Hot, Luminous Stars in Selected Regions of NGC 6822, M31, and M33

Massey, Philip; Armandroff, T. E.; Pyke, R.; Patel, Kanan; Wilson, C. D.

doi:10.1086/117725

Cited by 102 publications

(142 citation statements)

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“…3, red crosses) but is also present in the data by Humphreys et al (1988;Fig. 3, blue diamonds) and Massey et al (1995;Fig. 3, yellow four-ray star).…”

Section: Light Curve Of Var Csupporting

confidence: 76%

“…Clearly, a hunt for more historic plates will be very fruitful. Hubble & Sandage (1953); (2) Sharov et al (1975); (3) Humphreys (1975); (4) Humphreys (1978); (5) Kenyon & Gallagher (1985); (6) Humphreys et al (1988); (7) Szeifert et al (1996); (8) Massey et al (1995); (9) Clark et al (2012); (10) this paper; (11) Viotti et al (2006); (12) Humphreys et al (2014); (13) Viotti et al (2013); (14) Valeev et al (2013). …”

Section: Discussionmentioning

confidence: 98%

“…8. B and V light curves and B − V colour curve of Var C. Crosses: TLS plate data; filled upwards triangles: DIRECT; stars: NOAO; filled downwards triangles: WIYN; stars with six rays: TLS CCD data; filled squares: COoSAI; filled diamonds: Humphreys (1978), , Humphreys et al (1984Humphreys et al ( , 1988; open four-ray stars: Massey et al (1995) Viotti et al (2013); open small dot: Roberto Viotti, Franco Montagni (priv. comm.…”

Section: Discussionmentioning

confidence: 99%

“…Further B CCD-photometry values came from Wilson (1991), Massey et al (1995), Szeifert et al (1996), Mochejska et al (2001), Viotti et al (2006), Humphreys et al (2013b), and Valeev et al (2013).…”

Section: Historical Data Taken From Literaturementioning

confidence: 99%

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Var C: Long-term photometric and spectral variability of a luminous blue variable in M 33

Burggraf

Weis

Bomans

et al. 2015

A&A

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Aims. So far the highly unstable phase of luminous blue variables (LBVs) has not been understood well. It is still uncertain why and which massive stars enter this phase. Investigating the variabilities by looking for a possible regular or even (semi-)periodic behaviour could give a hint at the underlying mechanism for these variations and might answer the question of where these variabilities originate. Finding out more about the LBV phase also means understanding massive stars better in general, which have (e.g. by enriching the ISM with heavy elements, providing ionising radiation and kinetic energy) a strong and significant influence on the ISM, hence also on their host galaxy. Methods. Photometric and spectroscopic data were taken for the LBV Var C in M 33 to investigate its recent status. In addition, scanned historic plates, archival data, and data from the literature were gathered to trace Var C's behaviour in the past. Its long-term variability and periodicity was investigated. Results. Our investigation of the variability indicates possible (semi-)periodic behaviour with a period of 42.3 years for Var C. That Var C's light curve covers a time span of more than 100 years means that more than two full periods of the cycle are visible. The critical historic maximum around 1905 is less strong but discernible even with the currently rare historic data. The semi-periodic and secular structure of the light curve is similar to the one of LMC R71. Both light curves hint at a new aspect in the evolution of LBVs.

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“…3, red crosses) but is also present in the data by Humphreys et al (1988;Fig. 3, blue diamonds) and Massey et al (1995;Fig. 3, yellow four-ray star).…”

Section: Light Curve Of Var Csupporting

confidence: 76%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Historical Data Taken From Literaturementioning

confidence: 99%

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Var C: Long-term photometric and spectral variability of a luminous blue variable in M 33

Burggraf

Weis

Bomans

et al. 2015

A&A

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“…This reddening is higher than the (mostly Galactic foreground) reddening E(B − V) = 0.24-0.36 mag (Gallart et al 1996;Massey et al 1995;McAlary et al 1985). Although our value is comparable to the median reddening of early type stars in NGC 6822 (E(B − V) = 0.45 mag (Wilson 1992b;Bianchi et al 2001), it must be considered a lower limit, because neither the Paβ nor the Brγ fluxes represent all the flux of Hubble V sampled in Hα.…”

Section: Hubble V Foreground Extinctionmentioning

confidence: 70%

Dust and molecules in the Local Group galaxy NGC 6822

Israel

Baas

Rudy

et al. 2002

A&A

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Abstract. We present maps of the first-ranked HII region complex Hubble V in the metal-poor Local Group dwarf galaxy NGC 6822 in the first four transitions of 12 CO, the 158 µm transition of C + , the 21-cm line of HI, the Paβ line of HII, and the continuum at 21 cm and 2.2 µm wavelengths. We have also determined various integrated intensities, notably of HCO + and near-IR H 2 emission. Although the second-ranked HII region Hubble X is located in a region of relatively strong HI emission, our mapping failed to reveal any significant CO emission from it. The relatively small CO cloud complex associated with Hubble V is comparable in size to the ionized HII region. The CO clouds are hot (T kin = 150 K) and have high molecular gas densities (n( H 2 ) ≈ 10 4 cm −3 ). Molecular hydrogen probably extends well beyond the CO boundaries. C + column densities are more than an order of magnitude higher than those of CO. The total mass of the complex is about 10 6 M and molecular gas accounts for more than half of this. The complex is excited by luminous stars reddened or obscured at visual, but apparent at near-infrared wavelengths. The total embedded stellar mass may account for about 10% of the total mass, and the mass of ionized gas for half of that. Hubble V illustrates that modest star formation efficiencies may be associated with high CO destruction efficiencies in low-metallicity objects. The analysis of the Hubble V photon-dominated region (PDR) confirms in an independent manner the high value of the CO-to-H 2 conversion factor X found earlier, characteristic of starforming low-metallicity regions.

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The Importance of Astrophysical Distance Measurements

Grijs

2011

An Introduction to Distance Measurement in Astronomy

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Hot, Luminous Stars in Selected Regions of NGC 6822, M31, and M33

Cited by 102 publications

References 1 publication

Var C: Long-term photometric and spectral variability of a luminous blue variable in M 33

Var C: Long-term photometric and spectral variability of a luminous blue variable in M 33

Dust and molecules in the Local Group galaxy NGC 6822

The Importance of Astrophysical Distance Measurements

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