Abstract The existence of a population of low-accretion-rate symbiotic stars (SySts), consisting of a giant star and a compact companion (usually a white dwarf), has been proposed recently. However, ...their population has not been fully understood. In this work, we present an investigation on SySts candidates consisting of asymptotic giant branch stars (AGBs) by cross-correlating the Gaia DR3, the Galaxy Evolution Explorer All-Sky Imaging Survey, and the 4XMM DR13 catalogs. We first build a sample of AGBs within 500 pc based on their locations in the Gaia color–absolute magnitude diagram. We then explore the UV and X-ray properties of the sampled AGBs and compare them to known SySts and candidates. We find 10 SySts candidates based on the far-ultraviolet excess. The typical UV luminosity of the candidates is 10 31 erg s −1 , which corresponds to a typical accretion rate of 10 −12 –10 −11 M ⊙ yr −1 , which is more than 1 order of magnitude lower than known SySts. Based on these findings, the total number of SySts within 500 pc is estimated to be 18. The number of AGBs with X-ray flux above 10 −14 erg s −1 cm −2 within 500 pc is estimated to be 37. Our finding implies that a large number of low-accretion-rate SySts are yet to be detected, which provides a base for a complete understanding of their population.
ABSTRACT The properties of the Galactic Ridge X-ray Emission (GRXE) observed in the 2-10 keV band place fundamental constraints on various types of X-ray sources in the Milky Way. Although the ...primarily discrete origin of the emission is now well established, the responsible populations of these sources remain uncertain, especially at relatively low fluxes. To provide insights into this issue, we systematically characterize the Fe emission line properties of the candidate types of the sources in the solar neighborhood and compare them with those measured for the GRXE. Our source sample includes 6 symbiotic stars, 16 intermediate polars (IPs), 3 polars, 16 quiescent dwarf novae, and 4 active binaries (ABs); they are all observed with the Suzaku X-ray Observatory. The data of about one-fourth of these sources are analyzed for the first time. We find that the mean equivalent width (EW6.7) of the 6.7 keV line and the mean 7.0/6.7 keV line ratio are 107 16.0 eV and 0.71 0.04 for IPs and 221 135 eV and 0.44 0.14 for polars, respectively, which are all substantially different from those (490 15 eV and 0.2 0.08) for the GRXE. Instead, the GRXE values are better agreed by the EW6.7 (438 84.6 eV) and the ratio (0.27 0.06) observed for the DNe. We further find that the EW6.7 is strongly correlated with the 2-10 keV luminosity of the DNe, which can be characterized by the relation . Accounting for this correlation, the agreement can be improved further, especially when the contributions from other class sources to the GRXE are considered, which all have low EW6.7 values. We conclude that the GRXE mostly consists of typically faint but numerous DNe, plus ABs, while magnetic cataclysmic variables are probably mainly the high-flux representatives of the responsible populations and dominate the GRXE only in harder energy bands.
The flux ratio of Fe xxvi-Ly to Fe xxv-He lines (I7.0/I6.7) is a sensitive indicator of the maximum temperature (Tmax), and therefore the mass of white dwarf stars (MWD) in cataclysmic variables ...(CVs). To examine and calibrate the theoretical I7.0/I6.7-Tmax-MWD relations, reliable measurements of Tmax and I7.0/I6.7 are necessary. In this work, we conduct a thorough investigation of 3-50 keV X-ray spectra of 25 solar neighborhood magnetic and nonmagnetic CVs based on archival NuSTAR and Suzaku observations. The measured Tmax are compared to the I7.0/I6.7 and MWD. The results show that the sampled CVs closely follow the theoretical I7.0/I6.7-Tmax relation. Moreover, all the MWD estimated from I7.0/I6.7 are consistent with the dynamically measured ones. We conclude that I7.0/I6.7 can be used as a good diagnostic for Tmax and MWD in both magnetic and nonmagnetic CVs.
Supplier selection is of great significance and role, which influence the quality of major product development, and economic security and life safety. However, there exists a variety of uncertain ...information as a result of evaluation experts’ strong subjective consciousness and complexity of decision environment in the process of supplier selection evaluation. To deal with these problems, by exploiting gray incidence analysis, cloud models and TOPSIS, we establish a multi-attribute decision-making supplier selection method for complex product based on gray group clustering and improved criteria importance through intercriteria correlation, and then a case verifies the validity and feasibility of the proposed method. The results show that (1) the proposed model can provide a better portrayal of the uncertainty of the evaluation process in terms of both the fuzziness of the semantic concept and the randomness of the affiliation degree, while taking into account the differences between the evaluated solution and the positive and negative ideal solutions. (2) The proposed model can fully voice the decision-maker’s attitude on the basis of available information, allowing the decision-making process to be better tailored to reality by taking into account the ambiguity and randomness of the evaluation process.
Lactate dehydrogenase A (LDHA), a critical component of the glycolytic pathway, relates to the development of various cancers, including thyroid cancer. However, the regulatory mechanism of LDHA ...inhibition and the physiological significance of the LDHA inhibitors in papillary thyroid cancer (PTC) are unknown. Long non-coding RNA (lncRNA) plays a vital role in tumor growth and progression. Here, we identified a novel lncRNA LINC00671 negatively correlated with LDHA, downregulating LDHA expression and predicting good clinical outcome in thyroid cancer. Moreover, hypoxia inhibits LINC00671 expression and activates LDHA expression largely through transcriptional factor STAT3. STAT3/LINC00671/LDHA axis regulates thyroid cancer glycolysis, growth, and lung metastasis both in vitro and in vivo. In thyroid cancer patients, LINC00671 expression is negatively correlated with LDHA and STAT3 expression. Our work established STAT3/LINC00671/LDHA as a critical axis to regulate PTC growth and progression. Inhibition of LDHA or STAT3 or supplement of LINC00671 could be potential therapeutic strategies in thyroid cancer.
Previous X-ray observations toward the nuclear star cluster (NSC) at the Galactic center have discovered thousands of point sources, most of which were believed to be cataclysmic variables (CVs), ...i.e., a white dwarf (WD) accreting from a low-mass companion. However, the population properties of these CVs remain unclear, which otherwise would provide important information about the evolutionary history of the NSC. In this work we utilize ultra-deep archival Chandra observations to study the spectral properties of the NSC CVs, in close comparison with those in the solar vicinity. We find that the NSC CVs have strong Fe xxv and Fe xxvi lines (both of which show equivalent widths ∼200-300 eV), indicating metal-rich companions. Moreover, their Fe xxvi to Fe xxv line flux ratio is used to diagnose the characteristic WD mass (MWD) of NSC CVs. The results show that the CVs with erg s−1 have a mean MWD of ∼0.6/1.0 M if they are magnetic/nonmagnetic CVs; while those with between 1 and 6 × 1031 erg s−1 have a mean MWD of ∼0.8/1.2 M if they are magnetic/nonmagnetic CVs. All these Chandra detected CVs collectively contribute ∼30%-50% of the unresolved 20-40 keV X-ray emission from the NSC. The CV population with massive (i.e., MWD ∼ 1.2 M ) WDs have not been observed in the solar vicinity or the Galactic bulge, and they might have been formed via dynamical encounters in the NSC.
The X-ray emissivity (i.e., luminosity per unit stellar mass) of globular clusters (GCs) is an important indicator of their dynamical evolution history. Based on deep archival Chandra observations, ...we report a stacking analysis of 44 GCs with 0.5-8 keV luminosities LX 1035 erg s−1 in the M31 bulge, which are supposed to be dominated by cataclysmic variables (CVs) and coronally active binaries (ABs). We obtain a significant detection at the 5 level in 0.5-8 keV band. The average X-ray luminosity per GC and the average X-ray emissivity are determined to be 5.3 1.6 × 1033 erg s−1 and 13.2 4.3 × 1027 erg s−1 , respectively. Both of these values are consistent with those of Milky Way GCs. Moreover, the measured emissivity of M31 GCs is also consistent with that of the Milky Way field stars. Massive GCs have X-ray luminosities that are marginally higher than those of less massive ones. Massive GCs also show a lower emissivity ( ) than less massive ones ( ), which is consistent with the scenario that the (progenitors of) CVs and ABs were more efficiently destroyed via stellar encounters in the more massive GCs. No dependence of the X-ray emissivity on GC color or on the projected galactocentric distance of GCs is found.
Y Gem: A White Dwarf Symbiotic Star? Yu, Zhuo-li; Xu, Xiao-jie; Shao, Yong ...
The Astrophysical journal,
06/2022, Letnik:
932, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
In this work we conduct a thorough investigation of the X-ray and ultraviolet (UV) properties of Y Gem based on six archival XMM-Newton and Chandra observations to explore the nature of the ...system. The results show that Y Gem has strong (10
32–34
erg s
−1
) X-ray emission, including a hard (with a maximum emission temperature of 8–16 keV) and a soft (with emission temperatures of 0.02–0.2 and 0.2–0.9 keV) component. The integrated UV luminosity of Y Gem reaches ∼10
35
erg s
−1
. We show that the previous asymptotic giant branch-main-sequence (AGB-MS) Roche-lobe overflow (RLOF) scenario is dynamically unstable and can hardly explain the ∼10 keV X-ray emission temperature. We propose Y Gem as a symbiotic star, where a white dwarf (WD) accretes from its AGB companion based on its X-ray and UV properties. We make numerical simulations to examine the evolutionary history of this system. The simulations can produce the observed properties of Y Gem in the wind WRLOF scenario. An ∼0.8
M
⊙
WD with a ∼1.0–1.8
M
⊙
companion in a ∼2000–32,000 day initial orbit may evolve to a Y Gem-like system. Our finding implies a potential population of symbiotic stars that may have been misclassified as AGB-MS binaries. What is more, their high mass accretion rates may enable mass accumulation to the WD and makes them candidates of Type Ia supernovae progenitors.
In this work, organic supramolecular linkers involving cucubit6urils CB6 and
N
,
N
′-hexamethylene-bis(pyrazinyl hexafluorophosphate) (BPHF@CB6) were utilized to assemble dodenuclear silver ...chalcogenolate clusters into three one-dimensional (1D) materials under different synthesis conditions. These three crystal structures of CB6-based sliver cluster-organic rotaxane frameworks were well resolved, and their emission properties were investigated systematically. This construction strategy involving organic supramolecular linkers gives a new methodology for cluster-assembled materials with intriguing structural and functional properties.
A series of cluster-assembled luminescent materials featuring intriguing alternating CB6 units and silver(
i
) clusters have been prepared and systematically investigated.
•Two polysaccharides fractions (SGP-1 and SGP-2) were isolated from S. glabra for the first time.•Present study for the first time demonstrates the potential anti-inflammation of SGP-1 and SGP-2 in ...vitro.•The anti-inflammation effects of SGP are partially via suppression of ERK and JNK MAPKs.
The rhizomes of Smilax glabra have been used as both food and folk medicine in many countries for a long time. However, little research has been reported on polysaccharides of S. glabra. In the present study, two polysaccharide fractions, SGP-1 and SGP-2, were isolated from the rhizomes of S. glabra with the number average molecular weights of 1.72×102kDa and 1.31×102kDa, and the weight average molecular weights of 1.31×105kDa and 1.18×105kDa, respectively, and their mainly monosaccharide compositions were both galactose and rhamnose (2.5:1). Both SGP-1 and SGP-2 significantly suppressed the release of nitric oxide (NO), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) from LPS-induced RAW 264.7 cells, as well as the mRNA expression of inducible nitric oxide synthase (iNOS), TNF-α and IL-6. Additionally, SGP-1 and SGP-2 repressed the extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK). These findings strongly suggested polysaccharides were also the anti-inflammatory active ingredient for S. glabra, and the potential of SGP-1 and SGP-2 as the anti-inflammatory agents.
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