Luminous and Variable Stars in NGC 2403 and M81*

Humphreys, R. M.; Stangl, S.; Gordon, Michael S.; Davidson, Kris; Grammer, Skyler H.

doi:10.3847/1538-3881/aaf1ac

Cited by 18 publications

(21 citation statements)

References 32 publications

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“…Most promising for dedicated searches are the nearby large spiral galaxies M81, M101, and NGC 2403, for which pioneering ground-based surveys have been conducted already in the eighties and nineties of the last century ( [146][147][148][149]) and which are nowadays extended to fainter objects thanks to the capabilities of the Hubble Space Telescope (e.g., [150]). Spectroscopic follow-up investigations revealed a number of variable luminous objects ( [151][152][153][154][155]), but only in one of these galaxies, M81, three B[e]SG candidates have been found so far ( [156]). They all display the typical B[e] features in their optical spectra, but without complementary information about the presence of (warm) circumstellar dust, their classification remains preliminary.…”

Section: Byond the Local Groupmentioning

confidence: 99%

“…The B[e]SG candidates in M81 are listed in Table 8. For lack of proper SIMBAD identifiers for these objects, the table contains the star ID ( [156]) along with the coordinates and, where available, the V band magnitudes. [156] (10584-9-1) 9:55:18.97 +69:08:27.…”

Section: Byond the Local Groupmentioning

confidence: 99%

“…For lack of proper SIMBAD identifiers for these objects, the table contains the star ID ( [156]) along with the coordinates and, where available, the V band magnitudes. [156] (10584-9-1) 9:55:18.97 +69:08:27. 54 19.10 [156] In the past few years, additional surveys have been performed, using large ground-based facilities (e.g., [157]) and space telescopes (e.g., [158,159]).…”

Section: Byond the Local Groupmentioning

confidence: 99%

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A Census of B[e] Supergiants

Kraus

2019

Galaxies

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Stellar evolution theory is most uncertain for massive stars. For reliable predictions of the evolution of massive stars and their final fate, solid constraints on the physical parameters, and their changes along the evolution and in different environments, are required. Massive stars evolve through a variety of short transition phases, in which they can experience large mass-loss either in the form of dense winds or via sudden eruptions. The B[e] supergiants comprise one such group of massive transition objects. They are characterized by dense, dusty disks of yet unknown origin. In the Milky Way, identification and classification of B[e] supergiants is usually hampered by their uncertain distances hence luminosities, and by the confusion of low-luminosity candidates with massive pre-main sequence objects. The extragalactic objects are often mistaken as quiescent or candidate luminous blue variables, with whom B[e] supergiants share a number of spectroscopic characteristics. In this review, proper criteria are provided, based on which B[e] supergiants can be unambiguously classified and separated from other high luminosity post-main sequence stars and pre-main sequence stars. Using these criteria, the B[e] supergiant samples in diverse galaxies are critically inspected, to achieve a reliable census of the current population.In the HR diagram these objects are all found beyond the main-sequence and with luminosities spreading from about log L/L ∼ 4 to about log L/L ∼ 6 implying that they are all evolved, massive stars. This luminosity range was determined from the sample residing in the Magellanic Clouds (MCs), for which the luminosity determination is unquestionable, due to the low extinction towards the MCs and their well constraint distances. The classification of Galactic objects as supergiants bears much higher uncertainties due to their often poorly constraint distances hence luminosities. We will come back to this issue in Section 4.4.The position of the MC sample in the HR diagram is shown in Figure 1 for the values of luminosity and effective temperature listed in Table 1. The stellar parameters (effective temperature T eff , visual magnitude V, and color excess E(B − V)) of the sample have been taken from the references listed in the last column of Table 1. For the calculations of the luminosities, distance moduli of 18.5 and 18.9 mag for the Large respectively Small Magellanic Clouds have been utilized (see the review paper by Humphreys, this volume) along with bolometric corrections from [29].The presence of dust around an early-type (typically of spectral type B) supergiant, along with the often pure emission-line spectra with numerous forbidden lines predominantly of [Fe II] and [O I] finally resulted in the designation of these objects as B[e] supergiants (B[e]SGs) 1 . 1 Note that these objects have previously been abbreviated sgB[e] ([24]), to separate them from other stars showing the B[e] phenomenon. We prefer the designation B[e]SG, to be in line with the naming and abbreviation of other type o...

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Section: Byond the Local Groupmentioning

confidence: 99%

Section: Byond the Local Groupmentioning

confidence: 99%

Section: Byond the Local Groupmentioning

confidence: 99%

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A Census of B[e] Supergiants

Kraus

2019

Galaxies

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“…Therefore its seen as a giant eruption LBV candidate with the above caveat. Just recently Humphreys [140] report that the following objects are not LBVs: I 8 in M 81 is an F supergiant, furthermore V 52 in NGC 2403 and I 3 in M 81 are foreground objects and not even part of those galaxies! HD 168625, He 3-519, Pistol star, and Sher 25 are LBV candidates due to the fact that they posses a circumstellar nebula.…”

Section: The Population Of Lbvsmentioning

confidence: 99%

Luminous Blue Variables

Weis

Bomans

2020

Galaxies

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Luminous Blue Variables are massive evolved stars, here we introduce this outstanding class of objects. Described are the specific characteristics, the evolutionary state and what they are connected to other phases and types of massive stars. Our current knowledge of LBVs is limited by the fact that in comparison to other stellar classes and phases only a few “true” LBVs are known. This results from the lack of a unique, fast and always reliable identification scheme for LBVs. It literally takes time to get a true classification of a LBV. In addition the short duration of the LBV phase makes it even harder to catch and identify a star as LBV. We summarize here what is known so far, give an overview of the LBV population and the list of LBV host galaxies. LBV are clearly an important and still not fully understood phase in the live of (very) massive stars, especially due to the large and time variable mass loss during the LBV phase. We like to emphasize again the problem how to clearly identify LBV and that there are more than just one type of LBVs: The giant eruption LBVs or η Car analogs and the S Dor cycle LBVs.

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“…Intermediate luminosity optical transients (ILOTs) are exotic outbursts with luminosities which fall between those of novae and supernovae (SN). Many new ILOTs are being discovered by modern surveys and dedicated campaigns (e.g., [1,[7][8][9][10][11][12][28][29][30][36][37][38][39][40][41][42][43][43][44][45][46][47][48][49]51,52,57,58,64,66,70,73]. The group consists of many different astronomical eruptions which are diverse, but are found to have shared properties [32,33,59].…”

Section: Introductionmentioning

confidence: 99%

ASASSN-13db 2014–2017 Eruption as an Intermediate Luminosity Optical Transient

2019

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The low mass star ASASSN-13db experienced an EXor outburst in 2013, which identified it as a Young Stellar Object (YSO). Then, from 2014 to 2017 it had another outburst, longer and more luminous than the earlier. We analyze the observations of the second outburst, and compare it to eruptions of Intermediate Luminosity Optical Transients (ILOTs). We show that the decline of the light curve is almost identical to that of the V838 Mon, a prototype of a type of ILOT known as Luminous Red Nova (LRN). This similarity becomes conspicuous when oscillations that are associated with rotation are filtered out from the light curve of ASASSN-13db. We suggest that the eruption was the result of accretion of a proto-planet of a few Earth masses. The proto-planet was shredded by tidal forces before it was accreted onto the YSO, releasing gravitational energy that powered the outburst for ≈ 800 days, and ended in a ≈ 55 days decline phase. When the accretion material started depleting the accretion rate lowered and the eruption light curve declined for almost two months. Then it exhausted completely, creating a sharp break in the light curve. Another possibility is that the mass was a result of an instability in the proto-planetary disk that lead to a large episode of accretion from an inner viscous disk. We find that the variation of the temperature of the outburst is consistent with the surface temperature expected from a depleted viscous accretion disk. The 2014-2017 outburst of ASASSN-13db may be the least energetic ILOT to have been discovered to date, with an energy budget of only ≈ 10 42 erg.Galaxies 2020, xx, 5 2 of 16The Energy-Time Diagram (ETD; [33], [32]) is used for classifying transients in terms of their characteristic time of decline and their total energy (The ETD webpage: phsites.technion.ac.il/soker/ilotclub/.). In the ETD many of the transients form a slated stripe more energetic, for a given time scale, than novae yet less energetic than SNe. We refer to this stripe as the Optical Transient Stripe. In [33] it was suggested that most objects that populate the stripe share a similar powering mechanism, that they suggest to be accretion energy. The different time scale are related to the accretion rate or the mass supply rate, that in some cases can be limited by the time it takes to dissipate the angular momentum of the accreted mass through viscosity.One well studied transient is the 2002 outburst of V838 Mon [11]. It is considered a prototype of a sub-type of ILOTs, known as Luminous Red Novae (LRN). Both classical nova and He-shell flash were suggested as explanations for the unusual eruption, but later ruled out [67]. The star involved in the V838 Mon eruption was a massive star, possibly even on the main-sequence (MS). Perhaps the most unusual observation was that as time passed V838 Mon became redder [16,63], which is exactly opposite to the evolution of classical novae.A model for the eruption of V838 Mon that involves a stellar merger event followed by an accretion process, in which the surviving star a...

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Luminous and Variable Stars in NGC 2403 and M81*

Cited by 18 publications

References 32 publications

A Census of B[e] Supergiants

A Census of B[e] Supergiants

Luminous Blue Variables

ASASSN-13db 2014–2017 Eruption as an Intermediate Luminosity Optical Transient

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