In this study, we present the results of photoionization modeling for 124 planetary nebulae (PNe) in the Galactic bulge. Utilizing the CLOUDY code, we derived the effective temperatures (Teff) of the central stars, with a peak distribution around similar to 100,000 K, and luminosities clustering around 3,000 L . The inner radii of the ionized regions range from 0.003 to 0.31 pc, with nebula diameters varying from 1.8" to 34", averaging 7% larger than the observed visible diameters. Elemental abundances for Helium, Nitrogen, Oxygen, Neon, Sulphur, Chlorine and Argon relative to hydrogen derived from the models show consistency within 0.5 dex, with notable variations in Sulphur, Nitrogen, and Chlorine. The study also compares elemental abundances from photoionization models with previous observations, showing overall good agreement, particularly for Cl/H, but notable discrepancies in He/H and S/H ratios. The models' goodness of fit, quantified by values, varies widely, with higher values linked to discrepancies in WISE photometric data. The evolutionary tracks of the central stars from H-R diagrams suggest progenitor masses ranging from 0.8 to 4.2 M an d progenitor final masses between 0.53 and 0.87 M circle dot, indicating significant mass loss during evolution. These PNe have post-AGB ages ranging from 150 to 20,000 years, consistent with the Galactic PNe distribution. Most of the PNe are in an intermediate evolutionary stage with larger nebular sizes. Our results provide the most comprehensive photoionization modeling to date, with key implications for central stars of PNe, gas, and dust. (c) 2025 COSPAR. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

International Dark-Sky Places (IDSPs) is a global project led by the International Dark-Sky Association (IDA) to protect dark-sky areas for astronomical observation and astro-tourism. Currently, there are 216 IDSPs in the world. This study analyses light pollution trends in International Dark-Sky Places (IDSPs) using VIIRS night light composite data. IDSPs are mostly located near urbanised areas in Europe and away from urbanisation in North America. Dark and large areas away from urbanisation in South America, Africa, Central Asia and Australia offer great potential. Linear regression analysis shows that in 94 ^2 > 0.6). Seasonal patterns were assessed using the Lomb–Scargle periodogram, but detected periodicities were considered false positives. These results emphasise the need for strategic planning to reduce light pollution in IDSPs, especially in underused areas.

We present the results of chemical abundance measurements for four compact planetary nebulae (PNe) located in the Northern Hemisphere, selected from the HASH (Hong Kong/Australian Astronomical Observatory/Strasbourg H-alpha Planetary Nebula) database. Spectral data were collected using the medium-resolution TUG Faint Object Spectrograph and Camera mounted on the 1.5 m RTT telescope at the TUBITAK National Observatory. For each object, we determined key physical parameters, including the extinction coefficient, electron density, electron temperature, and ionization correction factors. Additionally, we constructed the spectral energy distribution across multiple wavelengths for each PN using advanced photoionization modeling with the cloudy code. The elemental abundance analysis, focusing on He, N, O, Ne, S, Cl, and Ar, indicates that the chemical composition of these PNe is consistent with both solar and Galactic values. The central stars exhibit effective temperatures ranging from approximately 53,000 to 180,000 K and luminosities between 2,500 and 9,000 L-circle dot. Based on their positions on the H-R diagram and post-AGB evolutionary tracks, their initial masses are estimated to range from 1 to 3 M-circle dot, with nebular masses between 0.69 and 2.34 M-circle dot. The ages of the nebulae, calculated to be between similar to 300 and 5,000 years, align with previous findings, emphasizing their evolutionary importance.

The TR61 province in Turkiye, which includes the cities of Antalya, Burdur, and Isparta, was chosen as the study area. Long-term (2012-2022) Artificial Light (AL) data from VIIRS on the Suomi-NPP satellite, along with cloud cover and elevation data, were analyzed in a GIS environment. The study identified 84 potential IDSP areas, concentrated mainly in Manavgat, Ibrad & imath;, and Akseki. The largest site spans 1,180 hectares, while the darkest shows a sky brightness of 21.57 mag arcsec-2 . Koprulu Canyon National Park, with 14 potential areas, was selected as the primary IDSP candidate. The measured AL values were consistent with the site selection, confirming the accuracy of the identified areas. Ground-based SQM observations in two regions of the park validated the satellite-derived AL data. Ongoing monitoring and the use of simple GIS techniques with available satellite data are recommended for future IDSP site selection Published by Elsevier B.V. on behalf of COSPAR.

Kütleleri 1 ila 8 M⊙ arasında değişen ata yıldızlar olan Gezegenimsi Bulutsular (PNe), galaksilerin kimyasal evriminde önemli bir rol oynamaktadır. Bu çalışma, HASH veritabanından PNe’deki oksijene göre α-elementlerinin (C, N, O, Ne, S, Cl, Ar) bolluklarını araştırmakta ve bunları Samanyolu’nun bileşenleriyle karşılaştırmaktadır. Gaia EDR3’ten alınan Galaktik koordinatlar ve mesafeler analiz edilerek PNe’ler şişkinlik, ince disk, kalın disk ve halo olarak kategorize edildi. Sonuçlar, He ve Cl bolluklarının Güneş değerlerine daha yakın olduğunu, O, Ne, S ve Ar’ın ise özellikle halede daha düşük olduğunu göstermektedir. Bu bulgular, ISM’nin kimyasal zenginleşmesi ve Samanyolu’nun evrimsel süreçleri hakkında fikir vermektedir.

Astronomi sitelerinde ışık kirliliği trendlerini incelemek amacıyla yapılan çalışmalar, gözlemevlerinin geleceği açısından büyük önem taşımaktadır. Günümüzde dünya genelinde 2225 kayıtlı amatör ve profesyonel astronomi sitesi bulunmaktadır. Bu çalışmada, tüm bu astronomi siteleri için 2002-2023 dönemine ait zamansal trendler, uydu verileri kullanılarak analiz edilmiştir. Mann-Kendall (MK) ve Sen’s Slope (SS) istatistikleri hesaplanarak, ışık kirliliğinde gözlemlenen artış veya azalışların istatistiksel olarak anlamlı olup olmadığı değerlendirilmiştir. Analiz sonucunda 570 gözlemevinde anlamlı bir değişim tespit edilmiştir; bu gözlemevlerinden 182’sinde ışık kirliliğinde azalma, 388’inde ise artış görülmüştür.

ABSTRACT We conducted a study to investigate the relationship between X-ray binaries (XRBs) and compact star clusters in the nearby star-forming galaxies NGC 4490 and NGC 4214. By analysing archival data from Chandra, we identified a total of 32 XRBs with X-ray luminosities Lx > 1036 erg s−1 in both galaxies. Utilizing data from HST/WFC3/UVIS, we presented a new catalogue of 715 compact star clusters in NGC 4490 and identified 312 such clusters in NGC 4214. In the case of NGC 4490, 14 of the 17 XRBs are associated with clusters, whereas in NGC 4214 all 15 XRBs are connected to clusters within a radius of <200 pc. Furthermore, among the XRBs in NGC 4490, 12 out of the 17 have optical counterparts. Similarly, in NGC4214, 11 out of the 15 XRBs exhibit optical counterparts. We have evidence for a substantial population of high-mass X-ray binaries (HMXBs) associated with clusters, accounting for ∼70 per cent and 40 per cent of the detected XRBs in NGC 4490 and NGC 4214, respectively. HMXBs are often found near young, less massive clusters, while low-mass X-ray binaries (LMXBs) are associated with older, more massive clusters in these galaxies. Intermediate-mass XRBs in NGC 4214, on the other hand, tend to be close to young clusters, suggesting that their formation mechanism is more similar to HMXBs than to LMXBs.

Astronomical observatories require sites with high altitudes, a high number of clear nights, and minimal light pollution. This study utilizes Geographic Information Systems and Multi-Criteria Decision Analysis to evaluate the suitability of Balkan regions for establishing International Dark Sky Parks (IDSP) based on the criteria set by the International Dark Sky Association. Three scenarios (DSPI A, B and C) were formulated to assess suitability under different conditions using satellite data on light pollution, cloud cover, elevation and water bodies. Although no ‘Conservation Area’ or ‘International Dark Sky Park’ sites were found due to the prevalence of light pollution, promising ‘reserve areas’ and astronomical observatory sites were identified, mainly concentrated in the southern Balkans inside the Montenegro-Bulgaria-Greece triangle. The southern part of Macedonia has twice as many clear nights (an average of approximately 240 nights) compared to the north. The southern region of Macedonia exhibited a range of brightness levels, while the Rozhen National Astronomical Observatory in Bulgaria had the darkest recorded sky brightness (20.89 mag_SQM arcsec−2) and the highest suitability score (0.69). The Peloponnese offers suitable locations for astronomical sites in all scenarios. Higher altitudes and lower latitudes have more favorable conditions. The Balkans contain a significant proportion of reserve areas (24.8

Astronomical sites have to be selected according to many factors whereas the geographic location of the site and the quality of the atmosphere above the site play an important role in the decision process. The following factors were chosen to create layers 1907 northern and 235 southern observatories: CC (cloud coverage), PWV (precipitable water vapor), AOD (aerosol optical depth), VWV (vertical wind velocity), and HWV (horizontal wind velocity). To estimate the astronomical importance of the sites, DEM (digital elevation model) and LAT (latitude of observatory location) layers were also included. In addition to the variations or trends, a complete statistical analysis was carried out for all factors to investigate the potential correlations between the factors. There is a clear difference between the northern and southern hemispheres. The exchange of meteorological seasons between hemispheres is also compliant with factors. The geographical locations of most of the observatories were found to be “not suitable”. There seem to be no apparent long-term variations and/or patterns in all factors.

ABSTRACT We update the ephemerides of 16 transiting exoplanets using our ground-based observations, new Transiting Exoplanet Survey Satellite data, and previously published observations including those of amateur astronomers. All these light curves were modelled by making use of a set of quantitative criteria with the exofast code to obtain mid-transit times. We searched for statistically significant secular and/or periodic trends in the mid-transit times. We found that the timing data are well modelled by a linear ephemeris for all systems except for XO-2 b, for which we detect an orbital decay with the rate of −12.95 ± 1.85 ms yr−1 that can be confirmed with future observations. We also detect a hint of potential periodic variations in the transit timing variation data of HAT-P-13 b, which also requires confirmation with further precise observations.

ABSTRACT We conducted research on the classification and physical properties of 10 objects from the HASH [Hong Kong/Australian Astronomical Observatory/Strasbourg Observatory H-alpha Planetary Nebula (PN)] data base with small angular sizes (<8 arcsec) in the Northern hemisphere. The sample consisted of six Likely PNe, two new candidates, one emission-line star, and one object of unknown nature. Among them, we observed four objects for the first time using the medium-resolution TUG Faint Object Spectrograph and Camera spectrograph located on the RTT150 cm of the TÜBİTAK National Observatory. To investigate the classification of the observed objects, we utilized the emission line ratios of [O iii]/Hγ, [O iii]/Hβ, [N ii]/Hα, and [S ii]/Hα, and diagnostic diagrams such as the Sabbadin–Minello–Bianchini and Baldwin–Phillips–Terlevich diagrams. When considering a broader range of diagnostic criteria compared to those provided in the literature, our analyses resulted in the reclassification of four objects from Likely PNe to True PNe and the retention of the previous classification for the remaining six objects. In addition, we obtained various physical conditions such as electron temperatures, electron densities, logarithmic extinction coefficients, and excitation classes for the 10 objects under study. Our analysis revealed that the ionic abundances of the majority of these objects were in agreement with Galactic PNe. Our spectral observations have led to the updating of 10 PNe in the HASH data base.

The primary objective of this study is to employ Multi-Criteria Decision Analysis (MCDA) and Geographical Information System (GIS) techniques to identify and assess potential sites for astronomical observations in Antarctica. Our study focuses on the development of the Suitability Index for Astronomical Sites in Antarctica (SIASA). This index is formulated by merging data from satellites and models, providing extensive temporal and spatial coverage over two decades. To assess its suitability, we employed a combination of MCDA and GIS techniques, allowing us to evaluate various data, including cloud cover (CC), precipitable water vapor (PWV) levels, elevation, atmospheric temperature and wind speed. Our analysis confirmed the exceptional characteristics of Antarctica: An average of 361 cloud-free days per year, exceptionally low PWV values (0 mm), and an average elevation of 2.300 meters. The stable atmospheric wind profile further enhances its suitability for astronomical observations. Long-term trends and correlations of the data were also studied. SIASA values identified the eastern and inner parts of the Transatlantic Mountains as highly favorable for astronomical observations, while the coastal areas were considered less suitable. The best sites cover 10

Teorik çalışmalara göre Gökadamızda $\sim$25000 Gezegenimsi Bulutsu (GB) olması tahmin edilmektedir. Ancak şimdiye kadar $\sim$3800 GB ve adayı kataloglanmıştır. Adaylar arasından (i) Dec. > -10$^{o}$, (ii) açısal çapı < 8 açısaniyesi ve (iii) Yeni aday (new candidate), Muhtemel (Likely) ve Olası (Possible) kriterlerine göre seçilen 13 kaynağın tayfsal gözlemleri RTT150 üzerine monteli TFOSC ile TÜBİTAK Ulusal Gözlemevi’nde yapılmıştır. Tayf gözlemlerinden [OIII]/H$\beta$, [NII]/H$\alpha$, [SII]/H$\alpha$ çizgi oranları hesaplanmış ve SMB ile BPT tanısal grafikleri üretilmiştir. Böylece kaynakların GB olup olmadığı, bulundukları ortamın elektron yoğunluğu, sıcaklığı, ortamın sönümleme katsayısı gibi parametreleri ilk defa belirlenmiştir.

Türkiye'de ve gözlemevlerinde ışık kirliliği, https://www.astrogis.org, astroGIS veritabanı kullanılarak 2012--2020 yılları arasında incelenmiştir. 2019 yılında Türkiye'den uzaya salınan toplam enerji 2012 yılına göre %80 artmıştır Aksaker ve ark. 2020 Veri seti kapsamında ülkenin tüm illerinde ve hemen hemen tüm gözlemevi yerleşkelerinde istikrarlı ve sürekli bir artış gözlemlenmiştir. Öte yandan Karanlık Gökyüzü Park konumları, Doğu ve Güneydoğu Anadolu bölgeleri ve çoğunlukla şehirlerin çevresindeki kırsal alanlarda ışık kirliliği seviyelerinin sabit olduğu yerler bulunmuştur.

We investigated for a possible connection between the types of X-ray binaries (XRBs) and the properties of compact star clusters in the nearby galaxy NGC 628. Using {\it Chandra} archival data covering the years 2001-2018, 75 X-ray sources were detected within the field of view of observations. A total of 69 XRBs, one of which is an ultraluminous X-ray source (ULX), were found to be in the luminosity range of 3$\times10^{36}\leq L_{X}$ $\leq $ 2$\times10^{39}$ erg s$^{-1}$. We identified the optical counterpart(s) of 15 of the 42 XRBs that coincide with the {\it HST} field of view via improved astrometry. We classified 15 of them as HMXBs based on the presence of the optical counterparts. The remaining sources with no optical counterparts were classified as LMXBs. We also search compact star clusters in this galaxy using the multi-band optical images drawn from {\it HST} archives. 864 compact star clusters were identified and their ages and masses were determined by applying the best-fit SSP (Simple Stellar Population) model to their color-color diagram. We found that in NGC 628, HMXBs are associated with younger star clusters and LMXBs with older ones. Our findings support a connection between different types of XRBs and cluster ages, already known to exist for other galaxies.

Antartika, sıradışı şartlara (düşük sıcaklık, düşük nem vb.) sahip uzun süren karanlık geceler ve kutup soğuğunda dedektörlerin düşük kara akımlarda kalmasına bağlı sürekli ve duyarlı gözlem imkanı nedeniyle astronomi açısından değerli bir konumdur. Astronomların ve gözlemevi kurmak isteyen ülkelerin ve karar vericilerin en cazip tercihlerinden biridir. Bu durum da astronomi için coğrafi bilgi sistemleri ve uzaktan algılama kullanarak yer seçimi yapmanın gerekliliğini ortaya çıkarmıştır. Bulutluluk, yoğuşabilir su buharı, yükseklik ve rüzgar hızı gibi uzaktan algılama ve model verileri kullanılarak bu çalışmada Antarktika’da gözlemevleri için uydu verileri kullanılarak yer seçimi yapılmıştır. Kullanılan veriler astroGIS veri tabanından edinilmiş olup en az 20 yıllık zamansal, 1 km2 uzamsal çözünürlüğe sahip şimdiye kadar en güncel verilerdir.

We present the results of a temporal and spectral analysis of the transient source ULX-4 in the galaxy M51. The data used were drawn from Chandra, XMM-Newton and Swift-XRT archives, spanning the years 2000-2019. The X-ray flux of the source is seen to vary by two orders of magnitudes within a month but a short-term variability was not observed over the time intervals of 100-2000 second in the 0.3-10 keV energy band. We find some evidence for the existence of bi-modality feature in the flux distribution of ULX-4. We identified two optical sources as possible counterparts within an error radius of 0."18 at 95 confidence level for ULX-4 based on the archival HST/ACS and HST/WFC3 data. Blackbody fits of the spectral energy distributions (SEDs) indicate the spectral type to be B-type stars. One of these counterparts exhibits a low-amplitude optical periodicity of 264 days in the F606W filter; if we assume this apparent periodicity is associated with the orbital motion of the donor, then it is more likely that the donor is a red supergiant satisfying the long periodicity and accretion via Roche-lobe overflow. Consequently, the SED would then have to be interpreted as a superposition of emissions from a cold donor and a hot flow component, most likely from an accretion disk. If, on the other hand, the periodicity is super orbital in nature i.e., due to possible interactions of the compact object with a circumstellar disk, the donor could then be a Be/X star hosting a neutron star.

Bu çalışmada sıcak-Jüpiter türü çok sayıda ötegezegenin barınak yıldızlarının önünden geçiş zamanlarının değişimleri ile büyük çoğunluğu ortak zarf evresini tamamlamış bir grup çift yıldızın tutulma zamanlarının değişimleri üzerine yapılan uzun süreli bir araştırma ve bu araştırma kapsamında Türkiye’deki beş ayrı gözlemevinde yapılan gözlemlerin sonuçları sunulmaktadır. Son olarak, geçiş zamanları değişimi gösterdiğinden şüphelenilen TrES-5 sistemine ilişkin ön analizler bir örnek çalışma olarak sunulmuştur.

We present the photometric analysis of six short-period systems (EI Oct, V336 TrA, NX Boo, V356 Boo, PS Boo, and V2282 Cyg). This is the first photometric analysis of these systems except for V336 TrA. Observations were conducted for 27 nights at three observatories in the northern and southern hemispheres. We calculated a new ephemeris for each of the systems using our minimum times and additional literature. The Markov Chain Monte Carlo (MCMC) approach was used to determine the eclipse timing variation trends of the systems. We found a likely orbital growth for V336 TrA and PS Boo; four other systems show a linear trend in orbital period changes, which is most likely due to the accumulation of measurement errors in their linear ephemeris parameters. The light curve analysis was performed using the Physics of Eclipsing Binaries (PHOEBE) 2.3.59 version code with the MCMC approach. The absolute parameters of the systems were calculated by using the Gaia Early Data Release 3 (EDR3) parallax. The positions of the systems were also depicted on the Hertzsprung–Russell (H-R) and log J 0 – log M diagrams. According to a sample, we were able to present relations for the mass–radius ( M – R ) relationships of contact binary systems. There is also a strong relationship between the mass ratio and the radius ratio in the W UMa systems for which we also provided a new relation. We compared the M – R updated relationships in this study with seven systems in other studies obtained using the spectroscopic method. In addition, we estimated some of the absolute parameters for 1734 EW systems, based on the new relationships.