SN 2016gkg is a nearby SN IIb discovered shortly after explosion. Like several other Type IIb events with early-time data, SN 2016gkg displays a double-peaked light curve, with the first peak ...associated with the cooling of a low-mass extended progenitor envelope. We present unprecedented intranight-cadence multi-band photometric coverage of the first light curve peak of SN 2016gkg obtained from the Las Cumbres Observatory Global Telescope network, the Asteroid Terrestrial-impact Last Alert System, the Swift satellite, and various amateur-operated telescopes. Fitting these data to analytical shock-cooling models gives a progenitor radius of ∼40-150 with ∼2-40 × 10−2 of material in the extended envelope (depending on the model and the assumed host-galaxy extinction). Our radius estimates are broadly consistent with values derived independently (in other works) from HST imaging of the progenitor star. However, the shock-cooling model radii are on the lower end of the values indicated by pre-explosion imaging. Hydrodynamical simulations could refine the progenitor parameters deduced from the shock-cooling emission and test the analytical models.
The ASAS-SN bright supernova catalogue – II. 2015 Holoien, T. W.-S; Brown, J. S; Stanek, K. Z ...
Monthly notices of the Royal Astronomical Society,
05/2017, Letnik:
467, Številka:
1
Journal Article
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Abstract
This manuscript presents information for all supernovae discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN) during 2015, its second full year of operations. The same ...information is presented for bright (mV ≤ 17), spectroscopically confirmed supernovae discovered by other sources in 2015. As with the first ASAS-SN bright supernova catalogue, we also present redshifts and near-ultraviolet through infrared magnitudes for all supernova host galaxies in both samples. Combined with our previous catalogue, this work comprises a complete catalogue of 455 supernovae from multiple professional and amateur sources, allowing for population studies that were previously impossible. This is the second of a series of yearly papers on bright supernovae and their hosts from the ASAS-SN team.
Abstract
We analyze the MOA-2020-BLG-208 gravitational microlensing event and present the discovery and characterization of a new planet, MOA-2020-BLG-208Lb, with an estimated sub-Saturn mass. With a ...mass ratio
q
=
3.17
−
0.26
+
0.28
×
10
−
4
, the planet lies near the peak of the mass-ratio function derived by the MOA collaboration and near the edge of expected sample sensitivity. For these estimates we provide results using two mass-law priors: one assuming that all stars have an equal planet-hosting probability, and the other assuming that planets are more likely to orbit around more massive stars. In the first scenario, we estimate that the lens system is likely to be a planet of mass
m
planet
=
46
−
24
+
42
M
⊕
and a host star of mass
M
host
=
0.43
−
0.23
+
0.39
M
⊙
, located at a distance
D
L
=
7.49
−
1.13
+
0.99
kpc
. For the second scenario, we estimate
m
planet
=
69
−
34
+
37
M
⊕
,
M
host
=
0.66
−
0.32
+
0.35
M
⊙
, and
D
L
=
7.81
−
0.93
+
0.93
kpc
. The planet has a projected separation as a fraction of the Einstein ring radius
s
=
1.3807
−
0.0018
+
0.0018
. As a cool sub-Saturn-mass planet, this planet adds to a growing collection of evidence for revised planetary formation models.
We report the discovery of a planetary system from observation of the high-magnification microlensing event OGLE-2012-BLG-0026. The lensing light curve exhibits a complex central perturbation with ...multiple features. We find that the perturbation was produced by two planets located near the Einstein ring of the planet host star. We identify four possible solutions resulting from the well-known close/wide degeneracy. By measuring both the lens parallax and the Einstein radius, we estimate the physical parameters of the planetary system. According to the best-fit model, the two planet masses are ~0.11 M sub(J) and 0.68 M sub(J) and they are orbiting a G-type main-sequence star with a mass ~0.82 M sub(middot in circle). The projected separations of the individual planets are beyond the snow line in all four solutions, being ~3.8 AU and 4.6 AU in the best-fit solution. The deprojected separations are both individually larger and possibly reversed in order. This is the second multi-planet system with both planets beyond the snow line discovered by microlensing. This is the only such system (other than the solar system) with measured planet masses without sin i degeneracy. The planetary system is located at a distance 4.1 kpc from the Earth toward the Galactic center. It is very likely that extra light from stars other than the lensed star comes from the lens itself. If this is correct, it will be possible to obtain detailed information about the planet host star from follow-up observation.
We present basic statistics for all supernovae discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN) during its first year-and-a-half of operations, spanning 2013 and 2014. We also ...present the same information for all other bright (mV less than or equal to 17), spectroscopically confirmed supernovae discovered from 2014 May 1 through the end of 2014, providing a comparison to the ASAS-SN sample starting from the point where ASAS-SN became operational in both hemispheres. In addition, we present collected redshifts and near-UV through IR magnitudes, where available, for all host galaxies of the bright supernovae in both samples. This work represents a comprehensive catalogue of bright supernovae and their hosts from multiple professional and amateur sources, allowing for population studies that were not previously possible because the all-sky emphasis of ASAS-SN redresses many previously existing biases. In particular, ASAS-SN systematically finds bright supernovae closer to the centres of host galaxies than either other professional surveys or amateurs, a remarkable result given ASAS-SN's poorer angular resolution. This is the first of a series of yearly papers on bright supernovae and their hosts that will be released by the ASAS-SN team.
We present a photometric and spectroscopic study of a reddened type Ic supernova (SN) 2005at. We report our results based on the available data of SN 2005at, including late-time observations from the ...Spitzer Space Telescope and the Hubble Space Telescope. In particular, late-time mid-infrared observations are something rare for type Ib/c SNe. In our study we find SN 2005at to be very similar photometrically and spectroscopically to another nearby type Ic SN 2007gr, underlining the prototypical nature of this well-followed type Ic event. The spectroscopy of both events shows similar narrow spectral line features. The radio observations of SN 2005at are consistent with fast evolution and low luminosity at radio wavelengths. The late-time Spitzer data suggest the presence of an unresolved light echo from interstellar dust and dust formation in the ejecta, both of which are unique observations for a type Ic SN. The late-time Hubble observations reveal a faint point source coincident with SN 2005at, which is very likely either a declining light echo of the SN or a compact cluster. For completeness we study ground-based pre-explosion archival images of the explosion site of SN 2005at, however this only yielded very shallow upper limits for the SN progenitor star. We derive a host galaxy extinction of AV ≈ 1.9 mag for SN 2005at, which is relatively high for a SN in a normal spiral galaxy not viewed edge-on.
We report the detection of sub-Saturn-mass planet MOA-2008-BLG-310Lb and argue that it is the strongest candidate yet for a bulge planet. Deviations from the single-lens fit are smoothed out by ...finite-source effects and therefore are not immediately apparent from the light curve. Nevertheless, we find that a model in which the primary has a planetary companion is favored over the single-lens model by DELTAchi{sup 2} {approx} 880 for an additional 3 degrees of freedom. Detailed analysis yields a planet/star mass ratio q = (3.3 +- 0.3) x 10{sup -4} and an angular separation between the planet and star within 10% of the angular Einstein radius. The small angular Einstein radius, theta{sub E} = 0.155 +- 0.011 mas, constrains the distance to the lens to be D{sub L} >6.0 kpc if it is a star (M{sub L} >0.08 M{sub sun}). This is the only microlensing exoplanet host discovered so far that must be in the bulge if it is a star. By analyzing VLT NACO adaptive optics images taken near the baseline of the event, we detect additional blended light that is aligned to within 130 mas of the lensed source. This light is plausibly from the lens, but could also be due to a companion to the lens or source, or possibly an unassociated star. If the blended light is indeed due to the lens, we can estimate the mass of the lens, M{sub L} = 0.67 +- 0.14 M{sub sun}, planet mass m = 74 +- 17 M{sub +}, and projected separation between the planet and host, 1.25 +- 0.10 AU, putting it right on the 'snow line'. If not, then the planet has lower mass, is closer to its host and is colder. To distinguish among these possibilities on reasonable timescales would require obtaining Hubble Space Telescope images almost immediately, before the source-lens relative motion of mu= 5 mas yr{sup -1} causes them to separate substantially.
Social, genetic and reproductive consequences of natal dispersal were investigated in female horses,Equus caballus, living in a herd with a natural social structure. Dispersal did not as a rule ...reduce the level of competition the young mares faced: they did not selectively join groups with fewer resident females than the groups they left, and they did not attain higher ranks; there was also no tendency for females to disperse to groups with the fewest resident females, and they suffered more aggression from the mares in their new groups than in their natal groups. These results therefore do not support the hypothesis that a function of natal dispersal is to reduce intra-sexual competition. The young mares nevertheless dispersed non-randomly, generally joining harems with one stallion and at least two subadult females; and they preferred to move to groups with familiar females but no familiar males. As a result, most were closely related to some females of their new groups, but distantly related or unrelated to the male(s). Since after dispersal the young mares bred only with a male of their new groups, inbreeding coefficients of most (85%) of their offspring were lower than from matings between half siblings. These results are consistent with the hypothesis that a function of natal dispersal is to avoid close inbreeding. Dispersal did not appear to involve reproductive costs: the young mares suffered no delay in age at first reproduction, and the survival rates of their first foals tended to be higher if the females had emigrated, although not significantly so.
We report on the time-resolved optical CCD photometry of newly discovered SU UMa-type dwarf novae, FL TrA and CTCVJ0549
$-$
4921. During a 2006 August outburst, we detected superhumps with a period ...of 0.59897(11) days for FL TrA, clarifying the SU UMa nature of the system. On the first night of our observations of FL TrA, the object showed no superhumps. This implies that it takes a few days for the full development of superhumps. The superhump period variation diagram of FL TrA was similar to that observed in some WZ Sge stars and short-period SU UMa-type stars. This indicates that the system is closely related to WZ Sge stars and SU UMa stars having short orbital periods. For CTCV J0549
$-$
4921, the candidates of the mean superhump period are 0.083249(10) days and 0.084257(8) days, respectively. Due to a lack of observations, we cannot determine the true superhump period, but the latter period is favorable. Using the ASAS-3 archive, it turned out that the system showed only four outbursts over the past 6 years. The outburst amplitude of CTCV J0549
$-$
4921 was relatively small, with about 4.5 mag. One possibility is that mass evaporation may play a role during quiescence.
Variations in birth sex ratios and sex differences in juvenile mortality occur in a number of mammalian species, and in many cases have been linked to resource availability. Most of these biases in ...offspring sex ratios concern polygynous species with pronounced sexual dimorphism, and where females only are philopatric. Data on species with unusual life-history strategies, such as slight sexual dimorphism or dispersal by both sexes, are of particular interest. In this study of a natural herd of horses (Equus caballus) which experienced an eruptive cycle, and therefore a period of nutritional stress, male offspring had higher neonatal mortality rates in nutritionally poor years than in good ones, whereas "year quality" had no effect on the mortality of female offspring; year quality could therefore be used by mares as predictor of sex-specific offspring survival. We show that the environmental conditions that predicted lower survival of males were negatively related to their production: the birth sex ratio the following year was female-biased; and mares were less likely to produce a son when they had produced a son the preceding year. There was no significant effect of mother's parity, age or rank, or the timing of conception or birth on offspring sex ratios. The mechanism leading to biases in the birth sex ratio could have been the loss of male embryos by mares that did not foal. As there was no evidence for selective abortion of male foetuses in females that did foal the next year, it is not necessary to invoke maternal adjustment, though this remains a possibility. Finally, there was a suggestion that male offspring were more costly to raise than females, since mothers that reared a son in poor years tended to experience an increase in the interbirth interval between their two subsequent offspring.
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