Mbarara University of Science and Technology Institutional Repository (MUST-IR)

MUST-IR preserves research output from the MUST Community

Student Forms and Guides

Download the documents needed for self-archiving your research in MUST IR.

Self-Archiving Consent Form

Download, complete and sign the consent form.

Download Consent Form (PDF)

Student Self-Archiving Guide

Follow the steps for submitting research to MUST IR.

Download Student Guide (PDF)

Communities in MUST-IR

Select a community to browse its collections.

Now showing 1 - 11 of 11

Central Administration 133
This community will contain collections from the general Administrative staff
Faculty of Agriculture, Enviroment and Veterinary Sciences 2
Faculty of Applied Sciences and Technology 75
Faculty of Business and Management Sciences 134
Faculty of Computing and Informatics 154
Faculty of Health Science 2473
Faculty of Interdisciplinary Studies 226
Faculty of Science 600
Institute of Tropical Forest Conservation 124
Maternal Newborn and Child Health Institute 18
MUST Research Institute 5

Recent Submissions

Analysis of a Mathematical Model on the Dynamics of TB–HCV Coinfection With Medication
(Journal of Applied Mathematics, 2026) Kizito, Mohammed; Nampala, Hasifa; Ariho, Pius
This study employs a deterministic model that describes the combined dynamics of TB and HCV aimed at determining the impact of medication in the management of TB–HCV coinfection. The analytical and numerical analyses indicate that if the TB–HCV coinfection effective reproduction number is less than unity, the absence of both TB and HCV infections constitutes a stable equilibrium. Additionally, the stability analysis reveals that when the TB–HCV coinfection effective reproduction number is greater than one, the endemic equilibria become stable attractors, thus, a long-term coexistence of both infections. Sensitivity analysis shows that an increase in the rate of human-to-human contact between the TB (or HCV)-infected individuals and the susceptible population and the likelihood of a contact resulting in TB (or HCV) transmission results in a higher endemicity of the infection. Numerical simulations indicate that increasing the rate at which humans with coinfection are treated decreases the widespread presence of TB and HCV in the population. We therefore recommend that health facilities be stocked with antibiotics for TB and antiviral medications for HCV for easy access by individuals who test positive to the respective infections.
Optimizing Protection and Treatment Strategies for Childhood Pneumonia amid Vaccine-Unresponsive Serotypes
(Journal of Applied Mathematics and Physics, 2025) Byamukama, Michael; Kizito, Mohammed
A mathematical model integrating both vaccination and treatment strategies for childhood pneumonia is developed to assess conditions for effective dis ease control. Special attention is given to individuals who do not respond to the vaccine, and their role in pneumonia transmission dynamics is analyzed. The effective reproduction number is derived, and conditions for the asymptotic stability of both the disease-free and endemic equilibria are established. An optimal control analysis is conducted to determine the most effective strategies for minimizing pneumonia cases. Three time-dependent control measures are considered: 1) pneumonia prevention, 2) identification and treatment of carriers, and 3) enhanced treatment of infected individuals. Numerical simulations and sensitivity analysis reveal that while vaccination and treatment significantly reduce pneumonia prevalence, the presence of vaccine-unresponsive serotypes poses a challenge to disease eradication. Additionally, results indicate that implementing multiple control strategies is more effective than relying on a single intervention. A combination of all three measures yields the best outcomes in reducing both infection and carriage rates.
Supplier management orientation, information integration, organizational culture and supplier delivery performance
(Management Science Letters, 2026) Aryatwijuka, Wilbroad; Mutebi, Henry; Muhwezi, Moses; Tukamuhabwa, Benjamin R.; Arimpa, Joan; Olupot, Peter Simon
This paper explores the association between supplier management orientation (SMO), information integration (II), organizational culture (OC) and supplier delivery performance (SDP). A systematic questionnaire survey was employed to gather cross-sectional data from 403 manufacturing firms in Uganda’s Greater Kampala Metropolitan Area were analyzed using SmartPLS 4. The study shows a full mediating role of OC in the relationship between SMO, II and SDP. A positively significant relationship was established between II and OC, and between OC and SDP. Also, the relationship between SMO and OC was positively significant. Whereas the effect of SMO, II, OC on SDP is significant, related literature remains limited. This signifies a deficiency in the current literature that necessitates additional research to investigate other external factors that substantially impact SDP. Managers need to nurture cultural qualities, like teamwork, openness, and responsiveness, that enhance employees to effectively interpret in formation and act in a coordinated manner. This study extends the Resource-Based View Theory to the SDP domain, by drawing insights on the mediating role of OC in the relationship between SMO and SDP
Fuzzy logic based hybrid load balancing for solar–grid supply with tiered load shedding: a simulation study
(Scientific Reports., 2026) Wanzala, Jimmy Nabende; Byamukama, Michael
Hybrid installations that combine a solar inverter and battery with the utility grid are increasingly common in Uganda, yet they are typically managed by threshold-based automatic transfer switches (ATS) that ignore solar availability, grid quality, and load criticality. This paper presents the design, modelling, and simulation based evaluation of a multi-input fuzzy logic based hybrid load balancing controller. The framework fuses four inputs (solar output, battery state of charge (SOC), grid status, and load demand) through a Mamdani-type fuzzy inference system to produce two coordinated outputs: a source-priority signal and a tiered load-shedding signal spanning three load classes (critical, flexible, and non-essential). The study is entirely simulation-based. The system was implemented in Python at one-minute resolution over a synthetic but representative 24-hour scenario featuring two grid outages, a brownout, and cloud-induced solar variability, and was benchmarked against a conventional threshold-based transfer switch, an ATS with critical-load priority, and a crisp rule-based tiered controller; it was further tested on seven stress cases and a 100-run Monte Carlo evaluation. In the head line scenario the fuzzy controller sustained 100% availability of critical load against 91.9% for the baseline, which suffered 67 minutes of complete blackout; raised solar utilisation from 47.1% to 100%; cut grid energy from 13.43 kWh to 7.95 kWh (40.8%); and reduced source-switching events from four to two. These gains came from deliberately curtailing all non-essential load and 4.6% of flexible load, so they are not a pure effi ciency gain: total unserved energy rose from 1.84 to 3.18 kWh, although a criticality-weighted reliability index still favoured the fuzzy controller (96.4% versus 92.6%). Broader testing confirmed the solar-utilisation and grid-energy advantages over the threshold baseline, but showed that an ATS with simple critical-load priority protected critical load at least as well under stress, identifying rule-base tuning as the main need. The results support a simulation-based proof of concept. A real-time embedded demonstration, in which the controller and plant model ran on a Raspberry Pi 5 with an external touch display using emulated inputs, reproduced the simulated behaviour; testing with live sensors and relays and field validation remain future work.
Optimal control analysis of transmission dynamics and treatment pathways in a TB–HCV co-infection model
(Mathematics Open, 2026) Byamukama, Michael; Kizito, Mohammed
This study develops a deterministic compartmental model to investigate the effects of partial treatment on the transmission dynamics of tuberculosis (TB) and hepatitis C virus (HCV) co-infection and to identify effective intervention strategies. The basic reproduction number was derived using the next-generation matrix method, and sensitivity analysis was conducted to determine the parameters most influential in disease transmission. The results show that transmission-related parameters have the greatest influence on the reproduction number, while treatment-related parameters substantially reduce the burden of TB–HCV co-infection. Numerical simulations further indicate that partial treatment prolongs infectiousness, accelerates disease progression, and enhances interactions between TB and HCV, with TB identified as the dominant contributor to co-infection dynamics. An optimal control model incorporating awareness, detection, and treatment interventions was formulated using Pontryagin's Maxi mum Principle. Numerical simulations demonstrate that the simultaneous implementation of these interventions can substantially reduce TB–HCV co-infection, with near elimination achievable within two years. Based on these findings, individuals diagnosed with either TB or HCV should be routinely screened for the other infection to facilitate early detection and timely concurrent treatment.
Modelling the Role of Treatment, Public Health Education, and Chemical Control Strategies on Transmission Dynamics of Schistosomiasis
(Journal of Mathematics, 2022) Kamara, Timothy; Byamukama, Michael; Karuhanga, Martin
In this study, a mathematical model for the transmission dynamics and control of schistosomiasis is studied using a system of nonlinear ordinary differential equations. The basic reproduction number R0 for the model is obtained, and its dependence on model parameters is discussed. Analytical results reveal that the disease-free equilibrium point is globally stable if and only if the basic reproduction number R0 1 and the disease would persist at the endemic steady state. Numerical simulations reveal that a combination of treatment, public health education, and chemical control intervention strategies significantly in creased the number of susceptible human population and susceptible snail population while significantly decreasing the number of infected humans, miracidia, infected snails, and cercariae. The results further indicate that a combination of treatment, public health education, and chemical control intervention strategies can effectively manage the transmission of schistosomiasis in endemic areas.
Mathematical Analysis of a Reaction-Diffusion Pneumococcal Pneumonia Epidemic Model
(Abstract and Applied Analysis,, 2026) Ainembabazi, Amos; Byamukama, Michael; Karuhanga, Martin
Pneumococcal pneumonia, caused by Streptococcuspneumoniae, remains a significant health threat, particularly for children, the elderly, and immunocompromised individuals. This study presents a reaction-diffusion model using partial differential equations. The model ensures the positivity and boundedness of all solutions. The model also exhibits both disease-free and endemic equilibrium solutions. The effective reproduction number, Reisderived and conditions for the asymptotic stability of both the disease-free and endemic equilibrium are established. Sensitivity analysis highlights the parameters which are critical in the disease transmission. Numerical simulations confirm the global asymptotic stability of the equilibrium points. The findings further indicate that a combined strategy of vaccination and treatment is more effective than treat mental one in controlling infections and curbing disease transmission, where elevated vaccine failure rates are observed to weaken the overall control efforts again stpneumococcalpneumonia
Sustainable Procurement Practices in Humanitarian Organizations: Adaptive Capability and Co-Evolution as Antecedents in a Developing Economy
(International Journal of Disaster Risk Management, 2026) Aryatwijuka, Wilbroad; Mutebi, Henry; Arimpa, Joan; Tusiime, Wilson
This study examines the interplay among co-evolution, adaptive capability, and sustainable procurement practices in Humanitarian Organisations (HOs). In addition, it examines the mediating role of adaptive capability in the relationship between co-evolution and sustainable procurement practices. Following a positivistic stance, data collected from 79 HOs at a particular point in time were evaluated using partial least squares structural equation modelling (PLS-SEM) with SmartPLS version 4.0.9.0. The results reveal significant positive relationships between co-evolution, adaptive capability, and sustainable procurement practices. Further, adaptive capability mediates the relationship between co-evolution and sustainable procurement practices. In order to achieve sustain able procurement practices in HOs, the study concludes and recommends that co-evolution with agents in the procurement environment needs to be considered and adaptive capability strengthened and streamlined. The findings should, however, be interpreted within the limitations of the research design, since the results do not capture the different levels at which HOs practice procurement sustainability; hence, future research is encouraged to employ longitudinal and qualitative analysis. This study is novel in demonstrating how co-evolution relates to adaptive capability and sustainable procurement practices. It also explains the role that adaptive capability plays in the relationship between co-evolution and sustainable procurement practices.
Cross-cultural validity of the Pediatric Symptom Checklist – Youth Report (PSC-Y) in five Global South countries: Implications for equitable child mental health screening
(BMC medicine, 2026) Scharpf, Florian; Sievert, Milena; Mattonet, Katharina; Goretzko, David; Emiles, Joseph; Karikari, Amoah Kwaku; Khan, Alaptagin; Kirika, Anette; Muwonge, Charles Magoba; Mabula, Nkuba; Hoeffler, Anke; Hecker, Tobias
Background Despite a high global burden of mental health disorders in childhood and adolescence, access to adequate care remains limited, particularly in low- and middle-income countries . Valid and reliable self-report instruments are essential for early identification and equitable care, yet measurement invariance as a prerequisite for valid group comparisons remains understudied. The Pediatric Symptom Checklist (PSC) is a brief, open-access screening tool with practical advantages for global use. This study examined the factor structure and measurement invariance of the 35-item PSC youth self-report (PSC-Y) across five Global South countries. Methods We analyzed baseline data from 5,810 children and adolescents (age 6–18 years) participating in school based randomized controlled trials in Ghana, Tanzania, Uganda, Haiti, and Pakistan. Using confirmatory factor analysis (CFA) and exploratory structural equation modeling (ESEM), we tested competing models (unidimensional, three factor, second-order, bifactor). Multi-group CFA examined measurement invariance across countries. Within each of the five countries, we tested invariance across gender and across age groups in each of the three African countries where both primary and secondary students were represented, using school level as a proxy for developmental stage. Multiple Indicators Multiple Causes (MIMIC) models served as sensitivity analyses. Results A strong general factor emerged across all countries (omega hierarchical > 0.90). Configural invariance was supported across countries, but metric invariance failed, with items related to empathy, rule-breaking, and anger expression showing differential functioning. Full metric, scalar, and strict invariance were achieved across gender in all five countries. The Tanzania and Uganda samples demonstrated full invariance across school level as a proxy for age, while Ghana required partial invariance after freeing five items (e.g., empathy, fighting). MIMIC models supported these findings. Conclusions The PSC-Y exhibits a strong general factor across diverse Global South settings, supporting total score use for screening within countries. However, because metric invariance was not established across countries, cross country comparisons of PSC-Y scores are not methodologically defensible. Within countries, full gender invariance validates direct comparisons between boys and girls. Findings underscore the need for ongoing local validation and cultural contextualization for advancing equitable global mental health research and practice.
An uncertainty-aware ensemble of support vector machine and Gaussian process models for maternal mental health risk prediction using psychosocial and clinical risk factors
(Discover Artificial Intelligence, 2026-10-31) Ahimbisibwe, Shallon; Ahishakiye, Emmanuel; Maling, Samuel; Kawuma, Simon; Ntwari, Richard; Twinamasiko, Boaz; Kaggwa, Fred
Postpartum depression (PPD) is a major maternal mental health condition that can adversely affect mothers and infants if not identified and managed early. This study developed and evaluated an uncertainty-aware ensemble framework integrating Support Vector Machine (SVM) and Gaussian Process (GP) models for maternal mental health risk prediction using psychosocial, demographic, socioeconomic, obstetric and clinical factors. A pooled dataset comprising 14,008 retrospective maternal records from Kawempe National Referral Hospital and Mukono General Hospital in Uganda and the publicly available PERI_DEP dataset was analysed. Preprocessing included missing-value imputation, categorical encoding, feature engineering, Mutual Information-based feature selection, Kernel Principal Component Analysis and Synthetic Minority Oversampling Technique-based class balancing. All preprocessing and oversampling procedures were restricted to the training data. The Hybrid SVM–GP framework was compared with Logistic Regression, Random Forest and CatBoost using stratified five-fold cross-validation and a held-out internal test set. To assess potential target leakage, analyses were conducted using both the complete feature set and a leakage-free feature set that excluded individual Edinburgh Postnatal Depression Scale items and directly related depression-symptom variables. In the full-feature analysis, Random Forest achieved the strongest discrimination, with an accuracy of 97.75% and a Receiver Operating Characteristic Area Under the Curve of 0.996. The Hybrid SVM–GP achieved an accuracy of 93.54%, a Receiver Operating Characteristic Area Under the Curve of 0.982 and the lowest Expected Calibration Error (ECE) of 0.015, whereas Random Forest achieved lower Brier score and log loss. The Hybrid SVM-GP also provided explicit case-level uncertainty information based on the normalised predictive entropy of the fused probability, with GP posterior variance providing a complementary measure of uncertainty in the latent prediction. These findings indicate that the Hybrid SVM–GP may complement models such as Random Forest by identifying potentially ambiguous predictions requiring further assessment, rather than providing universal performance superiority. Shapley Additive explanations from the leakage-free analysis identified family relationships, socioeconomic conditions, social support and reproductive history as influential contributors to model predictions. However, the retrospective design and absence of independent external validation limit immediate clinical application. Prospective external validation and clinical-utility assessment are required before routine maternal healthcare deployment.
Linking Big Data Analytics Capabilities to Humanitarian Supply Chain Resilience: The Mediating Mechanism of Inter-Organizational Coordination
(Journal of Economics and Behavioral Studies, 2026) Aryatwijuka, Wilbroad; Mutebi, Henry; Twongyirwe, Ronald; Tumebembeire, Naster; Tugiramasiko, Miriam
This study examines the relationships among big data analytics capabilities, inter-organizational coordination capabilities and humanitarian supply chain resilience. Drawing on Dynamic Capability Theory (DCT), the study explains how humanitarian organizations leverage data analytics and inter-organizational coordination to strengthen supply chain resilience in uncertain and disruption-prone environments. A quantitative cross-sectional survey was conducted among 88 humanitarian organizations operating in Uganda. Data were analyzed using partial least squares structural equation modeling (PLS-SEM) in SmartPLS to assess the hypothesized direct relationships and the mediating effect of IOCC. The findings reveal that BDAC has a significant positive effect on both IOCC and HSCR. IOCC also significantly enhances HSCR. Furthermore, IOCC partially mediates the relationship between BDAC and HSCR, indicating that the resilience benefits of big data analytics arise both directly and indirectly through strengthened inter-organizational coordination. The cross-sectional design limits the ability to capture how analytics capabilities, coordination mechanisms, and resilience evolve. Future research could employ longitudinal and qualitative designs to examine the dynamic processes through which humanitarian organizations develop and deploy these capabilities across different stages of disruptions. Humanitarian organizations should complement investments in big data analytics and digital infrastructure with mechanisms that strengthen information sharing, joint planning, resource coordination, and collaborative decision-making among supply chain partners. Integrating analytics with strong coordination capabilities can improve preparedness, responsiveness, and recovery from humanitarian supply chain disruptions. This study extends the application of DCT to humanitarian supply chains by demonstrating that IOCC constitutes an important mechanism through which BDAC translates into HSCR.
Firm Age and Financial Performance: The Firm Life-Cycle Theoretical Perspective of Private Limited Companies In Uganda
(International Journal of Business Strategies, 2023) Rwakihembo, John; Aryatwijuka, Wilbroad; Kalinda, Peter; Nimusiima, Pereez
Purpose: While the financial performance of private companies has invoked intense interest globally, this study aimed to investigate the relationship between firm age and the financial performance of private limited companies in Uganda. Methodology: The study adopted a positivist paradigm and a cross-sectional design. A structured self-administered questionnaire was deployed to gather quantitative data from Accountants, Auditors, CEOs, and Board Members who were purposively selected. The relationship was assessed using Pearson correlation and standard regression analysis techniques. Findings: The study established a positive relationship between firm age and financial performance. It was established that firm age accounts for 14% of the variance in financial performance companies among in private Uganda. The study recommends that managers prioritize factors that guarantee the long-term existence of businesses by devising sound investment and operational policies that match the life-cycle stages of their firms. Recommendations: This study cements our insights on a firm age-financial performance nexus in Uganda’s private sector and highlights the significance of age towards financial performance. Findings provide insights into devising promising business approaches and guide management in setting priorities to achieve long-term business survival and better financial performance
Co-evolution, organizational capacity building, logistics capabilities and operational agility during health emergencies
(International Journal of Emergency Services, 2024) Mutebi, Henry; Muhwezi, Moses; Byarugaba, Pontius; Mayanja, Ssekajja S.; Aryatwijuka, Wilbroad; Munduru, Sharon Brenda
Purpose– Globally, health care facilities often fail to respond quickly to health emergencies, resulting in significant deaths. Thus, the study examines the mediating effect of logistics capabilities in the relationship between co-evolution, organization capacity building and operational agility. Design/methodology/approach–SmartPLS4.0.8.3,variance-basedstructuralequation models (VB-SEM) were used to test direct and indirect hypotheses across 45 health facilities. The respondents were 140 nurses and doctors. Disproportionate stratified simple random sampling was used based on government and private health facilities in Kampala City, Uganda. Findings–A significant and positive relationship exists between logistics capability and operational agility. However, co-evolution and organizational capacity are intimately linked to operational agility via logistics capability. Research limitations/implications– A quantitative cross-sectional survey was conducted using self administered questionnaires. The results did not show any variation in the operational agility of health facilities during emergency management; thus, qualitative approaches are needed. Practical implications– During emergency management, health facilities need to cooperate by sharing information, building capacity to increase their responsiveness and flexibility. This should be done by sharing equipment, tools, drugs and medical supplies, and we hope to encourage joint medical research. Originality/value– A complex adaptive systems(CAS) frame work is used in this study to examine how co evolution, organizational capacity building and logistical capability relate to the operational agility of healthcare during times of emergency.
Coordination and disaster response: A humanitarian organizational network perspective in Uganda
(Journal of Emergency Management and Disaster Communications, 2024) Masaba, Ayub Kutosi; Aryatwijuka, Wilbroad; Ntayi, Joseph M.; Bagire, Vincent
This paper examined the relationship between humanitarian organizational network, coordination and disaster response in Uganda. Contextually, most research in the area of disaster management rotates around the entire disaster management process/stages. There is inadequate research that tends to study a single stage in the disaster management cycle especially the response stage. Additionally, there are limited studies that have been conducted in developing countries like Uganda, most studies have been and continue to be conducted in highly disaster-prepared, coordinated and developed states. The study used a cross-sectional survey design in which quantitative methods were applied. Findings indicate that coordination positively influenced disaster response. Based on the literature and findings, the study concludes that disaster response is dependent on coordination. The study recommends that responding organizations should establish clear communication channels, build trust and social capital, and ensure that there is learning and adaptation to complex disaster environments. This will lead to better coordination within the humanitarian organizational networks and in turn successful disaster response operations.
Network Structure in Disaster Response: The Mediating Role of Coordination Within a Humanitarian Organizational Network in Uganda
(International Journal of Disaster Risk Management, 2026) Masaba, Ayub Kutosi; Aryatwijuka, Wilbroad; Ntayi, Joseph M.; Bagire, Vincent
There is limited academic endeavour to study the mediating role of coordination in the relation ship between network structure and disaster response in the context of humanitarian organisations. Furthermore, much of the research focuses on identifying challenges rather than offering deeper insights about this study. Moreover, most disaster management research centres on Western countries with well-established response systems and planned coordination. This overlooks the unique realities of less developed countries, such as Uganda, where humanitarian contexts are more com plex and response systems are less organised. The study employed a cross-sectional survey design, utilising quantitative methods. A survey was conducted using questionnaires administered to seventy (70) humanitarian organisations, particularly those that participated in the three (3) Ugandan disasters highlighted in this study. Findings suggest that the structure of the humanitarian organisational network impacts disaster response, and coordination mediates the relationship between network structure and disaster response. The study concludes that disaster response is dependent on a well-structured humanitarian organisational network, and without coordination, disaster response efforts are likely to be ineffective. This study further provides both theoretical and practical implications, especially for disaster scholars and practitioners in developing countries
Facilitators and barriers to nurses’ adherence to traumatic brain injury management guidelines at the accident and emergency unit in a national referral hospital in Uganda: a qualitative study
(BMJ open, 2026) Nyakuni, Peter; Mubuuke, Aloysius Gonzaga; Izudi, Jonathan; Ngabirano, Tom Denis; Mpirirwe, Ruth; Muwanguzi, Patience
Objective This study explored the facilitators and barriers to adherence to traumatic brain injury management guidelines among nurses at the accident and emergency unit in a national referral hospital in Uganda. Design An exploratory qualitative study was conducted among nurses. Data collection and analysis were guided by the Consolidated Framework for Implementation Research (CFIR). Setting The study was conducted in the Accident and Emergency unit at the Mulago National Referral Hospital in Kampala, Uganda. Participants The participants included nurses working at the Accident and Emergency unit of Mulago National Referral Hospital. Results 15 nurses were enrolled in the study, but transcripts for 13 of them were analysed as two audio recordings were corrupted before transcription. The facilitators of TBI management guidelines included the perceived simplicity of stepwise assessment, nurses’ motivation, experience and knowledge of TBI care, supportive peer relationships and nurses’ ability to adapt during emergencies. Conversely, barriers to TBI management guidelines included inaccessible or outdated protocols, severe understaffing, inadequate in- service training, shortages of equipment, sundries and medicines, delays in imaging fee- waiver processes, limited dissemination of TBI guidelines, external pressure from political actors and family members, overcrowding, unpredictable patient surges and difficulty maintaining monitoring fidelity. Conclusion Nurses’ adherence to TBI management guidelines was shaped by the interaction between individual commitment, guideline accessibility and the wider emergency care environment.
Asteroseismology of HD 23734, HD 68703, and HD 73345 using K2 –TESS space-based photometry and high-resolution spectroscopy
(Monthly Notices of the Royal Astronomical Society, 2025) Santosh, Joshi; Dileep, Athul; Semenko, Eugene; Sarkar, Mrinmoy; Otto, Trust; Peter, De Cat; Lampens, Patricia; Dupret, Marc-Antoine; Ghosh, Surath C.; Mkrtichian, David; Vanrespaille, Mathijs; Sugyan, Parida; Yadav, Abhay Pratap; Pramod, Kumar S.; Goswami, P. P.; Riyas, Muhammed; Karinkuzhi, Drisya
In this paper, we present a comprehensive study of three stars, HD 23734, HD 68703, and HD 73345, which were previously observed as chemically peculiar candidates within the Nainital-Cape survey and reported as null results for the pulsational variability. Frequency analyses of K2 and TESS time-series photometric data reveal the co-existence of rotational modulation and pulsation. We use the spectrum synthesis technique to determine fundamental parameters and chemical composition, which shows that all the three stars are likely to be chemically normal. The evolutionary status of the target stars corresponds to the main-sequence phases and places them within the δ Scuti instability strip of the Hertzsprung–Russell diagram. The line profile variability is observed in all three stars, especially intriguing in HD 68703 and a typical signature of the non-radial pulsation, demands further detailed examination. Using TESS photometry, we identified the radial modes of orders n = 3 and 4 for HD 23734, n = 1, 3, and 4 for HD 68703, and n = 3, 4, and 5 for HD 73345. In addition to the presence of pulsation and rotation, HD 73345 exhibits a steady increase in radial velocity that we interpret as the star being likely to be part of a long-period binary system. Finally, we propose an extended campaign aimed for the in-depth spectroscopic and spectropolarimetric study of selected pulsating stars monitored under the Nainital-Cape survey project.
Asteroseismology of the mild Am δ Sct star HD 118660: TESS photometry and modelling
(Monthly Notices of the Royal Astronomical Society, 2024) Sarkar, Mrinmoy; Santosh, Joshi; Dupret, Marc-Antoine; Otto, Trust; Peter, De Cat; Semenko, Eugene; Lampens, Patricia; Goswami, Aruna; Mkrtichian, David; Karinkuzhi, Drisya; Yakunin, Ilya; Gupta, Archana
We present the results of an asteroseismic study of HD 118660 (TIC 171729860), being a chemically peculiar (mild Am) star exhibiting δ Scuti ( δ Sct) pulsations. It is based on the analysis of two sectors of time-series photometry from the space mission TESS ( Transiting Exoplanet Survey Satellite ) and seismic modelling. It yielded the detection of 15 and 16 frequencies for TESS sectors 23 and 50, respectively. The identified pulsation modes include four radial ( ℓ = 0) and five dipolar ( ℓ = 1) ones. The radial modes are o vertones with order n ranging from 3 and 6. Such high values of n are theoretically not expected for stars with the effective temperature of HD 118660 ( T eff ≈ 7550 K) located near the red edge of the δ Sct instability strip. To estimate the asteroseismic parameters, we have generated a grid of stellar models assuming a solar metallicity ( Z = 0 . 014) and different values for the convective overshooting parameter (0 . 1 ≤ αov ≤ 0 . 3). We conclude that the analysis of the radial modes is insufficient to constrain αov and Z for δ Sct stars. The value for the equatorial velocity of HD 118660 derived from the seismic radius and the rotational frequency is consistent with values found in the literature
Unveiling the Variability and Chemical Composition of ALCol
(Galaxies, 2025) Ghosh, Surath C.; Santosh, Joshi; Samrat, Ghosh; Dileep, Athul; Otto, Trust; Sarkar, Mrinmoy; Guzmán, Jaime Andrés Rosales; Castro-Toledo, Nicolás Esteban; Malkov, Oleg; Singh, Harinder P.; Kefeng, Tan; Bedi, Sarabjeet S.
In this study, we present analysis of TESS photometry, spectral energy distribution (SED), high-resolution spectroscopy, and spot modeling of the α2 CVn-type star ALCol (HD46462). The primary objective is to determine its fundamental physical parameters and investigate its surface activity characteristics. Using TESS short-cadence (120s) SAP flux, we identified a rotational frequency of 0.09655d−1 (Prot = 10.35733d). Wavelet analysis reveals that while the amplitudes of the harmonic components vary over time, the strength of the primary rotational frequency remains stable. A SED analysis of multi-band photometric data yields Academic Editor: MargoAller Received: 17June2025 Revised: 1August2025 Accepted: 5August2025 Published: 14 August2025 Citation: Ghosh, S.C.;Joshi, S.; Ghosh,S.; Dileep, A.; Trust, O.; Sarkar, M.; Rosales Guzmán,J.A.; Castro-Toledo, N.E.; Malkov, O.; Singh, H.P.; et al. Unveiling the Variability and Chemical Composition of ALCol. Galaxies 2025, 13, 93. https:// doi.org/10.3390/galaxies13040093 Copyright: ©2025bytheauthors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/ licenses/by/4.0/). an effective temperature (Teff) of 11,750K. High-resolution spectroscopic observations covering wave length range 4500–7000Å provide refined estimates of Teff = 13,814 ± 400K, log g= 4.09 ± 0.08dex, and υsini = 16 ± 1kms−1. Abundance analysis shows solar-like composition of OII, MgII, SII, and CaII, while helium is under-abundant by 0.62dex. Rare earth elements (REEs) exhibit over-abundances of up to 5.2dex, classifying the star as an Ap/Bp-type star. ALCol has a radius of R = 3.74 ± 0.48R⊙, with its H–R diagram position estimating a mass of M = 4.2 ± 0.2M⊙ and an age of 0.12 ± 0.01 Gyr, indicating that the star has slightly evolved from the main sequence. The TESS light curves were modeled using a three-evolving-spot configuration, suggesting the presence of differential rotation. This star is a promising candidate for future investigations of magnetic field diagnostics and the vertical stratification of chemical elements in its atmosphere.
Chemical abundances and Doppler imaging of the Ap Si/He-wk star HD 100357
(Monthly Notices of the Royal Astronomical Society, 2025) Dileep, Athul; Santosh, Joshi; Sofya, Alexeeva; Kochukhov, Oleg; Semenko, Eugene; Peter, De Cat; Zuniga-Fernandez, Sebastian; Otto, Trust; Pollard, Karen; Crause, Lisa; Barkaoui, Khalid; Gillon, Michael; Jehin, Emmanuel; Rathore, Neeraj
We present the results of time-resolved photometry, abundance analysis, and Doppler imaging of an Ap star, HD 100357. The TESS photometry revealed rotational modulation with a period of 1.6279247 d. Upon inspecting the residuals after removing the rotational period and its harmonics, we found additional frequencies around 15.8054 d−1 , which we later confirmed with ground-based observations as originating from a nearby star. Using high-resolution spectroscopy, we identified HD 100357 as an Ap Si/He-wk star exhibiting rotational modulation caused by surface abundance spots. The stellar parameters of HD 100357 were determined as Teff = 11 850 K, log g = 4.57, υ sin i = 60 km s−1 , and an inclination angle i = 72◦. The detailed abundance analysis revealed strongly overabundant stratified silicon, an overabundance of iron-peak elements and rare earth elements combined with remarkably deficient helium. Mapping of Fe and Cr abundances revealed the existence of ring-shaped regions with a lower concentration of the elements. Their geometry might reflect the orientation of the hypothetical magnetic field of the star, oriented ∼ 90◦ to the rotational axis. HD 100357, with its strong chemical peculiarities and indications of possible magnetic fields, represents an interesting candidate for follow-up spectropolarimetric observations aimed at investigating its magnetic field topology and stellar activity.