scholarly journals V899 Mon: A Peculiar Eruptive Young Star Close to the End of Its Outburst

2021 ◽  
Vol 923 (2) ◽  
pp. 171
Author(s):  
Sunkyung Park ◽  
Ágnes Kóspál ◽  
Fernando Cruz-Sáenz de Miera ◽  
Michał Siwak ◽  
Marek Dróżdż ◽  
...  
Keyword(s):  
Loss Rate ◽  
Near Infrared ◽  
Accretion Rate ◽  
Mass Loss Rate ◽  
Young Star ◽  
Light Curves ◽  
Emission Lines ◽  
Spectroscopic Observations ◽  
Photometric Monitoring ◽  
Physical Changes

Abstract The eruptive young star V899 Mon shows characteristics of both FUors and EXors. It reached a peak brightness in 2010, then briefly faded in 2011, followed by a second outburst. We conducted multifilter optical photometric monitoring, as well as optical and near-infrared spectroscopic observations, of V899 Mon. The light curves and color–magnitude diagrams show that V899 Mon has been gradually fading after its second outburst peak in 2018, but smaller accretion bursts are still happening. Our spectroscopic observations taken with Gemini/IGRINS and VLT/MUSE show a number of emission lines, unlike during the outbursting stage. We used the emission line fluxes to estimate the accretion rate and found that it has significantly decreased compared to the outbursting stage. The mass-loss rate is also weakening. Our 2D spectroastrometric analysis of emission lines recovered jet and disk emission of V899 Mon. We found that the emission from permitted metallic lines and the CO bandheads can be modeled well with a disk in Keplerian rotation, which also gives a tight constraint for the dynamical stellar mass of 2 M ⊙. After a discussion of the physical changes that led to the changes in the observed properties of V899 Mon, we suggest that this object is finishing its second outburst.

scholarly journals A He I upper atmosphere around the warm Neptune GJ 3470 b

2020 ◽  
Vol 638 ◽  
pp. A61 ◽  
Author(s):  
E. Palle ◽  
L. Nortmann ◽  
N. Casasayas-Barris ◽  
M. Lampón ◽  
M. López-Puertas ◽  
...  
Keyword(s):  
Loss Rate ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Mass Loss Rate ◽  
Light Curves ◽  
Signal To Noise ◽  
Reliable Technique ◽  
Infrared Observations ◽  
Physical Mechanisms

High resolution transit spectroscopy has proven to be a reliable technique for the characterization of the chemical composition of exoplanet atmospheres. Taking advantage of the broad spectral coverage of the CARMENES spectrograph, we initiated a survey aimed at characterizing a broad range of planetary systems. Here, we report our observations of three transits of GJ 3470 b with CARMENES in search of He (23S) absorption. On one of the nights, the He I region was heavily contaminated by OH− telluric emission and, thus, it was not useful for our purposes. The remaining two nights had a very different signal-to-noise ratio (S/N) due to weather. They both indicate the presence of He (23S) absorption in the transmission spectrum of GJ 3470 b, although a statistically valid detection can only be claimed for the night with higher S/N. For that night, we retrieved a 1.5 ± 0.3% absorption depth, translating into a Rp(λ)∕Rp = 1.15 ± 0.14 at this wavelength. Spectro-photometric light curves for this same night also indicate the presence of extra absorption during the planetary transit with a consistent absorption depth. The He (23S) absorption is modeled in detail using a radiative transfer code, and the results of our modeling efforts are compared to the observations. We find that the mass-loss rate, Ṁ, is confined to a range of 3 × 1010 g s−1 for T = 6000 K to 10 × 1010 g s−1 for T = 9000 K. We discuss the physical mechanisms and implications of the He I detection in GJ 3470 b and put it in context as compared to similar detections and non-detections in other Neptune-size planets. We also present improved stellar and planetary parameter determinations based on our visible and near-infrared observations.

scholarly journals The transitional gap transient AT 2018hso: new insights into the luminous red nova phenomenon

2019 ◽  
Vol 632 ◽  
pp. L6 ◽  
Author(s):  
Y.-Z. Cai ◽  
A. Pastorello ◽  
M. Fraser ◽  
S. J. Prentice ◽  
T. M. Reynolds ◽  
...  
Keyword(s):  
Near Infrared ◽  
Early Time ◽  
Light Curves ◽  
Binary Interaction ◽  
Strong Decrease ◽  
Link Type ◽  
Photometric Monitoring ◽  
Absolute Magnitudes ◽  
Second Peak ◽  
The Continuum

Context. The absolute magnitudes of luminous red novae (LRNe) are intermediate between those of novae and supernovae (SNe), and show a relatively homogeneous spectro-photometric evolution. Although they were thought to derive from core instabilities in single stars, there is growing support for the idea that they are triggered by binary interaction that possibly ends with the merging of the two stars. Aims. AT 2018hso is a new transient showing transitional properties between those of LRNe and the class of intermediate-luminosity red transients (ILRTs) similar to SN 2008S. Through the detailed analysis of the observed parameters, our study supports that it actually belongs to the LRN class and was likely produced by the coalescence of two massive stars. Methods. We obtained ten months of optical and near-infrared photometric monitoring, and 11 epochs of low-resolution optical spectroscopy of AT 2018hso. We compared its observed properties with those of other ILRTs and LRNe. We also inspected the archival Hubble Space Telescope (HST) images obtained about 15 years ago to constrain the progenitor properties. Results. The light curves of AT 2018hso show a first sharp peak (reddening-corrected Mr = −13.93 mag), followed by a broader and shallower second peak that resembles a plateau in the optical bands. The spectra dramatically change with time. Early-time spectra show prominent Balmer emission lines and a weak [Ca II] doublet, which is usually observed in ILRTs. However, the strong decrease in the continuum temperature, the appearance of narrow metal absorption lines, the great change in the Hα strength and profile, and the emergence of molecular bands support an LRN classification. The possible detection of a MI ∼ −8 mag source at the position of AT 2018hso in HST archive images is consistent with expectations for a pre-merger massive binary, similar to the precursor of the 2015 LRN in M101. Conclusions. We provide reasonable arguments to support an LRN classification for AT 2018hso. This study reveals growing heterogeneity in the observables of LRNe than has been thought previously, which is a challenge for distinguishing between LRNe and ILRTs. This suggests that the entire evolution of gap transients needs to be monitored to avoid misclassifications.

scholarly journals Dust Size Effect On IR Colors Of AGB Stars

2008 ◽  
Vol 4 (S252) ◽  
pp. 263-264
Author(s):  
Huan Wang ◽  
B. W. Jiang ◽  
R. Szczerba
Keyword(s):  
Size Effect ◽  
Loss Rate ◽  
Near Infrared ◽  
Mass Loss Rate ◽  
Mie Theory ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Agb Stars ◽  
Ir Sources ◽  
The Difference

AbstractWith the Mie theory and the radiative transfer model, we studied the effect of dust size on the infrared color indexes concerning special filters used in the space infrared missions and typical filters in the near-infrared, of AGB stars with typical oxygen-rich and carbon-rich dust shells. It is found the most affected bands are the near-infrared bands JHK and the Spitzer IRAC bands, meanwhile the wavebands with reference wavelength longer than 10 μm is little affected. The effect increases fast with the mass loss rate. We also discussed the potential to distinguish the O-rich and C-rich dusts, and the difference in IR colors between the AGB stars and other IR sources like YSOs and galaxies.

scholarly journals On the evolutionary status and instability mechanism of the Luminous Blue Variables (LBV)

1989 ◽  
Vol 113 ◽  
pp. 15-26
Author(s):  
André Maeder
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Light Curves ◽  
Evolutionary Status ◽  
Average Mass ◽  
Luminous Blue Variables ◽  
Ir Sources ◽  
Order Of Magnitude ◽  
Lower Luminosity

AbstractVarious evolutionary sequences leading to LBV are examined. The sequence O-Of-LBV-WR-SN is well supported by the models; some LBV with relatively lower luminosity may turn into OH/IR sources. The overall duration of the LBV phase depends mainly on the average mass loss rate; for <Ṁ> = 10−3M⊙y−1, it lasts about 104y.Very massive stars undergo, when they reach logTeff= 3.9, strong departure from hydrostatic equilibrium due to supra-Eddington luminosities at some depth in the outer layers. This results in heavy mass loss, as the growth rate of the instability is very fast. We suggest that the amount of mass ejected in a shell episode is mainly determined by the mass of such a layer that its thermal adjustment timescale is within an order of magnitude of the stellar dynamical timescale. Simulations of B-light curves due to shell ejections by LBV are performed and some sensitive properties are identified.

scholarly journals Radio view of a broad-line Type Ic supernova ASASSN-16fp

2020 ◽  
Vol 494 (1) ◽  
pp. 84-96
Author(s):  
Nayana A. J. ◽  
Poonam Chandra
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Light Curves ◽  
Broad Line ◽  
Frequency Range ◽  
Density Enhancement ◽  
Circumstellar Shell ◽  
Equipartition Of Energy ◽  
Relativistic Particles

ABSTRACT We present extensive radio observations of a Type Ic supernova, ASASSN-16fp. Our data represent the lowest frequency observations of the supernova beyond 1000 d with a frequency range of 0.33–25 GHz and a temporal range of ∼8–1136 d post-explosion. The observations are best represented by a model of synchrotron emission from a shocked circumstellar shell initially suppressed by synchrotron self-absorption. Assuming equipartition of energy between relativistic particles and magnetic fields, we estimate the velocity and radius of the blast wave to be $v$ ∼ 0.15c and r ∼ 3.4 × 1015 cm, respectively, at t0 ∼ 8 d post-explosion. We infer the total internal energy of the radio-emitting material evolves as E ∼ 0.37 × 1047 (t/t0)0.65 erg. We determine the mass-loss rate of the progenitor star to be $\dot{M} \sim (0.4\!-\!3.2) \times 10^{-5}\, \mathrm{M}_{\odot }\, \rm yr^{-1}$ at various epochs post-explosion, consistent with the mass-loss rate of Galactic Wolf–Rayet stars. The radio light curves and spectra show a signature of density enhancement in the circumstellar medium at a radius of ∼1.10 × 1016 cm from the explosion centre.

scholarly journals Modeling the Radio and X-ray Emission of SN 1993J and SN 2002ap

2005 ◽  
Vol 192 ◽  
pp. 59-69
Author(s):  
Claes Fransson ◽  
Claes-Ingvar Björnsson
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Loss Rate ◽  
Relativistic Particle ◽  
Mass Loss Rate ◽  
Light Curves ◽  
Magnetic Field Generation ◽  
Absorption Mechanism ◽  
X Ray ◽  
Physical Mechanisms

SummaryModeling of radio and X-ray observations of supernovae interacting with their circumstellar media are discussed, with special application to SN 1993J and SN 2002ap. We emphasize the importance of including all relevant physical mechanisms, especially for the modeling of the radio light curves. The different conclusions for the absorption mechanism (free-free or synchrotron self-absorption), as well as departures from an ρ ∝ r−2 CSM, as inferred by some authors, are discussed in detail. We conclude that the evidence for a variation in the mass loss rate with time is very weak. The results regarding the efficiencies of magnetic field generation and relativistic particle acceleration are summarized.

scholarly journals SMBH Luminosity in the Starburst Environment

2009 ◽  
Vol 5 (S267) ◽  
pp. 336-336
Author(s):  
Sergiy Silich ◽  
Guillermo Tenorio-Tagle ◽  
Filiberto Hueyotl-Zahuantitla ◽  
Jan Palouš ◽  
Richard Wünsch
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Accretion Rate ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Intermediate Mass ◽  
Star Forming ◽  
Intermediate Mass Stars

We claim that in the starburst environment there is no accretion of the ISM onto the BH and thus, in such cases, the BH luminosity is regulated by the mass-loss rate from massive stars in the star forming region. We calculate the accretion rate and show that it is usually small during the superwind stage and grows at the post-starburst stage, when the matter reinserted by intermediate–mass stars remains gravitationally bound and fuels the central BH.

scholarly journals The Role of Electron Scattering in Probing the Wind from the Hot Star in Symbiotic Binaries

2011 ◽  
Vol 7 (S282) ◽  
pp. 315-316
Author(s):  
Matej Sekeráš ◽  
Augustin Skopal
Keyword(s):  
Electron Scattering ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Empirical Relationship ◽  
Emission Measure ◽  
Emission Lines ◽  
Symbiotic Stars ◽  
Symbiotic Binaries ◽  
Scattering Contribution

AbstractWe modeled the broad wings of the OVI 1032,1038Å resonance lines and HeII 1640Å line in the spectra of some symbiotic stars by the electron-scattering process. We determined an empirical relationship between the emission measure of the symbiotic nebula and the electron optical depth. This allowed us to determine a contribution from the electron-scattering also to emission lines, which originate in a more extended, low density part of the nebula. For example, subtracting the electron-scattering contribution from the Hα line profile makes it possible to determine more precisely the mass loss rate via the wind from the hot star in symbiotic binaries.

scholarly journals The Influence of the Ratio of Total to Selective Extinction on the Determination of the Mass Loss Rate of Wolf Rayet Stars from Infrared Excess Measurements

1982 ◽  
Vol 99 ◽  
pp. 197-201
Author(s):  
P.S. The ◽  
K.A. van der Hucht ◽  
M. Arens
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Near Infrared ◽  
Mass Loss Rate ◽  
Infrared Excess ◽  
Photometric Observations ◽  
Order Of Magnitude ◽  
Selective Extinction ◽  
Loss Rates

It is shown that the mass loss rate of the WN7 star HD 93162 decreases with larger values of the ratio of total to selective extinction R. for HD 93162 the mass loss rate will change one order of magnitude, only if ΔR ∼ 2. Mass loss rates are derived for nine other WR stars of which visual, red and near-infrared photometric observations were obtained.

scholarly journals Measuring the physical conditions of accreting gas in T Tauri systems

2007 ◽  
Vol 3 (S243) ◽  
pp. 95-102
Author(s):  
Jeffrey S. Bary ◽  
Sean P. Matt
Keyword(s):  
Near Infrared ◽  
Young Star ◽  
Emission Lines ◽  
Line Flux ◽  
Star Forming ◽  
Physical Conditions ◽  
T Tauri ◽  
Hydrogen Emission Lines ◽  
Line Theory ◽  
Magnetospheric Accretion

AbstractHydrogen emission lines observed from T Tauri stars (TTS) are associated with the accretion/outflow of gas in these young star forming systems. Magnetospheric accretion models have been moderately successful at reproducing the shapes of several Hi emission line profiles, suggesting that the emission arises in the accretion funnels. Despite considerable effort to model and observe these emission features, the physical conditions of the gas confined to the funnel flows remain poorly constrained by observation. We conducted a mutli-epoch near-infrared spectroscopic survey of 16 actively accreting classical TTS in the Taurus-Auriga star forming region. We present an analysis of these simultaneously acquired line flux ratios of many Paschen and Brackett series emission lines, in which we compare the observed ratios to those predicted by the Case B approximation of hydrogen recombination line theory. We find that the line flux ratios for the Paschen and Brackett decrements as well as a comparison between Brγ and Paschen transitions agree well with the Case B models with T < 5000 K and ne ≈ 1010 cm−3.

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