From our models, we have difficulties explaining the spectral evolution of iPTF14atg within the SD progenitor channel. In contrast, we find that a violent merger of two carbon-oxygen white dwarfs with 0.9 and 0.76 M-aS (TM), respectively, provides an excellent match to the spectral evolution of iPTF14atg from 10 d before to several weeks after maximum light. Our merger model does not naturally explain the initial UV flash of iPTF14atg. We discuss several possibilities like interactions of the SN ejecta with the circumstellar medium and surface radioactivity from an He-ignited merger that may be able to account for the early UV emission in violent merger models.
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| 59. |
- Malyali, A., et al.
(författare)
-
AT 2019avd : a novel addition to the diverse population of nuclear transients
- 2021
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 647
-
Tidskriftsartikel (refereegranskat)abstract
- We report on SRG/eROSITA, ZTF, ASAS-SN, Las Cumbres, NEOWISE-R, and Swift XRT/UVOT observations of the unique ongoing event AT 2019avd, located in the nucleus of a previously inactive galaxy at z = 0.029. eROSITA first observed AT 2019avd on 2020-04-28 during its first all sky survey, when it was detected as an ultra-soft X-ray source (kT ~ 85 eV) that was ≳90 times brighter in the 0.2−2 keV band than a previous 3σ upper flux detection limit (with no archival X-ray detection at this position). The ZTF optical light curve in the ~450 days preceding the eROSITA detection is double peaked, and the eROSITA detection coincides with the rise of the second peak. Follow-up optical spectroscopy shows the emergence of a Bowen fluorescence feature and high-ionisation coronal lines ([Fe X] 6375 Å, [Fe XIV] 5303 Å), along with persistent broad Balmer emission lines (FWHM ~ 1400 km s−1). Whilst the X-ray properties make AT 2019avd a promising tidal disruption event (TDE) candidate, the optical properties are atypical for optically selected TDEs. We discuss potential alternative origins that could explain the observed properties of AT 2019avd, such as a stellar binary TDE candidate, or a TDE involving a super massive black hole binary.
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| 60. |
- Mazzali, P. A., et al.
(författare)
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High-Velocity Features : A Ubiquitous Property of Type Ia Supernovae
- 2005
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 623, s. L37-L40
-
Tidskriftsartikel (refereegranskat)abstract
- Evidence of high-velocity features (HVFs) such as those seen in the near-maximum spectra of some Type Ia supernovae (SNe Ia; e.g., SN 2000cx) has been searched for in the available SN Ia spectra observed earlier than 1 week before B maximum. Recent observational efforts have doubled the number of SNe Ia with very early spectra. Remarkably, all SNe Ia with early data (seven in our Research Training Network sample and 10 from other programs) show signs of such features, to a greater or lesser degree, in Ca II IR and some also in the Si II λ6355 line. HVFs may be interpreted as abundance or density enhancements. Abundance enhancements would imply an outer region dominated by Si and Ca. Density enhancements may result from the sweeping up of circumstellar material (CSM) by the highest velocity SN ejecta. In this scenario, the high incidence of HVFs suggests that a thick disk and/or a high-density companion wind surrounds the exploding white dwarf, as may be the case in single degenerate systems. Large-scale angular fluctuations in the radial density and abundance distribution may also be responsible: this could originate in the explosion and would suggest a deflagration as the more likely explosion mechanism. CSM interaction and surface fluctuations may coexist, possibly leaving different signatures on the spectrum. In some SNe, the HVFs are narrowly confined in velocity, suggesting the ejection of blobs of burned material.
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| 61. |
- Miller, A. A., et al.
(författare)
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Color Me Intrigued : The Discovery of iPTF 16fnm, an SN 2002cx-like Object
- 2017
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 848:1
-
Tidskriftsartikel (refereegranskat)abstract
- 0 Modern wide-field, optical time-domain surveys must solve a basic optimization problem: maximize the number of transient discoveries or minimize the follow-up needed for the new discoveries. Here, we describe the Color Me Intrigued experiment, the first from the intermediate Palomar Transient Factory (iPTF) to search for transients simultaneously in the g(PTF') and R-PTF bands. During the course of this experiment, we discovered iPTF 16fnm, a new member of the 02cx-like subclass of Type Ia supernovae (SNe). iPTF 16fnm peaked at Mg-PTF = -15.09 +/- 0.17 mag, making it the second-least-luminous known SN Ia. iPTF 16fnm exhibits all the hallmarks of the 02cx-like class: (i) low luminosity at peak, (ii) low ejecta velocities, and (iii) a non-nebular spectrum several months after peak. Spectroscopically, iPTF 16fnm exhibits a striking resemblance to two other low-luminosity 02cx-like SNe: SN. 2007qd and SN 2010ae. iPTF 16fnm and SN 2005hk decline at nearly the same rate, despite a 3 mag difference in brightness at peak. When considering the full subclass of 02cx-like SNe, we do not find evidence for a tight correlation between peak luminosity and decline rate in either the g ' or r ' band. We measure the relative rate of 02cx-like SNe to normal SNe Ia and find r(N02cx/NIa) = 33(-25)(+158)%. We further examine the g ' - r ' evolution of 02cx-like SNe and find that their unique color evolution can be used to separate them from 91bg-like and normal SNe Ia. This selection function will be especially important in the spectroscopically incomplete Zwicky Transient Facility/Large Synoptic Survey Telescope (LSST) era. Finally, we close by recommending that LSST periodically evaluate, and possibly update, its observing cadence to maximize transient science.
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| 62. |
- Nordin, J., et al.
(författare)
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Lensed Type Ia supernovae as probes of cluster mass models
- 2014
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 440:3, s. 2742-2754
-
Tidskriftsartikel (refereegranskat)abstract
- Using three magnified Type Ia supernovae (SNe Ia) detected behind CLASH (Cluster Lensing and Supernovae with Hubble) clusters, we perform a first pilot study to see whether standardizable candles can be used to calibrate cluster mass maps created from strong lensing observations. Such calibrations will be crucial when next-generation Hubble Space Telescope cluster surveys (e.g. Frontier) provide magnification maps that will, in turn, form the basis for the exploration of the high-redshift Universe. We classify SNe using combined photometric and spectroscopic observations, finding two of the three to be clearly of Type Ia and the third probable. The SNe exhibit significant amplification, up to a factor of 1.7 at similar to 5 Sigma significance (SN-L2). We conducted this as a blind study to avoid fine-tuning of parameters, finding a mean amplification difference between SNe and the cluster lensing models of 0.09 +/- 0.09(stat) +/- 0.05(sys) mag. This impressive agreement suggests no tension between cluster mass models and high-redshift-standardized SNe Ia. However, the measured statistical dispersion of Sigma(mu) = 0.21 mag appeared large compared to the dispersion expected based on statistical uncertainties (0.14). Further work with the SN and cluster lensing models, post-unblinding, reduced the measured dispersion to Sigma(mu) = 0.12. An explicit choice should thus be made as to whether SNe are used unblinded to improve the model, or blinded to test the model. As the lensed SN samples grow larger, this technique will allow improved constraints on assumptions regarding e.g. the structure of the dark matter halo.
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| 63. |
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| 64. |
- Perley, Daniel A., et al.
(författare)
-
The fast, luminous ultraviolet transient AT2018cow : extreme supernova, or disruption of a star by an intermediate-mass black hole?
- 2019
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 484:1, s. 1031-1049
-
Tidskriftsartikel (refereegranskat)abstract
- Wide-field optical surveys have begun to uncover large samples of fast (t(rise) less than or similar to 5 d), luminous (M-peak < 18), blue transients. While commonly attributed to the breakout of a supernova shock into a dense wind, the great distances to the transients of this class found so far have hampered detailed investigation of their properties. We present photometry and spectroscopy from a comprehensive worldwide campaign to observe AT 2018cow (ATLAS 18qqn), the first fast-luminous optical transient to be found in real time at low redshift. Our first spectra (<2 days after discovery) are entirely featureless. A very broad absorption feature suggestive of near-relativistic velocities develops between 3 and 8 days, then disappears. Broad emission features of H and He develop after >10 days. The spectrum remains extremely hot throughout its evolution, and the photospheric radius contracts with time (receding below R < 10 (14) cm after 1 month). This behaviour does not match that of any known supernova, although a relativistic jet within a fallback supernova could explain some of the observed features. Alternatively, the transient could originate from the disruption of a star by an intermediate-mass black hole, although this would require long-lasting emission of highly super-Eddington thermal radiation. In either case, AT 2018cow suggests that the population of fast luminous transients represents a new class of astrophysical event. Intensive follow-up of this event in its late phases, and of any future events found at comparable distance, will be essential to better constrain their origins.
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| 65. |
- Perley, Daniel A., et al.
(författare)
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The Zwicky Transient Facility Bright Transient Survey. II. A Public Statistical Sample for Exploring Supernova Demographics
- 2020
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 904:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present a public catalog of transients from the Zwicky Transient Facility (ZTF) Bright Transient Survey, a magnitude-limited (m g or r filter) survey for extragalactic transients in the ZTF public stream. We introduce cuts on survey coverage, sky visibility around peak light, and other properties unconnected to the nature of the transient, and show that the resulting statistical sample is spectroscopically 97% complete at <18 mag, 93% complete at <18.5 mag, and 75% complete at <19 mag. We summarize the fundamental properties of this population, identifying distinct duration-luminosity correlations in a variety of supernova (SN) classes and associating the majority of fast optical transients with well-established spectroscopic SN types (primarily SN Ibn and II/IIb). We measure the Type Ia SN and core-collapse (CC) SN rates and luminosity functions, which show good consistency with recent work. About 7% of CC SNe explode in very low-luminosity galaxies (M-i > -16 mag), 10% in red-sequence galaxies, and 1% in massive ellipticals. We find no significant difference in the luminosity or color distributions between the host galaxies of SNe Type II and SNe Type Ib/c, suggesting that line-driven wind stripping does not play a major role in the loss of the hydrogen envelope from their progenitors. Future large-scale classification efforts with ZTF and other wide-area surveys will provide high-quality measurements of the rates, properties, and environments of all known types of optical transients and limits on the existence of theoretically predicted but as yet unobserved explosions.
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| 66. |
- Phillips, M. M., et al.
(författare)
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Carnegie Supernova Project-II : Extending the Near-infrared Hubble Diagram for Type Ia Supernovae to z ∼ 0.1
- 2019
-
Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:995
-
Tidskriftsartikel (refereegranskat)abstract
- The Carnegie Supernova Project-II (CSP-II) was an NSF-funded, four-year program to obtain optical and near-infrared observations of a Cosmology sample of similar to 100 Type. Ia supernovae located in the smooth Hubble flow (0.03 less than or similar to z less than or similar to 0.10). Light curves were also obtained of a Physics sample composed of 90 nearby Type. Ia supernovae at z <= 0.04 selected for near-infrared spectroscopic timeseries observations. The primary emphasis of the CSP-II is to use the combination of optical and near-infrared photometry to achieve a distance precision of better than 5%. In this paper, details of the supernova sample, the observational strategy, and the characteristics of the photometric data are provided. In a companion paper, the near-infrared spectroscopy component of the project is presented.
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| 67. |
- Savage, C., et al.
(författare)
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Turning the tables : When the student teaches the professional - A case description of an innovative teaching approach as told by the students
- 2011
-
Ingår i: Nurse Education Today. - : Elsevier BV. - 0260-6917 .- 1532-2793. ; 31:8, s. 803-808
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Is it possible to increase the value, meaningfulness, and relevance of a course experience by integrating it with the healthcare context? Students and teachers from a course on organization, learning and leadership sought to explore this possibility through a collaborative effort with nurses from an affiliated teaching hospital. Methods: Working as teachers, students created continuing nursing education (CNE) courses using the Adaptive Reflection process. The students and teachers then researched the experience in terms of: 1) content analysis of student self-reflections (discussion notes and logbooks) on the learning process, 2) a student self-assessed outcome achievement survey, and 3) perceived relevance of the CNE courses by the clinical nurse educators. Results: Thirteen nursing students created three CNE courses together with sixteen nurses. Each course consisted of multiple 20-minute long web-based modules with automatic formative feedback. In the process, students exceeded course outcome-levels, journeyed from chaos to confidence and experienced new ways of viewing the group and their own capabilities. Conclusions: The innovative design of the course moved the focus from student-centered learning to learning by contributing to health care. Working in a real world context, the content of the students' efforts and the skills they developed not only met course requirements, but were also aligned with the needs of the wards. This contribution was valued by the students and the RNs which enhanced students' feelings of self-confidence. Further research lies in testing the model in other contexts.
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| 68. |
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| 69. |
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| 70. |
- Abdurahman, S, et al.
(författare)
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Selected amino acid substitutions in the C-terminal region of human immunodeficiency virus type 1 capsid protein affect virus assembly and release
- 2004
-
Ingår i: The Journal of general virology. - : Microbiology Society. - 0022-1317 .- 1465-2099. ; 85:Pt 10, s. 2903-2913
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Tidskriftsartikel (refereegranskat)abstract
- The capsid protein (CA or p24) of human immunodeficiency virus type 1 (HIV-1) plays a major role both early and late in the virus replication cycle. Many studies have suggested that the C-terminal domain of this protein is involved in dimerization and proper assembly of the viral core. Point mutations were introduced in two conserved sites of this region and their effects on viral protein expression, particle assembly and infectivity were studied. Eight different mutants (L205A+P207A, L205A, P207A, 223GPG225AAA, G223A, P224A, G225A and V221G) of the infectious clone pNL4-3 were constructed. Most substitutions had no substantial effect on HIV-1 protein synthesis, yet they impaired viral infectivity and particle production. The two mutants P207A and V221G also had a profound effect on Gag–Pol protein processing in HeLa–tat cells. However, these results were cell line-specific and Gag–Pol processing of P207A was not affected in 293T cells. In HeLa–tat cells, no virus particles were detected with the P207A mutation, whereas the other mutant virus particles were heterogeneous in size and morphology. None of the mutants showed normal, mature, conical core structures in HeLa–tat cells. These results indicate that the two conserved sequences in the C-terminal CA domain are essential for proper morphogenesis and infectivity of HIV-1 particles.
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| 71. |
- Altavilla, G., et al.
(författare)
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The early spectral evolution of SN2004dt
- 2007
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 475:2, s. 585-595
-
Tidskriftsartikel (refereegranskat)abstract
- Aims. We study the optical spectroscopic properties of Type Ia Supernova (SNIa) 2004dt, focusing our attention on the early epochs. Methods. Observation triggered soon after the SN 2004dt discovery allowed us to obtain a spectrophotometric coverage from day -10 to almost one year (similar to 353 days) after the B band maximum. Observations carried out on an almost daily basis allowed us a good sampling of the fast spectroscopic evolution of SN 2004dt in the early stages. To obtain this result, low-resolution, long-slit spectroscopy was obtained using a number of facilities. Results. This supernova, which in some absorption lines of its early spectra showed the highest degree of polarization ever measured in any SN Ia, has a complex velocity structure in the outer layers of its ejecta. Unburnt oxygen is present, moving at velocities as high as similar to 16 700 km s(-1), with some intermediate-mass elements (Mg, Si, Ca) moving equally fast. Modeling of the spectra based on standard density profiles of the ejecta fails to reproduce the observed features, whereas enhancing the density of outer layers significantly improves the fit. Our analysis indicates the presence of clumps of high-velocity, intermediate-mass elements in the outermost layers, which is also suggested by the spectropolarimetric data.
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| 72. |
- Andreoni, Igor, et al.
(författare)
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Constraining the Kilonova Rate with Zwicky Transient Facility Searches Independent of Gravitational Wave and Short Gamma-Ray Burst Triggers
- 2020
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 904:2
-
Tidskriftsartikel (refereegranskat)abstract
- The first binary neutron star merger, GW170817, was accompanied by a radioactivity-powered optical/infrared transient called a kilonova. To date, no compelling kilonova has been found in all-sky optical surveys, independently of short gamma-ray burst and gravitational-wave triggers. In this work, we searched the first 23 months of the Zwicky Transient Facility (ZTF) data stream for candidate kilonovae in the form of rapidly evolving transients. We combined ZTF alert queries with forced point-spread-function photometry and nightly flux stacking to increase our sensitivity to faint and fast transients. Automatic queries yielded >11,200 candidates, 24 of which passed quality checks and selection criteria based on a grid of kilonova models tailored for both binary neutron star and neutron star-black hole mergers. None of the candidates in our sample was deemed a possible kilonova after thorough vetting. The sources that passed our selection criteria are dominated by Galactic cataclysmic variables. We identified two fast transients at high Galactic latitude, one of which is the confirmed afterglow of long-duration GRB.190106A, the other is a possible cosmological afterglow. Using a survey simulation code, we constrained the kilonova rate for a range of models including top-hat, linearly decaying light curves, and synthetic light curves obtained with radiative transfer simulations. For prototypical GW170817-like kilonovae, we constrain the rate to be R < 1775 Gpc(-3) yr(-1) (95% confidence). By assuming a population of kilonovae with the same geometry and composition of GW170817 observed under a uniform viewing angle distribution, we obtained a constraint on the rate of R.<.4029 Gpc(-3) yr(-1).
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| 73. |
- Andreoni, Igor, et al.
(författare)
-
GROWTH on S190814bv : Deep Synoptic Limits on the Optical/Near-infrared Counterpart to a Neutron Star-Black Hole Merger
- 2020
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 890:2
-
Tidskriftsartikel (refereegranskat)abstract
- On 2019 August 14, the Advanced LIGO and Virgo interferometers detected the high-significance gravitational wave (GW) signal S190814bv. The GW data indicated that the event resulted from a neutron star-black hole (NSBH) merger, or potentially a low-mass binary BH merger. Due to the low false-alarm rate and the precise localization (23 deg(2) at 90%), S190814bv presented the community with the best opportunity yet to directly observe an optical/near-infrared counterpart to an NSBH merger. To search for potential counterparts, the GROWTH Collaboration performed real-time image subtraction on six nights of public Dark Energy Camera images acquired in the 3 weeks following the merger, covering >98% of the localization probability. Using a worldwide network of follow-up facilities, we systematically undertook spectroscopy and imaging of optical counterpart candidates. Combining these data with a photometric redshift catalog, we ruled out each candidate as the counterpart to S190814bv and placed deep, uniform limits on the optical emission associated with S190814bv. For the nearest consistent GW distance, radiative transfer simulations of NSBH mergers constrain the ejecta mass of S190814bv to be M-ej < 0.04 M-circle dot at polar viewing angles, or M-ej < 0.03 M-circle dot if the opacity is kappa < 2 cm(2)g(-1). Assuming a tidal deformability for the NS at the high end of the range compatible with GW170817 results, our limits would constrain the BH spin component aligned with the orbital momentum to be chi < 0.7 for mass ratios Q < 6, with weaker constraints for more compact NSs.
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| 74. |
- ASKEBJER, P, et al.
(författare)
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AMANDA - STATUS-REPORT FROM THE 1993-94 CAMPAIGN AND OPTICAL-PROPERTIES OF THE SOUTH-POLE ICE
- 1995
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Ingår i: NUCLEAR PHYSICS B. - : ELSEVIER SCIENCE BV. - 0550-3213. ; , s. 287-292
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We report the first results of the AMANDA detector. During the antarctic summer 1993-94 four strings were deployed between 0.8 an 1 km depth, each equipped with 20 photomultiplier tubes (PMTs). A laser source was used to investigate the optical properties
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| 75. |
- Askebjer, P, et al.
(författare)
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Optical properties of deep ice at the South Pole: Absorption
- 1997
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Ingår i: APPLIED OPTICS. - : OPTICAL SOC AMER. - 0003-6935. ; 36:18, s. 4168-4180
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We discuss recent measurements of the wavelength-dependent absorption coefficients in deep South Pole ice. The method uses transit-time distributions of pulses from a variable-frequency laser sent between emitters and receivers embedded in the ice. At dep
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| 76. |
- ASKEBJER, P, et al.
(författare)
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OPTICAL-PROPERTIES OF THE SOUTH-POLE ICE AT DEPTHS BETWEEN 0.8 AND 1 KILOMETER
- 1995
-
Ingår i: SCIENCE. - : AMER ASSOC ADVAN SCIENCE. - 0036-8075. ; 267:5201, s. 1147-1150
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The optical properties of the ice at the geographical South Pole have been investigated at depths between 0.8 and 1 kilometer. The absorption and scattering lengths of visible light (similar to 515 nanometers) have been measured in situ with the use of th
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| 77. |
- Askebjer, P, et al.
(författare)
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UV and optical light transmission properties in deep ice at the South Pole
- 1997
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Ingår i: GEOPHYSICAL RESEARCH LETTERS. - : AMER GEOPHYSICAL UNION. - 0094-8276. ; 24:11, s. 1355-1358
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Both absorption and scattering of light at wavelengths 410 to 610 nanometers were measured in tile South Pole ice at depths 0.8 to 1 kilometer with the laser calibration system of the Antarctic Muon And Neutrino Detector Array (AMANDA). At the shortest wa
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| 78. |
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| 79. |
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| 80. |
- Cao, Yi, et al.
(författare)
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A strong ultraviolet pulse from a newborn type Ia supernova
- 2015
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 521:7552, s. 328-
-
Tidskriftsartikel (refereegranskat)abstract
- Type Ia supernovae(1) are destructive explosions of carbon-oxygen white dwarfs(2,3). Although they are used empirically to measure cosmological distances(4-6), the nature of their progenitors remains mysterious(3). One of the leading progenitor models, called the single degenerate channel, hypothesizes that a white dwarf accretes matter from a companion star and the resulting increase in its central pressure and temperature ignites thermonuclear explosion(3,7,8). Here we report observations with the Swift Space Telescope of strong but declining ultraviolet emission from a type Ia supernova within four days of its explosion. This emission is consistent with theoretical expectations of collision between material ejected by the supernova and a companion star(9), and therefore provides evidence that some type Ia supernovae arise from the single degenerate channel.
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| 81. |
- Cao, Yi, et al.
(författare)
-
ABSENCE OF FAST-MOVING IRON IN AN INTERMEDIATE TYPE Ia SUPERNOVA BETWEEN NORMAL AND SUPER-CHANDRASEKHAR
- 2016
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 823:2
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we report observations of a peculiar SN Ia iPTF13asv (a.k.a., SN2013cv) from the onset of the explosion to months after its peak. The early-phase spectra of iPTF13asv show an absence of iron absorption, indicating that synthesized iron elements are confined to low-velocity regions of the ejecta, which, in turn, implies a stratified ejecta structure along the line of sight. Our analysis of iPTF13asv's light curves and spectra shows that it is an intermediate case between normal and super-Chandrasekhar events. On the one hand, its light curve shape (B-band Delta m(15)=1.03 +/- 0.01) and overall spectral features resemble those of normal SNe Ia. On the other hand, its large peak optical and UV luminosity (M-B = -19.84 mag, M-uvm2 = -15.5 mag) and its low but almost constant Si II velocities of about 10,000 km s (1) are similar to those in super-Chandrasekhar events, and its persistent carbon signatures in the spectra are weaker than those seen commonly in super-Chandrasekhar events. We estimate a Ni-56 mass of 0.81(-0.18)(+0.10) M-circle dot and a total ejecta mass of 1.59(-0.12)(+0.45) M-circle dot. The large ejecta mass of iPTF13asv and its stratified ejecta structure together seemingly favor a double-degenerate origin.
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| 82. |
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| 83. |
- Coughlin, Michael W., et al.
(författare)
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GROWTH on S190425z : Searching Thousands of Square Degrees to Identify an Optical or Infrared Counterpart to a Binary Neutron Star Merger with the Zwicky Transient Facility and Palomar Gattini-IR
- 2019
-
Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 885:1
-
Tidskriftsartikel (refereegranskat)abstract
- The third observing run by LVC has brought the discovery of many compact binary coalescences. Following the detection of the first binary neutron star merger in this run (LIGO/Virgo S190425z), we performed a dedicated follow-up campaign with the Zwicky Transient Facility (ZTF) and Palomar Gattini-IR telescopes. The initial skymap of this single-detector gravitational wave (GW) trigger spanned most of the sky observable from Palomar Observatory. Covering 8000 deg(2) of the initial skymap over the next two nights, corresponding to 46% integrated probability, ZTF system achieved a depth of 21 m(AB) in g- and r-bands. Palomar Gattini-IR covered 2200 square degrees in J-band to a depth of 15.5 mag, including 32% integrated probability based on the initial skymap. The revised skymap issued the following day reduced these numbers to 21% for the ZTF and 19% for Palomar Gattini-IR. We narrowed 338,646 ZTF transient ?alerts? over the first two nights of observations to 15 candidate counterparts. Two candidates, ZTF19aarykkb and ZTF19aarzaod, were particularly compelling given that their location, distance, and age were consistent with the GW event, and their early optical light curves were photometrically consistent with that of kilonovae. These two candidates were spectroscopically classified as young core-collapse supernovae. The remaining candidates were ruled out as supernovae. Palomar Gattini-IR did not identify any viable candidates with multiple detections only after merger time. We demonstrate that even with single-detector GW events localized to thousands of square degrees, systematic kilonova discovery is feasible.
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| 84. |
- Dhawan, Suhail, et al.
(författare)
-
Magnification, dust, and time-delay constraints from the first resolved strongly lensed Type Ia supernova iPTF16geu
- 2020
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 491:2, s. 2639-2654
-
Tidskriftsartikel (refereegranskat)abstract
- We report lensing magnifications, extinction, and time-delay estimates for the first resolved, multiply imaged Type Ia supernova iPTF16geu, at z = 0.409, using Hubble Space Telescope (HST) observations in combination with supporting ground-based data. Multiband photometry of the resolved images provides unique information about the differential dimming due to dust in the lensing galaxy. Using HST and Keck AO reference images taken after the SN faded, we obtain a total lensing magnification for iPTF16geu of mu = 67.8(-2.9)(+2.6), accounting for extinction in the host and lensing galaxy. As expected from the symmetry of the system, we measure very short time-delays for the three fainter images with respect to the brightest one: -0.23 +/- 0.99,-1.43 +/- 0.74, and 1.36 +/- 1.07 d. Interestingly, we find large differences between the magnifications of the four supernova images, even after accounting for uncertainties in the extinction corrections: Delta m(1) = -3.88(-0.06)(+0.07), Delta m(2) = -2.99(-0.08)(+0.09), Delta m(3) = -2.19(-0.15)(+0.14), and Delta m(4) = -2.40(-0.12)(+0.14) mag, discrepant with model predictions suggesting similar image brightnesses. A possible explanation for the large differences is gravitational lensing by substructures, micro- or millilensing, in addition to the large-scale lens causing the image separations. We find that the inferred magnification is insensitive to the assumptions about the dust properties in the host and lens galaxy.
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| 85. |
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| 86. |
- Harris, C. E., et al.
(författare)
-
Don't Blink : Constraining the Circumstellar Environment of the Interacting Type Ia Supernova 2015cp
- 2018
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 868:1
-
Tidskriftsartikel (refereegranskat)abstract
- Despite their cosmological utility, the progenitors of Type Ia supernovae (SNe Ia) are still unknown, with many efforts focused on whether accretion from a nondegenerate companion can grow a carbon-oxygen white dwarf to near the Chandrasekhar mass. The association of SNe Ia resembling SN 1991T (91T-like) with circumstellar interaction may be evidence for this single-degenerate channel. However, the observed circumstellar medium (CSM) in these interacting systems is unlike a stellar wind-of particular interest, it is sometimes detached from the stellar surface, residing at similar to 10(16) cm. A Hubble Space Telescope (HST) program to discover detached CSM around 91T-like SNe Ia successfully discovered interaction nearly two years after explosion in SN 2015cp (Graham et al. 2018). In this work, we present radio and X-ray follow-up observations of SN 2015cp and analyze them in the framework of Harris et al. (2016) to limit the properties of a constant-density CSM shell in this system. Assuming the HST detection took place shortly after the shock crossed the CSM, we constrain the total CSM mass in this system to be <0.5 M-circle dot. This limit is comparable to the CSM mass of supernova PTF11kx, but does not rule out lower masses predicted for recurrent novae. From lessons learned modeling PTF11kx and SN 2015cp, we suggest a strategy for future observations of these events to increase the sample of known interacting SNe Ia.
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| 87. |
- Ho, Anna Y. Q., et al.
(författare)
-
ZTF20aajnksq (AT 2020blt) : A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart
- 2020
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 905:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present ZTF20aajnksq (AT 2020blt), a fast-fading (Delta r = 2.3 mag in Delta t = 1.3 days) red (g - r 0.6 mag) and luminous (M-1626 A = -25.9 mag) optical transient at z = 2.9 discovered by the Zwicky Transient Facility (ZTF). AT 2020blt shares several features in common with afterglows to long-duration gamma-ray bursts (GRBs): (1) an optical light curve well-described by a broken power law with a break at t(j) = 1 d (observer frame); (2) a luminous (L0.3-10 KeV = 10(46) erg s(-1)) X-ray counterpart; and (3) luminous (L-10 GHz = 4 x 10(31) erg s(-1) Hz(-1)) radio emission. However, no GRB was detected in the 0.74 days between the last ZTF nondetection (r > 21.36 mag) and the first ZTF detection (r = 19.60 mag), with an upper limit on the isotropic-equivalent gamma-ray energy release of E-gamma,E-iso < 7 x 10(52) erg. AT 2020blt is thus the third afterglow-like transient discovered without a detected GRB counterpart (after PTF11agg and ZTF19abvizsw) and the second (after ZTF19abvizsw) with a redshift measurement. We conclude that the properties of AT 2020blt are consistent with a classical (initial Lorentz factor Gamma(0) greater than or similar to 100) on-axis GRB that was missed by high-energy satellites. Furthermore, by estimating the rate of transients with light curves similar to that of AT 2020blt in ZTF high-cadence data, we agree with previous results that there is no evidence for an afterglow-like phenomenon that is significantly more common than classical GRBs, such as dirty fireballs. We conclude by discussing the status and future of fast-transient searches in wide-field high-cadence optical surveys.
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| 88. |
- Miller, A. A., et al.
(författare)
-
Early Observations of the Type Ia Supernova iPTF 16abc : A Case of Interaction with Nearby, Unbound Material and/or Strong Ejecta Mixing
- 2018
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 852:2
-
Tidskriftsartikel (refereegranskat)abstract
- Early observations of Type Ia supernovae (SNe Ia) provide a unique probe of their progenitor systems and explosion physics. Here we report the intermediate Palomar Transient Factory (iPTF) discovery of an extraordinarily young SN Ia, iPTF 16abc. By fitting a power law to our early light curve, we infer that first light for the SN, that is, when the SN could have first been detected by our survey, occurred only 0.15 +/-(0.15)(0.07) days before our first detection. In the similar to 24 hr after discovery, iPTF 16abc rose by similar to 2mag, featuring a near-linear rise in flux for. greater than or similar to 3 days. Early spectra show strong C II absorption, which disappears after similar to 7 days. Unlike the extensively observed Type Ia SN 2011fe, the (B - V)(0) colors of iPTF 16abc are blue and nearly constant in the days after explosion. We show that our early observations of iPTF 16abc cannot be explained by either SN shock breakout and the associated, subsequent cooling or the SN ejecta colliding with a stellar companion. Instead, we argue that the early characteristics of iPTF 16abc, including (i) the rapid, near-linear rise, (ii) the nonevolving blue colors, and (iii) the strong C II absorption, are the result of either ejecta interaction with nearby, unbound material or vigorous mixing of radioactive Ni-56 in the SN ejecta, or a combination of the two. In the next few years, dozens of very young normal SNe Ia will be discovered, and observations similar to those presented here will constrain the white dwarf explosion mechanism.
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| 89. |
- Mock, P. C., et al.
(författare)
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Status and capabilities of AMANDA-94
- 1995
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Ingår i: Proceedings, 24th International Conference, Rome, Italy, August 28-September 8, 1995.
-
Konferensbidrag (refereegranskat)
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| 90. |
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| 91. |
- Pearson Johansson, Joel, et al.
(författare)
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Near-infrared Supernova Ia Distances : Host Galaxy Extinction and Mass-step Corrections Revisited
- 2021
-
Ingår i: Astrophysical Journal. - : IOP Publishing Ltd. - 0004-637X .- 1538-4357. ; 923:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present optical and near-infrared (NIR, Y-, J-, H-band) observations of 42 Type Ia supernovae (SNe Ia) discovered by the untargeted intermediate Palomar Transient Factory survey. This new data set covers a broad range of redshifts and host galaxy stellar masses, compared to previous SN Ia efforts in the NIR. We construct a sample, using also literature data at optical and NIR wavelengths, to examine claimed correlations between the host stellar masses and the Hubble diagram residuals. The SN magnitudes are corrected for host galaxy extinction using either a global total-to-selective extinction ratio, R-V = 2.0, for all SNe, or a best-fit R-V for each SN individually. Unlike previous studies that were based on a narrower range in host stellar mass, we do not find evidence for a "mass step," between the color- and stretch-corrected peak J and H magnitudes for galaxies below and above log(M-*/M-circle dot) = 10. However, the mass step remains significant (3 sigma) at optical wavelengths (g, r, i) when using a global R-V, but vanishes when each SN is corrected using their individual best-fit R-V. Our study confirms the benefits of the NIR SN Ia distance estimates, as these are largely exempted from the empirical corrections dominating the systematic uncertainties in the optical.
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| 92. |
- Pérez-García, M. A., et al.
(författare)
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Hubble constant and nuclear equation of state from kilonova spectro-photometric light curves
- 2022
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
-
Tidskriftsartikel (refereegranskat)abstract
- The merger of two compact objects of which at least one is a neutron star is signalled by transient electromagnetic emission in a kilonova (KN). This event is accompanied by gravitational waves and possibly other radiation messengers such as neutrinos or cosmic rays. The electromagnetic emission arises from the radioactive decay of heavy r-process elements synthesized in the material ejected during and after the merger. In this paper we show that the analysis of KNe light curves can provide cosmological distance measurements and constrain the properties of the ejecta. In this respect, MAAT, the new Integral Field Unit in the OSIRIS spectrograph on the 10.4 m Gran Telescopio CANARIAS (GTC), is well suited for the study of KNe by performing absolute spectro-photometry over the entire 3600 − 10 000 Å spectral range. Here, we study the most representative cases regarding the scientific interest of KNe from binary neutron stars, and we evaluate the observational prospects and performance of MAAT on the GTC to do the following: (a) study the impact of the equation of state on the KN light curve, and determine to what extent bounds on neutron star (NS) radii or compactness deriving from KN peak magnitudes can be identified and (b) measure the Hubble constant, H0, with precision improved by up to 40%, when both gravitational wave data and photometric-light curves are used. In this context we discuss how the equation of state, the viewing angle, and the distance affect the precision and estimated value of H0.
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| 93. |
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| 94. |
- Rubin, D., et al.
(författare)
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Looking Beyond Lambda with the Union Supernova Compilation
- 2009
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 695, s. 391-403
-
Tidskriftsartikel (refereegranskat)abstract
- The recent robust and homogeneous analysis of the world's supernova distance-redshift data, together with cosmic microwave background and baryon acoustic oscillation data—provides a powerful tool for constraining cosmological models. Here we examine particular classes of scalar field, modified gravity, and phenomenological models to assess whether they are consistent with observations even when their behavior deviates from the cosmological constant Λ. Some models have tension with the data, while others survive only by approaching the cosmological constant, and a couple are statistically favored over Λ cold dark matter. Dark energy described by two equation-of-state parameters has considerable phase space to avoid Λ and next-generation data will be required to constrain such physics, with the level of complementarity between probes varying with cosmology.
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| 95. |
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| 96. |
- White, Christopher J., et al.
(författare)
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SLOW-SPEED SUPERNOVAE FROM THE PALOMAR TRANSIENT FACTORY : TWO CHANNELS
- 2015
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 799:1
-
Tidskriftsartikel (refereegranskat)abstract
- Since the discovery of the unusual prototype SN 2002cx, the eponymous class of Type I (hydrogen-poor) supernovae with low ejecta speeds has grown to include approximately two dozen members identified from several heterogeneous surveys, in some cases ambiguously. Here we present the results of a systematic study of 1077 Type I supernovae discovered by the Palomar Transient Factory, leading to nine new members of this peculiar class. Moreover, we find there are two distinct subclasses based on their spectroscopic, photometric, and host galaxy properties: SN 2002cx-like supernovae tend to be in later-type or more irregular hosts, have more varied and generally dimmer luminosities, have longer rise times, and lack a Ti II trough when compared to SN 2002es-like supernovae. None of our objects show helium, and we counter a previous claim of two such events. We also find that the occurrence rate of these transients relative to Type Ia supernovae is 5.6(-3.8)(+22) % (90% confidence), lower compared to earlier estimates. Combining our objects with the literature sample, we propose that these subclasses have two distinct physical origins.
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| 97. |
- Williams, S. C., et al.
(författare)
-
See Change : VLT spectroscopy of a sample of high-redshift Type Ia supernova host galaxies
- 2020
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 495:4, s. 3859-3880
-
Tidskriftsartikel (refereegranskat)abstract
- The Supernova Cosmology Project has conducted the 'See Change' programme, aimed at discovering and observing high-redshift (1.13 <= z <= 1.75) Type Ia supernovae (SNe Ia). We used multifilter Hubble Space Telescope (HST) observations of massive galaxy clusters with sufficient cadence to make the observed SN Ia light curves suitable for a cosmological probe of dark energy at z > 0.5. This See Change sample of SNe Ia with multi-colour light curves will be the largest to date at these redshifts. As part of the See Change programme, we obtained ground-based spectroscopy of each discovered transient and/or its host galaxy. Here, we present Very Large Telescope (VCT) spectra of See Change transient host galaxies, deriving their redshifts, and host parameters such as stellar mass and star formation rate. Of the 39 See Change transients/hosts that were observed with the VLT, we successfully determined the redshift for 26, including 15 SNe Ia at z > 0.97. We show that even in passive environments, it is possible to recover secure redshifts for the majority of SN hosts out to z = 1.5. We find that with typical exposure times of 3-4h on an 8-m-class telescope we can recover similar to 75 per cent of SN Ia redshifts in the range of 0.97 < z < 1.5. Furthermore, we show that the combination of HST photometry and VLT spectroscopy is able to provide estimates of host galaxy stellar mass that are sufficiently accurate for use in a mass-step correction in the cosmological analysis.
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| 98. |
- Wischnewski, R, et al.
(författare)
-
The AMANDA Neutrino Detector
- 1999
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Ingår i: NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS. - : ELSEVIER SCIENCE BV. - 0920-5632. ; 75A, s. 412-414
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The first stage of the AMANDA High Energy Neutrino Detector at the South Pole, the 302 PMT array AMANDA-B with an expected effective area for TeV neutrinos of similar to 10(4) m(2), has been taking data since 1997. Progress with calibration, investigation
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| 99. |
- Yao, Yuhan, et al.
(författare)
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ZTF Early Observations of Type Ia Supernovae. I. Properties of the 2018 Sample
- 2019
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 886:2
-
Tidskriftsartikel (refereegranskat)abstract
- Early-time observations of Type Ia supernovae (SNe Ia) are essential to constrain the properties of their progenitors. In this paper, we present high-quality light curves of 127 SNe Ia discovered by the Zwicky Transient Facility (ZTF) in 2018. We describe our method to perform forced point-spread function photometry, which can be applied to other types of extragalactic transients. With a planned cadence of six observations per night (three g + three r), all of the 127 SNe Ia are detected in both g and r bands more than 10 days (in the rest frame) prior to the epoch of g-band maximum light. The redshifts of these objects range from z = 0.0181 to 0.165; the median redshift is 0.074. Among the 127 SNe, 50 are detected at least 14 days prior to maximum light (in the rest frame), with a subset of nine objects being detected more than 17 days before g-band peak. This is the largest sample of young SNe Ia collected to date; it can be used to study the shape and color evolution of the rising light curves in unprecedented detail. We discuss six peculiar events in this sample: one 02cx-like event ZTF18abclfee (SN 2018crl), one Ia-CSM SN ZTF18aaykjei (SN 2018cxk), and four objects with possible super-Chandrasekhar mass progenitors: ZTF18abhpgje (SN 2018eul), ZTF18abdpvnd (SN 2018dvf), ZTF18aawpcel (SN 2018cir), and ZTF18abddmrf (SN 2018dsx).
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| 100. |
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