A search for the presence of magnetic fields in the two Supergiant Fast X-ray Transients IGR J08408-4503 and IGR J11215-5952

A significant fraction of high-mass X-ray binaries are supergiant fast X-ray transients (SFXTs). The prime model for the physics governing their X-ray behaviour suggests that the winds of donor OB supergiants are magnetized. To investigate if magnetic fields are indeed present in the optical counterparts of such systems, we acquired low-resolution spectropolarimetric observations of the two optically brightest SFXTs, IGR J08408-4503 and IGR J11215-5952 with the ESO FORS2 instrument during two different observing runs. No field detection at a significance level of 3sigma was achieved for IGR J08408-4503. For IGR J11215-5952, we obtain 3.2sigma and 3.8sigma detections (_hydr = -978+-308G and _hydr = 416+-110G) on two different nights in 2016. These results indicate that the model involving the interaction of a magnetized stellar wind with the neutron star magnetosphere can indeed be considered to characterize the behaviour of SFXTs. We detected long-term spectral variability in IGR J11215-5952, while for IGR J08408-4503 we find an indication of the presence of short-term variability on a time scale of minutes.Comment: 5 pages, 1 table, 7 figures, accepted for publication in MNRA

System of galactic planetary nebulae

Нами уточнены расстояния до 554 галактических планетарных туманностей (ПТ) с использованием соотношения между ионизированной массой туманности μ и параметром оптической толщины, полученного [1]. Мы определили типы туманностей согласно [2] в модификации [3]. Полученные нами расстояния до галактических ПТ использовались для получения шкалы высот h различных подсистем Млечного Пути. Были найдены следующие значения: h = 208 ± 10 пк для объектов тонкого диска, h = 600 ± 54 пк для толстого диска и h = 1378 ± 180 пк для ПТ гало.We recalculated the distance to 554 galactic Planetary Nebulae (PNe) using the relation between the ionized mass of the nebula μ and the optical thickness parameter obtained by [1]. We classified these nebulae according to [2] types modified by [3]. The obtained by us distances to galactic PNe were used to obtain the scale heights h for different subsystems of the Milky Way. The following values of h were obtained: h = 208 ± 10 pc for thin disk objects, h = 600 ± 54 pc for thick disk ones, and h = 1378 ± 180 pc for halo PNe

New spectroscopic and polarimetric observations of the A0 supergiant HD92207

Our recent search for the presence of a magnetic field in the bright early A-type supergiant HD92207 using FORS2 in spectropolarimetric mode revealed the presence of a longitudinal magnetic field of the order of a few hundred Gauss. However, the definite confirmation of the magnetic nature of this object remained pending due to the detection of short-term spectral variability probably affecting the position of line profiles in left- and right-hand polarized spectra. We present new magnetic field measurements of HD92207 obtained on three different epochs in 2013 and 2014 using FORS2 in spectropolarimetric mode. A 3sigma detection of the mean longitudinal magnetic field using the entire spectrum, _all=104+-34G, was achieved in observations obtained in 2014 January. At this epoch, the position of the spectral lines appeared stable. Our analysis of spectral line shapes recorded in opposite circularly polarized light, i.e. in light with opposite sense of rotation, reveals that line profiles in the light polarized in a certain direction appear slightly split. The mechanism causing such a behaviour in the circularly polarized light is currently unknown. Trying to settle the issue of short-term variability, we searched for changes in the spectral line profiles on a time scale of 8-10min using HARPS polarimetric spectra and on a time scale of 3-4min using time series obtained with the CORALIE spectrograph. No significant variability was detected on these time scales during the epochs studied.Comment: 10 pages, 11 figures, 2 tables, accepted for publication in Astronomische Nachrichte