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Probing the accretion geometry of the atoll source 4U 1702-429 in different spectral states with NICER, NuSTAR, and AstroSat
Homan, Jeroen; Banerjee, Srimanta
We perform a comprehensive spectral study of a carefully selected sample (total exposure ~50.5 ks) of NICER observations of the atoll neutron star low-mass X-ray binary 4U 1702-429. Our sample encompasses nearly all classical spectral states found within the NICER data set. We require two thermal emission components, originating from the accretion…
Surveys of clumps, cores, and condensations in Cygnus-X. Searching for circumstellar disks
Qiu, Keping; Cao, Yue; Yang, Kai +2 more
Context. Theories and models have suggested that circumstellar disks could channel material to the central protostar, and resist star formation feedback. Our current knowledge of the picture and role of disks around massive protostars is unclear because the observational evidence of these circumstellar disks is limited.
Aims: To investigate w…
Testing the asteroseismic estimates of stellar radii with surface brightness-colour relations and Gaia DR3 parallaxes: Red giants and red clump stars
Valle, G.; Dell'Omodarme, M.; Prada Moroni, P. G. +1 more
Aims. We compared stellar radii derived from asteroseismic scaling relations with those estimated using two independent surface brightness-colour relations (SBCRs) combined with Gaia DR3 parallaxes. Methods. We cross-matched asteroseismic and astrometric data for over 6400 red giant branch (RGB) and red clump (RC) stars from the APO-K2 catalogue w…
Double-lined Spectroscopic Binaries from the LAMOST Low-resolution Survey
Ting, Yuan-Sen; Liu, Junhui; Zhang, Bo +1 more
We report on a data-driven spectral model that we have developed for the identification of double-lined spectroscopic binary stars (SB2s) in the Large Sky Area Multi-Object fiber Spectroscopic Telescope low-resolution survey (R ∼ 1800). Employing simultaneous fitting with both single-star and binary-star models, we detected over 4800 SB2 candidate…
A survey for variable young stars with small telescopes - VIII. Properties of 1687 Gaia selected members in 21 nearby clusters
Scholz, Aleks; Eislöffel, Jochen; Dvorak, Shawn +60 more
The Hunting Outbursting Young Stars (HOYS) project performs long-term, optical, multifilter, high cadence monitoring of 25 nearby young clusters and star-forming regions. Utilizing Gaia DR3 data, we have identified about 17 000 potential young stellar members in 45 coherent astrometric groups in these fields. Twenty one of them are clear young gro…
Is It Possible to Detect Coronal Mass Ejections on Solar-type Stars through Extreme-ultraviolet Spectral Observations?
Tian, Hui; Yang, Zihao; Xu, Yu +3 more
Stellar coronal mass ejections (CMEs) from host stars are an important factor that affects the habitability of exoplanets. Although their solar counterparts have been well observed for decades, it is still very difficult to find solid evidence of stellar CMEs. Using the spectral line profile asymmetry caused by the Doppler shift of erupting plasma…
Photometric determination of main-sequence binaries with Gaia
Wallace, A. L.
Since its launch in 2013, the Gaia space telescope has provided precise measurements of the positions and magnitudes of over 1 billion stars. This has enabled extensive searches for stellar and substellar companions through astrometric and radial velocity measurements. However, these surveys require a prior knowledge of any unresolved companion af…
AB Dor: Coronal Imaging and Activity Cycles
Pandey, J. C.; Singh, Gurpreet
Using long-term X-ray observations, we present short-term and long-term X-ray variability analysis of the ultrafast rotating active star AB Dor. Flaring events are common in X-ray observations of AB Dor and occupy a substantial portion of the total observation time, averaging at around 57% ± 23%. The flare-free X-ray light curves show rotational m…
First High-resolution Spectroscopy of X-Ray Absorption Lines in the Obscured State of NGC 5548
Gu, Liyi; Kriss, Gerard A.; Mehdipour, Missagh +5 more
Multiwavelength spectroscopy of NGC 5548 revealed remarkable changes due to the presence of an obscuring wind from the accretion disk. This broadened our understanding of obscuration and outflows in active galactic nuclei. Swift monitoring of NGC 5548 shows that over the last 10 yr, the obscuration has gradually declined. This provides a valuable …
An Infrared Census of R Coronae Borealis Stars II—Spectroscopic Classifications and Implications for the Rate of Low-mass White Dwarf Mergers
Soria, Roberto; Clayton, Geoffrey C.; De, Kishalay +18 more
We present results from a systematic infrared (IR) census of R Coronae Borealis (RCB) stars in the Milky Way, using data from the Palomar Gattini IR (PGIR) survey. RCB stars are dusty, erratic variable stars presumably formed from the merger of a He-core and a CO-core white dwarf (WD). PGIR is a 30 cm J-band telescope with a 25 deg2 cam…