Hen 3-160 is a symbiotic binary with Mira variable star, study suggests

January 4, 2019 by Tomasz Nowakowski, Phys.org report
V and IC light curves of Hen 3-160. Image credit: Gałan et al., 2018.

A new study conducted by a team of astronomers from Poland and South Africa provides more insights into the nature of Hen 3-160, a symbiotic binary system in the southern Milky Way. The research, presented in a paper published December 22 on arXiv.org, proposes that this object is a symbiotic binary containing a Mira variable star.

It is assumed that symbiotic binaries showcase dramatic, episodic changes in the spectra of their light because one star of pair is a very hot, small star while the other is a cool giant. In general, such systems are essential for researchers studying various aspects of stellar evolution.

Astronomers divide symbiotic (SySt) into two main classes: S-type and D-type. Most known SySts are of S-type, which have near-infrared spectra generally dominated by the cool star's photosphere, and are indistinguishable from ordinary late-type giants. D-type symbiotic stars exhibit additional emission attributed to thick circumstellar dust shells. SySts of this class experience large amplitude variations due to the presence of Mira variables (red giants with pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wavelengths) and other long-period variable .

Although Hen 3-160 (other designations: SS73 9, WRAY 15-208, Schwartz 1 and 2MASS 08245314-512832) was first spotted in the 1960s, no detailed studies of this binary have been conducted, and very little is known about the parameters of its components. Thus, a group of astronomers led by Cezary Gałan of Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences in Warsaw, Poland, decided to analyze data from spectroscopic and photometric observations of Hen 3-160 collected during a timespan of over two decades.

Gałan's team used optical spectra obtained with SpUpNIC spectrograph on the 1.9-m Radcliffe telescope in Sutherland, South Africa, and photometric optical data acquired with a 35-cm Meade RCX400 telescope in Klein Karoo Observatory, near Sutherland. Analysis of this data sheds new light on the nature of Hen 3-160.

"In this work, we present new observations collected over two decades which enabled us to reveal its very interesting nature," the astronomers wrote in the paper.

The main conclusion from this study is that the giant in the Hen 3-160 system is a Mira variable pulsating with 242.5-day period. Moreover, it is the first known symbiotic Mira that is simultaneously the S-process enhanced star of MS spectral type.

In particular, the researchers found that the large-amplitude periodic variations observed in the optical V and IC-band light curves with the pulse period of over 100 days, which were correlated with changes in other bands as well in the spectra, indicate that the cool component is a Mira star. Furthermore, the presence of comparably strong ZrO and TiO bands are indicative of the MS spectral type for this object, and place it among the S , proving that it is enhanced in the S-process elements.

The astronomers also estimated the distance of the Hen 3-160 system. They found that the binary is located some 30,600 light years away from the Earth, about 4,200 light years above the disk of the Milky Way galaxy. They added that galactic coordinates of Hen 3-160, together with relatively high proper motions, make it a galactic extended thick disc object.

Explore further: Astronomers discover nine new variable stars

More information: C. Galan et al. Hen 3-160 - the first symbiotic binary with Mira variable S star. arXiv:1812.09535 [astro-ph.SR]. arxiv.org/abs/1812.09535

Related Stories

Astronomers discover nine new variable stars

December 19, 2018

A team of astronomers from Chile has detected nine new variable stars in the globular cluster NGC 6652 and its background stream. Six of the newly found stars were classified as eclipsing binaries, one as an SX Phoenicis ...

Astronomers detect flickering from the star EF Aquilae

March 1, 2017

(Phys.org)—European researchers have detected optical flickering from a distant symbiotic star known as EF Aquilae (EF Aql for short). The new findings, presented Feb. 27 on the arXiv pre-print server, offer important hints ...

Symbiotic star AG Pegasi observed after ourburst

October 1, 2018

Using ESA's XMM-Newton space telescope, two researchers have observed the symbiotic star AG Pegasi after the end of its outburst in 2015. The observations, detailed in a paper published September 24 on the arXiv pre-print ...

Recommended for you

Coffee-based colloids for direct solar absorption

March 22, 2019

Solar energy is one of the most promising resources to help reduce fossil fuel consumption and mitigate greenhouse gas emissions to power a sustainable future. Devices presently in use to convert solar energy into thermal ...

EPA adviser is promoting harmful ideas, scientists say

March 22, 2019

The Trump administration's reliance on industry-funded environmental specialists is again coming under fire, this time by researchers who say that Louis Anthony "Tony" Cox Jr., who leads a key Environmental Protection Agency ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.