7 research outputs found
Modeling of multimode radially pulsating High-Amplitude Delta Scuti stars from the OGLE Galactic bulge sample
No full textThanks to relatively firm mode identification, possible based on period
ratios only, High Amplitude Delta Scuti Stars pulsating in at least three
radial modes are promising targets for asteroseismic inference. In this study
we used the most numerous sample of HADS from the OGLE inner bulge fields that
likely pulsate in either three or four radial modes simultaneously. We have
computed a grid of pulsation models along evolutionary tracks and determined
the physical parameters of stars by matching their pulsation periods and period
ratios. For 176 HADS we determined physical parameters, i.e. masses,
luminosities, effective temperatures, metallicities and ages. We present the
distribution of physical parameters and discuss their properties. We selected
16 candidates for SX Phoenicis stars.Comment: 13 pages, 14 figures, 2 tables, accepted for publication in MNRA
Asteroseismology of RR Lyrae stars with non-radial modes
No full textThe additional signals observed in the frequency spectra of the
first-overtone RR Lyrae stars, that form a period ratio around 0.61 with the
period of the first overtone, are a common phenomenon for RRc and RRd stars, as
well as for first-overtone classical Cepheids. The recently proposed model
explains these signals as harmonics of non-radial modes of degrees 8 or 9 in
the case of RR Lyrae stars and 7, 8, or 9 in the case of classical Cepheids. We
selected at least triple-mode RR Lyrae stars pulsating in radial and non-radial
modes for asteroseismic modeling. We assume the identification of the
non-radial modes as predicted by the model. We calculated a dense grid of
models for RR Lyrae stars using envelope pulsation code. By matching first
overtone period and period ratios we obtained physical parameters for the
selected sample of triple-mode stars. It is the very first attempt of modeling
RR Lyrae stars with non-radial modes. We compared our results with predictions
of stellar evolution theory, which resulted in a mass discrepancy more
noticeable for long-period stars: pulsation masses seem higher than
evolutionary masses. We compared metallicity estimates for RRc stars from
modeled sample with metallicities determined spectroscopically for a sample of
RRc stars in the solar neighbourhood: both distributions are consistent.Comment: 13 pages, 15 figures, 5 tables, accepted for publication in MNRA
Signature of High-amplitude Pulsations in Seven δ Sct Stars via TESS Observations
No full textThe regular behavior of the pulsations of high-amplitude δ Sct (HADS) stars gives a greater chance to investigate the interiors of stars. We analyzed seven HADS stars showing peak-to-peak amplitudes of more than 0.3 mag that were newly observed by TESS. We obtained that TIC 374753270, TIC 710783, and TIC 187386415 pulsate in fundamental radial mode; also, TIC 130474019 and TIC 160120432 show double radial modes. On the other hand, TIC 148357344 and TIC 278119167 demonstrate triple-mode behavior. Our analysis shows that these seven stars are close to the red edge of the (inside) instability strip in the Hertzsprung–Russell diagram. The fundamental mode of these seven targets follows the period–luminosity (PL) relation for δ Sct stars. However, TIC 278119167 deviates slightly from the fundamental PL relation. The double-mode and triple-mode HADS stars (TIC 130474019, TIC 160120432, TIC 148357344, and TIC 278119167) are in agreement with the period ratio ranges (fundamental to first and second overtones). Using the information of 176 HADS stars (Netzel and Smolec), we find a scaling relation ([\mathrm{Fe}/{\rm{H}}]\propto \mathrm{log}({M}^{7.95\pm 0.15}{L}^{-1.83\pm 0.11}{\rm{P}}{0}^{0.79\pm 0.14}{T}_{\mathrm{eff}}^{0.047\pm 0.02})) between the metallicity ([Fe/H]) and mass (M), luminosity (L), effective temperature (Teff), and the fundamental period (P0). We estimate the metallicity of the seven newly identified HADS stars ranging from −0.62 to 0.37 dex.. © 2024. The Author(s). Published by the American Astronomical Society.This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Funding for the TESS mission is provided by the NASA Explorer Program. Funding for the TESS Asteroseismic Science Operations Centre is provided by the Danish National Research Foundation (grant agreement No.: DNRF106), ESA PRODEX (PEA 4000119301), and Stellar Astrophysics Centre (SAC) at Aarhus University. We would like to thank the Gaia team for providing accurate data from the European Space Agency (ESA) mission Gaia, processed by the Gaia Data Processing and Analysis Consortium (DPAC). Funding for the DPAC has been provided by national institutions, in particular, the institutions participating in the Gaia Multilateral Agreement. This work has been supported by the Iran National Science Foundation (INSF) under grant No. 4002562. E.Z. expresses gratitude for that. Also, E.Z. acknowledges financial support from project PID2019-107061GB-C63 from the "Programas Estatales de Generación de Conocimiento y Fortalecimiento Científico y Tecnológico del Sistema de I+D+i y de I+D+i Orientada a los Retos de la Sociedad" and the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/10.13039/501100011033.With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).Peer reviewe
VELOcities of CEpheids (VELOCE) : I. High-precision radial velocities of Cepheids
No full textWe present the first data release of VELOcities of CEpheids (VELOCE), dedicated to measuring the high-precision radial velocities (RVs) of Galactic classical Cepheids (henceforth, Cepheids). The first data release (VELOCE DR1) comprises 18 225 RV measurements of 258 bona fide classical Cepheids on both hemispheres collected mainly between 2010 and 2022, along with 1161 observations of 164 stars, most of which had previously been misclassified as Cepheids. The median per-observation RV uncertainty for Cepheids is 0.037 km s-1 and reaches 2 m s-1 for the brightest stars observed with Coralie. Non-variable standard stars were used to characterize RV zero-point stability and to provide a base for future cross-calibrations. We determined zero-point differences between VELOCE and 31 literature data sets using template fitting, which we also used to investigate linear period changes of 146 Cepheids. In total, 76 spectroscopic binary Cepheids and 14 candidate binary Cepheids were identified using VELOCE data alone, which are investigated in detail in a companion Paper (VELOCE II). VELOCE DR1 provides a number of new insights into the pulsational variability of Cepheids, most importantly: a) the most detailed description of the Hertzsprung progression based on RVs to date; b) the identification of double-peaked bumps in the pulsation curve; and c) clear evidence that virtually all Cepheids feature spectroscopic variability signals that lead to modulated RV variability at the level of tens to hundreds of m s-1 and that cannot be satisfactorily modeled using single-periodic Fourier series. We identified 36 stars exhibiting such modulated variability, of which 4 also exhibit orbital motion. Linear radius variations depend strongly on pulsation period and a steep increase in slope of the ΔR/p vs. log P-relation is found near 10 days. This effect, combined with significant RV amplitude differences at fixed period, challenges the existence of a tight relation between Baade-Wesselink projection factors and pulsation periods. We investigated the accuracy of RV time series measurements, Uγ, and RV amplitudes published by Gaia's third data release (Gaia DR3) and determined an offset of 0.65 ± 0.11 km s-1 relative to VELOCE. Whenever possible, we recommend adopting a single set of template correlation parameters for distinct classes of large-amplitude variable stars to avoid systematic offsets in Uγ among stars belonging to the same class. The peak-to-peak amplitudes of Gaia RVs exhibit significant (16%) dispersion. Potential differences of RV amplitudes require further inspection, notably in the context of projection factor calibration
Gaia 18dvy : a new FUor in the Cygnus OB3 association
No full textWe present optical-infrared photometric and spectroscopic observations of Gaia 18dvy, located in the Cygnus OB3 association at a distance of 1.88 kpc. Gaia 18dvy was noted by the Gaia alerts system when its light curve exhibited a greater than or similar to 4 mag rise in 2018-2019. the brightening was also observable at mid-infared wavelengths. the infrared colors of Gaia 18dvy became bluer as the outburst progressed. Its optical and near-infrared spectroscopic characteristics in the outburst phase are consistent with those of bona fide FU Orionis-type young eruptive stars. the progenitor of the outburst is probably a low-mass K-type star with an optical extinction of similar to 3 mag. A radiative transfer modeling of the circumstellar structure, based on the quiescent spectral energy distribution, indicates a disk with a mass of 4 x 10(-3)M. Our simple accretion disk modeling implies that the accretion rate had been exponentially increasing for more than 3 yr until mid-2019, when it reached a peak value of 6.9 x 10(-6)M yr(-1). in many respects, Gaia 18dvy is similar to the FU Ori-type object HBC 722.European Research Council (ERC) under the European UnionEuropean Research Council (ERC) [716155]; Hungarian Academy of SciencesHungarian Academy of Sciences [LP2018-7/2019, KEP-7/2018]; Hungarian National Research, Development and Innovation Office [GINOP 2.3.2-15-2016-00003, PD-128360]; Polish NCN DAINA [2017/27/L/ST9/03221]; European CommissionEuropean CommissionEuropean Commission Joint Research Centre [730890]; Polish MNiSWMinistry of Science and Higher Education, Poland [DIR/WK/2018/12]; Research Council of LithuaniaResearch Council of Lithuania (LMTLT) [S-LL-19-2]; Ministry of Education, Science and Technological Development of the Republic of Serbia [176011]; DFGGerman Research Foundation (DFG) [SPP 1992, WA 1047/11-1]; MINECO (Spanish Ministry of Economy) [RTI2018-095076-B-C21]; Polish NCN MAESTRO [2014/14/A/ST9/00121]We thank the anonymous referee, whose questions and comments significantly improved the paper. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program under grant agreement No. 716155 (SACCRED), Lendulet LP2018-7/2019 and KEP-7/2018 of the Hungarian Academy of Sciences, GINOP 2.3.2-15-2016-00003 and PD-128360 of the Hungarian National Research, Development and Innovation Office, Polish NCN DAINA grant 2017/27/L/ST9/03221, European Commission's Horizon 2020 OPTICON grant 730890, Polish MNiSW grant DIR/WK/2018/12, grant No..S-LL-19-2 of the Research Council of Lithuania, Project No..176011 "Dynamics and kinematics of celestial bodies and systems" of the Ministry of Education, Science and Technological Development of the Republic of Serbia, DFG priority program SPP 1992 "Exploring the Diversity of Extrasolar Planets" (WA 1047/11-1), the MINECO (Spanish Ministry of Economy) through grant RTI2018-095076-B-C21 (MINECO/FEDER, UE). the Joan Oro Telescope (TJO) of the Montsec Astronomical Observatory (OAdM) is owned by the Catalan Government and is operated by the Institute for Space Studies of Catalonia (IEEC). MG is supported by the Polish NCN MAESTRO grant 2014/14/A/ST9/00121. We acknowledge ESA Gaia, DPAC, and the Photometric Science Alerts Team. We thank Christina Conner, Megan Davis, Alessandro Dellarovere, Hannah Gallamore, Mira Ghazali, Aaron Kruskie, Dylan Mankel, Jesse Leahy-McGregor, Brandon McIntyre, Barrett Ross, Courtney Wicklund, and Evan Zobel for observing Gaia 18dvy at the Michigan State University Observatory. Based on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. Based on observations obtained with telescopes of the University Observatory Jena, which is operated by the Astrophysical Institute of the Friedrich-Schiller-University
Full orbital solution for the binary system in the Northern Galactic Disk microlensing event Gaia16aye
No full textFunding: UK STFC consolidated grant ST/M001296/1 (KH); European Commission H2020 OPTICON grant 730890 (OPTICON) (MD).Gaia16aye was a binary microlensing event discovered in the direction towards the northern Galactic disc and was one of the first microlensing events detected and alerted to by the Gaia space mission. Its light curve exhibited five distinct brightening episodes, reaching up to I = 12 mag, and it was covered in great detail with almost 25 000 data points gathered by a network of telescopes. We present the photometric and spectroscopic follow-up covering 500 days of the event evolution. We employed a full Keplerian binary orbit microlensing model combined with the motion of Earth and Gaia around the Sun to reproduce the complex light curve. The photometric data allowed us to solve the microlensing event entirely and to derive the complete and unique set of orbital parameters of the binary lensing system. We also report on the detection of the first-ever microlensing space-parallax between the Earth and Gaia located at L2. The properties of the binary system were derived from microlensing parameters, and we found that the system is composed of two main-sequence stars with masses 0.57 ± 0.05 M⊙ and 0.36 ± 0.03 M⊙ at 780 pc, with an orbital period of 2.88 years and an eccentricity of 0.30. We also predict the astrometric microlensing signal for this binary lens as it will be seen by Gaia as well as the radial velocity curve for the binary system. Events such as Gaia16aye indicate the potential for the microlensing method of probing the mass function of dark objects, including black holes, in directions other than that of the Galactic bulge. This case also emphasises the importance of long-term time-domain coordinated observations that can be made with a network of heterogeneous telescopes.Peer reviewe
The function and origin of the CD4+ T cell in the classical Hodgkin lymphoma microenvironment
No full textPhDClassical Hodgkin lymphoma (CHL) is a germinal centre B cell malignancy where the bulk of the tumour comprises a non-clonal immune infiltrate enriched for CD4+ T cells. The role of these cells in the pathophysiology of CHL is poorly understood. Biomarkers predictive of clinical outcome in CHL are limited. This thesis examines microenvironment biomarkers with the goal of identifying the 10-20% of patients who are not cured by conventional therapy, and also investigates the function of the CD4+ T cell in CHL.
The prognostic power of FOXP3, a marker of regulatory T cells, CD68, a macrophage marker and CD20, a B cell marker, is validated in a new patient cohort and for the first time CD68 and FOXP3 are combined in a statistically robust scoring system. The data presented challenge the assumption that the microenvironment is Th2-polarised or senescent and demonstrates relative over-expression of T-BET, a Th1 marker and under-expression of PD1, a marker of senescence/exhaustion, with little evidence for Th2 marker expression. A cytokine-enriched in vitro culture system was developed demonstrating superior proliferation and longevity of CHL-derived T cells compared to non-malignant tissue-derived controls. These cells sustain expression of markers associated with proliferation and longevity (e.g. CD27, CD28) and remain functional (express cytokines) for many weeks. A panel of CD4+ T cell-specific markers was determined capable of differentiating CHL-derived from non-malignant or non-Hodgkin lymphoma-derived CD4+ T cells, in which markers of central memory (CD62L and CCR7) and early activation (CD69) are over-represented and markers of senescence (CD57 and PD1) are under-represented. Cytokine profiles were found to resemble Th1 (expression of IL2, IFN- and TNF expression) rather than Th2 (IL4, IL13, IL21, IL10 and IL6) responses.
The data presented confirm a new prognostic biomarker signature and show a Th1 rather than Th2-dominated microenvironment enriched for cytokine-secreting functional effector CD4+ T cells and long-lived, proliferative cells resembling central memory cells rather than hypoproliferative, anergic, non-functional T cells
