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Akbar, Evan Irawan
Astronomy Study Program, Faculty Of Mathematics And Natural Sciences, Institut Teknologi Bandung, Indonesia; Bosscha Observatory, Faculty Of Mathematics And Natural Sciences, Institut Teknolog Bandung, Indonesia
Astronomy Chemistry Earth & Planetary Sciences Mathematics Physics

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B-emission Stars in Southern Sky Observed in Bosscha Observatory: Spectroscopic Study of Hα Spectral Line Variability Aprilia Aprilia; Hakim Luthfi Malasan; Geavani Eva Ramadhania; Agus Triono Puri Jatmiko; Mochamad Irfan; Dhimaz Gilang Ramadhan; Ade Nur Istiqomah; Evan Irawan Akbar
Journal of Mathematical and Fundamental Sciences Vol. 51 No. 3 (2019)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2019.51.3.3

Abstract

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.
Optical Spectroscopy and Photoionization Model of Planetary Nebula NGC 6572 Muhammad Fajrin; Hakim Luthfi Malasan; Evan Irawan Akbar
Journal of Mathematical and Fundamental Sciences Vol. 55 No. 2 (2023)
Publisher : Directorate for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2023.55.2.2

Abstract

We investigated NGC 6572 through optical spectroscopy to determine its kinematical and chemical properties. Two intermediate dispersion spectra (R~5000) centered around Hα and Hβ were used to derive the nebular expansion velocity from emission lines associated with Hα, Hβ, [OIII], [NII], and [SII] ions. A low dispersion spectrum (R~1000) was used to determine the nebular electron temperature, density, and chemical composition. We performed photoionization modeling to construct a self-consistent nebular model, while intermediate-resolution spectral images showed the global elliptical structure of the nebula. The expansion velocity deduced from most of the emission lines is consistent with the typical expansion velocity of planetary nebulae, i.e., around 15-20 kms-1. The nebular physical properties align well with those determined by other studies. The nebular abundances were found to be lower than the solar abundances (except for oxygen) but still comparable with the abundances derived by other researchers. The photoionization model generated spectral lines that are consistent with the lines found in the observations. Further spectroscopic observations with higher resolution and wider range at various position angles will be very useful to reveal a more complete and detailed structure of the nebula and to improve the determination of the nebular physical properties.
Co-Authors Ade Nur Istiqomah Agus Triono Puri Jatmiko Aprilia Aprilia Dhimaz Gilang Ramadhan Geavani Eva Ramadhania Hakim Luthfi Malasan Hakim Luthfi Malasan Mochamad Irfan Muhammad Fajrin