FS CMa stars form a group of objects with the B[e] phenomenon that were previously known as unclassified B[e] stars or B[e] stars with warm dust (B[e]WD) until recently. They exhibit strong emission-line spectra and strong IR excesses, most likely due to recently formed circumstellar dust. These properties have been suggested to be due to ongoing or recent rapid mass exchange in binary systems with hot primaries and various types of secondaries. The first paper of this series reported an analysis of the available information about previously known Galactic objects with the B[e] phenomenon, the initial selection of the FS CMa group objects, and a qualitative explanation of their properties. This paper reports the results of our new search for more FS CMa objects in the IRAS Point Source Catalog. We present new photometric criteria for identifying FS CMa stars as well as the first results of our observations of nine new FS CMa group members. With this addition, the FS CMa group has now 40 members, becoming the largest among the dust-forming hot star groups. We also present nine objects with no evidence for the B[e] phenomenon, but with newly discovered spectral line emission and/or strong IR excesses.

Context. Understanding the origin of the instabilities of LBVs is important for shedding light on the late evolutionary stages of massive stars and on the chemical evolution of galaxies. Aims. To investigate the physical nature of variable stars in the upper H-R diagram, we performed a spectrophotometric study of the Romano's star GR 290 and the Hubble-Sandage variables A, B, and C in the close galaxy M 33. Methods. New spectroscopic and photometric data were employed in conjunction with already published data of these stars in order to derive spectral types, energy distribution and bolometric luminosities. Results. The yellow hypergiant Var A is still at minimum, with a ∼G-type spectrum and strong Hα emission (W eq −35 Å). Var B is in a low luminosity hot state (V = 17.5, B − V = −0.15) with very strong Hα emission (W eq = −310 Å). Its absolute bolometric luminosity is 0.6 × 10 6 L . Var C, at V = 16.4, is fainter than in the mid 1980s, but its spectrum shows the typical features of LBVs at maximum, a spectrum that is very rich in Fe ii emission lines. Its L bol is about 0.7 × 10 6 L . The Romano's star GR 290 has a rich hot emission-line spectrum and is very bright with L bol = 3 × 10 6 L . During 2004 the star brightened by ∼half magnitude in each of the BVR filters. Conclusions. Our observations confirm that Var A probably is an intermediate type hypergiant star surrounded by an expanding envelope with a collisionally excited hydrogen emission, largely obscured by dusty disk and nebula. In recent years, Var B has undergone a blueward transition in the H-R diagram, probably at constant bolometric luminosity, while Var C is in a post-maximum phase with an η Car-type spectrum. GR 290 is notable for its spectrum and luminosity, and it is likely to develop ample spectral variations in the near future, similar to those observed in AG Car.

We have investigated the past light history of the luminous variable star GR 290 (M33/V532, Romano’s Star) in the M33 galaxy, and collected new spectrophotometric observations in order to analyze links between this object, the LBV category, and the Wolf–Rayet stars of the nitrogen sequence. We have built the historical light curve of GR 290 back to 1901, from old observations of the star found in several archival plates of M33. These old recordings together with published and new data on the star allowed us to infer that for at least half a century the star was in a low luminosity state, with B ≃ 18–19, most likely without brighter luminosity phases. After 1960, five large variability cycles of visual luminosity were recorded. The amplitude of the oscillations was seen increasing toward the 1992–1994 maximum, then decreasing during the last maxima. The recent light curve indicates that the photometric variations have been quite similar in all the bands and that the B – V color index has been constant within ±0.1 m despite the 1.5 m change of the visual luminosity. The spectrum of GR 290 at the large maximum of 1992–94 was equivalent to late-B-type, while, during 2002–2014, it varied between WN10h-11h near the visual maxima to WN8h-9h at the luminosity minima. We have detected, during this same period, a clear anti-correlation between the visual luminosity, the strength of the He ii 4686 Å emission line, the strength of the 4600–4700 Å lines’ blend, and the spectral type. From a model analysis of the spectra collected during the whole 2002–2014 period, we find that the Rosseland radius R 2/3, changed between the minimum and maximum luminosity phases by a factor of three while T eff varied between about 33,000 and 23,000 K. We confirm that the bolometric luminosity of the star has not been constant, but has increased by a factor of ∼1.5 between minimum and maximum luminosity, in phase with the apparent luminosity variations. Presently, GR 290 falls in the H–R diagram close to WN8h stars and is probably younger than them. In the light of current evolutionary models of very massive stars, we find that GR 290 has evolved from an ∼60 M ☉ progenitor star and should have an age of about four million years. From its physical charcteristics, we argue that GR 290 has left the LBV stage and is presently moving from the LBV stage to a Wolf–Rayet stage of a late nitrogen spectral type.

Abstract.We report the first spectroscopic study of the LBV candidate GR 290 in M 33 ("Romano's star") taken in February 2003, showing, besides prominent hydrogen and He  emission lines, the 4630-60 Å blend and weak He  4686 Å emission typical of Of stars. Our broad-band photometry shows that the star was observed during a phase of minimum optical luminosity, with B = 17.91 ± 0.03, and a slightly positive colour index, which we tentatively attribute to an anomalous continuum energy distribution. We argue that GR 290 is indeed an LBV star presently in a high temperature phase, that should be followed -also in a short time -by ample spectroscopic and associated photometric variations.Key words. stars: evolution -stars: emission-lines, Be -stars: individual: GR 290 -stars: mass-lossgalaxies: individual: M 33Since the discovery of a small number of blue, intrinsically bright variable stars in M 31 and M 33 by Hubble & Sandage (1953), the LBV phenomenon has represented an evolutionary problem which still seems far from solution. Extensive descriptions of LBVs and in general of the S Dor type stars can be found in several review papers (e.g., Humphreys & Davidson 1994;van Genderen 2001, and reference therein). We recall briefly that to be defined as an LBV, a star must fulfil a number of photometric and spectroscopic observational conditions. It must be -or should have been in the far past -subject to sporadic violent events of photometric variability as well as to minor eruptions. These instability phases are confirmed by associated deep spectroscopic changes, with signatures of strong mass loss episodes. At minimum in the visual LBVs exhibit a blue colour and a hotter spectrum; in some cases an Of/WN spectrum has been observed. During the high luminosity phases they present a cooler continuum and display a lower excitation emission line spectrum. The variations seem to occur at constant bolometric luminosity, but in some cases light fading was caused by the formation of opaque dust shells.With these characteristics, the identification of a star as an LBV requires a long monitoring, and, in spite of the enormous progress in observational technologys since the first work of Hubble & Sandage, the population numbers are still very low. So far the total estimated number of confirmed and Send offprint requests to: V. F. Polcaro, e-mail: polcaro@rm.iasf.cnr.it Based on observations collected at 1.52 m Cassini telescope of the Loiano Observing Station, Bologna Astronomical Observatory.candidate LBVs is 21, 4, and 21 in the Milky Way, SMC and LMC, respectively (van Genderen 2001). As far as the Local Group galaxies are concerned, the richest is M 33, where a total of about ten LBVs have so far been recognised, although their total number may be underestimated due to their possible low photometric quiescent phase (Massey et al. 1996).The suggested evolutionary status of the LBVs is that of evolved objects. Their emission spectra are enriched in He and N and poor in oxygen, indicating that their winds and ejecta are supplyi...

Abstract. We report on the discovery and confirmation of the optical counterparts of the two transient X-ray pulsars, RX J0052.1-7319 and XTE J0111.2-7317. In the narrow (∼3 radius) X-ray error circle of RX J0052.1-7319 we found a V = 14.6 (B − V = 0.1) 09.5IIIe (a classification as a B0Ve star is also possible, since the luminosity class depends on the uncertainty on the adopted reddening). Medium resolution spectra for this object show Balmer lines in emission with an equivalent width of Hα = −12 ÷ −16Å. In the X-ray error box of XTE J0111.2-7317 we found a relatively bright object (V = 15.4, B − V = 0.06) which has been classified as a B0.5-B1Ve star and that was later confirmed by Coe et al. (2000) as the most plausible counterpart for XTE J0111.2-7317. Also in this case we easily detect Balmer emission lines with an Hα equivalent width of about −21Å. There is also evidence for the presence of a surrounding nebula, possibly a supernova remnant. A further bright B0Ve star was found just outside the X-ray error circle of XTE J0111.2-7317. We discuss the implication of these results in the light of the current knowledge of Be/X-ray binary systems in the Magellanic Clouds and within our Galaxy.