We present the ATLAS discovery and initial analysis of the first 18 days of the unusual transient event, ATLAS18qqn/AT2018cow. It is characterized by a high peak luminosity (∼1.7 × 1044 erg s−1), ...rapidly evolving light curves (>5 mag rise to peak in ∼3.5 days), and hot blackbody spectra, peaking at ∼27,000 K that are relatively featureless and unchanging over the first two weeks. The bolometric light curve cannot be powered by radioactive decay under realistic assumptions. The detection of high-energy emission may suggest a central engine as the powering source. Using a magnetar model, we estimated an ejected mass of 0.1-0.4 M , which lies between that of low-energy core-collapse events and the kilonova, AT2017gfo. The spectra cooled rapidly from 27,000 to 15,000 K in just over two weeks but remained smooth and featureless. Broad and shallow emission lines appear after about 20 days, and we tentatively identify them as He i although they would be redshifted from their rest wavelengths. We rule out that there are any features in the spectra due to intermediate mass elements up to and including the Fe group. The presence of r-process elements cannot be ruled out. If these lines are due to He, then we suggest a low-mass star with residual He as a potential progenitor. Alternatively, models of magnetars formed in neutron star mergers, or accretion onto a central compact object, give plausible matches to the data.
We present here the c-o colors for identified Flora, Vesta, Nysa-Polana, Themis, and Koronis family members within the historic data set (2015-2018) of the Asteroid Terrestrial-impact Last Alert ...System (ATLAS). The Themis and Koronis families are known to be relatively pure C- and S-type Bus-DeMeo taxonomic families, respectively, and the extracted color data from the ATLAS broadband c- and o-filters of these two families are used to demonstrate that the ATLAS c-o color is a sufficient parameter to distinguish between the C- and S-type taxonomies. The Vesta and Nysa-Polana families are known to display a mixture of taxonomies possibly due to Vesta's differentiated parent body origin and Nysa-Polana actually consisting of two nested families with differing taxonomies. Our data show that the Flora family also displays a large degree of taxonomic mixing and the data reveal a substantial H-magnitude dependence on color. We propose and exclude several interpretations for the observed taxonomic mix. Additionally, we extract rotation periods of all of the targets reported here and find good agreement with targets that have previously reported periods.
ABSTRACT
We present observations and analysis of 18 stripped-envelope supernovae observed during 2013–2018. This sample consists of five H/He-rich SNe, six H-poor/He-rich SNe, three narrow lined SNe ...Ic, and four broad lined SNe Ic. The peak luminosity and characteristic time-scales of the bolometric light curves are calculated, and the light curves modelled to derive 56Ni and ejecta masses (MNi and Mej). Additionally, the temperature evolution and spectral line velocity curves of each SN are examined. Analysis of the O i line in the nebular phase of eight SNe suggests their progenitors had initial masses <20 M⊙. The bolometric light curve properties are examined in combination with those of other SE events from the literature. The resulting data set gives the Mej distribution for 80 SE–SNe, the largest such sample in the literature to date, and shows that SNe Ib have the lowest median Mej, followed by narrow-lined SNe Ic, H/He-rich SNe, broad-lined SNe Ic, and finally gamma-ray burst SNe. SNe Ic-6/7 show the largest spread of Mej ranging from ∼1.2–11 M⊙, considerably greater than any other subtype. For all SE–SNe = 2.8 ± 1.5 M⊙ which further strengthens the evidence that SE–SNe arise from low-mass progenitors which are typically <5 M⊙ at the time of explosion, again suggesting MZAMS <25 M⊙. The low and lack of clear bimodality in the distribution implies <30 M⊙ progenitors and that envelope stripping via binary interaction is the dominant evolutionary pathway of these SNe.
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.
We probe the systematic uncertainties from the 113 Type Ia supernovae (SN Ia) in the Pan-STARRS1 (PS1) sample along with 197 SN Ia from a combination of low-redshift surveys. The companion paper by ...Rest et al. describes the photometric measurements and cosmological inferences from the PS1 sample. The largest systematic uncertainty stems from the photometric calibration of the PSI and low-z samples. We increase the sample of observed Calspec standards from 7 to 10 used to define the PS1 calibration system. The PS1 and SDSS-II calibration systems are compared and discrepancies up to ~0.02 mag are recovered. We find uncertainties in the proper way to treat intrinsic colors and reddening produce differences in the recovered value of w up to 3%. We estimate masses of host galaxies of PS1 supernovae and detect an insignificant difference in distance residuals of the full sample of 0.037 + or - 0.031 mag for host galaxies with high and low masses. Assuming flatness and including systematic uncertainties in our analysis of only SNe measurements, we find w =-1.120 super(+0.360) sub(-0.206) (Stat) super(-0.291) (Sys). With additional constraints from Baryon acoustic oscillation, cosmic microwave background (CMB) (Planck) and H sub(0) measurements, we find w = super(- 1.166) super(0.069) and Omegam = 0.280 super(+0.013) super(-0.012) (statistical and systematic errors added in quadrature). The significance of the inconsistency with w = -1 depends on whether we use Planck or Wilkinson Microwave Anisotropy Probe measurements of the CMB: w sub(BAO+H0+SN+WMAP) = -1.124 super(+0.083) sub(-0.065).
The Thousand Asteroid Light Curve Survey Masiero, Joseph; Jedicke, Robert; Ďurech, Josef ...
Icarus (New York, N.Y. 1962),
11/2009, Letnik:
204, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We present the results of our Thousand Asteroid Light Curve Survey (TALCS) conducted with the Canada–France–Hawaii Telescope in September 2006. Our untargeted survey detected 828 Main Belt asteroids ...to a limiting magnitude of
g
′
∼
22.5
corresponding to a diameter range of 0.4
km
⩽
D
⩽
10
km
. Of these, 278 objects had photometry of sufficient quality to perform rotation period fits. We debiased the observations and light curve fitting process to determine the true distribution of rotation periods and light curve amplitudes of Main Belt asteroids. We confirm a previously reported excess in the fraction of fast rotators but find a much larger excess of slow rotating asteroids (∼15% of our sample). A few percent of objects in the TALCS size range have large light curve amplitudes of ∼1 mag. Fits to the debiased distribution of light curve amplitudes indicate that the distribution of triaxial ellipsoid asteroid shapes is proportional to the square of the axis ratio,
(
b
/
a
)
2
, and may be bi-modal. Finally, we find six objects with rotation periods that may be less than 2
h with diameters between 400
m and 1.5
km, well above the break-up limit for a gravitationally-bound aggregate. Our debiased data indicate that this population represents <4% of the Main Belt in the 1–10
km size range.
Using a large optically selected sample of field and group galaxies drawn from the Pan-STARRS1 Medium-Deep Survey (PS1/MDS), we present a detailed analysis of the specific star formation rate ...(SSFR)-stellar mass (M sub(*)) relation, as well as the quiescent fraction versus M sub(*) relation in different environments. Using this large galaxy sample, we confirm that the fraction of quiescent galaxies is strongly dependent on environment at a fixed stellar mass, but that the amplitude and the slope of the star-forming sequence is similar between the field and groups: in other words, the SSFR-density relation at a fixed stellar mass is primarily driven by the change in the star-forming and quiescent fractions between different environments rather than a global suppression in the star formation rate for the star-forming population.
Corrigendum Smith, K. W.; Smartt, S. J.; Young, D. R. ...
Publications of the Astronomical Society of the Pacific,
02/2021, Letnik:
133, Številka:
1020
Journal Article
Recenzirano
In Smith et al. we published estimates of the volumetric rate of supernovae within 100 Mpc. These were incorrect and we present the correct values in this corrigendum.
ATLAS Tonry, J. L.; Denneau, L.; Heinze, A. N. ...
Publications of the Astronomical Society of the Pacific,
06/2018, Letnik:
130, Številka:
988
Journal Article
Recenzirano
Technology has advanced to the point that it is possible to image the entire sky every night and process the data in real time. The sky is hardly static: many interesting phenomena occur, including ...variable stationary objects such as stars or QSOs, transient stationary objects such as supernovae or M dwarf flares, and moving objects such as asteroids and the stars themselves. Funded by NASA, we have designed and built a sky survey system for the purpose of finding dangerous near-Earth asteroids (NEAs). This system, the “Asteroid Terrestrial-impact Last Alert System” (ATLAS), has been optimized to produce the best survey capability per unit cost, and therefore is an efficient and competitive system for finding potentially hazardous asteroids (PHAs) but also for tracking variables and finding transients. While carrying out its NASA mission, ATLAS now discovers more bright (m < 19) supernovae candidates than any ground based survey, frequently detecting very young explosions due to its 2 day cadence. ATLAS discovered the afterglow of a gamma-ray burst independent of the high energy trigger and has released a variable star catalog of 5 × 10⁶ sources. This is the first of a series of articles describing ATLAS, devoted to the design and performance of the ATLAS system. Subsequent articles will describe in more detail the software, the survey strategy, ATLAS-derived NEA population statistics, transient detections, and the first data release of variable stars and transient light curves.
ABSTRACT In this work, we report the detection of seven Neptune Trojans (NTs) in the Pan-STARRS 1 (PS1) survey. Five of these are new discoveries, consisting of four L4 Trojans and one L5 Trojan. Our ...orbital simulations show that the L5 Trojan stably librates for only several million years. This suggests that the L5 Trojan must be of recent capture origin. On the other hand, all four new L4 Trojans stably occupy the 1:1 resonance with Neptune for more than 1 Gyr. They can, therefore, be of primordial origin. Our survey simulation results show that the inclination width of the NT population should be between 7° and 27° at >95% confidence, and most likely ∼11°. In this paper, we describe the PS1 survey, the Outer Solar System pipeline, the confirming observations, and the orbital/physical properties of the new NTs.
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