Abstract
Stellar chemical abundances are crucial and fundamental in astrophysics. However, they could suffer from substantial systematic errors according to several investigations but still lack ...calibrations in bulk. By using Gaia wide binaries, we find the temperature-dependent bias between the two binary components for Fe/H and
α
/Fe measurements from the LAMOST low-resolution spectra and Gaia RVS spectra. At
T
eff
= 4000 K, the LAMOST Fe/H is significantly underestimated by approximately 0.4 dex when compared with its typical uncertainty of 0.1 dex. Its
α
/Fe is overestimated by about 0.2 dex. For Gaia, the underestimation of M/H and overestimation of
α
/Fe becomes pronounced near 7000 K with smaller magnitudes. We perform an internal calibration by minimizing the differences between the binary components and provide the correction curves. After corrections, the standard deviations of the residuals compared to the PASTEL catalog decrease from about 0.045/0.1 to 0.02/0.043 for LAMOST and Gaia, respectively. The chemical homogeneity of the open cluster M 44 is also improved by a factor of two. We stress that the underestimation of Fe/H could lead to an overestimation of binary fractions when selecting binary stars by the excess of luminosity. The method of this work could be applied to other data sets in the future. Our results will benefit statistic studies that use LAMOST and Gaia samples with a wide temperature range.
Abstract During the early merger of the Milky Way, intermediate-mass black holes (BHs) in merged dwarf galaxies may have been ejected from the center of their host galaxies due to gravitational ...waves, carrying some central stars along. This process can lead to the formation of hypercompact star clusters, potentially hosting BHs in the mass range of 10 4 –10 5 solar masses. These clusters are crucial targets for identifying and investigating intermediate-mass BHs. However, no hypercompact star clusters in the Milky Way have been identified so far. In this paper, taking advantage of the high spatial resolution power of Gaia, we used data from Gaia Early Data Release (EDR) 3 and Large-Area Multi-Object Fiber Optic Spectroscopic Telescope Data Release 7, along with additional data from Pan-STARRS and the Sloan Digital Sky Survey, to conduct an initial screening of 6,138,049 sources using various parameters of Gaia EDR3. A total of 4786 sources were selected for in-depth analysis. Each of these sources was meticulously scrutinized by examining their images, spectra, and nearby celestial objects to exclude various false positives, such as contaminations, galaxies, wide binaries, or wrong matches. We finally identified one likely hypercompact star cluster candidate in the Milky Way, laying the foundation for further high-resolution imaging and spectral verification.
Abstract Type IIb supernovae are an important subclass of stripped-envelope supernovae (SNe), which show H lines only at early times. Their progenitors are believed to contain a low-mass H envelope ...before explosion. This work reports the discovery of a progenitor candidate in preexplosion Hubble Space Telescope images for the Type IIb SN 2017gkk. With detailed analysis of its spectral energy distribution and local environment, we suggest that the progenitor is most likely a yellow supergiant with significant circumstellar extinction and has an initial mass of about 16 M ⊙ , effective temperature log( T eff /K) = 3.72 ± 0.08, and luminosity log( L / L ⊙ ) = 5.17 ± 0.04. This progenitor is not massive enough to strip envelope through stellar wind, and it supports an interacting binary progenitor channel and adds to the growing list of direct progenitor detections for Type IIb SNe. Future late-time observations will confirm whether this progenitor candidate has disappeared and reveal the putative binary companion that has survived the explosion.
Abstract Type IIn supernovae (SNe) exhibit narrow hydrogen lines that arise from the strong interaction between ejecta and circumstellar material. It remains poorly understood, however, what ...progenitor stars give rise to these explosions. In this work, we perform a detailed analysis of the progenitor and environment of the nearby Type IIn SN 2010jl. With newer images taken by the Hubble Space Telescope, we confirm that the previously reported progenitor candidate is a blend of the progenitor itself and a field star cluster in its close vicinity. SN 2010jl has now become much fainter than the progenitor. The progenitor is very blue and luminous with an effective temperature of log T eff /K = 4.26 − 0.09 + 0.11 and a luminosity of log L / L ⊙ = 6.52 − 0.16 + 0.20 . It is located in a very young star-forming region, but its luminosity is much higher than that expected from the environmental stellar populations. We suggest that the progenitor was in outburst when observed. Its nature and evolutionary history remain to be investigated.
Abstract By combining spectra from the CALSPEC and NGSL, as well as spectroscopic data from the LAMOST Data Release 7 (DR7), we have analyzed and corrected the systematic errors of the Gaia DR3 BP/RP ...(XP) spectra. The errors depend on the normalized spectral energy distribution (simplified by two independent “colors”) and G magnitude. Our corrections are applicable in the range of approximately −0.5 < BP − RP < 2, 3 < G < 17.5, and E ( B − V ) < 0.8. To validate our correction, we conduct independent tests by comparisons with the MILES and LEMONY spectra. The results demonstrate that the systematic errors of BP − RP and G have been effectively corrected, especially in the near-ultraviolet. The consistency between the corrected Gaia XP spectra and the MILES and LEMONY is better than 2% in the wavelength range of 336–400 nm and 1% in redder wavelengths. A global absolute calibration is also carried out by comparing the synthetic Gaia photometry from the corrected XP spectra with the corrected Gaia DR3 photometry. Our study opens up new possibilities for using XP spectra in many fields. A Python package is publicly available to do the corrections (doi: 10.12149/101375 or https://github.com/HiromonGON/GaiaXPcorrection ).
Abstract
As one of the closest supernovae (SNe) in the last decade, SN 2023ixf is an unprecedented target to investigate the progenitor star that exploded. However, there is still significant ...uncertainty in the reported progenitor properties. In this work, we present a detailed study of SN 2023ixf’s progenitor with two independent analyses. We first modeled its spectral energy distribution (SED) based on Hubble Space Telescope optical, Spitzer mid-infrared (IR), and ground-based near-IR data. We find that stellar pulsation and circumstellar extinction have great impacts on SED fitting, and the result suggests a relatively massive red supergiant surrounded by C-rich dust with an initial mass of 16.2–17.4
M
⊙
. The corresponding rate of mass loss occurring at least 3 yr before the SN explosion is about 2 × 10
−4
M
⊙
yr
−1
. We also derived the star formation history of the SN environment based on resolved stellar populations, and the most recent star-forming epoch corresponds to a progenitor initial mass of 17–19
M
⊙
, in agreement with that from our SED fitting. Therefore, we conclude that the progenitor of SN 2023ixf is close to the high-mass end for Type II SN progenitors.
Abstract
We have found 50 new globular cluster (GC) candidates around M31 with Gaia Early Data Release 3 (EDR3), with the help of Pan-STARRS1 DR1 magnitudes and Pan-Andromeda Archaeological Survey ...(PAndAS) images. Based on the latest Revised Bologna Catalog and
simbad
, we trained two random forest (RF) classifiers, the first one to distinguish extended sources from point sources and the second one to further select GCs from extended sources. From 1.85 million sources of 16
m
<
g
< 19.5
m
and within a large area of ∼392 deg
2
around M31, we selected 20,658 extended sources and 1934 initial GC candidates. After visual inspection of the PAndAS images, to eliminate the contamination from noncluster sources, particularly galaxies, we finally got 50 candidates. These candidates are divided into three types (a, b, and c), according to their projected distance
D
to the center of M31 and their probability of being a true GC,
P
GC
, which is calculated by our second RF classifier. Among these candidates, 14 are found to be associated (in projection) with the large-scale structures within the halo of M31. We also provide several simple parameter criteria for selecting extended sources effectively from Gaia EDR3, which can reach a completeness of 92.1% with a contamination fraction lower than 10%.
Abstract
The second Gaia data release (DR2) delivers accurate and homogeneous photometry data of the whole sky of an exquisite quality, reaching down to the unprecedented millimagnitude (mmag) level ...for the
G
,
G
RP
, and
G
BP
passbands. However, the presence of magnitude-dependent systematic effects at the 10 mmag level limits its power in scientific exploitation. In this work, using about a half million stars in common with the LAMOST DR5, we apply the spectroscopy-based stellar color regression method to calibrate the Gaia
G
−
G
RP
and
G
BP
−
G
RP
colors. With an unprecedented precision of about 1 mmag, systematic trends with
G
magnitude are revealed for both colors in great detail, reflecting changes in instrument configurations. Color-dependent trends are found for the
G
BP
−
G
RP
color and for stars brighter than
G
∼ 11.5 mag. The maximum correction term of the calibration is about 20 mmag in general and varies by a few mmag/mag. A revised color–color diagram of Gaia DR2 is given, and some applications are briefly discussed.
Abstract
In this work, we use the spectroscopy-based stellar color regression method with ∼0.7 million common stars between LAMOST DR7 and Gaia EDR3 to acquire color corrections in
G
−
G
RP
and
G
BP
...−
G
RP
. A sub-millimagnitude precision is achieved. Our results demonstrate that improvements in the calibration process of the EDR3 have removed the color term in
G
BP
−
G
RP
and eliminated the discontinuity caused by the changes of instrument configurations to a great extent. However, modest systematic trends with
G
magnitude are still detected. The corresponding color correction terms as a function of
G
are provided for 9.5 mag <
G
< 17.5 mag and compared with other determinations. We conclude that the corrections given in this work are particularly suited for cases where the color–color investigations are required, while for color–magnitude investigations other corrections may be better owing to systematics with reddening. Possible applications of our results are discussed.
Abstract
Based on the large volume Gaia Early Data Release 3 and LAMOST Data Release 5 data, we estimate the bias-corrected binary fractions of the field late G and early K dwarfs. A stellar locus ...outlier method is used in this work, which works well for binaries of various periods and inclination angles with single-epoch data. With a well-selected, distance-limited sample of about 90,000 GK dwarfs covering wide stellar chemical abundances, it enables us to explore the binary fraction variations with different stellar populations. The average binary fraction is 0.42 ± 0.01 for the whole sample. Thin-disk stars are found to have a binary fraction of 0.39 ± 0.02, thick-disk stars have a higher one of 0.49 ± 0.02, while inner halo stars possibly have the highest binary fraction. For both the thin- and thick-disk stars, the binary fractions decrease toward higher Fe/H,
α
/H, and M/H abundances. However, the suppressing impacts of Fe/H,
α
/H, and M/H are more significant for the thin-disk stars than those for the thick-disk stars. For a given Fe/H, a positive correlation between
α
/Fe and the binary fraction is found for the thin-disk stars. However, this tendency disappears for the thick-disk stars. We suspect that it is likely related to the different formation histories of the thin and thick disks. Our results provide new clues for theoretical works on binary formation.
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