Search Publications
Near-UV and Optical Spectroscopic Investigation of Late-type Stars from the MIRA/Oliver Observing Station
Karmakar, Subhajeet; Pandey, Jeewan Chandra; Shedge, Riddhi +4 more
Late-type stars are the most abundant in the galactic stellar population. These stars, with the similar internal structure to the Sun, are expected to have solar-like atmospheres. Investigating the stellar parameters and chemical abundances on late-type stars is essential to provide valuable constraints about stellar age, chemical evolution, and a…
Prolonged and Extremely Non-radial Solar Wind Flows
Fujiki, Ken'ichi; Chakrabarty, Dibyendu; Rout, Diptiranjan +3 more
We present a study of three highly non-radial solar wind events in which the azimuthal solar wind flow angle exceeds 6° for one day or more. None of the events are associated with coronal mass ejections and co-rotating interaction regions observed at 1 AU. For all events, the solar wind outflows at 1 AU exhibit low velocity and density. Based on t…
The fastest hot subdwarfs revisited
Heber, U.; Muchfuss
Hyper-velocity stars (HVS) are enigmatic objects because they are travelling so fast that they escape from the Galaxy. Among hot subdwarfs, only one such star is known, the He-sdO US 708. The Hyper-MUCHFUSS collaboration provided additional HVS candidates. Here we revisit the fastest candidates including US 708 by analysing optical spectra and spe…
The sdBV+dM close-to-synchronization binary TIC 137608661: inclination and thin disk population
Silvotti, Roberto
TIC 137608661 is a new sdBV+dM reflection-effect binary discovered by the TESS space mission with an orbital period of 7.21 hours. In addition to the detailed study of this system that was recently published (Silvotti et al., 2022), this article contains a further discussion on its inclination. Moreover, from the 3D space velocities of the binary …
Kepler, K2, and TESS observations: ensemble and comparative asteroseismology
Reed, M. D.; Jeffery, C. S.; Baran, A. S. +2 more
The original Kepler mission detected 18 pulsating subdwarf B (sdBV) stars, K2 observed 161 of our proposed targets with 41 sdB stars found to show p- or g-mode pulsations, and TESS has observed about 1,000 of our proposed targets. All these data should provide ∼300 sdBV stars, from which asteroseismology will provide a host of measurables. Combine…
New Hot Subdwarf Variables from Gaia eDR3
Kupfer, Thomas; Kosakowski, Alekzander; Barlow, Brad N. +1 more
We present a search for new variable hot subdwarfs from Gaia eDR3 using the Zwicky Transient Facility DR9 and the 2.1 m Otto Struve Telescope at McDonald Observatory. We report the discovery of 22 HW Vir binaries, 24 reflection effect binaries, and 14 ellipsoidally modulated systems. Candidate selection for our high-speed observations was based on…
The origin of subdwarf B stars
Aubrey, Callum; Napiwotzki, Ralf
The origin of subdwarf B stars (sdBs) is unclear. Different formation channels are proposed including: close-binary evolution, helium-mixing on the red giant branch and the hot flasher scenario. Circumstantial evidence exists that sdBs can result from single star evolution in high metallicity populations. We investigate this possibility by using m…
Magnetic activities on active solar-type stars
Pandey, J. C.; Raj, A.; Savanov, I. S. +2 more
We present results obtained from the studies of magnetic activities on four solar-type stars (F-type star KIC 6791060, K-type star LO Peg, and two M-type planet-hosting stars K2-33 and EPIC 211901114) by using optical observations from several ground- and space-based telescopes. In this study, we investigate magnetic activities such as spot-topogr…
Photometric study of the open cluster NGC 381
Joshi, Y. C.; Maurya, J.
We present UBVRcIc photometry of stars, down to the 20th magnitude, in the region of the intermediate- age open cluster NGC 381. The core and the cluster radii are estimated to be 2.99 +/- 0.93 and 5.6 +/- 0.1 arcmin, respectively. A total of 350 probable cluster member stars are identified by using proper motion from GAIA as the criterion of memb…
High-mass Star Formation towards the southern infrared Bubble S10
Vig, S.; Ghosh, S. K.; Ishwara-Chandra, C. H. +2 more
We present a multi-wavelength analysis of the southern infrared bubble S10. Radio continuum emission is detected towards the bubble at 610 and 1280 MHz, and the bubble is estimated to be powered by massive stars of spectral type B0.5 - B0. A Class I/II type source, with an estimated mass of 6.2 Msol, lies 7'' from the radio peak. Six massive clump…