scholarly journals The dipper light curve of V715 Persei: is there dust in the magnetosphere?

2020 ◽  
Vol 643 ◽  
pp. A157
Author(s):  
E. Nagel ◽  
J. Bouvier
Keyword(s):  
Light Curve ◽  
Vertical Component ◽  
Young Star ◽  
Light Curves ◽  
Young Stellar Objects ◽  
Rotational Axis ◽  
Stellar Objects ◽  
Optical Light Curve ◽  
Dust Distribution ◽  
Extinction Events

Context. The dipper optical light curves in young stellar objects are commonly interpreted as partial or total occultation of the stellar radiation by dust surrounding the star. Aims. In this work, we analyze the amplitude of the optical light curve of V715 Per, located in the young star forming region IC 348. Observations gathered over the years suggest that the light curve can be explained by dust extinction events. Methods. In our model, the dust is distributed inside the magnetosphere according to the strength of the stellar magnetic field. The dust distribution is modulated by the vertical component of the field whose axis is misaligned with respect to the rotational axis. We include a model for evaporation of the dust reaching the magnetosphere in order to consistently calculate its distribution. Results. For V715 Per, there is dust in the optically thick warp at the disk truncation radius. We suggest that the optical light curve is explained by extinction caused by dust reaching inside the magnetosphere. The dust distribution is optically thin, and it cannot survive for a long time because of the high temperature and low density. However, as the grains rapidly move towards the stellar surface and the sublimation is not instantaneous, there is a layer of dust covering the magnetosphere responsible for the extinction. Conclusions. Dust surviving the harsh conditions of the magnetospheric accretion flow may be responsible for some of the dipper light curves.

scholarly journals Young Stellar Object Variability at IRAC Wavelengths: Clues to Star and Planet Formation

2009 ◽  
Vol 5 (H15) ◽  
pp. 734-734
Author(s):  
John R. Stauffer ◽  
Maria Morales ◽  
Luisa Rebull
Keyword(s):  
Light Curve ◽  
Density Profile ◽  
Hot Spot ◽  
Light Curves ◽  
Young Stellar Objects ◽  
Circumstellar Disk ◽  
Stellar Objects ◽  
Mid Infrared ◽  
Stellar Photosphere ◽  
Disk Plane

In Morales et al. (2009), we have recently investigated the mid-infrared (3.6 to 8.0 micron) variability of young-stellar objects (YSOs) using the IRAC camera on the Spitzer Space Telescope. Specifically, we obtained synoptic photometry of about 70 YSOs in the ~1 Myr old IC1396A globule over a 14 day period. More than half of the YSOs were detectably variable, with amplitudes up to about 0.2 magnitudes. About a third of these objects showed quasi-sinusoidal light curves with apparent periods of typically 5 to 12 days. At least two families of models can explain such light curves: (a) a Class II YSO with a photospheric hot spot which locally heats the inner circumstellar disk which is viewed from slightly above the disk plane, and (b) a YSO with a warped disk or with some other non-axisymmetric inner disk density profile, also seen with a view angle slightly above the disk plane. The two models can both yield light curve shapes and amplitudes similar to what we observe in the mid-infrared, but produce very different light curves at shorter wavelengths dominated by the stellar photosphere. Because we only had IRAC photometry for IC1396A, we were not able to discriminate between the two models for this set of data.

Oscillations in Young Stellar Objects

2002 ◽  
Vol 185 ◽  
pp. 352-353
Author(s):  
F.J.G. Pinheiro ◽  
D.F.M. Folha ◽  
M.J.P.F.G. Monteiro ◽  
M. Marconi ◽  
V. Ripepi ◽  
...  
Keyword(s):  
Light Curve ◽  
Main Sequence ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Stellar Oscillations ◽  
Pms Stars

AbstractWe report the discovery of periodicities in the light curve of the Herbig Ae star V346 Ori. We interpret these variations as the superposition of at least two signals with periods P1=42±6 min and P2=68±12 min resulting from stellar oscillations. The computation of linear non-adiabatic pulsation models for Pre-Main Sequence (PMS) stars reproduces these periods for a 1.5 M⊙ star with Teff= 7300 K and log L/L⊙= 0.74, pulsating in the fundamental and second overtones.

scholarly journals Modeling of Circumstellar Dust by the DUSTY Code

2011 ◽  
Vol 7 (S282) ◽  
pp. 247-250
Author(s):  
Tomislav Jurkić ◽  
Dubravka Kotnik-Karuza
Keyword(s):  
Near Infrared ◽  
Dynamical Behaviour ◽  
Light Curves ◽  
Young Stellar Objects ◽  
Numerical Code ◽  
Circumstellar Dust ◽  
Be Stars ◽  
Stellar Objects ◽  
Near Ir ◽  
Dust Temperature

AbstractWe present a circumstellar dust model around the symbiotic Mira RR Tel obtained by modeling the near-infrared JHKL magnitudes and ISO spectra. In order to follow the evolution of infrared colours in time, the published JHKL magnitudes were corrected by removing the Mira pulsations. The RR Tel light curves show three obscuration events in the near-IR. Using the simultaneously available JHKL magnitudes and ISO spectra in three different epochs, we obtained SEDs in the near- and mid-IR spectral region (1-20 μm) in epochs with and without obscuration.The DUSTY numerical code was used to solve the radiative transfer and to determine the circumstellar dust properties of the inner dust regions around the Mira, assuming a spherical dust temperature distribution in its close neighbourhood. The physical properties of the dust, mass loss and optical depth during intervals with and without obscuration have been obtained. Both JHKL and ISO observations during the obscuration period can be reproduced with a spherical dust envelope, while ISO spectra outside obscuration show a different behaviour. The dynamical behaviour of the circumstellar dust was obtained by modeling the JHKL magnitudes observed during the span of more than 30 years.The DUSTY code was also successfully applied in the modeling of circumstellar dust envelopes of young stellar objects, such as Herbig Ae/Be stars.

scholarly journals A Simple Model for the Secular Light Curve of Comet C/1996 B2 Hyakutake

2009 ◽  
Vol 5 (S263) ◽  
pp. 293-297
Author(s):  
Eduardo Rondón ◽  
Ignacio Ferrín
Keyword(s):  
Simple Model ◽  
Light Curve ◽  
Optical Thickness ◽  
Cometary Nucleus ◽  
Light Curves ◽  
Rotational Axis ◽  
Water Production ◽  
Physical Information ◽  
Axis I ◽  
Water Production Rate

AbstractThe secular light curves of comets (Ferrín, 2005) give a large amount of physical information on the cometary nucleus. We have developed a model that allows the prediction of a secular light curve, from which we derive parameters like the orientation of the rotational axis (I, φ) and optical thickness of the cometary coma. The model is based on the paper published by (Cowan & A'Hearn, 1979). To do the calculation we found a correlation between the water production rate and the reduced magnitude. We obtain probable orientations of the nucleus pole for several combinations of parameters for comet C/1996 B2 Hyakutake.

scholarly journals Light Curve Models for SN 1987A and Diagnosis of Supernova Interior

1988 ◽  
Vol 108 ◽  
pp. 319-334
Author(s):  
Ken’ichi Nomoto ◽  
Toshikazu Shigeyama ◽  
Masa-aki Hashimoto
Keyword(s):  
Light Curve ◽  
Reasonable Agreement ◽  
Light Curves ◽  
Shock Propagation ◽  
Helium Abundance ◽  
X Ray ◽  
Sn 1987A ◽  
Shock Heating ◽  
Helium Stars ◽  
Optical Light Curve

AbstractPresupernova evolution of the progenitor of SN 1987A, hydrodynamics of explosion (shock propagation, explosive nucleosynthesis), optical light curve due to shock heating and 56Co decay, and X-ray and γ-ray light curves are calculated and compared with the observations of SN 1987A. Constraints on the mass of the hydrogen-rich envelope Menv (i.e., mass loss history) and the helium abundance in the envelope are obtained from the progenitor’s blue-red-blue evolution as well as from the light curve. The explosion energy E and the mass and distribution of 56Ni are inferred from the light curves. Models and observations are in reasonable agreement for E/Menv = 1.5 ± 0.5 × 1050 erg/M⊙, Menv = 5 - 10 M⊙, and MNi ∼ 0.07 M⊙. Mixing of 56Ni into the envelope is indicated.Light curves of exploding bare helium stars are also calculated to see whether the observed Type Ib supernova light curves can be accounted for.

scholarly journals Infrared variability, maser activity, and accretion of massive young stellar objects

2017 ◽  
Vol 13 (S336) ◽  
pp. 37-40 ◽  
Author(s):  
Bringfried Stecklum ◽  
Alessio Caratti o Garatti ◽  
Klaus Hodapp ◽  
Hendrik Linz ◽  
Luca Moscadelli ◽  
...  
Keyword(s):  
Light Curve ◽  
Young Stellar Objects ◽  
High Mass ◽  
Periodic Activity ◽  
Intermediate Mass ◽  
Stellar Objects ◽  
Methanol Masers ◽  
Water Masers ◽  
First Time ◽  
Ir Light

AbstractMethanol and water masers indicate young stellar objects. They often exhibit flares, and a fraction shows periodic activity. Several mechanisms might explain this behavior but the lack of concurrent infrared (IR) data complicates the identification of its cause. Recently, 6.7 GHz methanol maser flares were observed, triggered by accretion bursts of high-mass YSOs which confirmed the IR-pumping of these masers. This suggests that regular IR changes might lead to maser periodicity. Hence, we scrutinized space-based IR imaging of YSOs associated with periodic methanol masers. We succeeded to extract the IR light curve from NEOWISE data for the intermediate mass YSO G107.298+5.639. Thus, for the first time a relationship between the maser and IR variability could be established. While the IR light curve shows the same period of ~34.6 days as the masers, its shape is distinct from that of the maser flares. Possible reasons for the IR periodicity are discussed.

scholarly journals Quasi-periodic behaviour in the optical and γ-ray light curves of blazars 3C 66A and B2 1633+38

2020 ◽  
Vol 492 (4) ◽  
pp. 5524-5539 ◽  
Author(s):  
J Otero-Santos ◽  
J A Acosta-Pulido ◽  
J Becerra González ◽  
C M Raiteri ◽  
V M Larionov ◽  
...  
Keyword(s):  
Light Curve ◽  
Confidence Level ◽  
Light Curves ◽  
Data Set ◽  
Spectrum Radio ◽  
Periodic Behaviour ◽  
Optical Light Curve ◽  
Emission Models ◽  
Γ Ray ◽  
Radio Quasar

ABSTRACT We report on quasi-periodic variability found in two blazars included in the Steward Observatory Blazar Monitoring data sample: the BL Lac object 3C 66A and the Flat Spectrum Radio Quasar B2 1633+38. We collect optical photometric and polarimetric data in V and R bands of these sources from different observatories: St. Petersburg University, Crimean Astrophysical Observatory, WEBT–GASP, Catalina Real-Time Transient Survey, Steward Observatory, STELLA Robotic Observatory, and Katzman Automatic Imaging Telescope. In addition, an analysis of the γ-ray light curves from Fermi–LAT is included. Three methods are used to search for any periodic behaviour in the data: the Z-transform Discrete Correlation Function, the Lomb–Scargle periodogram and the Weighted Wavelet Z-transform. We find pieces of evidence of possible quasi-periodic variability in the optical photometric data of both sources with periods of ∼3 yr for 3C 66A and ∼1.9 yr for B2 1633+38, with significances between 3σ and 5σ. Only B2 1633+38 shows evidence of this behaviour in the optical polarized data set at a confidence level of 2σ–4σ. This is the first reported evidence of quasi-periodic behaviour in the optical light curve of B2 1633+38. Also, a hint of quasi-periodic behaviour is found in the γ-ray light curve of B2 1633+38 with a confidence level ≥2σ, while no periodicity is observed for 3C 66A in this energy range. We propose different jet emission models that could explain the quasi-periodic variability and the differences found between these two sources.

scholarly journals The dual nature of blazar fast variability: Space and ground observations of S5 0716+714

2020 ◽  
Vol 501 (1) ◽  
pp. 1100-1115
Author(s):  
C M Raiteri ◽  
M Villata ◽  
D Carosati ◽  
E Benítez ◽  
S O Kurtanidze ◽  
...  
Keyword(s):  
Light Curve ◽  
Time Scales ◽  
Light Curves ◽  
Spectral Variability ◽  
Short Term ◽  
Dual Nature ◽  
X Ray ◽  
Geometric Origin ◽  
Optical Light Curve ◽  
Doppler Factor

ABSTRACT Blazar S5 0716+714 is well-known for its short-term variability, down to intraday time-scales. We here present the 2-min cadence optical light curve obtained by the TESS space telescope in 2019 December–2020 January and analyse the object fast variability with unprecedented sampling. Supporting observations by the Whole Earth Blazar Telescope Collaboration in B, V, R, and I bands allow us to investigate the spectral variability during the TESS pointing. The spectral analysis is further extended in frequency to the UV and X-ray bands with data from the Neil Gehrels Swift Observatory. We develop a new method to unveil the shortest optical variability time-scales. This is based on progressive de-trending of the TESS light curve by means of cubic spline interpolations through the binned fluxes, with decreasing time bins. The de-trended light curves are then analysed with classical tools for time-series analysis (periodogram, autocorrelation, and structure functions). The results show that below 3 d there are significant characteristic variability time-scales of about 1.7, 0.5, and 0.2 d. Variability on time-scales $\lesssim 0.2$ d is strongly chromatic and must be ascribed to intrinsic energetic processes involving emitting regions, likely jet substructures, with dimension less than about 10−3 pc. In contrast, flux changes on time-scales $\gtrsim 0.5$ d are quasi-achromatic and are probably due to Doppler factor changes of geometric origin.

scholarly journals Young Stellar Objects in the Low-Metallicity Small Magellanic Cloud

2012 ◽  
Vol 8 (S292) ◽  
pp. 112-112
Author(s):  
M. Sewiło ◽  
L. R. Carlson ◽  
J. P. Seale ◽  
R. Indebetouw ◽  
M. Meixner ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Magellanic Cloud ◽  
Young Stellar Objects ◽  
High Mass ◽  
Optical Data ◽  
Small Magellanic Cloud ◽  
Stellar Objects ◽  
Near Ir ◽  
Low Metallicity ◽  
Dust Distribution

AbstractThe Spitzer Legacy Program “Surveying the Agents of Galaxy Evolution in the Tidally-Stripped, Low-Metallicity Small Magellanic Cloud” (SAGE-SMC; Gordon et al. 2011) allows a global study of star formation in the SMC at high enough resolution to resolve individual cores and protostars at a range of mid-IR wavelengths. Using the SAGE-SMC IRAC (3.6 - 8.0 μm) and MIPS (24 and 70 μm) catalogs and images combined with the near-IR and optical data, we identified a population of ∼1100 intermediate- to high-mass Young Stellar Objects (YSOs) in the SMC (3 × more than previously known). We investigate the properties of the YSOs and how they relate to the galaxy's structure and gas and dust distribution.

scholarly journals An investigation of 56Ni shells as the source of early light curve bumps in type Ia supernovae

2020 ◽  
Vol 642 ◽  
pp. A189
Author(s):  
M. R. Magee ◽  
K. Maguire
Keyword(s):  
Light Curve ◽  
Light Curves ◽  
Radioactive Material ◽  
Type Ia Supernovae ◽  
Spectral Evolution ◽  
Strong Suppression ◽  
Shell Models ◽  
Type Ia ◽  
Optical Light Curve ◽  
Ia Supernovae

An excess of flux (i.e. a bump) in the early light curves of type Ia supernovae has been observed in a handful of cases. Multiple scenarios have been proposed to explain this excess flux. Recently, it has been shown that for at least one object (SN 2018oh) the excess emission observed could be the result of a large amount of 56Ni in the outer ejecta (∼0.03 M⊙). We present a series of model light curves and spectra for ejecta profiles containing 56Ni shells of varying masses (0.01, 0.02, 0.03, and 0.04 M⊙) and widths. We find that even for our lowest mass 56Ni shell, an increase of >2 magnitudes is produced in the bolometric light curve at one day after explosion relative to models without a 56Ni shell. We show that the colour evolution of models with a 56Ni shell differs significantly from those without and shows a colour inversion similar to some double-detonation explosion models. Furthermore, spectra of our 56Ni shell models show that strong suppression of flux between ∼3700–4000 Å close to maximum light appears to be a generic feature for this class of model. Comparing our models to observations of SNe 2017cbv and 2018oh, we show that a 56Ni shell of 0.02–0.04 M⊙ can match shapes of the early optical light curve bumps, but the colour and spectral evolution are in disagreement. Our models also predict a strong UV bump that is not observed. This would indicate that an alternative origin for the flux excess is necessary. In addition, based on existing explosion scenarios, producing such a 56Ni shell in the outer ejecta as required to match the light curve shape, without the presence of additional short-lived radioactive material, may prove challenging. Given that only a small amount of 56Ni in the outer ejecta is required to produce a bump in the light curve, such non-monotonically decreasing 56Ni distributions in the outer ejecta must be rare, if they were to occur at all.

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