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تسجيل مستخدم جديدNew data for the LBV in NGC 4736
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We present new spectral and photometric data of confirmed LBV star from the NGC4736 galaxy. The star NGC4736_1 (Mbol = -11.5 mag) showed noticeable spectral variability from 2015 to 2018, which was accompanied by a significant change in the brightness. We also have estimated possible initial mass of the object NGC4736_1 as ~130 Msun.
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We have found three new LBV candidates in the star-forming galaxy NGC 4736. They show typical well-known LBV spectra, broad and strong hydrogen lines, He I lines, many Fe II lines, and forbidden [Fe II] and [Fe III]. Using archival Hubble Space Teles
cope and ground-based telescope data, we have estimated the bolometric magnitudes of these objects from -8.4 to -11.5, temperatures, and reddening. Source NGC 4736_1 (Mv = -10.2 +/- 0.1 mag) demonstrated variability between 2005 and 2018 as Delta V = 1.1 mag and Delta B = 0.82 mag, the object belongs to LBV stars. NGC 4736_2 (Mv < -8.6 mag) shows P Cyg profiles and its spectrum has changed from 2015 to 2018. The brightness variability of NGC 4736_2 is Delta V = 0.5 mag and Delta B = 0.4 mag. In NGC 4736_3 (Mv = -8.2 +/- 0.2 mag), we found strong nebular lines, broad wings of hydrogen; the brightness variation is only 0.2 mag. Therefore, the last two objects may reside to LBV candidates.
A multi-epoch H$alpha$ survey of the early-type spiral galaxy M94 (NGC 4736) has been completed as part of a program to establish the galaxys nova rate. A total of four nova candidates were discovered in seven epochs of observation during the period
from 2005 to 2007. After making corrections for temporal coverage and spatial completeness, a global nova rate of 5.0$^{+1.8}_{-1.4}$ yr$^{-1}$ was determined. This rate corresponds to a specific-luminosity nova rate of 1.4 $pm$ 0.5 novae per year per 10$^{10} L_{odot,K}$ when the $K$ luminosity is determined from the $B-K$ color, or 1.5 $pm$ 0.4 novae per year per 10$^{10} L_{odot,K}$ when the $K$ luminosity is derived from the Two Micron All Sky Survey. These values are slightly lower than that of other galaxies with measured nova rates, which typically lie in the range of $2-3$ novae per year per 10$^{10} L_{odot}$ in the $K$ band.
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ity spectra of the source have been obtained using Fast Fourier Transform. Also the spectral parameters of the source have been calculated by obtaining and fitting the energy spectra. Power density spectrum of this source reveals a QPO peak at $0.73_{-0.14}^{+0.16}$ mHz with an fractional rms variability of 16% using the Chandra data (in the year 2000-lower state of the source). The XMM-Newton data analysis indicates a peak at $0.53_{-0.35}^{+0.09}$ mHz with a fractional rms variation of 5% (in the year 2006-higher state of the source). These recovered QPOs overlap within errors and may be the same oscillation. In addition, we detect a long periodicity or a QPO in the Chandra data of about $(5.2pm2.0)times10^{-5}$ Hz ($sim$ 5.4 hrs) over 3 $sigma$ confidence level. If this is a QPO, it is the lowest QPO detected from a ULX. The mass of the compact object in ULX X-2 is estimated using the Eddington luminosity and a disk blackbody model in the range (10$-$80) M_{sun}.
Stellar archeology of nearby LINER galaxies may reveal if there is a stellar young population that may be responsible for the LINER phenomenon. We show results for the classical LINER galaxies NGC 4579 and NGC 4736 and find no evidence of such populations.
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