Spectral states in Be/X-ray pulsars

In the last quarter of a century, a unified characterization of the spectral evolution of low-mass X-ray binaries, both containing a neutron star and a black hole, was possible. In this context, the notion of source states characterizing the X-ray emission from black-hole binaries and neutron-star low-mass X-ray binaries revealed to be a very useful tool to disentangle the complex spectral and aperiodic phenomenology displayed by those classes of accreting objects. Be/X-ray binaries constitute another major class of transient accreting binaries, for which very little work has been done on the correlated timing and spectral variability. Especially, no definition of source states exists for this class, in spite of their highly variable X-ray emission. When active, Be/X-ray binaries are among the brightest objects in the X-ray sky and are characterized by dramatic variability in brightness on timescales ranging from seconds to years. It is then worth it to ask whether a definition of spectral states is possible for these systems. In this work, we try to address such a question, investigating whether accreting X-ray pulsars display source states and characterizing those states through their spectral properties. Our results show that Be/X-ray pulsars trace two different branches in their hardness-intensity diagram: the horizontal branch, a low-intensity state, and the diagonal branch, a high-intensity state that only appears when the X-ray luminosity exceeds a critical limit. We propose that the two branches are the phenomenological signature of two different accretion modes -- in agreement with recently proposed models -- depending on whether the luminosity of the source is above or below a critical value.Comment: Proceedings of "An INTEGRAL view of the high-energy sky (the first 10 years)" the 9th INTEGRAL Workshop, October 15-19, 2012, Paris, France, in Proceedings of Science (INTEGRAL 2012), Eds. A. Goldwurm, F. Lebrun and C. Winkler, (http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=176), id 02

Unveiling the nature of IGR J16493-4348 with IR spectroscopy

The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) is discovering a large number of new hard X-ray sources, many of them being HMXBs. The identification and spectral characterization of their optical/infrared counterparts is a necessary step in undertaking a detailed study of these systems. In a previous paper, we presented spectral analyses and classifications of six newly discovered INTEGRAL sources. In this paper, we extend the analysis to IGR J16493-4348. We used the ESO/VLT ISAAC spectrograph to observe the proposed IR counterpart to the source, obtaining a Ks medium-resolution spectrum (R = 500) with a signal-to-noise ratio (S/N) >150. We classified the source by comparing with published atlases. We spectrally classified the source as a B0.5-1 supergiant and estimated its interstellar extinction. We compared the extinction derived from X-ray data with effective interstellar extinction obtained from our data, discussing the absorption component associated with the circumstellar environment.Comment: 4 pages, 1 figure, 3 tables. Accepted for publication in Astronomy and Astrophysics

K-band spectroscopy of IGR J16358-4726 and IGR J16393-4643: two new symbiotic X-ray binaries

Symbiotic X-ray Binaries (SyXBs) are a recently discovered subclass of Low Mass X-ray Binaries. Their growing number makes them an important evolutionary channel of X-ray Binaries. Our goal is to perform spectral analysis and classification of the proposed counterparts to IGR J16358-4726 and IGR J16393-4643 and to establish their nature as X-ray systems. We used the ESO/UT1 ISAAC spectrograph to observe the proposed counterparts to the two sources, obtaining K-band medium resolution spectra (R = 500) with a S/N > 140. Data reduction was performed with the standard procedure. We classified them by means of comparison with published atlases. We performed SED fitting in order to refine the spectral classification. The two counterparts clearly exhibit the typical features of late-type stars, notably strong CO absorption bands in the red part of the spectrum. With information from previous X-ray studies, we classify the two systems as two new members of the SyXB class. For IGR J16393-4643, we considered the most probable counterpart to the system, although three other objects cannot be completely discarded. For this system, we compared our findings with available orbital solutions, constraining the orbital parameters and the mass of the companion star. By including two more systems, we increased to eight the number of known SyXBs, which emerges as a non-negligible category of galactic X-ray binaries.Comment: 7 pages, 3 figures, 4 tables; this version includes referee's comments and language editing. Accepted for publication in Astronomy and Astrophysics

User Behavior Clustering Based Method for EV Charging Forecast

The increasing adoption of electric vehicles poses new problems for the electrical distribution network. For this reason, proper electric vehicle forecasting will be of fundamental importance for a predictive energy management system, which could greatly help the operation of the grid. This paper proposes a comprehensive novel methodology to forecast single charging sessions of electric vehicle and the resulting cumulative energy forecast of the charging infrastructure. Historical charging sessions are first clustered on the basis of similar user characteristics and their respective probability density functions are defined. From this, every charging session is predicted with a triplet of parameters, namely the arrival time, the charging duration and the average power expected during the process. The proposed method has been evaluated by considering a real case study. The results showed the ability to greatly improve the accuracy with respect to the chosen benchmark, both in terms of energy required by the station and the predicted number of charging sessions. The overall performance measured by Skill Score is 0.37 for the year 2019

Childbearing women’s experiences of early pushing urge

AIM: To explore childbearing women’s experiences of early pushing urge (EPU). STUDY DESIGN: A qualitative phenomenological study was undertaken in an Italian maternity hospital. The sample included 8 women that experienced EPU during labor. Data were collected through semi-structured interviews. FINDINGS: The findings are presented as three main themes: (a) women’s perceptions of EPU, (b) bodily sensations versus midwives’ advice: struggling between conflicting messages, and (c) the “a posteriori” feeling of women about midwives’ guidance during EPU. The perception of EPU was characterized by sense of obstruction, bone pain, and different intensity of pushing efforts when compared with those of the expulsive phase. Women found it difficult to follow the midwife’s suggestion to stop pushing because this contradicted their bodily sensations. However, the women recognized a posteriori the importance of the midwife’s support while experiencing EPU. Women appreciated the midwives’ presence and emotional support most of all because they seemed to be more concerned with the personal relationship they formed in labor rather than the usefulness or appropriateness of their advice. CONCLUSION: Midwives should consider women’s physical perceptions to help them cope with EPU, acknowledging that women may struggle when caregivers’ suggestions are in contrast to their physical perceptions. The women’s overall positive experiences of birth suggest that EPU might be considered as a physiological event during labor, reinforcing the hypotheses of previous research. The optimal response to the EPU phenomenon remains unclear and should be studied, considering EPU at different dilatation ranges and related clinical outcomes

Midwives’ approaches to early pushing urge in labour

The objectives of this mixed-methods study were: a) to investigate midwives' approaches to early pushing urge (EPU); and b) to explore midwives' perspectives and experiences of helping women cope with EPU. A quantitative observational methodology was adopted to investigate midwives' approaches to EPU in 60 cases. A qualitative phenomenological approach was carried out in order to gain more in-depth understanding of midwives' views and experiences of EPU management strategies. It was found that midwives mainly adopt two approaches in the case of EPU: letting the woman do what she feels, and a stop-pushing technique. The findings are presented as four main domains: a) midwives' approaches to EPU; b) drivers guiding midwives' approaches to EPU; c) influencing factors in helping women cope with EPU; d) variation of midwives' approaches to EPU over time

Recent activity of the Be/X-ray binary system SAX J2103.5+4545

Aims. We present a multiwavelength study of the Be/X-ray binary system SAX J2103.5+4545 with the goal of better characterizing the transient behaviour of this source. Methods. SAX J2103.5+4545 was observed by Swift-XRT four times in 2007 from April 25 to May 5, and during quiescence in 2012 August 31. In addition, this source has been monitored from the ground-based astronomical observatories of El Teide (Tenerife, Spain), Roque de los Muchachos (La Palma, Spain) and Sierra Nevada (Granada, Spain) since 2011 August, and from the TUBITAK National Observatory (Antalya, Turkey) since 2009 June. We have performed spectral and photometric temporal analyses in order to investigate the different states exhibited by SAX J2103.5+4545. Results. In X-rays, an absorbed power law model provided the best fit for all the XRT spectra. An iron-line feature at ~6.42 keV was present in all the observations except for that taken during quiescence in 2012. The photon indexes are consistent with previous studies of SAX J2103.5+4545 in high/low luminosity states. Pulsations were found in all the XRT data from 2007 (2.839(2) mHz; MJD 54222.02), but not during quiescence. Both optical outbursts in 2010 and 2012 lasted for about 8/9 months (as the one in 2007 probably did and the current one in 2014 might do) and were most probably caused by mass ejection events from the Be star that eventually fed the circumstellar disc. All of these outbursts started about 3 months before the triggering of the X-ray activity, and about the same period before the maximum of the H_alpha line equivalent width (in emission) was reached at only ~ -5 \AA. In this work we found that the global correlation between the BV variability and the X-ray intensity was also observed at longer wavelengths in the IR domain.Comment: 11 pages, 7 figures, and online material (2 tables). Submitted to A&A in 2014 Januar

Disorientation, self-awareness and ongoing learning: student midwives’ experiences of clinical placements in Italy

Objective: To explore student midwives’ perspectives, experiences and concerns regarding clinical placements in the Italian setting. Design: A qualitative phenomenological study was undertaken, with data collected through semi-structured interviews and diaries. Ethical approval was obtained. Data analysis was conducted using a thematic analysis approach. Setting: One university in Northern Italy including a midwifery undergraduate programme. Participants: Purposeful sample of 19 third-year student midwives. Findings: Four themes emerged from the data: a) becoming a midwife: disorientation, self-awareness and ongoing learning; b) mentor as key figure; c) practice and theory: a ‘chicken and egg’ situation; d) clinical placements: a window on the uniqueness of the midwifery profession. Student midwives reported a journey through different learning phases within clinical placements, from feeling disoriented while facing initial challenges in the first year of the course to having increasing awareness of their role in the second and third year of the programme. The phase of disorientation was mainly due to not being aware of the theoretical evidence behind practice, not feeling part of the team, not knowing what their role was and lack of appropriate supervision from mentors. A positive relationship with the mentor encouraged students to share perspectives and doubts, stimulating a problem solving approach. The students found it helpful when the mentor involved them in the decision making and praised them when they deserved it. A good rapport with the midwife was reported by the participants as inspiring self-confidence and cognitive enquiries; it also allowed the students to feel part of the multidisciplinary team. An overall sense of ongoing learning was still present at the end of the midwifery programme. Key conclusions and implications for practice: Continuity of mentorship and mentors’ commitment to supporting students emerged as key aspects for a positive and fruitful learning experience within practice settings. Other pivotal elements to be considered by mentors are making the students feel welcome and part of the team; orienting them on the first day of placement; allowing some time for familiarisation with the placement area and clinical policies; involving the students in the decision-making process and care planning/implementation/ evaluation. Appropriate national mandatory training should be put in place for mentors to allow a more effective learning experience in practice settings for student midwives

GX 339-4: back to life

We report preliminary results of a RossiXTE campaign on the 2002 outburst of the black-hole candidate GX 339-4. We show power density spectra of five observations during the early phase of the outburst. The first four power spectra show a smooth transition between a Low State and a Very High State. The fifth power spectrum resembles a High State, but a strong 6 Hz QPO appears suddenly within 16 seconds.Comment: 3 pages, 3 figures; to appear in Proceedings of the 4th Microquasar Workshop, eds. Ph Durouchoux, Y. Fuchs and J. Rodriguez, published by the Center for Space Physics: Kolkat