TY - JOUR A1 - Gvaramadze, Vasily V. A1 - Kniazev, Alexei Y. A1 - Hamann, Wolf-Rainer A1 - Berdnikov, Leonid N. A1 - Fabrika, Sergei Nikolaevich A1 - Valeev, Azamat F. T1 - A new Wolf-Rayet star and its circumstellar nebula in Aquila N2 - We report the discovery of a new Wolf-Rayet star in Aquila via detection of its circumstellar nebula (reminiscent of ring nebulae associated with late WN stars) using the Spitzer Space Telescope archival data. Our spectroscopic follow-up of the central point source associated with the nebula showed that it is a WN7h star (we named it WR121b). We analysed the spectrum of WR 121b by using the Potsdam Wolf-Rayet model atmospheres, obtaining a stellar temperature of similar or equal to 50 kK. The stellar wind composition is dominated by helium with similar to 20 per cent of hydrogen. The stellar spectrum is highly reddened [E(B - V) = 2.85 mag]. Adopting an absolute magnitude of M-v = 5.7, the star has a luminosity of log L/L-circle dot = 5.75 and a mass-loss rate of 10(-4.7)M(circle dot)yr(-1), and resides at a distance of 6.3 kpc. We searched for a possible parent cluster of WR 121b and found that this star is located at similar or equal to 1 degrees from the young star cluster embedded in the giant HII region W43 (containing a WN7+a/OB? star - WR121a). We also discovered a bow shock around the O9.5III star ALS 9956, located at similar or equal to 0 degrees.5 from the cluster. We discuss the possibility that WR121b and ALS 9956 are runaway stars ejected from the cluster in W43. Y1 - 2010 UR - http://www3.interscience.wiley.com/cgi-bin/issn?DESCRIPTOR=PRINTISSN&VALUE=0035-8711 U6 - https://doi.org/10.1111/j.1365-2966.2009.16126.x SN - 0035-8711 ER - TY - JOUR A1 - Gvaramadze, V. V. A1 - Kniazev, Alexei Y. A1 - Oskinova, Lida T1 - Discovery of a putative supernova remnant around the long-period X-ray pulsar SXP 1323 in the Small Magellanic Cloud JF - Monthly notices of the Royal Astronomical Society N2 - We report the discovery of a circular shell centred on the Be X-ray binary (BeXB) SXP 1323 in the Small Magellanic Cloud. The shell was detected in an H α image obtained with the Very Large Telescope. Follow-up spectroscopy with the Southern African Large Telescope showed that the shell expands with a velocity of ≈100kms−1 and that its emission is due to shock excitation. We suggest that this shell is a remnant of the supernova explosion that led to the formation of SXP 1323’s neutron star ≈40000 yr ago. SXP 1323 represents the second known case of a BeXB associated with a supernova remnant (the first one is SXP 1062). Interestingly, both of these BeXBs harbour long-period pulsars and are located in a low-metallicity galaxy. KW - stars: emission-line, Be KW - stars: individual: [MA93] 1393 KW - stars: massive KW - ISM: supernova remnants KW - X-rays: binaries KW - X-rays: individual: SXP 1323 Y1 - 2019 U6 - https://doi.org/10.1093/mnrasl/slz018 SN - 0035-8711 SN - 1365-2966 VL - 485 IS - 1 SP - L6 EP - L10 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Burgemeister, S. A1 - Gvaramadze, Visily V. A1 - Stringfellow, G. S. A1 - Kniazev, Alexei Y. A1 - Todt, Helge Tobias A1 - Hamann, Wolf-Rainer T1 - WR 120bb and WR 120bc: a pair of WN9h stars with possibly interacting circumstellar shells JF - Monthly notices of the Royal Astronomical Society N2 - Two optically obscured Wolf-Rayet (WR) stars have been recently discovered by means of their infrared (IR) circumstellar shells, which show signatures of interaction with each other. Following the systematics of the WR star catalogues, these stars obtain the names WR 120bb and WR 120bc. In this paper, we present and analyse new near-IR, J-, H- and K-band spectra using the Potsdam Wolf-Rayet model atmosphere code. For that purpose, the atomic data base of the code has been extended in order to include all significant lines in the near-IR bands. The spectra of both stars are classified as WN9h. As their spectra are very similar the parameters that we obtained by the spectral analyses hardly differ. Despite their late spectral subtype, we found relatively high stellar temperatures of 63 kK. The wind composition is dominated by helium, while hydrogen is depleted to 25 per cent by mass. Because of their location in the Scutum-Centaurus Arm, WR 120bb and WR 120bc appear highly reddened, A(Ks) approximate to 2 mag. We adopt a common distance of 5.8 kpc to both stars, which complies with the typical absolute K-band magnitude for the WN9h subtype of -6.5 mag, is consistent with their observed extinction based on comparison with other massive stars in the region, and allows for the possibility that their shells are interacting with each other. This leads to luminosities of log(L/L-circle dot) = 5.66 and 5.54 for WR 120bb and WR 120bc, with large uncertainties due to the adopted distance. The values of the luminosities of WR 120bb and WR 120bc imply that the immediate precursors of both stars were red supergiants (RSG). This implies in turn that the circumstellar shells associated with WR 120bb and WR 120bc were formed by interaction between the WR wind and the dense material shed during the preceding RSG phase. KW - line: identification KW - circumstellar matter KW - stars: fundamental parameters KW - stars: massive KW - stars: Wolf-Rayet Y1 - 2013 U6 - https://doi.org/10.1093/mnras/sts588 SN - 0035-8711 SN - 1365-2966 VL - 429 IS - 4 SP - 3305 EP - 3315 PB - Oxford Univ. Press CY - Oxford ER -