scholarly journals A new and unusual LBV-like outburst from a Wolf–Rayet star in the outskirts of M33

2020 ◽  
Vol 492 (4) ◽  
pp. 5897-5915 ◽  
Author(s):  
Nathan Smith ◽  
Jennifer E Andrews ◽  
Maxwell Moe ◽  
Peter Milne ◽  
Christopher Bilinski ◽  
...  
Keyword(s):  
Wind Speed ◽  
Light Curve ◽  
Spectral Type ◽  
Fold Increase ◽  
Small Magellanic Cloud ◽  
Bolometric Luminosity ◽  
Type Spectrum ◽  
Low Metallicity ◽  
Rayet Star ◽  
Luminous Blue Variable

ABSTRACT MCA-1B (also called UIT003) is a luminous hot star in the western outskirts of M33, classified over 20 yr ago with a spectral type of Ofpe/WN9 and identified then as a candidate luminous blue variable (LBV). Palomar Transient Factory data reveal that this star brightened in 2010, with a light curve resembling that of the classic LBV star AF And in M31. Other Ofpe/WN9 stars have erupted as LBVs, but MCA-1B was unusual because it remained hot. It showed a WN-type spectrum throughout its eruption, whereas LBVs usually get much cooler. MCA-1B showed an almost four-fold increase in bolometric luminosity and a doubling of its radius, but its temperature stayed ≳29 kK. As it faded, it shifted to even hotter temperatures, exhibiting a WN7/WN8-type spectrum, and doubling its wind speed. MCA-1B is reminiscent of some supernova impostors, and its location resembles the isolated environment of SN 2009ip. It is most similar to HD 5980 (in the Small Magellanic Cloud) and GR 290 (also in M33). Whereas these two LBVs exhibited B-type spectra in eruption, MCA-1B is the first clear case where a Wolf–Rayet (WR) spectrum persisted at all times. Together, MCA-1B, HD 5980, and GR 290 constitute a class of WN-type LBVs, distinct from S Doradus LBVs. They are most interesting in the context of LBVs at low metallicity, a possible post-LBV/WR transition in binaries, and as likely Type Ibn supernova progenitors.

scholarly journals Variable C – “a typical” LBV in M 33?

2014 ◽  
Vol 9 (S307) ◽  
pp. 148-149
Author(s):  
Kerstin Weis ◽  
Roberta M. Humphreys ◽  
Birgitta Burggraf ◽  
Dominik J. Bomans
Keyword(s):  
Light Curve ◽  
Spectral Type ◽  
Data Sets ◽  
Observational Signature ◽  
Luminous Blue Variable

AbstractOne of the original Hubble-Sandage variables, Variable C in M33 is thought to be a very typical Luminous Blue Variable (LBV). An observational signature of LBVs is a variable brightness which is coupled to a change in spectral type. We compiled a 110 year long light curve of Var C and a set of spectra covering several decades. Analyzing both data sets, various astonishing changes of Var C, some very recent, emerged. Is Var C a typical or an atypical LBV?

scholarly journals The Wolf-Rayet Eclipsing Binary HD 5980 in the Small Magellanic Cloud

1982 ◽  
Vol 99 ◽  
pp. 317-320
Author(s):  
Jacques Breysacher ◽  
Anthony F. J. Moffat ◽  
Virpi S. Niemelä
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Orbital Period ◽  
Spectroscopic Data ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Eccentric Orbit ◽  
Eclipsing Binary ◽  
Hii Region ◽  
Rayet Star

The Wolf-Rayet star HD 5980, which is probably associated with the bright HII region NGC 346 of the Small Magellanic Cloud, was found to be an eclipsing binary by Hoffmann, Stift and Moffat (1978). Breysacher and Perrier (1980) determined the orbital period, P=19.266±0.003d, of the system whose light curve reveals a strongly eccentric orbit (e=0.47 for i=80°). The behaviour of the light curve outside the eclipses shows that we are dealing with a rather complex binary system. An analysis of the spectroscopic data is presented here.

The Eclipsing Binary WX Eridani

1979 ◽  
Vol 46 ◽  
pp. 385
Author(s):  
M.B.K. Sarma ◽  
K.D. Abhankar
Keyword(s):  
Light Curve ◽  
Spectral Type ◽  
Orbital Period ◽  
Primary Component ◽  
Light Curves ◽  
Absorption Feature ◽  
Primary Star ◽  
Eclipsing Binary ◽  
The Times ◽  
Phase Angles

AbstractThe Algol-type eclipsing binary WX Eridani was observed on 21 nights on the 48-inch telescope of the Japal-Rangapur Observatory during 1973-75 in B and V colours. An improved period of P = 0.82327038 days was obtained from the analysis of the times of five primary minima. An absorption feature between phase angles 50-80, 100-130, 230-260 and 280-310 was present in the light curves. The analysis of the light curves indicated the eclipses to be grazing with primary to be transit and secondary, an occultation. Elements derived from the solution of the light curve using Russel-Merrill method are given. From comparison of the fractional radii with Roche lobes, it is concluded that none of the components have filled their respective lobes but the primary star seems to be evolving. The spectral type of the primary component was estimated to be F3 and is found to be pulsating with two periods equal to one-fifth and one-sixth of the orbital period.

scholarly journals Light-curve properties of SN 2017fgc and HV SNe Ia

2021 ◽  
Vol 502 (3) ◽  
pp. 4112-4124
Author(s):  
Umut Burgaz ◽  
Keiichi Maeda ◽  
Belinda Kalomeni ◽  
Miho Kawabata ◽  
Masayuki Yamanaka ◽  
...  
Keyword(s):  
Light Curve ◽  
Near Infrared ◽  
Light Curves ◽  
Normal Velocity ◽  
External Effects ◽  
Band Maximum ◽  
Bolometric Luminosity ◽  
V Band ◽  
Photometric And Spectroscopic Observations ◽  
Type Ia

ABSTRACT Photometric and spectroscopic observations of Type Ia supernova (SN) 2017fgc, which cover the period from −12 to + 137 d since the B-band maximum are presented. SN 2017fgc is a photometrically normal SN Ia with the luminosity decline rate, Δm15(B)true  = 1.10 ± 0.10 mag. Spectroscopically, it belongs to the high-velocity (HV) SNe Ia group, with the Si ii λ6355 velocity near the B-band maximum estimated to be 15 200 ± 480 km s−1. At the epochs around the near-infrared secondary peak, the R and I bands show an excess of ∼0.2-mag level compared to the light curves of the normal velocity (NV) SNe Ia. Further inspection of the samples of HV and NV SNe Ia indicates that the excess is a generic feature among HV SNe Ia, different from NV SNe Ia. There is also a hint that the excess is seen in the V band, both in SN 2017fgc and other HV SNe Ia, which behaves like a less prominent shoulder in the light curve. The excess is not obvious in the B band (and unknown in the U band), and the colour is consistent with the fiducial SN colour. This might indicate that the excess is attributed to the bolometric luminosity, not in the colour. This excess is less likely caused by external effects, like an echo or change in reddening but could be due to an ionization effect, which reflects an intrinsic, either distinct or continuous, difference in the ejecta properties between HV and NV SNe Ia.

scholarly journals Supernovae from blue supergiant progenitors: What a mess!

2019 ◽  
Vol 622 ◽  
pp. A70 ◽  
Author(s):  
Luc Dessart ◽  
D. John Hillier
Keyword(s):  
Light Curve ◽  
Line Width ◽  
Spectroscopic Properties ◽  
Blue Color ◽  
Type Ii ◽  
Spectral Evolution ◽  
Sn 1987A ◽  
Rich Diversity ◽  
Alternative Power ◽  
Low Metallicity

Supernova (SN) 1987A was classified as a peculiar Type II SN because of its long rising light curve and the persistent presence of H I lines in optical spectra. It was subsequently realized that its progenitor was a blue supergiant (BSG), rather than a red supergiant (RSG) as for normal, Type II-P, SNe. Since then, the number of Type II-pec SNe has grown, revealing a rich diversity in photometric and spectroscopic properties. In this study, using a single 15 M⊙ low-metallicity progenitor that dies as a BSG, we have generated explosions with a range of energies and 56Ni masses. We then performed the radiative transfer modeling with CMFGEN, from 1 d until 300 d after explosion for all ejecta. Our models yield light curves that rise to optical maximum in about 100 d, with a similar brightening rate, and with a peak absolute V-band magnitude spanning −14 to −16.5 mag. All models follow a similar color evolution, entering the recombination phase within a few days of explosion, and reddening further until the nebular phase. Their spectral evolution is analogous, mostly differing in line width. With this model set, we study the Type II-pec SNe 1987A, 2000cb, 2006V, 2006au, 2009E, and 2009mw. The photometric and spectroscopic diversity of observed SNe II-pec suggests that there is no prototype for this class. All these SNe brighten to maximum faster than our limited set of models, except perhaps SN 2009mw. The spectral evolution of SN 1987A conflicts with other observations in this set and conflicts with model predictions from 20 d until maximum: Hα narrows and weakens while Ba II lines strengthen faster than expected, which we interpret as signatures of clumping. SN 2000cb rises to maximum in only 20 d and shows weak Ba II lines. Its spectral evolution (color, line width and strength) is well matched by an energetic ejecta but the light curve may require strong asymmetry. The persistent blue color, narrow lines, and weak Hα absorption, seen in SN 2006V conflicts with expectations for a BSG explosion powered by 56Ni and may require an alternative power source. In contrast with theoretical expectations, observed spectra reveal a diverse behavior for lines like Ba II 6142 Å, Na I D, and Hα. In addition to diversity arising from different BSG progenitors, we surmise that their ejecta are asymmetric, clumped, and, in some cases, not solely powered by 56Ni decay.

scholarly journals SN 2016gsd: an unusually luminous and linear Type II supernova with high velocities

2020 ◽  
Vol 493 (2) ◽  
pp. 1761-1781 ◽  
Author(s):  
T M Reynolds ◽  
M Fraser ◽  
S Mattila ◽  
M Ergon ◽  
L Dessart ◽  
...  
Keyword(s):  
Light Curve ◽  
Massive Star ◽  
Absolute Magnitude ◽  
Host Galaxy ◽  
Type Ii ◽  
High Luminosity ◽  
Linear Type ◽  
Circumstellar Material ◽  
Low Metallicity ◽  
Edge Tracing

ABSTRACT We present observations of the unusually luminous Type II supernova (SN) 2016gsd. With a peak absolute magnitude of V = −19.95 ± 0.08, this object is one of the brightest Type II SNe, and lies in the gap of magnitudes between the majority of Type II SNe and the superluminous SNe. Its light curve shows little evidence of the expected drop from the optically thick phase to the radioactively powered tail. The velocities derived from the absorption in H α are also unusually high with the blue edge tracing the fastest moving gas initially at 20 000 km s−1, and then declining approximately linearly to 15 000 km s−1 over ∼100 d. The dwarf host galaxy of the SN indicates a low-metallicity progenitor which may also contribute to the weakness of the metal lines in its spectra. We examine SN 2016gsd with reference to similarly luminous, linear Type II SNe such as SNe 1979C and 1998S, and discuss the interpretation of its observational characteristics. We compare the observations with a model produced by the jekyll code and find that a massive star with a depleted and inflated hydrogen envelope struggles to reproduce the high luminosity and extreme linearity of SN 2016gsd. Instead, we suggest that the influence of interaction between the SN ejecta and circumstellar material can explain the majority of the observed properties of the SN. The high velocities and strong H α absorption present throughout the evolution of the SN may imply a circumstellar medium configured in an asymmetric geometry.

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