Sunday, Aug 9 2020 | Time 22:54 Hrs(IST)
image
  • Rashtriya Swachhta Kendra, tribute to Mahatma Gandhi's idea of clean India: Shekhawat
  • South Africa's Brad Binder wins Czech MotoGP
  • South Africa's Brad Binder wins Czech MotoGP
  • Indira Van Mitan Yojana to be launched in Chhattisgarh: Bhupesh
  • Plane crash: Three passengers remain critical, rest recovering
  • Sikkim records 6 new Covid cases, tally at 866
  • Huge cache of arms and ammunition recovered in Jharkhand's Dumka
  • Earthquake of 3 8 magnitude jolts Gangtok
  • Karnataka reports highest single-day spike of 5985 cases
  • Ensure developmental schemes reach every person in their territory: PM Modi to BJP workers of Andamans
  • COVID-19: 10,820 fresh cases reported, 97 more patients die in AP
  • Newly-appointed UPSC Chairman calls on Jitendra Singh
  • Punjab Guv tests negative while his Principal Secy & 4 others found Covid positive
  • Nagaland COVID-19 cases reach 2781, 93 new cases in 24 hrs
  • Punjab: 987 test +ve, 24 die
States » East


Detection of fluorine in hot extreme Helium Stars solves their evolution mystery

Detection of fluorine in hot extreme Helium Stars solves their evolution mystery

Kolkata, Jun 22 (UNI) An extreme helium star or EHe is a low-mass supergiant that is almost devoid of hydrogen, the most common chemical element of the universe.

There are 21 of them detected so far in our galaxy. The origin and evolution of these Hydrogen deficient objects have been shrouded in mystery. Their severe chemical peculiarities challenge the theory of well-accepted stellar evolution as the observed chemical composition of these stars do not match with that predicted for low mass evolved stars.

A study by the Indian Institute of Astrophysics (IIA) an autonomous institute of Department of Science and Technology which detected the presence of singly ionised fluorine for the first time in the atmospheres of hot Extreme Helium Stars makes a strong case that the main formation of these objects involves a merger of a carbon-oxygen (CO) and a Helium (He) white dwarf.

The research published in the Astrophysical Journal, led by Anirban Bhowmick (Ph.D. student, IIA, Bengaluru), Prof. Gajendra Pandey (IIA) and Prof. David Lambert (University of Texas at Texas-Austin), which showed fluorine abundances determined from singly ionized fluorine (F II) lines suggest a very high enrichment of fluorine, about a factor of 100 to 10000 times higher than normal stars.

Clues to evolution of extreme helium stars require accurate determinations of their chemical composition, and the peculiarities, if any, become very important. Fluorine plays a very crucial role in this regard to determine the actual evolutionary sequence of these hydrogen deficient objects.

Severe fluorine enrichment w.r.t normal stars (of the order of 800 − 8000) was observed in the cool EHes along-with the cooler classical hydrogen deficient stars, the RCB variables (R Coronae Borealis Stars) hinting at close evolutionary connection between them.

The scientists explored the relationship of hot EHes (EHes having effective temperature ≥ 14000K), with the cooler EHes, based on their fluorine abundance and spotted it in the former, thus establishing an evolutionary connection across a wide range of effective temperature.

High-resolution echelle spectra of 10 hot EHes were obtained from Hanle Echelle Spectrograph (HESP) mounted on the 2-m Himalayan Chandra Telescope at the Indian Astronomical Observatory (IAO) in Hanle, Ladakh, (remotely operated by IIA) including data from McDonald Observatory, USA, and ESO archives.

By comparing the observed fluorine abundances with other abundances of the key elements, the scientists could determine the formation channels responsible for fluorine enrichment. The varied range of observed fluorine abundance across stars having similar atmospheric parameters points out the difference in the individual star’s evolution and the ensuing nucleosynthesis.

Particularly, the enrichment of fluorine in the atmospheres of carbon-rich EHes and absence of the same in carbon-poor EHes suggest that fluorine is profusely produced during the merger of a He-CO WD resulting in a carbon-rich EHe, whereas He-He WD merger that results in carbon-poor EHes does not account for fluorine overabundance.

The detection of enhanced fluorine abundances in the atmospheres of hot EHes solves a decade-old mystery about their formation. It firmly places hot EHes in an evolutionary sequence with cool EHes and other hydrogen-deficient stars and zeros in the evolutionary scenario, which involves the merger of two double degenerate white dwarfs (WDs).

UNI BM SJC AND

More News
Earthquake of 3 8 magnitude jolts Gangtok

Earthquake of 3 8 magnitude jolts Gangtok

09 Aug 2020 | 10:43 PM

Gangtok,Aug 9 (UNI) Gangtokians experienced Earthquake at 6.49 am today.

see more..

Against target of 2 51 Crores, 3 47 Crores saplings planted : Modi

09 Aug 2020 | 10:36 PM

Patna, Aug 09 (UNI) Bihar Deputy Chief Minister Sushil Kumar Modi today said that against the target of plantation of 2.51 Crores saplings this year, a total of 3.47 Crores saplings were planted this year even during the bad phase of Corona pandemic.

see more..

Flood water maroons 73 lakh people in Bihar

09 Aug 2020 | 10:35 PM

Pàtna, Aug 9 (UNI) The flood water has marooned 74 lakh 19 thousand people in 16 districts of Bihar where flood situation remained grim as seven rivers of North Bihar were flowing above the red mark following incessant rains in their catchment areas in the state and in Nepal.

see more..

Sikkim records 6 new Covid cases, tally at 866

09 Aug 2020 | 10:24 PM

Gangtok, Aug 9 (UNI) Sikkim recorded six new Coronavirus cases today, taking the overall tally to 866.

see more..

Huge cache of arms and ammunition recovered in Jharkhand's Dumka

09 Aug 2020 | 10:18 PM

Dumka, Aug 9 (UNI) In a joint operation conducted by Dumka and Bokaro Police along with jawans of SSB and CRPF huge quantity of arms and ammunition have been recovered from different police station areas of this district.

see more..
image