We present the results on the photometric and spectroscopic monitoring of a luminous Ap star HD103498. The time-series photometric observations were carried out on 17 nights using three-channel fast photometer attached to the 1.04-m optical telescope at ARIES, Nainital. The photometric data of five nights of year 2007 show clear signature of 15-min periodicity. However, the follow-up observations during 2007--2009 could not repeated any such periodicity. To confirm the photometric light variations, the time-series spectroscopic observations were carried out with the 2.56-m Nordic Optical Telescope (NOT) at La Palma on February 2, 2009. Any radial velocity variations were absent in this data set which is in full agreement with the photometric observations taken near the same night. Model atmosphere and abundance analysis of HD103498 show that the star is evolved from the Main Sequence and its atmospheric abundances are similar to two other evolved Ap stars HD133792 and HD204411: large overabundances of Si, Cr, and Fe and moderate overabundances of the rare-earth elements. These chemical properties and a higher effective temperature distinguish HD103498 from any known roAp star.
We present some preliminary results from our program of intensive near-infrared photometric monitoring of a sample of confirmed and candidate Luminous Blue Variables (LBVs) conducted from 2008 to 2010. Clear long-term variability has been observed for Wray 17-96 and V481 Sct, with overall brightness variation greater than 1 mag in the J band. Other sources, such as LBV 1806-20 showed detectable variability with amplitudes of few tenths of a magnitude with time-scale of about 60 days.
Pulsating stars in eclipsing binary systems play an important role in asteroseismology. The combination of their spectroscopic and photometric orbital solutions can be used to determine, or at least to constrain, the masses and radii of components. To successfully perform any seismic modelling of a star, one has to identify at least some of the detected modes, which requires precise time-series photometric and spectroscopic observations. This work presents a progress report on the analysis of two beta Cephei-type stars in eclipsing binaries: HD 101794 (V916 Cen) and HD 167003 (V4386 Sgr).
Be objects are stars of B spectral type showing lines of the Balmer series in emission. The presence of these lines is attributed to the existence of an extended envelope, disk type, around them. Some stars are observed in both the Be and normal B-type spectroscopic states and they are known as transient Be stars. In this paper we show the analysis carried out on a new possible transient Be star, labelled HD 112999, using spectroscopic optical observations and photometric data.
We report photometric and spectroscopic observations of the 2014 eclipse of EE Cep. This proved to be one of the shallower eclipses on record rather than one of the deepest as predicted. The general shape of the eclipse light curve was similar to that of the 2003 eclipse. The spectral type before and after eclipse was consistent with B5III and became slightly later at mid-eclipse. Total flux in the Hα emission line remained relatively constant through the eclipse.
Nearby, active stars with relatively rapid rotation and large starspot structures offer the opportunity to compare interferometric, spectroscopic, and photometric imaging techniques. In this paper, we image a spotted star with three different methods for the first time. The giant primary star of the RS Canum Venaticorum binary $σ$ Geminorum ($σ$ Gem) was imaged for two epochs of interferometric, high-resolution spectroscopic, and photometric observations. The light curves from the reconstructions show good agreement with the observed light curves, supported by the longitudinally-consistent spo…
By analyzing photometric and spectroscopic time series in this paper, we show that the pulsator V764 Mon, assumed to be the brightest RR Lyrae star in the sky, is in fact a rapidly rotating delta Scuti star with an unusually long dominant period (P1=0.29 d). Our spectroscopy confirmed the discovery of the Gaia satellite about the binarity of V764 Mon. In the case of HY Com, a `bona fide' RRc star, we present its first complete radial velocity curve. Additionally, we found that the star continues its strong phase variation reported before.
One of the most attractive events in the pre-main sequence evolution is the FU Orionis (FUor) outburst. Because only a small number of FUor stars have been detected to date, photometric and spectral studies of every new object are of great interest. Recently, a new FUor candidate was discovered by Anton Khruslov - V582 Aur. To confirm the FUors nature of this object we started regular photometric observations with the telescopes of the National Astronomical Observatory Rozhen (Bulgaria). A high-resolution spectrum of V582 Aur was obtained with the 1.93 m telescope in Haute-Provence Observatory…
We have observed Eta Carinae over 34 nights between 4th January 2009 and 27th March 2009 covering the estimated timeframe for a predicted spectroscopic event related to a suspected binary system concealed within the homunculus nebula. A photometric minimum feature was confirmed to be periodic and comparison to a previous event indicated that the period to within our error at 2022.6 +/-1.0 d. Using the E-region standard star system, the apparent V magnitudes determined for the local comparison stars were HD303308 8.14+/-0.02, HD 93205 7.77 +/-0.03 and HD93162 8.22 +/-0.05. The latter star was f…
The symbiotic star AG Dra experienced a double-peaked outburst of 0.6 magnitudes in April and May 2016. Photometry and spectroscopy through the outburst showed the B-V colour index varying linearly with the V magnitude and enabled the temperature variation of the hot star to be calculated from the changing flux in the H beta and He II 4686A emission lines.
We summarize our ground-based program of spectroscopic and photometric observations of the asteroseismic targets of the Kepler space telescope. We have already determined atmospheric parameters, projected velocity of rotation, and radial velocity of 62 Kepler asteroseismic targets and 33 other stars in the Kepler field of view. We discovered six single-lined and two double-lined spectroscopic binaries, we determined the interstellar reddening for 29 stars in the Kepler field of view, and discovered three delta Sct, two gamma Dor and 14 other variable stars in the field of NGC 6866.
In this series of papers we have presented the results of a spectroscopic survey of luminous and variable stars in the nearby spirals M31 and M33. In this paper, we present spectroscopy of 132 additional luminous stars, variables, and emission line objects. Most of the stars have emission line spectra, including LBVs and candidate LBVs, Fe II emission line stars and the B[e] supergiants, and the warm hypergiants. Many of these objects are spectroscopically similar and are often confused with each other. With this large spectroscopic data set including various types of emission line stars, we e…
The spectroscopic and photometric analysis of sample Am stars are carried out to determine the stellar characteristics of each studied star. The CCD photometric analysis of HD 98851 and HD 207561 show clear evidence of pulsation variability of 1.55 hr and 5.8 min respectively. Similarly, a clear evidence of the photometric variability is also found for an Am star HD 73045 which is likely to be pulsating in nature with a period of about 36-min. We are also found dissimilar behaviour of elemental abundances of various ions for HD 113878 and HD 118660. The basic stellar parameters (mass, luminosi…
New complete light and radial velocities curves were obtained for the eclipsing binaries CC Her and CM Lac. The data are analysed with modern techniques in order to derive the physical parameters of the systems and study their present evolutionary status. We found that CC Her is a classical Algol type binary, while CM Lac is a detached system with two Main Sequence stars in asynchronous orbit.
We present results from long-term optical photometric and spectroscopic observations of 5 pre-main sequence stars, located in the vicinity of the bight nebula NGC 7129. We obtained UBVRI photometric observations in the field centered on the star V391 Cep, north-west of the bright nebula NGC 7129. Our multicolor CCD observations spanned the period from February 1998 to November 2016. At the time of our photometric monitoring, a total of thirteen medium-resolution optical spectra of the stars were obtained. The results from our photometric study show that all stars exhibit strong variability in …
Miras are fascinating stars. A kappa-mechanism in their atmosphere drives pulsations which produce changes in their photometric brightness, apparent spectral type and effective temperature. These pulsations also drive the formation of Balmer emission lines in the spectrum. This behaviour can be observed and investigated with small telescopes. We report on a three-year project combining spectroscopy and photometry to analyse the behaviour of Mira stars SU Cam and RY Cep, and describe how their brightness, colour, spectral type, effective temperature and Balmer emission vary over four pulsation …
We have analyzed the available spectra of WW And and for the first time obtained a reasonably well defined radial velocity curve of the primary star. Combined with the available radial velocity curve of the secondary component, these data led to the first determination of the spectroscopic mass ratio of the system at q-spec = 0.16 +/- 0.03. We also determined the radius of the accretion disc from analysis of the double-peaked H-alpha emission lines. Our new, high-precision, Johnson VRI and the previously available Stromgren vby light curves were modelled with stellar and accretion disc models.…
We present a spectroscopic and photometric determination of the distance to the young Galactic open cluster Westerlund 2 using WFPC2 imaging from the Hubble Space Telescope and ground-based optical spectroscopy. HST imaging in the F336W, F439W, F555W, and F814W filters resolved many sources previously undetected in ground-based observations and yielded photometry for 1136 stars. We identified fifteen new O-type stars, along with two probable binary systems, including MSP 188 (O3 + O5.5). We fit reddened SEDs based on the Padova isochrones to the photometric data to determine individual reddeni…
We present results from an optical imaging and spectroscopic monitoring campaign on the young, low-mass eruptive variable star V1647 Orionis. The star and associated nebulosity (McNeil's Nebula) were observed over the period February 2004 to February 2006 with observations commencing a few months after the original outburst event occurred. Using the Gemini North telescope, we obtained multi-band optical imaging photometry and medium-resolution long-slit spectroscopy of V1647 Ori on an approximately monthly interval. During this period, V1647 Ori remained at, or close to, peak brightness and th…
In this paper we present a combined photometric, spectroscopic and orbital period study of three early-type eclipsing binary systems: XZ Aql, UX Her, and AT Peg. As a result, we have derived the absolute parameters of their components and, on that basis, we discuss their evolutionary states. Furthermore, we compare their parameters with those of other binary systems and with the theoretical models. An analysis of all available up-to-date times of minima indicated that all three systems studied here show cyclic orbital changes, their origin is discussed in detail. Finally, we performed a freque…
We present photometric and spectroscopic analysis of the Hubble Sandage variable AF And in M31. The data has been taken under the Nainital Microlensing Survey during 1998-2002 and follow-up observations were carried out until 2011. During this period, photometric observations in Cousins R and I bands were obtained for 169 nights spanning over about 5000 days. AF And has shown a prominent outburst around mid-January in 1999 followed by a gradual decrease in brightness of about 1.5 mag in the next 3 years with a declining rate of ~0.0015 mag/day leading to a quiescent phase at the end of 2001. A…
The recent results from photometric and spectroscopic study of the FUor star V2493 Cyg (HBC 722) are presented in the paper. The outburst of V2493 Cyg was registered during the summer of 2010 before the brightness of the star to reach the maximum value. V2493 Cyg is the first FUor object, whose outburst was observed from its very beginning in all spectral ranges. The recent photometric data show that the star keeps its maximum brightness during the period September 2013 - May 2016 and the recorded amplitude of the outburst is 5.1 mag. (V) Consequently, the outburst of V2493 Cyg lasts for more …
The prototype star for the γ Doradus class of pulsating variables was studied em- ploying photometric and spectroscopic observations to determine the frequencies and modes of pulsation. The four frequencies found were self-consistent between the obser- vation types and almost identical to those found in previous studies (1.3641 d-1 ,1.8783 d-1 , 1.4742 d-1 and 1.3209 d-1). Three of the frequencies are classified as l, m = (1, 1) pulsations and the other is ambiguous between l = 2 modes. Two frequencies are shown to be stable over twenty years since their first identification. The agreement in …
We analysed the wide-field near-infrared survey of the Praesepe cluster carried out by the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Clusters Survey (GCS) and released by the Data Release 9 (DR9). We compare our Praesepe mass function (MF) with the ones of the Pleiades, alpha Per, and the Hyades. We also present preliminary results of a spectroscopic follow-up for the low mass members (M=<0.1Msol) in Praesepe, alpha Per and Pleiades using the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) mounted on the 10.4m Gran Telescopio Canarias (GTC). We also presen…
A new investigation of the variability of the SPB-type star 53 Per is presented. The analysis of the BRITE photometry allowed us to determine eight independent frequencies and the combination one. Five of these frequencies and the combination one were not known before. In addition, we gathered more than 1800 new moderate and high-resolution spectra of 53 Per spread over approximately six months. Their frequency analysis revealed four independent frequencies and the combination one, all consistent with the BRITE results.
The multi-color photometric and spectroscopic observations of the newly discovered eclipsing binary T-Lyr0-08070 were obtained. The resultant light and radial velocities were analysed and the absolute parameters of the components were determined. The system is composed of an F3 and an M3 main-sequence stars. Masses and radii were estimated to be 1.37$\pm$0.23 M$_{\odot}$ and 1.60$\pm$0.09 R$_{\odot}$ for the primary and 0.32$\pm$0.04 M$_{\odot}$ and 0.86$\pm$0.06R$_{\odot}$ for the secondary star. The less massive secondary component has a radius at least two times larger with respect to its m…
The photometric analysis of sample Am stars is carried out to determine the stellar characteristics and to constrain the stellar dynamics. The spectroscopic analysis of the studied Am stars confirms their general characteristics of Am stars. The available data on elemental abundances for HD 113878 and HD 118660 have shown different characteristics during different epochs of observations. The basic stellar parameters (mass, luminosity, radius, life time, distance, proper-motion, etc.) are also determined to identify the stellar habitat zones for earth like exoplanet. Such information is importa…
P Cygni is a prototype of the Luminous Blue Variables (or S Doradus variables), and the star displays photometric and emission line variability on a timescale of years (known as the "short S Doradus phase" variations). Here we present new high resolution H-alpha spectroscopy of P Cyg that we combine with earlier spectra and concurrent V-band photometry to document the emission and continuum flux variations over a 24 y time span. We show that the emission and continuum fluxes vary in concert on timescales of 1.6 y and longer, but differ on shorter timescales. The H-alpha profile shape also vari…
We present simultaneous ground-based radial velocity (RV) measurements and space-based photometric measurements of the young and active K dwarf Epsilon Eridani. These measurements provide a data set for exploring methods of identifying and ultimately distinguishing stellar photospheric velocities from Keplerian motion. We compare three methods we have used in exploring this data set: Dalmatian, an MCMC spot modeling code that fits photometric and RV measurements simultaneously; the FF$'$ method, which uses photometric measurements to predict the stellar activity signal in simultaneous RV measu…
This is the first in a series of papers presenting methods and results from the Young Solar Analogs Project, which began in 2007. This project monitors both spectroscopically and photometrically a set of 31 young (300 - 1500 Myr) solar-type stars with the goal of gaining insight into the space environment of the Earth during the period when life first appeared. From our spectroscopic observations we derive the Mount Wilson $S$ chromospheric activity index ($S_{\rm MW}$), and describe the method we use to transform our instrumental indices to $S_{\rm MW}$ without the need for a color term. We i…
We present the analysis of several newly obtained and archived photometric and spectroscopic datasets of the intriguing and yet poorly understood 13.5-mag central star candidate of the bipolar planetary nebula Sh2-71. Photometric observations confirmed the previously determined quasi-sinusoidal lightcurve with a period of 68 days and also indicated periodic sharp brightness dips, possibly eclipses, with a period of 17.2 days. In addition, the comparison between U and V lightcurves revealed that the 68-day brightness variations are accompanied by a variable reddening effect of $ΔE(U-V)=0.38$. S…
We characterise the variability in the physical properties of the luminous blue variable AFGL2298 between 1989-2008. In conjunction with published data from 1989-2001, we have undertaken a long term (2001-2008) near-IR spectroscopic and photometric observational campaign for this star and utilise a non-LTE model atmosphere code to interpret these data. We find AFGL2298 to have been highly variable during the two decades covered by the observational datasets. Photometric variations of >1.6 mag have been observed in the JHK wavebands; however, these are not accompanied by correlated changes in n…
Deneb is often considered the prototypical A-type supergiant, and is one of the visually most luminous stars in the Galaxy. A-type supergiants are potential extragalactic distance indicators, but the variability of these stars needs to be better characterized before this technique can be considered reliable. We analyzed 339 high resolution echelle spectra of Deneb obtained over the five-year span of 1997 through 2001 as well as 370 Stromgren photometric measurements obtained during the same time frame. Our spectroscopic analysis included dynamical spectra of the H-alpha profile, H-alpha equiva…
We present a detailed spectroscopic and photometric analysis of DA and DB white dwarfs drawn from the Sloan Digital Sky Survey with trigonometric parallax measurements available from the Gaia mission. The temperature and mass scales obtained from fits to $ugriz$ photometry appear reasonable for both DA and DB stars, with almost identical mean masses of $\langle M \rangle = 0.617~M_\odot$ and $0.620~M_\odot$, respectively. The comparison with similar results obtained from spectroscopy reveals several problems with our model spectra for both pure hydrogen and pure helium compositions. In particu…
Subdwarf A star (sdA) is a spectral classification given to objects showing H-rich spectra and sub-main sequence surface gravities, but effective temperature lower than the zero-age horizontal branch. Their evolutionary origin is an enigma. In this work, we discuss the results of follow-up observations of selected sdAs. We obtained time resolved spectroscopy for 24 objects, and time-series photometry for another 19 objects. For two targets, we report both spectroscopy and photometry observations. We confirm seven objects to be new extremely-low mass white dwarfs (ELMs), one of which is a known…
We present observations of M31LRN 2015 (MASTER OT J004207.99+405501.1), discovered in M31 in 2015 January, and identified as a rare and enigmatic luminous red nova (LRN). Spectroscopic and photometric observations obtained by the Liverpool Telescope showed the LRN becoming extremely red as it faded from its M(V) = -9.4 +/- 0.2 peak. Early spectra showed strong Halpha emission that weakened over time as a number of absorption features appeared, including Na I D and Ba II. At later times strong TiO absorption bands were also seen. A search of archival Hubble Space Telescope data revealed a lumin…
Supernova 2012A was discovered on 7.39UT, January, 2012 in the nearby galaxy NGC 3239 at an unfiltered magnitude of 14.6 and classified spectroscopically as a Type IIP event. Here, we present the optical photometric and spectroscopic follow-up of the event during 14d to 130d post explosion.
The advent of space-based photometry provides the opportunity for the first precise characterizations of variability in Mercury-Manganese (HgMn/CP3) stars, which might advance our understanding of their internal structure. We have carried out a spectroscopic and photometric investigation of the candidate CP3 star KIC 6128830. A detailed abundance analysis based on newly-acquired high-resolution spectra was performed, which confirms that the star's abundance pattern is fully consistent with its proposed classification. Photometric variability was investigated using four years of archival Kepler…
We performed photometric and spectroscopic investigations of NSVS 5029961 for the first time. The new BV(RI)$_c$-band light curves were obtained with the 1.0-m telescope at Weihai Observatory of Shandong University. Applying the Wilson-Devinney program, we found that NSVS 5029961 is an A-subtype shallow contact binary with extremely low mass ratio (q = 0.1515, f = 19.1\%). Six spectra have been obtained by LAMOST, and many chromospheric activity emission line indicators were detected in the spectra, revealing that the target exhibits strong chromospheric activity. We calculated the absolute pa…
Hubble Space Telescope photometry of $η$ Carinae spans 23 years, including five spectroscopic events. The rapid brightening rate decreased after 2010, and the spectroscopic events in 2014 and 2020 had light curves different from their predecessors. Together with other indicators, these developments probably foretell the conclusion of $η$ Car's change of state.
In the present paper, we report the photometric and spectroscopic observations obtained by the 1.88 m telescope at the Kottamia astronomical observatory of the pulsating star BL Cam. Fourier analysis of the light curves reveals that the fundamental mode has two harmonics. The O-C method is used to establish the period changes. So far, the analysis has been very successful in mapping the pulsation amplitude of the star across the instability strip. By using the formalism of Eddington and Plakidis (1929), we found significant results and strong indications of the evolutionary period change. A to…
Context. TW Draconis is one of the best studied Algol-type eclipsing binaries. There is significant evidence for miscellaneous physical processes between interacting binary components manifesting themselves by period and light curve changes. Aims. Obtaining new set of photometric and spectroscopic observations, we analysed them together with the older spectroscopic and photometric data to build model of this eclipsing system with respect to observed changes of O-C diagram and light curve. Methods. Reduction of new spectra was carried out in the IRAF and SPEFO programs. Radial velocities were d…
We present a comparative analysis of atmospheric parameters obtained with the so-called photometric and spectroscopic techniques. Photometric and spectroscopic data for 1360 DA white dwarfs from the Sloan Digital Sky Survey (SDSS) are used, as well as spectroscopic data from the Villanova White Dwarf Catalog. We first test the calibration of the ugriz photometric system by using model atmosphere fits to observed data. Our photometric analysis indicates that the ugriz photometry appears well calibrated when the SDSS to AB_95 zeropoint corrections are applied. The spectroscopic analysis of the s…
Spectroscopic and photometric observations of the nearby Type Ia Supernova (SN Ia) SN 2014J are presented. Spectroscopic observations were taken -8 to +10 d relative to B-band maximum, using FRODOSpec, a multi-purpose integral-field unit spectrograph. The observations range from 3900 AA to 9000 AA. SN 2014J is located in M82 which makes it the closest SN Ia studied in at least the last 28 years. It is a spectrosopically normal SN Ia with high velocity features. We model the spectra of SN 2014J with a Monte Carlo (MC) radiative transfer code, using the abundance tomography technique. SN 2014J i…
We present spectroscopic time series observations on one of the brightest northern RRc star, T Sex. Additionally, we also analysed extended photometric data sets, particularly the recent observations of the TESS space telescope. The main findings of our studies are as follows: T Sex, unlike all RRc stars whose space photometry has been analysed, shows only the $0.5f_x$ frequency as an additional pulsation frequency. With this, T Sex may be the first represent of such rare RRc stars found from space photometry. The spectroscopic data show a periodic distortion of the H$α$ line with the pulsatio…
We present analysis of medium resolution optical spectra and long term V band photometry of four cool stars, BD+13 5000, BD+11 3024, TYC 3557-919-1 and TYC 5163-1764-1. Our spectroscopic analysis reveals that the stars are giant or sub-giant from K0 or K1 spectral type, and all of them exhibit emission features in their Ca ii H& K lines. These features appear to be modulated with the rotation of the stars. Except BD+11 3024, we observe that the radial velocities of the target stars are not stable, which suggests that each of them might be a member of a binary system. Global analysis of photome…
Reported are UBV and uvbybeta observations of 15 candidates for Kepler primary astero- seismic targets and 14 other stars in the Kepler field, carried out at the M.G. Fracastoro station of the Catania Astrophysical Observatory. These data serve to plot the 29 stars in two-parameter diagrams with the photometric indices (such as B-V or delta m1 and the atmospheric parameters (such as the MK type or [Fe/H]) as coordinates. The two-parameter diagrams show no evidence of interstellar reddening. The photometric indices B-V and beta are then used to derive photometric effective temperatures, Teff(B-…
The simultaneous photometric and spectroscopic observations of the RR Lyrae variables in the globular cluster, M3, published in Jurcsik et al. (2017, Paper I) made it possible to perform Baade-Wesselink (BW) analysis of a large sample of Blazhko stars for the first time. The BW distances of Blazhko stars turned out to be unreliable, as significantly different distances were obtained for the stars of the Blazhko sample and also for the same star in different modulation phases. Even the results of small modulation-amplitude Blazhko stars may be doubtful. This result warns that the application of…
We present an analysis of spectroscopic radial velocity and photometric data of three bright Galactic Cepheids: LR Trianguli Australis (LR TrA), RZ Velorum (RZ Vel), and BG Velorum (BG Vel). Based on new radial velocity data, these Cepheids have been found to be members of spectroscopic binary systems. The ratio of the peak-to-peak radial velocity amplitude to photometric amplitude indicates the presence of a companion for LR TrA and BG Vel. IUE spectra indicate that the companions of RZ Vel and BG Vel cannot be hot stars. The analysis of all available photometric data revealed that the pulsat…
Detached eclipsing binaries are remarkable systems to provide accurate fundamental stellar parameters. The fundamental stellar parameters and the metallicity values of stellar systems are needed to deeply understand the stellar evolution and formation. In this study, we focus on the detailed spectroscopic and photometric studies of three detached eclipsing binary systems, V372\,And, V2080\,Cyg, and CF\,Lyn to obtain their accurate stellar, atmospheric parameters,and chemical compositions. An analysis of light and radial velocity curves was carried out to derive the orbital and stellar paramete…
Luminous Blue Variables (LBVs) are massive stars that show strong spectral and photometric variability. The question of what evolutionary stages they represent and what exactly drives their instability is still open, and thus is it important to understand whether LBVs without significant ongoing activity exist, and for how long such dormant LBVs may ``sleep''. In this article we investigate the long-term variability properties of the LBV candidate MN112, by combining its optical and infrared spectral data covering 12 years with photometric data covering nearly a century acquired by both modern…
A photometric and spectroscopic investigation is performed on five W Ursae Majoris eclipsing binaries (EWs) J015818.6+260247 (hereinafter as J0158b), J073248.4+405538 (hereinafter as J0732), J101330.8+494846 (hereinafter as J1013), J132439.8+130747 (hereinafter as J1324) and J152450.7+245943 (hereinafter as J1524). The photometric data are collected with the help of the 1.3\,m Devasthal Fast Optical Telescope (DFOT), the 1.04\,m Sampurnanand Telescope (ST) and the TESS space mission. The low-resolution spectra of the 4\,m Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) are u…
We report the discovery of a new Galactic candidate Luminous Blue Variable (cLBV) via detection of an infrared circular nebula and follow-up spectroscopy of its central star. The nebula, MN112, is one of many dozens of circular nebulae detected at $24 μ$m in the {\it Spitzer Space Telescope} archival data, whose morphology is similar to that of nebulae associated with known (c)LBVs and related evolved massive stars. Specifically, the core-halo morphology of MN112 bears a striking resemblance to the circumstellar nebula associated with the Galactic cLBV GAL 079.29+00.46, which suggests that bot…
We report a spectroscopic study of 19 photometric variables and 55 blue, yellow and red straggler candidates in the field of omega Centauri. We confirm the cluster membership of 18 variables and 54 straggler candidates. Velocity variations are detected in 22 objects, and another 17 objects are classified as suspected of being velocity-variable. Velocity data of 11 photometric variables phase with their photometric periods, however none of these objects has a mass function indicating the presence of a massive degenerate component. Based on both photometric and spectroscopic data we find that th…
