We use all the Subaru/HSC-SSP photometric data to investigate spatial substructures in the outer halo of the Milky Way. In order to effectively detect them, an isochrone-filter is created for the old, metal-poor stellar systems on the color-magnitude diagram. As a result, previously discovered stellar streams (e.g. the Orphan Stream) are detected, while a new candidate substructure is discovered toward Pisces. Based on this filter, we conclude that the progenitor is an old and metal-poor system. This kind of stellar streams are expected to be found in the next-generation observation program.

The carbon-rich star V Hydrae is known to be in its transition from the asymptotic giant branch phase to a bipolar planetary nebula. However, the origin of its bipolar shape, as well as its long-term periodic obscuration, are not well understood. Using high-resolution spectra from the HERMES/Mercator spectrograph spanning over 10-yr monitoring, we disentangled the orbital signal from the intrinsic Mira-like variations of V Hya. The orbital solution obtained is compatible with the light-curve modulation, which we interpret as an obscuration caused by an extended dusty environment surrounding the unseen companion. Additionally, we report high-velocity phase-dependent absorption features in the sodium doublet and explain them by the presence of a conical jet ejected from the (accretion disc of the) companion. We confront our binary scenario with previous radio observations and discuss how this jet could shape the large-scale bipolar outflow of the system.

We correlate the annual Wolf numbers W and their time derivatives Wʹ by shifting time fragments of W and Wʹ relative to each other. The most significant (up to 0.874) correlation is with 3 years shifts for fragments covering 14 years. For longer and shorter periods, the correlation coefficients 0.771–0.855 with 2–3 years shift. The most significant 9 years shift corresponds to -0.852/-0.824 anti-correlation coefficient for 14/11 years period. The other periods are less significant. To evaluate predictive estimates, we use the times series fragments of W shifted back into the past. A forecast can be made using the leading graphs based upon the derived calibration factor. Test calculations show that the most effective is the calibration factor calculated for changing the phase of the cycle. The best linear pairwise correlation coefficient of the approximation is 0.94.

Statistical study of 3047 active regions (ARs) from 1996 to 2021 was performed using the catalog of the magneto-morphological classes (MMC) of ARs CrAO. According to the magneto-morphological classification of ARs proposed earlier, all ARs, except for unipolar spots, were sorted out between two categories: regular (bipolar groups obeying the Hale’s polarity law, the Joy’s law, etc.) and irregular ARs (all the rest). We analyzed the number and fluxes of ARs depending on their location in different (relative to the equator) hemispheres. We found that the trends for fluxes are more pronounced. For ARs of both MMC types, they demonstrate signs of both a multi-peak and double-peak structure. Some peaks coincide with the main maxima of the cycle. The second main maximum is mainly formed by the irregular ARs in the S-hemisphere. This might be due to the interaction of the dipole and quadrupole components of the global magnetic field.

OH masers are signpost of planetary nebulae (PNe) at a very young stage. In particular, Vy 2-2 was the first OH maser-emitting PN ever identified. It consists of a bright compact shell and a faint bipolar structure. The reported values for its O+2/H+ abundance discrepancy factor (ADF) are inconsistent:; 4.3, and; 11.8. To characterize the ionized gas and to redetermine the ADF(O+2), we have obtained medium-resolution optical spectra. We found that the ionized gas is oxygen-rich (C/O; 0.15), and an ADF(O+2); 13.6. Also, the N/O abundance ratio is; 0.39, implying a low-mass progenitor (Mi ≤ 1.5 Me). Unexpectedly, the detection of stellar weak emission lines (wels) suggests that the central star is carbon-rich. Alternatively, the wels may be emitted by an irradiated companion in a post-common envelope system. We have also obtained high-resolution optical spectroscopy on Vy 2-2. Our spectra kinematically resolve the bright shell and bipolar structure. We found that these expand at: 10 and: 20 km s-1, respectively.

Stellar activity depends on multiple parameters one of which is the age of the star. The members of open clusters are good targets to observe the activity at a given age of the stars since their ages are more precisely determined than that of field stars. Choosing multiple clusters, each with different age, gives us insight to the change in activity during the lifetime of stars. With the analysis of these stars we can also refine the parameters of gyrochronology (Barnes 2003), which is a method for estimating the age of low-mass, main sequence stars from their rotation periods.

On August 25 2013 Dana Patchick from the “Deep Sky Hunters” (DSH) amateur astronomer group discovered a diffuse nebulosity in the Wide-field Infrared Survey Explorer (WISE) mid-IR image archive that had no optical counterpart but appeared similar to many Planetary Nebulae (PNe) in WISE. As his 30th discovery he named it Pa 30 and it was added to the HASH PN database as a new PN candidate. Little did he know how important his discovery would become. 10 years later this object is the only known bound remnant of a violent double WD merger accompanied by a rare Type Iax SN, observed and recorded by the ancient Chinese and Japanese in 1181 AD. This makes Pa 30 and its central star IRAS 00500+6713 (WD J005311) the only SN Iax remnant in our Galaxy, the only known bound remnant of any SN, and based on the central star’s spectrum the only Wolf-Rayet star known that neither has a massive progenitor nor is the central star of a Planetary Nebula. We cover this story and our key role in it.

We present spectroscopy of NGC 3242, NGC 6153, and NGC 7009 at very high spectral resolution (λ / δλ = 75, 000 – 100, 000) obtained with the Manchester Echelle Spectrograph at the 2.1m telescope of the Observatorio Astronómico Nacional on the Sierra San Pedro Mártir. We study the kinematics of the plasma within the nebular shells, decomposing the observed line profiles considering the microscopic, macroscopic, and observational processes that broaden them. The residual kinematic structure, defined as the sum of velocity gradients, kinematic structure, and seeing dominates the broadening of the lines of heavy elements. We estimate the effect of velocity gradients, finding that it can account only for a minority of this residual kinematic structure. Whatever the origin of this residual kinematic structure, it is an important component of the kinematics of the ionized plasma within the nebular shell and implies an important energy source that is not contemplated in photoionization models of planetary nebulae.

We performed numerical simulations of the common envelope (CE) interaction between two intermediate-mass asymptotic giant branch (AGB) stars and their low-mass companions. For the first time, formation and growth of dust in the envelope is calculated explicitly. We find that the first dust grains appear as early as ∼1–3 yrs after the onset of the CE, and are smaller than grains formed later. As the simulations progress, a high-opacity dusty shell forms, resulting in the CE photosphere being up to an order of magnitude larger than it would be without the inclusion of dust. At the end of the simulations, the total dust yield is ∼8.2×10−3 M⊙ (∼2.2×10−2 M⊙) for a CE with a 1.7 M⊙ (3.7 M⊙) AGB star. Dust formation does not substantially lead to more mass unbinding or substantially alter the orbital evolution.

Magnetic fields are important physics in stellar evolutionary theory, which seriously affects the stellar structure and evolutionary statues. The small-scale magnetic fields in the photosphere are ubiquitous, and float on the stellar surface, which usually couple with the acoustic waves, affecting the propagation of the acoustic waves. Considering the effect of the magnetic fields in the stellar photosphere on the oscillation frequencies, we calculate the asteroseismology for solar-like star KIC 11295426 and KIC 10963065. We obtain the stellar fundamental parameters, especially the strength of small-scale magnetic fields in the stellar photosphere. We find that the small-scale magnetic fields in the stellar photosphere may obviously improve the agreement between the observations and the theoretical models for two stars. The magnetic strength for KIC 11295426 and KIC 10963065 from asteroseismology are in agreement with the stellar period-activity relation.

Planetary nebulae (PNe) are remnants of evolved stars, fundamental for understanding stellar life cycles and galactic enrichment. In this work, we present a summary of our recent work using three-dimensional models and spatially resolved constraints to examine the physical and chemical properties of PNe, with a particular focus on preliminary results for the PN NGC 3132. Our results indicate that a star of about 3M⊙, surrounded by a shell, wind, or disk with approximately 5.0×10−6M⊙ and extending to about 300AU is necessary to adequately reproduce the observations, consistent with recent JWST findings. We also discuss the importance of this methodology in studying the properties of the progenitor stars and making abundance determinations.

The formation of the Magellanic Bridge during an encounter between the Magellanic Clouds ∼ 200 Myr ago would be imprinted in the chemical evolution and kinematics of its stellar population, with sites of active star formation. Since it contains hundreds of stellar clusters and associations, we combined deep photometry from VISCACHA and SMASH surveys to explore this topic, by deriving structural parameters, age, metallicity, distance and mass for 33 Bridge clusters with robust statistical tools. We identified a group of 13 clusters probably stripped from the Small Magellanic Cloud (0.5 − 4.7 Gyr, [Fe/H] < −0.6 dex) and another 15 probably formed in-situ (< 200 Myr, [Fe/H] ∼ −0.4 dex). Two metallicity dips were detected in the age-metallicity relation, coeval to the Stream and Bridge formation epochs. Cluster masses range from 500 to ∼ 104 M⊙, and a new estimate of 3 − 5 × 105 M⊙ is obtained for the Bridge stellar mass.

I discuss circumgalactic gas flows in the extended Milky Way halo in the context of the on-going formation and evolution of the Local Group. UV absorption-line measurements, in combination with H i 21 cm observations, provide detailed information on the chemical composition, dust content, physical conditions, and large-scale kinematics of the so-called high-velocity clouds, which are believed to trace neutral and ionized gas in the gaseous halos of the Milky Way, M31, and in the intragroup medium of the Local Group. Recent results in this field and ideas for future observational studies are being presented.

Extinction correction is the quintessence of astronomy. To achieve precision astrophysics in plasma diagnostics as in the theme of the present Proceedings, one must perform extinction correction properly before executing any line diagnostics of line-emitting objects including planetary nebulae. By making use of the inseparable relationship between extinction correction and plasma diagnostics, we establish a novel method to determine the physical conditions of a line-emitting target and the extinction characteristics along the line of sight toward the target simultaneously and self-consistently. This approach is made possible by the exact analytical expressions for the extinction parameters in terms of the emission properties of the target and by statistical optimization of the extinction parameters to find the robust physical conditions of the target.

. We show that an extragalactic jet with a velocity shear gives rise to Fermi like acceleration process for photons scattering withing the shear layers of the jet. Such photons then gain energy to produce a high energy power law. These power law spectra at high energies are frequently observed in several extragalactic objects such as Gamma Ray Bursts (GRBs). We implement the model on GRBs to show that the obtained range of the photon indices are well within their observed values. The analytic results are confirmed with numerical simulations following Monte Carlo approach.

We present a method to measure the the oblateness parameter q of the dark matter halo of gas rich galaxies that have extended HI disks. We have applied our model to a sample of 20 nearby galaxies that are gas rich and close to face-on, of which 6 are large disk galaxies, 8 have moderate stellar masses and 6 are low surface brightness (LSB) dwarf galaxies. We have used the stacked HI velocity dispersion and HI surface densities to derive q in the outer disk regions. Our most important result is that gas dominated galaxies (such as LSB dwarfs) that have M(gas)/M(baryons)>0.5 have oblate halos (q<55), whereas stellar dominated galaxies have a range of q values from 0.2 to 1.3. We also find a significant positive correlation between q and stellar mass, which indicates that galaxies with massive stellar disks have a higher probability of having halos that are spherical or slightly prolate, whereas low mass galaxies preferably have oblate halos. We briefly also discuss how the halo shape affects the disks of galaxies, especially the oblate halos.

We investigate the evolution of subsurface flows during the emergence and the active phase of sunspot regions using the time–distance helioseismology analysis of the full-disk Dopplergrams from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We present an analysis of emerging active regions of various types, including delta-type active regions and regions with the reverse polarity order (‘anti-Hale active regions’). The results reveal strong vortical and shearing flows during the emergence of magnetic flux, as well as the process of formation of large-scale converging flow patterns around developing active regions, predominantly in the top 6 Mm deep layers of the convection zone. Our analysis revealed a significant correlation between the flow divergence and helicity in the active regions with their flaring activity, indicating that measuring characteristics of subsurface flows can contribute to flare forecasting.

AutoTAB is a state-of-the-art, fully automatic algorithm that tracks the Bipolar Magnetic Regions (BMRs) in magnetogram observations. AutoTAB employs identified BMR regions from Line-of-Sight magnetograms from MDI and HMI (1996–2022) to track the BMRs through their evolution on the nearside of the Sun. AutoTAB enables us to create a comprehensive and unique catalog of tracked information of 9232 BMRs in the mentioned time period. This dataset is used to study the collective statistical properties of BMRs and particularly to identify the correct theory for the BMR formation. Here, we discuss the algorithm’s functionality and the initial findings obtained from the AutoTAB BMRs catalog.

Due to the contamination from omnipresent interstellar 21 cm emission, atomic hydrogen (H <sc>i</sc>) associated with planetary nebulae (PNe) has been insufficiently investigated. In this proceeding we report a project of searching for H i surrounding PNe using the Five hundred-meter Aperture Spherical radio Telescope (FAST), which is the most sensitive single-dish telescope at L-band. The observations may offer new insights into the interaction processes between PNe and the interstellar medium.

In most of the Babcock–Leighton (BL) type solar dynamo models, the toroidal magnetic field is assumed to be generated in the tachocline. However, magnetic activity of fully convective stars and MHD simulations of global stellar convection have recently raised serious doubts about the importance of the tachocline in the generation of the toroidal field. We have developed a BL-type dynamo model operating in the bulk of the convection zone, and are extending this model to solar-type stars. In this study, we aim at exploring how the starspot properties affect the stellar magnetic cycle. Observations show that faster rotating stars tend to have stronger magnetic activity and shorter magnetic cycles. By considering the higher latitudes and larger tilt angles of starspots for faster rotators, our simulations reproduce observations that faster rotating stars have shorter magnetic cycle and stronger activity.