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We investigate the spectral characteristics of the Be/X-ray binary system, EXO 051910+3737.7, in which Be/X-ray systems are the largest sub-class of high-mass X-ray binaries. Spectroscopic observations are taken by the Thai National Telescope (TNT) with a Medium-RESolution spectrograph (MRES) instrument for seven nights spanning from 2020 to 2021. Our primary focus is directed towards the analysis of two Balmer lines, namely Hα and Hβ, given that Be stars typically exhibit emission features in at least one of these hydrogen Balmer lines during certain phases. Our observations reveal split Balmer emission lines throughout the entire duration of our monitoring. Double Gaussian profiles were employed for line fitting to characterize these lines. The presence of double peaks in the Balmer lines indicates the presence of asymmetries within the circumstellar disc. We then analyze V/R variations and the changes in Hβ spectra. Our analysis of V/R variation which Violet (V) and Red (R) peak intensity components, revealed rapid fluctuations occurring within a single day, although determining the precise periodicity was constrained by instrumental limitations and the duration of observability. Furthermore, employing observed the wavelength differences (Δλ) in conjunction with typical Be star parameters allowed us to estimate the radius (rβ) of the Hβ emitting envelope. The average value was calculated to be 2.585r*, with a standard deviation of 0.050r*. [ABSTRACT FROM AUTHOR]

As the brightest gamma-ray burst ever observed, GRB 221009A provided a precious opportunity to explore spectral line features. In this article, we performed a comprehensive spectroscopy analysis of GRB 221009A jointly with GECAM-C and Fermi/GBM data to search for emission and absorption lines. For the first time we investigated the line feature throughout this GRB including the most bright part where many instruments suffered problems, and identified prominent emission lines in multiple time intervals. The central energy of the Gaussian emission line evolves from about 37 to 6 MeV, with a nearly constant ratio (about 10%) between the line width and central energy. Particularly, we find that both the central energy and the energy flux of the emission line evolve with time as a power law decay with power law index of −1 and −2, respectively. We suggest that the observed emission lines most likely origin from the blue-shifted electron positron pair annihilation 511 keV line. We find that a standard high latitude emission scenario cannot fully interpret the observation, thus we propose that the emission line comes from some dense clumps with electron positron pairs traveling together with the jet. In this scenario, we can use the emission line to directly, for the first time, measure the bulk Lorentz factor of the jet (Γ) and reveal its time evolution (i.e., Γ ∼ t−1) during the prompt emission. Interestingly, we find that the flux of the annihilation line in the co-moving frame keeps constant. These discoveries of the spectral line features shed new and important lights on the physics of GRB and relativistic jet. [ABSTRACT FROM AUTHOR]

Mass loss is one of the key parameters that determine stellar evolution. Despite the progress we have achieved over the last decades we still cannot match the observational derived values with theoretical predictions. Even worse, there are certain phases, such as the B[e] supergiants (B[e]SGs) and the Luminous Blue Variables (LBVs), where significant mass is lost through episodic or outburst activity. This leads to various structures forming around them that permit dust formation, making these objects bright IR sources. The ASSESS project aims to determine the role of episodic mass in the evolution of massive stars, by examining large numbers of cool and hot objects (such as B[e]SGs/LBVs). For this purpose, we initiated a large observation campaign to obtain spectroscopic data for ∼1000 IR-selected sources in 27 nearby galaxies. Within this project we successfully identified seven B[e] supergiants (one candidate) and four Luminous Blue Variables of which six and two, respectively, are new discoveries. We used spectroscopic, photometric, and light curve information to better constrain the nature of the reported objects. We particularly noted the presence of B[e]SGs at metallicity environments as low as 0.14 Z ⊙ . [ABSTRACT FROM AUTHOR]

Mass loss is one of the key parameters that determine stellar evolution. Despite the progress we have achieved over the last decades we still cannot match the observational derived values with theoretical predictions. Even worse, there are certain phases, such as the B[e] supergiants (B[e]SGs) and the Luminous Blue Variables (LBVs), where significant mass is lost through episodic or outburst activity. This leads to various structures forming around them that permit dust formation, making these objects bright IR sources. The ASSESS project aims to determine the role of episodic mass in the evolution of massive stars, by examining large numbers of cool and hot objects (such as B[e]SGs/LBVs). For this purpose, we initiated a large observation campaign to obtain spectroscopic data for ∼1000 IR-selected sources in 27 nearby galaxies. Within this project we successfully identified seven B[e] supergiants (one candidate) and four Luminous Blue Variables of which six and two, respectively, are new discoveries. We used spectroscopic, photometric, and light curve information to better constrain the nature of the reported objects. We particularly noted the presence of B[e]SGs at metallicity environments as low as 0.14 Z⊙.

Hα line variations of 8 B-emission (Be) stars are presented. Stars that are listed in the Bright Star Catalogue were observed in 2009 at the Bosscha Observatory, Lembang, Indonesia. It was found that 4 stars showed phase changing from Be double-peaked to Be single-peaked emission line profiles, 1 showed single-peaked to double-peaked profiles, 1 showed double-peaked to B-normal, while two other stars did not show phase changing. The stars also showed variations in the V/R and E/C values, which represent the strength of the emission lines. The phase changes were detected from a comparison of the observed data to the current data in the BeSS database.

Özet: Bu çalışmada, η Tau yıldızının 2007 ile 2011 yılları arasında STEREO uydusundan alınan beş yıllık fotometrik verileri sunulmaktadır. Yüksek duyarlılığa sahip veriler, yıldızdaki Be olgusunu daha iyi anlamak için tayfsal bulgulardan elde edilen sonuçlarla karşılaştırılmıştır. Tayfsal veriler fotometrik gözlemlerle aynı zaman aralığını kapsamaktadır. η Tau, tayflarında çift pikli Hα salma profili göstermektedir. Bu profili analiz etmek için, Hα salma çizgileri, eşdeğer genişlikleri ve çizgi şiddetleri ölçülerek incelenmiştir. Fotometrik ve spektroskopik analizler sonucunda, yıldızın frekans dağılımı ve genlik şiddetlerinin tipik bir Be yıldızından farklı olduğu ortaya çıkmıştır. Sıcaklık ve parlaklık değerleri gibi fiziksel parametrelerine dayanarak yıldızın Yavaş Zonklayan B tipi bir emisyon yıldızı olduğu sonucuna varılabilir. Öte yandan, emisyon çizgilerinin eşdeğer genişlik değerleri, salınım frekansları ve genlikleri ile ilişkili görünmektedir. Bu da, fotometrik değişimlerin çevresel disk yapısıyla ilişkili olabileceğini göstermektedirDoğuş ÖZUYAR, dozuyar@ankara.edu.tr, ORCID: https://orcid.org/ 0000-0001-8544-0950

Indirect ablation laser-induced breakdown spectroscopy (IA-LIBS) was applied to the analysis of the nonmetallic constituents of engine oil and considered as a feasible technique for the evaluation of the consumption and/or combustion of engine oil during routine engine operation. The evolution of CN emission and C2 emission was investigated for different driving time intervals of the motor. The exponentially decaying curve showed that the intensity of CN emission and C2 emission decayed at different driving time intervals. The evolution of total CN emission and C2 emission was analyzed, and the ratio of CN to C2 was calculated, which might be taken as an indicator to evaluate the performance of the used engine oils and/or to diagnose the conditions of the motor engine. Thus, it is shown that IA-LIBS is a potential method for analyzing the metallic and nonmetallic constituents of engine oil. [ABSTRACT FROM AUTHOR]

In this short-note, I have discussed spherical deformation in rotationally perturbed spacetime which is valid for strong gravitational fields assuming star is homogenous and spherically symmetric. I have considered a photon emitted by a rapidly rotating star (pulsar) and calculated net deflection angle. In this case, we observed that rapidly emitted photon has shown bending under inertial frame drag effect which is opposite to non rotational case. I have also considered red-shift effect in this situation and observed that the red shift of a line emission shifted towards lower frequency with the effect of broadening. The rotation effect is also maximum on tangentially backward emitted photon which causes limbs of the stars moves away from observer [ABSTRACT FROM AUTHOR]

Surveys have shown radio-loud (RL) quasars constitute 10%-15% of the total quasar population and rest are radio-quiet (RQ). However, it is unknown if this radio-loud fraction (RLF) remains consistent among different parameter spaces. This study shows that RLF increases for increasing full width half maximum (FWHM) velocity of the Hβ broad emission line (z < 0.75). To analyse the reason, we compared bolometric luminosity of RL and RQ quasars sample which have FWHM of Hβ broad emission line greater than 15000km/s (High Broad Line or HBL) with which have FWHM of Hβ emission line less than 2500km/s (Low Broad Line or LBL). From the distributions we can conclude for the HBL, RQ and RL quasars are peaking separately and RL quasars are having higher values whereas for the LBL the peaks are almost indistinguishable. We predicted selection effects could be the possible reason but to conclude anything more analysis is needed. Then we compared our result with Wills & Brotherton (1995) and have shown that some objects from our sample do not follow the pattern of the logR vs FWHM plot where R is the ratio of 5 GHz radio core flux density with the extended radio lobe flux density. [ABSTRACT FROM AUTHOR]