scholarly journals The determination of the supernovae parameters from their light curves using the machine learning

2021 ◽  
pp. 1-11
Author(s):  
Egor Mikhailovich Urvachev
Keyword(s):  
Machine Learning ◽  
Light Curve ◽  
Learning Algorithm ◽  
Radioactive Decay ◽  
Light Curves ◽  
Radioactive Isotopes ◽  
Curve Model ◽  
Total Light ◽  
The Masses

The paper discusses the application of the machine learning library, CatBoost, to determine the masses of radioactive isotopes from the supernova light curve at a later epochs. The synthetic light curve model used for the demonstration is based on the contribution of the five major radioactive decay chains starting with <sup>56</sup>Ni, <sup>57</sup>Ni, <sup>44</sup>Ti, <sup>22</sup>Na, <sup>60</sup>Co. Separately, we considered sets of random light curves calculated for different isotope masses of both the three dominant chains (<sup>56</sup>Ni, <sup>57</sup>Ni, <sup>44</sup>Ti) and all five. It is shown that the masses of dominant isotopes are determined with acceptable accuracy in both cases, even with the standard settings of the machine learning algorithm. In the second case, the accuracy of determining the masses of the other two isotopes (<sup>22</sup>Na, <sup>60</sup>Co) turns out to be unsatisfactory, probably due to their weak contribution to the total light curve.

scholarly journals New Data on the Eclipsing Binary V1848 Ori and Improved Orbital and Light Curve Solutions

2020 ◽  
Vol 29 (1) ◽  
pp. 72-80 ◽  
Author(s):  
Fatemeh Davoudi ◽  
Atila Poro ◽  
Fahri Alicavus ◽  
Afshin Halavati ◽  
Saeed Doostmohammadi ◽  
...  
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Mass Function ◽  
Light Curves ◽  
Complete Analysis ◽  
Physical Parameters ◽  
Mass Ratio ◽  
Third Body ◽  
Eclipsing Binary

AbstractNew observations of the eclipsing binary system V1848 Ori were carried out using the V filter resulting in a determination of new times of minima and new ephemeris were obtained. We presented the first complete analysis of the system’s orbital period behavior and analysis of O-C diagram done by the GA and MCMC approaches in OCFit code. The O-C diagram demonstrates a sinusoidal trend in the data; this trend suggests a cyclic change caused by the LITE effect with a period of 10.57 years and an amplitude of 7.182 minutes. It appears that there is a third body with mass function of f (m3) = 0.0058 M⊙ in this binary system. The light curves were analyzed using the Wilson-Devinney code to determine some geometrical and physical parameters of the system. These results show that V1848 Ori is a contact W UMa binary system with the mass ratio of q = 0.76 and a weak fillout factor of 5.8%. The O’Connell effect was not seen in the light curve and there is no need to add spot.

scholarly journals Properties of CVSO 30 from TESS measurements: probably a binary T Tauri star with complex light curves and no obvious planets

2020 ◽  
Vol 494 (3) ◽  
pp. 4349-4356
Author(s):  
C Koen
Keyword(s):  
Light Curve ◽  
Small Group ◽  
T Tauri Stars ◽  
Light Curves ◽  
Tauri Star ◽  
Curve Shape ◽  
T Tauri

ABSTRACT ‘Transiting Exoplanet Survey Satellite’ (TESS) photometry of CVSO 30 spanned 21.8 d, with a single large gap of 1.1 d. This allows alias-free determination of the two periodicities in the data. It is confirmed that both of these are non-sinusoidal: the dominant P1 = 0.4990 d has two detectable harmonics and P2 = 0.4486 d has seven. The large number of harmonics in the second periodicity characterizes a very complex light curve shape. One of the features in the light curve is a sharp dip of duration ∼2 h: this is probably the source of the previously claimed planetary transit signature. The star is a member of a small group of T Tauri stars with complex light curves, which have recently been exhaustively studied using Kepler and TESS observations. The two non-commensurate periods are most simply interpreted as being from two stars, i.e. CVSO 30 is probably a binary.

SN 1987A: the Light Curve

1991 ◽  
Vol 9 (1) ◽  
pp. 105-106 ◽  
Author(s):  
Patricia Whitelock ◽  
John Menzies ◽  
John A. R. Caldwell
Keyword(s):  
Light Curve ◽  
Radioactive Decay ◽  
Radioactive Isotopes ◽  
Core Collapse ◽  
Additional Contribution ◽  
Decay Energy ◽  
Sn 1987A ◽  
Total Luminosity ◽  
Light Echoes ◽  
Γ Ray

AbstractThe changing total luminosity of SN 1987A between 2 and 1200 days after core collapse is illustrated and discussed. From about four weeks after outburst the supernova light curve was dominated by the release of radioactive decay energy; the major contributor being 0.078M⊙ of 56Co. Recently an additional contribution probably from the decay of 57Co and 44Ti appears to be manifesting itself in the light curve. A gradually increasing fraction of the radioactive decay energy has probably been emitted at X- and γ-ray wavelengths; the fluxes are low and no recent measurements have been published. Most of the remaining radioactive decay energy appears to be emitted in the IR and is very difficult to measure. Other factors influencing the interpretation of the recent light curve are the uncertain contribution from long-lived radioactive isotopes and light-echoes. It is therefore premature to make any definitive statements on the contribution from the neutron star, although it is probably less than a few times 1037 erg s−1.

scholarly journals Cepheid Variables: Period and Mass Determination

1995 ◽  
Vol 10 ◽  
pp. 594-596
Author(s):  
Pawel Moskalik
Keyword(s):  
Light Curve ◽  
Vibrational Modes ◽  
Mass Determination ◽  
The Galaxy ◽  
Cepheid Variables ◽  
Mass Calibration ◽  
The Masses ◽  
Standing Problem ◽  
Good Agreement

Determination of masses has been a long standing problem in the Cepheid research. Since the early days of Cepheid modeling different methods of mass calibration have lead to conflicting results, implying serious discrepancies between the evolution and pulsation theories (see Cox 1980 for a review). In recent years this situtation has been mostly remedied, and the Baade-Wesselink masses, pulsation masses and evolutionary masses are now in good agreement with each other (e.g., Gieren 1989). However, both the bump masses inferred from the position of the secondary bump on the light curve and the beat masses obtained from the period ratios of the double mode Cepheids turned out to be very resilient to a reconciliation.There are 13 Cepheids in the Galaxy in which two vibrational modes are simultaneously excited (e.g., Szabados 1988). The period ratios measured in these variables can be used in conjunction with the linear pulsation theory to infer the masses of these stars. The method was first applied by Petersen (1973) who obtained masses ranging from 1Mʘ to 3Mʘ for Cepheids with fundamental mode periods between 2.1 d and 6.3 d. Such ‘beat” masses are 2—4 times smaller than the evolutionary or Baade-Wesselink masses for these objects.

scholarly journals Fast and precise light-curve model for transiting exoplanets with rings

2019 ◽  
Vol 490 (1) ◽  
pp. 1111-1119 ◽  
Author(s):  
Edan Rein ◽  
Aviv Ofir
Keyword(s):  
Solar System ◽  
Light Curve ◽  
Source Code ◽  
Light Curves ◽  
Small Range ◽  
Silicate Material ◽  
Computationally Efficient ◽  
Curve Model ◽  
In Transit ◽  
Limb Darkening

ABSTRACT The presence of silicate material in known rings in the Solar system raises the possibility of ring systems existing even within the snow line – where most transiting exoplanets are found. Previous studies have shown that the detection of exoplanetary rings in transit light curves is possible, albeit challenging. To aid such future detection of exoplanetary rings, we present the Polygon + Segments model for modelling the light curve of an exoplanet with rings. This high-precision model includes full ring geometry as well as possible ring transparency and the host star’s limb darkening. It is also computationally efficient, requiring just a 1D integration over a small range, making it faster than existing techniques. The algorithm at its core is further generalized to compute the light curve of any set of convex primitive shapes in transit (e.g. multiple planets, oblate planets, moons, rings, combination thereof, etc.) while accounting for their overlaps. The python source code is made available.

scholarly journals Determining the 56Ni distribution of type Ia supernovae from observations within days of explosion

2020 ◽  
Vol 634 ◽  
pp. A37 ◽  
Author(s):  
M. R. Magee ◽  
K. Maguire ◽  
R. Kotak ◽  
S. A. Sim ◽  
J. H. Gillanders ◽  
...  
Keyword(s):  
Light Curve ◽  
Current Model ◽  
Light Curves ◽  
Radioactive Isotopes ◽  
Type Ia Supernovae ◽  
Maximum Light ◽  
Thermonuclear Supernovae ◽  
Type Ia ◽  
Model Set ◽  
Ia Supernovae

Recent studies have shown how the distribution of 56Ni within the ejected material of type Ia supernovae can have profound consequences on the observed light curves. Observations at early times can therefore provide important details on the explosion physics in thermonuclear supernovae, which are poorly constrained. To this end, we present a series of radiative transfer calculations that explore variations in the 56Ni distribution. Our models also show the importance of the density profile in shaping the light curve, which is often neglected in the literature. Using our model set, we investigate the observations that are necessary to determine the 56Ni distribution as robustly as possible within the current model set. We find that this includes observations beginning at least ∼14 days before B-band maximum, extending to approximately maximum light with a relatively high (≲3 day) cadence, and in at least one blue and one red band (such as B and R, or g and r) are required. We compare a number of well-observed type Ia supernovae that meet these criteria to our models and find that the light curves of ∼70–80% of objects in our sample are consistent with being produced solely by variations in the 56Ni distributions. The remaining supernovae show an excess of flux at early times, indicating missing physics that is not accounted for within our model set, such as an interaction or the presence of short-lived radioactive isotopes. Comparing our model light curves and spectra to observations and delayed detonation models demonstrates that while a somewhat extended 56Ni distribution is necessary to reproduce the observed light curve shape, this does not negatively affect the spectra at maximum light. Investigating current explosion models shows that observations typically require a shallower decrease in the 56Ni mass towards the outer ejecta than is produced for models of a given 56Ni mass. Future models that test differences in the explosion physics and detonation criteria should be explored to determine the conditions necessary to reproduce the 56Ni distributions found here.

scholarly journals Determination of Water Depth in Ports Using Satellite Data Based on Machine Learning Algorithms

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2486
Author(s):  
Vanesa Mateo-Pérez ◽  
Marina Corral-Bobadilla ◽  
Francisco Ortega-Fernández ◽  
Vicente Rodríguez-Montequín
Keyword(s):  
Machine Learning ◽  
Water Depth ◽  
Satellite Data ◽  
Learning Algorithm ◽  
Mean Absolute Error ◽  
Absolute Error ◽  
Machine Learning Algorithms ◽  
Support Vector ◽  
Single Beam

One of the fundamental maintenance tasks of ports is the periodic dredging of them. This is necessary to guarantee a minimum draft that will enable ships to access ports safely. The determination of bathymetries is the instrument that determines the need for dredging and permits an analysis of the behavior of the port bottom over time, in order to achieve adequate water depth. Satellite data processing to predict environmental parameters is used increasingly. Based on satellite data and using different machine learning algorithm techniques, this study has sought to estimate the seabed in ports, taking into account the fact that the port areas are strongly anthropized areas. The algorithms that were used were Support Vector Machine (SVM), Random Forest (RF) and the Multi-Adaptive Regression Splines (MARS). The study was carried out in the ports of Candás and Luarca in the Principality of Asturias. In order to validate the results obtained, data was acquired in situ by using a single beam provided. The results show that this type of methodology can be used to estimate coastal bathymetry. However, when deciding which system was best, priority was given to simplicity and robustness. The results of the SVM and RF algorithms outperform those of the MARS. RF performs better in Candás with a mean absolute error (MAE) of 0.27 cm, whereas SVM performs better in Luarca with a mean absolute error of 0.37 cm. It is suggested that this approach is suitable as a simpler and more cost-effective rough resolution alternative, for estimating the depth of turbid water in ports, than single-beam sonar, which is labor-intensive and polluting.

scholarly journals Late-Phase Observations of a Super-Chandrasekhar SN Ia

2011 ◽  
Vol 7 (S281) ◽  
pp. 319-321
Author(s):  
M. Yamanaka ◽  
K. S. Kawabata ◽  
K. Maeda ◽  
M. Tanaka ◽  
M. Yoshida ◽  
...  
Keyword(s):  
Light Curve ◽  
Early Phase ◽  
Late Phase ◽  
Phase Spectrum ◽  
Light Curves ◽  
High Luminosity ◽  
Slow Decline ◽  
Curve Model ◽  
Phase Spectra ◽  
Inner Parts

AbstractA super-Chandrasekhar (SC) supernova (SN) has an extremely high luminosity and a slow decline rate of the light curve in the early-phase. We present late-phase observations of the SC SN 2009dc. We find that the optical luminosity a year after maximum is much fainter than that expected from its early luminosity. We attempt to fit the analytic light curve model to the observations using Arnett's rule. The model successfully explains the light curves until 120 days. This suggests that the extremely high luminosity originates from the 56Ni decay. We suggest that the late-phase decline would be caused by dust formation. The existence of strong carbon features in early-phase spectra would support this scenario. We also find a blend of [Ca ii] and [Ni ii] in its late-phase spectrum. This indicates that the calcium is distributed in the inner layer along with nickel and iron. We conclude that the mixing may occur in the inner parts of the ejecta.

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