Red supergiants are the most common final evolutionary stage of stars that have initial masses between 8 and 35 times that of the Sun
. During this stage, which lasts roughly 100,000 years
, red ...supergiants experience substantial mass loss. However, the mechanism for this mass loss is unknown
. Mass loss may affect the evolutionary path, collapse and future supernova light curve
of a red supergiant, and its ultimate fate as either a neutron star or a black hole
. From November 2019 to March 2020, Betelgeuse-the second-closest red supergiant to Earth (roughly 220 parsecs, or 724 light years, away)
-experienced a historic dimming of its visible brightness. Usually having an apparent magnitude between 0.1 and 1.0, its visual brightness decreased to 1.614 ± 0.008 magnitudes around 7-13 February 2020
-an event referred to as Betelgeuse's Great Dimming. Here we report high-angular-resolution observations showing that the southern hemisphere of Betelgeuse was ten times darker than usual in the visible spectrum during its Great Dimming. Observations and modelling support a scenario in which a dust clump formed recently in the vicinity of the star, owing to a local temperature decrease in a cool patch that appeared on the photosphere. The directly imaged brightness variations of Betelgeuse evolved on a timescale of weeks. Our findings suggest that a component of mass loss from red supergiants
is inhomogeneous, linked to a very contrasted and rapidly changing photosphere.
Transition disks have large central cavities that have been resolved by imaging surveys during recent years. Cavities and other substructures in circumstellar disks are often interpreted as signposts ...to massive companions. Detecting companions at small angular separations is challenging with coronagraphic imaging observations. We aim to search for stellar and substellar companions in the central regions of transition disks. Such companions could be responsible for the large dust-depleted cavities. We want to determine if these disks might be circumbinary in their nature, similar to the HD\,142527 system. We observed four systems, HD\,100453, HD\,100546, HD\,135344\,B, and PDS\,70, with the sparse aperture masking mode of VLT/SPHERE, also leveraging the star-hopping method with the adaptive optics system. We extracted the complex visibilities and bispectra from the $H2$ and $H3$ imaging data. A binary model was fit to the closure phases to search for companions and estimate detection limits. For validation, we also analyzed four archival datasets of HD\,142527 and inferred the orbital elements and atmospheric parameters of its low-mass stellar companion. We have not detected any significant point sources in the four observed systems. With a contrast sensitivity of approx 0.004, we can rule out stellar companions down to approx 2 au and partially explore the substellar regime at separations gtrsim 3--5 au. The analysis of HD\,142527\,B revealed that its projected orbit is aligned with dust features in the extended inner disk and that the mutual inclination with the outer disk is close to coplanar for one of the two solutions. Atmospheric modeling confirms the low-gravity and slightly reddened spectral appearance ($ 3300$ K, $ 3.7$, and $A_V 0.7$). The inferred and derived bulk parameters ($ -0.65$, $M_ 0.4$ $M_ and $R_ 1.46$ $R_ are in agreement with dynamical constraints and evolutionary tracks. In contrast to HD\,142527, we find no evidence that a close-in stellar companion is responsible for the resolved disk features of HD\,100453, HD\,100546, HD\,135344\,B, and PDS\,70. Instead of a dynamical effect by a stellar companion, the formation of giant planets or even low-mass brown dwarfs could be shaping the innermost environment (lesssim 20 au) of these circumstellar disks, as is the case with the planetary system of PDS\,70.
Anemia is a common condition and a known risk factor for complications after primary total hip arthroplasty. Few studies have evaluated this topic in Latin American countries where this problem can ...be more important. The purpose of this study was to determine the role of preoperative anemia in 30-day complications after primary total hip arthroplasty.
This was a retrospective observational study involving patients who had a primary total hip arthroplasty aged more than 18 years and did not have any type of malignancy. Two hundred thirty six patients were divided into 2 groups: 58 who had anemia and 178 who did not have anemia. Multivariate logistic regressions were used to assess the relationship between anemia as a risk factor for blood transfusions, extended lengths of stay, and intensive care unit (ICU) admissions.
A higher proportion of patients in the anemia group required blood transfusions (24.1% versus 7.3%, < 0.001), ICU admission (39.7% versus 11.2%, P ≤ .001), and a hospital stay of more than 5 days (37.9% versus 11.8%, < .001). Preoperative anemia was identified as a risk factor for requiring transfusions (Odds ratio 3.82, Confidence Interval 95%: 1.47-9.94, P = .006) and ICU admission (Odds ratio 2.48, Confidence interval 95%: 1.11-5.50, P = .026).
Preoperative anemia proved to be a risk factor for requiring blood transfusions and ICU admission. Treating this potentially modifiable risk factor can improve patient morbidity and mortality, while positively impacting healthcare costs, reducing the need for postsurgical services such as ICU management, and extended hospitalizations.
Context. There exists an enigmatic population of massive stars around the Galactic center (GC) that were formed some Myr ago. A fraction of these stars has been found to orbit the supermassive black ...hole, Sgr A*, in a projected clockwise disk-like structure, which suggests that they were formed in a formerly existing dense disk around Sgr A*. Aims. We focus on a subgroup of objects, the extended, near-infrared (NIR) bright sources IRS 1W, IRS 5, IRS 10W, and IRS 21, that have been suggested to be young, massive stars that form bow shocks through their interaction with the interstellar medium (ISM). Their nature has impeded accurate determinations of their orbital parameters. We aim at establishing their nature and kinematics to test whether they form part of the clockwise disk. Methods. We performed NIR multiwavelength imaging with NACO/VLT using direct adaptive optics (AO) and AO-assisted sparse aperture masking (SAM). We introduce a new method for self-calibration of the SAM point spread function in dense stellar fields. The emission mechanism, morphology, and kinematics of the targets were examined via 3D models, combined with existing models of the gas flow in the central parsec. Results. We confirm previous findings that IRS 21, IRS 1W, and IRS 5 are bow-shocks created by the interaction between mass-losing stars and the interstellar gas. The nature of IRS 10W remains unclear. Our modeling shows that the bow-shock emission is caused by thermal emission, while the scattering of stellar light does not play a significant role. IRS 1W shows a morphology that is consistent with a bow shock produced by an anisotropic stellar wind or by locally inhomogeneous ISM density. Our best-fit models provide estimates of the local proper motion of the ISM in the Northern Arm that agree with previously published models that were based on radio interferometry and NIR spectroscopy. Assuming that all of the sources are gravitationally tied to Sagittarius A*, their orbital planes were obtained via a Monte Carlo simulation. Conclusions. Our sources appear to be Wolf-Rayet stars associated to the last starburst at the GC. Our orbital analysis suggests that they are not part of any of the previously suggested coherent stellar structures, in particular the clockwise disk. We thus add more evidence to recent findings that a large proportion of the massive stars show apparently random orbital orientations, suggesting either that not all of them were formed in the clockwise disk, or that their orbits were randomized rapidly after formation in the disk.
Recent findings in colon cancer cells indicate that inhibition of the mitochondrial H(+)-adenosine triphosphate (ATP) synthase by the ATPase inhibitory factor 1 (IF1) promotes aerobic glycolysis and ...a reactive oxygen species (ROS)-mediated signal that enhances proliferation and cell survival. Herein, we have studied the expression, biological relevance, mechanism of regulation and potential clinical impact of IF1 in some prevalent human carcinomas. We show that IF1 is highly overexpressed in most (>90%) of the colon (n=64), lung (n=30), breast (n=129) and ovarian (n=10) carcinomas studied as assessed by different approaches in independent cohorts of cancer patients. The expression of IF1 in the corresponding normal tissues is negligible. By contrast, the endometrium, stomach and kidney show high expression of IF1 in the normal tissue revealing subtle differences by carcinogenesis. The overexpression of IF1 also promotes the activation of aerobic glycolysis and a concurrent ROS signal in mitochondria of the lung, breast and ovarian cancer cells mimicking the activity of oligomycin. IF1-mediated ROS signaling activates cell-type specific adaptive responses aimed at preventing death in these cell lines. Remarkably, regulation of IF1 expression in the colon, lung, breast and ovarian carcinomas is exerted at post-transcriptional levels. We demonstrate that IF1 is a short-lived protein (t1/2 ∼100 min) strongly implicating translation and/or protein stabilization as main drivers of metabolic reprogramming and cell survival in these human cancers. Analysis of tumor expression of IF1 in cohorts of breast and colon cancer patients revealed its relevance as a predictive marker for clinical outcome, emphasizing the high potential of IF1 as therapeutic target.
ABSTRACT
Multiplicity is a ubiquitous characteristic of massive stars. Multiple systems offer us a unique observational constraint on the formation of high-mass systems. Herschel 36 A is a massive ...triple system composed of a close binary (Ab1-Ab2) and an outer component (Aa). We measured the orbital motion of the outer component of Herschel 36 A using infrared interferometry with the AMBER and PIONIER instruments of ESO’s Very Large Telescope Interferometer. Our immediate aims are to constrain the masses of all components of this system and to determine if the outer orbit is co-planar with the inner one. Reported spectroscopic data for all two components of this system and our interferometric data allow us to derive full orbital solutions for the outer orbit Aa-Ab and the inner orbit Ab1-Ab2. For the first time, we derive the absolute masses of mAa = 22.3 ± 1.7, mAb1 = 20.5 ± 1.5, and mAb2 = 12.5 ± 0.9 M⊙. Despite not being able to resolve the close binary components, we infer the inclination of their orbit by imposing the same parallax as the outer orbit. Inclinations derived from the inner and outer orbits imply a modest difference of about 22° between the orbital planes. We discuss this result and the formation of Herschel 36 A in the context of Core Accretion and Competitive Accretion models, which make different predictions regarding the statistic of the relative orbital inclinations.
We present high-angular-resolution radio observations of the Arches cluster in the Galactic centre, one of the most massive young clusters in the Milky Way. The data were acquired in two epochs and ...at 6 and 10 GHz with the
Karl G. Jansky
Very Large Array. The rms noise reached is three to four times better than during previous observations and we have almost doubled the number of known radio stars in the cluster. Nine of them have spectral indices consistent with thermal emission from ionised stellar winds, one is a confirmed colliding wind binary, and two sources are ambiguous cases. Regarding variability, the radio emission appears to be stable on timescales of a few to ten years. Finally, we show that the number of radio stars can be used as a tool for constraining the age and/or mass of a cluster and also its mass function.
Context.
The mass-loss mechanisms in M-type asymptotic giant branch (AGB) stars are still not well understood; these include, in particular, the formation of dust-driven winds from the innermost ...gaseous layers around these stars. One way to understand the gas-dust interaction in these regions and its impact on the mass-loss mechanisms is through the analysis of high-resolution observations of the stellar surface and its closest environment.
Aims.
We aim to characterize the inner circumstellar environment (~3
R
*
) of the M-type Mira star R Car in the near-infrared at different phases of a pulsation period.
Methods.
We used GRAVITY interferometric observations in the K band obtained during two different epochs over 2018. Those data were analyzed using parametric models and image reconstruction of both the pseudo-continuum and the CO band heads observed. The reported data are the highest angular resolution observations on the source in the
K
band.
Results.
We determined sizes of R Car’s stellar disk of 16.67 ± 0.05 mas (3.03 au) in January 2018 and 14.84 ± 0.06 mas (2.70 au) in February, 2018, respectively. From our physical model, we determined temperatures and size ranges for the innermost CO layer detected around R Car. The derived column density of the CO is in the ~9.18×10
18
–1×10
19
cm
−2
range, which is sufficient to permit dust nucleation and the formation of stable dust-driven winds. We find that magnesium composites, Mg
2
SiO
4
and MgSiO
3
, have temperatures and condensation distances consistent with the ones obtained for the CO layer model and pure-line reconstructed images, which are the dust types most likely to be responsible for wind formation. Our reconstructed images show evidence of asymmetrical and inhomogeneous structures, which might trace a complex and perhaps clumpy structure of the CO molecule distribution.
Conclusions.
Our work demonstrates that the conditions for dust nucleation and thus for initialising dust-driven winds in M-type AGB stars are met in R Car, and we identify magnesium composites as the most probable candidates. We find structural changes between two observing epochs (which are separated by ~10% of the full pulsation period of the star) and evidence of the effects of asymmetries and clumpiness. This observational evidence is crucial to constraining the role of convection and pulsation in M-type stars.
Using VLTI/GRAVITY and SINFONI data, we investigate the subparsec gas and dust structure around the nearby type 1 active galactic nucleus (AGN) hosted by NGC 3783. The
K
-band coverage of GRAVITY ...uniquely allows simultaneous analysis of the size and kinematics of the broad line region (BLR), the size and structure of the near-infrared(near-IR)-continuum-emitting hot dust, and the size of the coronal line region (CLR). We find the BLR, probed through broad Br
γ
emission, to be well described by a rotating, thick disc with a radial distribution of clouds peaking in the inner region. In our BLR model, the physical mean radius of 16 light-days is nearly twice the ten-day time-lag that would be measured, which closely matches the ten-day time-lag that has been measured by reverberation mapping. We measure a hot dust full-width at half-maximum (FWHM) size of 0.74 mas (0.14 pc) and further reconstruct an image of the hot dust, which reveals a faint (5% of the total flux) offset cloud that we interpret as an accreting or outflowing cloud heated by the central AGN. Finally, we directly measure the FWHM size of the nuclear CLR as traced by the Ca
VIII
and narrow Br
γ
line. We find a FWHM size of 2.2 mas (0.4 pc), fully in line with the expectation of the CLR located between the BLR and narrow line region. Combining all of these measurements together with larger scale near-IR integral field unit and mid-IR interferometry data, we are able to comprehensively map the structure and dynamics of gas and dust from 0.01 to 100 pc.
Context.
The ‘Great Dimming’ of the prototypical red supergiant Betelgeuse, which occurred between December 2019 and April 2020, gives us unprecedented insight into the processes occurring on the ...stellar surface and in the inner wind of this type of star. In particular it may bring further understanding of their dust nucleation and mass-loss processes.
Aims.
Here, we present and analyse VLTI/MATISSE observations in the N band (8–13 µm) taken near the brightness minimum in order to assess the status of the dusty circumstellar environment.
Methods.
We explored the compatibility of a dust clump obscuring the star with our mid-infrared interferometric observations using continuum 3D radiative transfer modelling, and probed the effect of adding multiple clumps close to the star on the observables. We also tested the viability of a large cool spot on the stellar surface without dust present in the ambient medium.
Results.
Using the visibility data, we derived a uniform disk diameter of 59.02 ± 0.64 mas in the spectral range 8–8.75 µm. We find that both the dust clump and the cool spot models are compatible with the data. Further to this, we note that the extinction and emission of our localised dust clump in the line of sight of the star directly compensate for each other, making the clump undetectable in the spectral energy distribution and visibilities. The lack of infrared brightening during the Great Dimming therefore does not exclude extinction due to a dust clump as one of the possible mechanisms. The visibilities can be reproduced by a spherical wind with dust condensing at 13 stellar radii and a dust mass-loss rate of (2.1–4.9) × 10
−10
M
⊙
yr
−1
; however, in order to reproduce the complexity of the observed closure phases, additional surface features or dust clumps would be needed.
PDF
