Diffuse interstellar bands of unprecedented strength in the line of sight towards high-mass X-ray binary 4U 1907+09

Cox, N. L. J.; Kaper, L.; Foing, B. H.; Ehrenfreund, P.

doi:10.1051/0004-6361:20042340

Cited by 46 publications

(49 citation statements)

References 42 publications

(65 reference statements)

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“…Ia supergiant (located at 2-6kpc) in 8.37d with an eccentricity of 0.28 (Makishima et al, 1984;in 't Zand et al, 1998b;Cox et al, 2005;Nespoli et al, 2008a). Its X-ray emission is highly variable and feature cyclotron absorption features Cusumano et al, 1998;Rivers et al, 2010;Fürst et al, 2011a;Hemphill et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

High-mass X-ray binaries in the Milky Way

Walter

Lutovinov

Bozzo

et al. 2015

Astron Astrophys Rev

228

234

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High-mass X-ray binaries are fundamental in the study of stellar evolution, nucleosynthesis, structure and evolution of galaxies and accretion processes. Hard X-rays observations by INTEGRAL and Swift have broadened significantly our understanding in particular for the super-giant systems in the Milky Way, which number has increased by almost a factor of three. INTEGRAL played a crucial role in the discovery, study and understanding of heavily obscured systems and of fast X-ray transients. Most super-giant systems can now be classified in three categories: classical/obscured, eccentric and fast transient.The classical systems feature low eccentricity and variability factor of ∼ 10 3 , mostly driven by hydrodynamic phenomena occurring on scales larger than the accretion radius. Among them, systems with short orbital periods and close to Roche-Lobe overflow or with slow winds, appear highly obscured. In eccentric systems, the variability amplitude can reach even higher factors, because of the contrast of the wind density along the orbit. Four super-giant systems, featuring fast outbursts, very short orbital periods and anomalously low accretion rates, are not yet understood.Simulations of the accretion processes on relatively large scales have progressed and reproduce parts of the observations. The combined effects of wind

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Section: Discussionmentioning

confidence: 99%

High-mass X-ray binaries in the Milky Way

Walter

Lutovinov

Bozzo

et al. 2015

Astron Astrophys Rev

228

234

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“…Unfortunately, the correlations between the Equivalent Width (EW) of most bands and reddening saturates at relatively low values (e.g., Munari & Zwitter 1997;Cox et al 2005). Munari et al (2008) find that the 8620Å DIB is an excellent tracer of reddening, with a very tight correlation E(B − V) = 2.72(±0.03) × EW (Å).…”

Section: Extinctionmentioning

confidence: 99%

The population of OB supergiants in the starburst cluster Westerlund 1

Negueruela¹,

Clark

Ritchie

2010

A&A

239

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Context. After leaving the main sequence, massive stars undergo complex evolution, which is still poorly understood. With a population of hundreds of OB stars, the starburst cluster Westerlund 1 offers an unparallelled environment to study their evolutionary tracks. Aims. We characterise a large sample of evolved OB stars in the cluster, with the aim of determining cluster parameters and place stars in an evolutionary sequence. Methods. We used the FORS2 instrument on the VLT to obtain intermediate-resolution spectroscopy over the range 5800-9000Å of about a hundred stars selected as likely members of the cluster based on their photometry. We developed criteria for their spectral classification using only spectral features in the range observed. We discuss these criteria, useful for spectral classification of earlytype stars in the GAIA spectral region, in the appendix. Using these criteria, we obtain spectral classifications, probably accurate to one subtype, for 57 objects, most of which had no previous classification or a generic classification. Results. We identify more than 50 objects as OB supergiants. We find almost 30 luminous early-B supergiants and a number of less luminous late-O supergiants. In addition, we find a few mid B supergiants with very high luminosity, some of them displaying signs of heavy mass loss. All these stars form a sequence compatible with theoretical evolutionary tracks. In addition, two early B supergiants also show indication of heavy mass loss and may represent the evolutionary phase immediately prior to the Wolf-Rayet stage. We investigate cluster properties using the spectral types and existing photometry. We find that the reddening law to the cluster does not deviate strongly from standard, even though extinction is quite variable, with an average value A V = 10.8. Though evolutionary tracks for high-mass stars are subject to large uncertainties, our data support an age of > ∼ 5 Myr and a distance d ≈ 5 kpc for Westerlund 1. Conclusions. The spectral types observed are compatible with a single burst of star formation (the age range is very unlikely to be > 1 Myr). Westerlund 1 shows its potentiality as a laboratory for massive star evolution, which can be fulfilled by detailed study of the population presented here.

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“…For the DIBs centered at 578.0, 579.7, and 661.4 nm, we measure an equivalent width of 0.063, 0.014, and 0.021 nm, respectively, with a typical error of 10%. Using the relations from Cox et al (2005), we arrive at an E(B − V) of 1.0 ± 0.1 mag. For an average value of R V = 3.1, these DIB strengths yield A V 3 mag of visual extinction.…”

Section: Interstellar Spectrummentioning

confidence: 99%

First firm spectral classification of an early-B pre-main-sequence star: B275 in M 17

Ochsendorf

Ellerbroek

Chini

et al. 2011

A&A

Self Cite

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The optical to near-infrared (300−2500 nm) spectrum of the candidate massive young stellar object (YSO) B275, embedded in the star-forming region M 17, has been observed with X-shooter on the ESO Very Large Telescope. The spectrum includes both photospheric absorption lines and emission features (H and Ca ii triplet emission lines, 1st and 2nd overtone CO bandhead emission), as well as an infrared excess indicating the presence of a (flaring) circumstellar disk. The strongest emission lines are double-peaked with a peak separation ranging between 70 and 105 km s −1 , and they provide information on the physical structure of the disk. The underlying photospheric spectrum is classified as B6−B7, which is significantly cooler than a previous estimate based on modeling of the spectral energy distribution. This discrepancy is solved by allowing for a larger stellar radius (i.e. a bloated star) and thus positioning the star above the main sequence. This constitutes the first firm spectral classification of an early-B pre-main-sequence (PMS) star. We discuss the position of B275 in the Hertzsprung-Russell diagram in terms of PMS evolution. Although the position is consistent with PMS tracks of heavily accreting protostars (Ṁ acc > ∼ 10 −5 M yr −1 ), the fact that the photosphere of the object is detectable suggests that the current mass-accretion rate is not very high.

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Diffuse interstellar bands of unprecedented strength in the line of sight towards high-mass X-ray binary 4U 1907+09

Cited by 46 publications

References 42 publications

High-mass X-ray binaries in the Milky Way

High-mass X-ray binaries in the Milky Way

The population of OB supergiants in the starburst cluster Westerlund 1

First firm spectral classification of an early-B pre-main-sequence star: B275 in M 17

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