We present griz sub(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 PSI 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 super(+0.360) sub(-0.206)(Stat) super(+0.269) sub(-0.291)(Sys). When combined with BAO+CMB(Planck)+H sub(0), the analysis yields Omega sub(M) = 0.280 super(0.013) sub(-0.012) and w = 1.166 super(+0.072) sub(-0.069) including all identified systematics. The value of w is inconsistent with the cosmological constant value of -1 at the 2.3sigma level. Tension endures after removing either the baryon acoustic oscillation (BAO) or the H sub(0) constraint, though it is strongest when including the H sub(0) constraint. If we include WMAP9 cosmic microwave background (CMB) constraints instead of those from Planck, we find w = -1.124 super(+0.083) sub(-0.065) which diminishes the discord to <2sigma. We cannot conclude whether the tension with flat ACDM 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.
Abstract
We present multiwavelength time-series spectroscopy of SN 2013aa and SN 2017cbv, two Type Ia supernovae (SNe Ia) on the outskirts of the same host galaxy, NGC 5643. This work utilizes new ...nebular-phase near-infrared (NIR) spectra obtained by the Carnegie Supernova Project-II, in addition to previously published optical and NIR spectra. Using nebular-phase Fe
ii
lines in the optical and NIR, we examine the explosion kinematics and test the efficacy of several common emission-line-fitting techniques. The NIR Fe
ii
1.644
μ
m line provides the most robust velocity measurements against variations due to the choice of the fit method and line blending. The resulting effects on velocity measurements due to choosing different fit methods, initial fit parameters, continuum and line profile functions, and fit region boundaries were also investigated. The NIR Fe
ii
velocities yield the same radial shift direction as velocities measured using the optical Fe
ii
λ
7155 line, but the sizes of the shifts are consistently and substantially lower, pointing to a potential issue in optical studies. The NIR Fe
ii
1.644
μ
m emission profile shows a lack of significant asymmetry in both SNe, and the observed low velocities elevate the importance for correcting for any velocity contribution from the host galaxy’s rotation. The low Fe
ii
velocities measured in the NIR at nebular phases disfavor progenitor scenarios in close double-degenerate systems for both SN 2013aa and SN 2017cbv. The time evolution of the NIR Fe
ii
1.644
μ
m line also indicates moderately high progenitor white dwarf central density and potentially high magnetic fields.
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.
Double-peaked oxygen lines in the nebular spectra of two peculiar Type Ib/c supernovae (SNe Ib/c) have been interpreted as off-axis views of a GRB jet or unipolar blob ejections. Here we present ...late-time spectra of eight SNe IIb, Ib, and Ic and show that this phenomenon is common and should not be so firmly linked to extraordinary explosion physics. The line profiles are most likely caused by ejecta expanding with a torus- or disk-like geometry. Double-peaked oxygen profiles are not necessarily the indicator of a misdirected GRB jet.
The Pan-STARRS1 (PS1) survey has obtained imaging in five bands (griz yP1) over 10 Medium Deep Survey (MDS) fields covering a total of 70 square degrees. This paper describes the search for ...apparently hostless supernovae (SNe) within the first year of PS1 MDS data with an aim of discovering superluminous supernovae (SLSNe). A total of 249 hostless transients were discovered down to a limiting magnitude of ... ~ 23.5, of which 76 were classified as Type Ia supernovae (SNe Ia). There were 57 SNe with complete light curves that are likely core-collapse SNe (CCSNe) or type Ic SLSNe and 12 of these have had spectra taken. Of these 12 hostless, non-Type Ia SNe, 7 were SLSNe of type Ic at redshifts between 0.5 and 1.4. This illustrates that the discovery rate of type Ic SLSNe can be maximized by concentrating on hostless transients and removing normal SNe Ia. We present data for two possible SLSNe; PS1-10pm (z = 1.206) and PS1-10ahf (z = 1.1), and estimate the rate of type Ic SLSNe to be ... that of the CCSN rate within 0.3 = z = 1.4 by applying a Monte Carlo technique. The rate of slowly evolving, type Ic SLSNe (such as SN2007bi) is estimated as a factor of 10 lower than this range. (ProQuest: ... denotes formulae/symbols omitted.)
The broad-lined Type Ic supernova 2003jd Valenti, S.; Benetti, S.; Cappellaro, E. ...
Monthly notices of the Royal Astronomical Society,
February 2008, Letnik:
383, Številka:
4
Journal Article
Recenzirano
Odprti dostop
The results of a worldwide coordinated observational campaign on the broad-lined Type Ic supernova (SN Ic) 2003jd are presented. In total, 74 photometric data points and 26 spectra were collected ...using 11 different telescopes. SN 2003jd is one of the most luminous SN Ic ever observed. A comparison with other Type Ic supernovae (SNe Ic) confirms that SN 2003jd represents an intermediate case between broad-line events (2002ap, 2006aj) and highly energetic SNe (1997ef, 1998bw, 2003dh, 2003lw), with an ejected mass of Mej= 3.0 ± 1 M⊙ and a kinetic energy of Ek(tot) = 7+3−2× 1051erg. SN 2003jd is similar to SN 1998bw in terms of overall luminosity, but it is closer to SNe 2006aj and 2002ap in terms of light-curve shape and spectral evolution. The comparison with other SNe Ic suggests that the V-band light curves of SNe Ic can be partially homogenized by introducing a time-stretch factor. Finally, because of the similarity of SN 2003jd to the SN 2006aj/XRF 060218 event, we discuss the possible connection of SN 2003jd with a gamma-ray burst (GRB).
When a massive star explodes as a supernova, substantial amounts of radioactive elements-primarily Ni-56, Ni-57 and Ti-44 are produced. After the initial from shock heating, the light emitted by the ...supernova is due to the decay of these elements. However, after decades, the energy powering a supernova remnant comes from the shock interaction between the ejecta and the surrounding medium. The transition to this phase has hitherto not been observed: supernovae occur too infrequently in the Milky Way to provide a young example, and extragalactic supernovae are generally too faint and too small. Here we report observations that show this transition in the supernova SN 1987A in the Large Magellan Cloud. From 1994 to 200l, the ejecta faded owing to radioactive decay of Ti-44 as predicted. Then the flux started to increase, more than doubling by the end of 2009. We show that this increase is the result of heat deposited by X-rays produced as the ejecta interacts with the surrounding material. In time, the X-rays will penetrate farther into the ejects, enabling us to analyse the structure and chemistry of the vanished star.
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. Four epochs of spectroscopy reveal a pair of transient broad absorption features in the UV on otherwise featureless spectra. 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. 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. 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.
We present extensive multi-wavelength observations of the extremely rapidly declining Type Ic supernova (SN Ic), SN 2005ek. Reaching a peak magnitude of M sub(R) = -17.3 and decaying by ~3 mag in the ...first 15 days post-maximum, SN 2005ek is among the fastest Type I supernovae observed to date. The spectra of SN 2005ek closely resemble those of normal SN Ic, but with an accelerated evolution. There is evidence for the onset of nebular features at only nine days post-maximum. Spectroscopic modeling reveals an ejecta mass of ~0.3 M sub(middot in circle) that is dominated by oxygen (~80%), while the pseudo-bolometric light curve is consistent with an explosion powered by ~0.03 M sub(middot in circle) of radioactive super(56)Ni. Although previous rapidly evolving events (e.g., SN 1885A, SN 1939B, SN 2002bj, SN 2010X) were hypothesized to be produced by the detonation of a helium shell on a white dwarf, oxygen-dominated ejecta are difficult to reconcile with this proposed mechanism. We find that the properties of SN 2005ek are consistent with either the edge-lit double detonation of a low-mass white dwarf or the iron-core collapse of a massive star, stripped by binary interaction. However, if we assume that the strong spectroscopic similarity of SN 2005ek to other SNe Ic is an indication of a similar progenitor channel, then a white-dwarf progenitor becomes very improbable. SN 2005ek may be one of the lowest mass stripped-envelope core-collapse explosions ever observed. We find that the rate of such rapidly declining Type I events is at least 1%-3% of the normal SN Ia rate.
We present observations of the Type Ia supernovae (SNe) 1999M, 1999N, 1999Q, 1999S, and 1999U, at redshift z - 0.5. They were discovered in early 1999 with the 4.0 m Blanco telescope at Cerro Tololo ...Inter-American Observatory by the High-z Supernova Search Team (HZT) and subsequently followed with many ground-based telescopes. SNe 1999Q and 1999U were also observed with the Hubble Space Telescope. We computed luminosity distances to the new SNe using two methods and added them to the high-z Hubble diagram that the HZT has been constructing since 1995. The new distance moduli confirm the results of previous work. At z - 0.5, luminosity distances are larger than those expected for an empty universe, implying that a "cosmological constant", or another form of "dark energy", has been increasing the expansion rate of the universe during the last few billion years. Combining these new HZT SNe Ia with our previous results and assuming a CDM cosmology, we estimate the cosmological parameters that best fit our measurements. For a sample of 75 low-redshift and 47 high-redshift SNe Ia with MLCS2k2 (Jha and coworkers) luminosity calibration we obtain sub(M)= 0.79 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(1) sub(1) super(5) sub(8) and sub( )= 1.57 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(2) sub(3) super(4) sub(2) (1 s uncertainties) if no constraints are imposed, or sub(M)= 0.29 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(0) sub(0) super(6) sub(05) if sub(M) + sub( )= 1 is assumed. For a different sample of 58 low-redshift and 48 high-redshift SNe Ia with luminosity calibrations done using the PRES method (a generalization of the m sub(15) method), the results are sub(M) = 0.43 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(1) sub(1) super(7) sub(9) and sub( )=1.18 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(2) sub(2) super(7) sub(8) (1 s uncertainties) if no constraints are imposed, or sub(M)= 0.18 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(0) sub(0) super(5) sub(4) if sub(M) + sub( )= 1 is assumed.
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