Emission-Line Fluxes of Northern Planetary Nebulae

We present long slit spectrophotometric emission line fluxes of bright and extended (<5 arcsec in diameter) Planetary Nebulae (PNe) selected from Acker et al. 1992 catalog with suitable equitorial coordinates for Northern hemisphere. In total, 17 PNe have been choosen and observed in 2008--2010. To measure absolute fluxes, broad slit sizes, ranging from 3.5\arcsec to 7.5\arcsec were used and thus equivalent widths of all observable emission line fluxes were also calculated. Among 17 PNe's observed, line flux measurements of 12 of them were made for the first time. This work also aims to extend the sky coverage of emission line flux standards in Northern hemisphere (Dopita & Hua 1997 - 52 PNe in Southern hemisphere; Wright et al. 2005 - 6 PNe in Northern hemisphere). Electron temperatures and densities, and chemical abundances of these PNe were also calculated in this work. These data is expected to lead the photometric or spectrometric further work for absolute emission line flux measurements needed for \hii regions, supernova remnants etc.Comment: 24 pages, 3 Figures, 21 Tables, Accepted for publication in Publications of the Astronomical Society of Australi

A Case study of light pollution in France after the change in legislation

France issued a decree to restrict and prohibit mainly outdoor lighting effective from January 1st, 2019. Effectiveness of this legislation has been evaluated in this study using GIS data which was first used in \cite{2020MNRAS.493.1204A} (so called astroGIS database - \url{astrogis.org}). A subset of Artificial Light layer of astroGIS database has been adapted for years between January 2012 and December 2019. During 2019, radiance of $1.9 \times 10^{9}$ W cm$^{-2}$ sr$^{-1}$ has been released into space. Annual light pollution in France decreased by 6\% after the enactment of artificial light legislation. France continue to have potential Dark Sky Park locations for example cities like Indre, Lot, Nievre and Creuse having the lowest light pollution values. A strong correlation between population and light pollution ($R\simeq 0.83$) has been observed. A similar but a weak correlation can also be observed for GDP ($R\simeq 0.28$). However, it is still too early to justify whether the improvements observed in the dataset are due to the enactment of the legislation or not.Comment: 10 pages, 4 figures, 2 tables, Submitted to Astrophysics and Space Scienc

The Transient Ultra-luminous X-ray Source, ULX-4, in M51

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.Comment: Accepted for publication in MNRAS. 16 pages, 12 figures, 6 table

Global Site Selection for Astronomy

A global site selection for astronomy was performed with 1 km spatial resolution ($\sim$ 1 Giga pixel in size) using long term and up-to-date datasets to classify the entire terrestrial surface on the Earth. Satellite instruments are used to get the following datasets of Geographical Information System (GIS) layers: Cloud Coverage, Digital Elevation Model, Artificial Light, Precipitable Water Vapor, Aerosol Optical Depth, Wind Speed and Land Use -- Land Cover. A Multi Criteria Decision Analysis (MCDA) technique is applied to these datasets creating four different series where each layer will have a specific weight. We introduce for the first time a ``Suitability Index for Astronomical Sites'' namely, SIAS. This index can be used to find suitable locations and to compare different sites or observatories. Mid-western Andes in South America and Tibetan Plateau in west China were found to be the best in all SIAS Series. Considering all the series, less than 3 \% of all terrestrial surfaces are found to be the best regions to establish an astronomical observatory. In addition to this, only approximately 10 \% of all current observatories are located in good locations in all SIAS series. Amateurs, institutions or countries aiming to construct an observatory could create a short-list of potential site locations using layout of SIAS values for each country without spending time and budget.The outcomes and datasets of this study has been made available through a web site, namely ``Astro GIS Database'' on \texttt{\url{www.astrogis.org}}.Comment: 19 Pages, 4 Figures, 7 tables, Accepted for publication in MNRA

Homogeneous transit timing analyses of ten exoplanet systems

We study the transit timings of 10 exoplanets in order to investigate potential transit timing variations in them. We model their available ground-based light curves, some presented here and others taken from the literature, and homogeneously measure the mid-transit times. We statistically compare our results with published values and find that the measurement errors agree. However, in terms of recovering the possible frequencies, homogeneous sets can be found to be more useful, of which no statistically relevant example has been found for the planets in our study. We corrected the ephemeris information of all 10 planets we studied and provide these most precise light elements as references for future transit observations with space-borne and ground-based instruments. We found no evidence for secular or periodic changes in the orbital periods of the planets in our sample, including the ultra-short period WASP-103 b, whose orbit is expected to decay on an observable time-scale. Therefore, we derive the lower limits for the reduced tidal quality factors (Q(*)') for the host stars based on best-fitting quadratic functions to their timing data. We also present a global model of all available data for WASP-74 b, which has a Gaia parallax-based distance value similar to 25 per cent larger than the published value

DEFPOS H? observations of the W80 Complex

We present H? emission line measurements of the W80 nebula complex. A total of 26 regions have been observed inside the nebula with the Dual Etalon Fabry-Perot Optical Spectrometer system at the f/48 Coudé focus of the 150 cm RTT150 telescope located at TUBITAK National Observatory in Antalya, Turkey. The intensities, local standard of rest velocities, heliocentric radial velocities and linewidths for full width at half maximum of the H? emission lines have been determined from these observations. They lie in the range of 259 to 1159 Rayleigh (R; 1R = 106/4? photons cm -2 sr-1 s-1 = 2.41 × 10-7 erg cm-2 sr-1 s-1 at H?), 4 to 12 km s -1, -3 to -11 km s-1 and 44 to 55 km s-1, respectively. The radial velocity measurements show that there are several maxima and minima inside W80. The new results confirm findings in the literature that the complex seems to be rather uniform in terms of radial velocity and no turbulent motion is seen inside the complex. The average value of the calculated emission measure for the region is 3.1 pc cm-6. © 2013 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd

Intensity calibration of DEFPOS data

In this study, details of the intensity calibration of Dual Etalon Fabry-Perot Optical Spectrometer (DEFPOS) were described. At TUBITAK National Observatory (TUG), The DEFPOS was redesigned so as to observe galactic H? emission line from the diffuse ionized gas with 4' field of view (FOV) and then was located at the coudé exit of the 150 cm RTT150 telescope (Şahan et al., Research in Astronomy and Astrophysics (RAA) 9(2), 2009). The Absolute intensity calibration of the spectrometer was made by utilizing the data obtained from nine selected regions of NGC 7000 nebula. These regions were selected within 49' FOV whose intensity calibration was determined to be 850±50 R by Scherb (Astrophys J 243:644-650, 1981). One of these regions was specially selected because of its intensity for the 4' FOV was estimated as 900 R by Morgenthaler et al. (Astrophys J 563(1):451-461, 2001). For calibration of the DEFPOS data, the intensity values from Ishida and Kawajiri (PASJ 20:95-121, 1968) and the VTSS H? maps were used and it was found that 1 ADU km s?-?1 equals 2337.4 R for a 1200 s exposure time. The radial velocities and the line widths from these regions were also determined and compared with the previous results. These calibrations have been in close agreement. © 2009 Springer Science+Business Media B.V