7 research outputs found
Toward a Spectral Foundation Model: An Attention-Based Approach with Domain-Inspired Fine-Tuning and Wavelength Parameterization
Astrophysical explorations are underpinned by large-scale stellar
spectroscopy surveys, necessitating a paradigm shift in spectral fitting
techniques. Our study proposes three enhancements to transcend the limitations
of the current spectral emulation models. We implement an attention-based
emulator, adept at unveiling long-range information between wavelength pixels.
We leverage a domain-specific fine-tuning strategy where the model is
pre-trained on spectra with fixed stellar parameters and variable elemental
abundances, followed by fine-tuning on the entire domain. Moreover, by treating
wavelength as an autonomous model parameter, akin to neural radiance fields,
the model can generate spectra on any wavelength grid. In the case with a
training set of O(1000), our approach exceeds current leading methods by a
factor of 5-10 across all metrics.Comment: 7 pages, 3 figures, accepted to ICML 2023 Workshop on Machine
Learning for Astrophysic
The Gaia alerted fading of the FUor-type star Gaia21elv
FU Orionis objects (FUors) are eruptive young stars, which exhibit outbursts
that last from decades to a century. Due to the duration of their outbursts,
and to the fact that only about two dozens of such sources are known,
information on the end of their outbursts is limited. Here we analyse follow-up
photometry and spectroscopy of Gaia21elv, a young stellar object, which had a
several decades long outburst. It was reported as a Gaia science alert due to
its recent fading by more than a magnitude. To study the fading of the source
and look for signatures characteristic of FUors, we have obtained follow-up
near infrared (NIR) spectra using Gemini South/IGRINS, and both optical and NIR
spectra using VLT/X-SHOOTER. The spectra at both epochs show typical FUor
signatures, such as a triangular shaped -band continuum, absorption-line
dominated spectrum, and P Cygni profiles. In addition to the typical FUor
signatures, [OI], [FeII], and [SII] were detected, suggesting the presence of a
jet or disk wind. Fitting the spectral energy distributions with an accretion
disc model suggests a decrease of the accretion rate between the brightest and
faintest states. The rapid fading of the source in 2021 was most likely
dominated by an increase of circumstellar extinction. The spectroscopy
presented here confirms that Gaia21elv is a classical FUor, the third such
object discovered among the Gaia science alerts.Comment: Accepted to MNRA
Presentation of Graves' orbitopathy within European Group On Graves' Orbitopathy (EUGOGO) centres from 2012 to 2019 (PREGO III)
Background: Graves' orbitopathy (GO) is subject to epidemiological and care-related changes. Aim of the survey was to identify trends in presentation of GO to the European Group On Graves' Orbitopathy (EUGOGO) tertiary referral centres and initial management over time. Methods: Prospective observational multicentre study. All new referrals with diagnosis of GO within September-December 2019 were included. Clinical and demographic characteristics, referral timelines and initial therapeutic decisions were recorded. Data were compared with a similar EUGOGO survey performed in 2012. Results: Besides age (mean age: 50.5±13 years vs 47.7±14 years; p 0.007), demographic characteristics of 432 patients studied in 2019 were similar to those in 2012. In 2019, there was a decrease of severe cases (9.8% vs 14.9; p<0.001), but no significant change in proportion of active cases (41.3% vs 36.6%; p 0.217). After first diagnosis of GO, median referral time to an EUGOGO tertiary centre was shorter (2 (0-350) vs 6 (0-552) months; p<0.001) in 2019. At the time of first visit, more patients were already on antithyroid medications (80.2% vs 45.0%; p<0.001) or selenium (22.3% vs 3.0%; p<0.001). In 2019, the initial management plans for GO were similar to 2012, except for lid surgery (2.4% vs 13.9%; p<0.001) and prescription of selenium (28.5% vs 21.0%; p 0.027). Conclusion: GO patients are referred to tertiary EUGOGO centres in a less severe stage of the disease than before. We speculate that this might be linked to a broader awareness of the disease and faster and adequate delivered treatment
Family courts vis-a-vis the situation on the Polish-Byelorussian border (methodological outline)
A possible nearby microlensing stellar remnant hiding in
Massive galactic lenses with large Einstein Radii should cause a measurable astrometric microlensing effect, that is, a light centroid shift due to the motion of the two images. Such a shift in the position of a background star due to microlensing was not included in the Gaia astrometric model, and therefore significant deviation should cause Gaia’s astrometric parameters to be determined incorrectly. Here we study one of the photometric microlensing events reported in the Gaia Data Release 3, GaiaDR3-ULENS-001, for which a poor goodness of Gaia fit and erroneous parallax could indicate the presence of an astrometric microlensing signal. Based on the photometric microlensing model, we simulated Gaia astrometric time series with the astrometric microlensing effect added. We find that including microlensing with an angular Einstein radius of mas ( mas) assuming a positive (negative) impact parameter, u0, reproduces the astrometric quantities reported by Gaia well. We estimate the mass of the lens to be () and its distance kpc ( kpc), proposing the lens could be a nearby isolated white dwarf
Dark lenses through the dust: parallax microlensing events in the VVV
We use near-infrared photometry and astrometry from the VISTA Variables in
the Via Lactea (VVV) survey to analyse microlensing events containing annual
microlensing parallax information. These events are located in highly extincted
and low-latitude regions of the Galactic bulge typically off-limits to optical
microlensing surveys. We fit a catalog of events previously found in the
VVV and extract microlensing parallax candidates. The fitting is done
using nested sampling to automatically characterise the multi-modal and
degenerate posterior distributions of the annual microlensing parallax signal.
We compute the probability density in lens mass-distance using the source
proper motion and a Galactic model of disc and bulge deflectors. By comparing
the expected flux from a main sequence lens to the baseline magnitude and
blending parameter, we identify 4 candidates which have probability %
that the lens is dark. The strongest candidate corresponds to a nearby
( kpc), medium-mass () dark
remnant as lens. In the next strongest, the lens is located at heliocentric
distance kpc. It is a dark remnant with a mass of
. Both of those candidates are most likely
neutron stars, though possibly high-mass white dwarfs. The last two events may
also be caused by dark remnants, though we are unable to rule out other
possibilities because of limitations in the data.Comment: 16 pages, 8 figures, submitted to MNRA
Rectum and Bladder Toxicity in Postoperative Prostate Bed Irradiation: Dose–Volume Parameters Analysis
Although prostate cancer treatment is increasingly effective, its toxicities pose a major concern. The aim of our study was to assess the rate of adverse events (AEs) and the prognostic value of dose–volume histogram (DVH) parameters for the occurrence of treatment toxicity in patients treated with post-prostatectomy prostate bed radiotherapy (RT). The AEs were scored according to the CTCAE v.5.0. The rectum and bladder were contoured according to the RTOG Guidelines. The DVH parameters were assessed using data exported from the ECLIPSE treatment-planning system. Genitourinary (GU) and gastrointestinal (GI) toxicity were analysed using consecutive dose thresholds for the percentage of an organ at risk (OAR) receiving a given dose and the QUANTEC dose constraints. A total of 213 patients were included in the final analysis. Acute grade 2 or higher (≥G2) GU AEs occurred in 18.7% and late in 21.3% of patients. Acute ≥G2 GI toxicity occurred in 11.7% and late ≥G2 in 11.2% of the patients. Five patients experienced grade 4 AEs. The most common adverse effects were diarrhoea, proctitis, cystitis, and dysuria. The most significant predictors of acute ≥G2 GI toxicity were rectum V47 and V46 (p p p = 0.001), whereas the most significant predictors of late ≥G2 GI AEs were rectum wall V47 and V48 (p = 0.019 and p = 0.021). None of the bladder or bladder wall parameters was significantly associated with the risk of acute toxicity. The minimum doses to bladder wall (p = 0.004) and bladder (p = 0.005) were the most significant predictors of late ≥G2 GU toxicity. Postoperative radiotherapy is associated with a clinically relevant risk of AEs, which is associated with DVH parameters, and remains even in patients who fulfil commonly accepted dose constraints. Considering the lack of survival benefit of postoperative adjuvant RT, our results support delaying treatment through an early salvage approach to avoid or defer toxicity