View Full Version : New Type of Star Discovered?

2003-Jan-10, 02:15 AM
Astronomers Identify New Type Of Star...
Science Daily Fri Jan 10 05:55:00 UTC+1000 2003.

This popped up on Moreover Technologies. It's the news provider we use for up to date space and nuclear information. For some reason the page can't be displayed.


Can anybody verify or disclaim this report and tell me what was in it?

A search on 'New Type Of Star' revealed the following rather dated links.

Report: Astronomers discover new type of star
June 1, 1999
(CNN) -- Astronomers have discovered a new category of cosmic objects that cannot be seen in visible light, yet may be as numerous as the stars, The New York Times reported Tuesday.

University News Service
University of Wyoming
Nov. 7, 1997 -- An international team of astronomers led by Steve Howell of the University of Wyoming has discovered a new type of star.

Tim Thompson
2003-Jan-11, 01:54 AM
The paper appeared on the preprint archive 2 years ago (Jan 2001), and was published in March, 2001 (also see RAS Press Release (http://www.jach.hawaii.edu/JACpublic/UKIRT/public/Press_Releases/pn01-05.htm), February 2001). I don't know what happened to suddenly make this old news, new news.

Spectroscopic Discovery of Brown Dwarf-like Secondary Stars in the Cataclysmic Variables LL And and EF Eri (http://cul.arXiv.org/abs/astro-ph/0101572)
Steve B. Howell & David R. Ciardi
Astrophysical Journal 550(1): L57-L59, Part 2, March 20, 2001
Abstract: Infrared spectroscopic observations of LL Andromedae (http://icarus.stsci.edu/~downes/cvcat/query_processor.cgi?setup_file=varcat.setup.cgi&query_decision=single_record&uid=6764&query_select=everything) and EF Eridani are presented. Our K-band spectrum of LL And reveals the presence of methane absorption in the secondary star indicating an effective temperature less than or similar to 1300 K, similar to a "T"-type methane brown dwarf. The secondary star in EF Eri is seen to be warmer with an effective temperature of similar to 1650 K and a spectroscopic classification consistent with an L4-5 star. Both secondaries have theoretical mass estimates of 0.04-0.055 M-solar (40-55 M-Jup). Our IR spectroscopic observations of LL And and EF Eri provide the first direct proof of the theoretical prediction that post-period minimum cataclysmic variables contain brown dwarf-like secondary stars.

There have been a few papers since then, on other possible sub-stellar companions in cataclysmic binary systems. The most recent appears to be this one.

A search for brown dwarf like secondaries in cataclysmic variables
R.E. Mennickent & M.P. Diaz
Monthly Notices of the Royal Astronomical Society 336(3): 767-773, November 1, 2002
Abstract: We present VLT/ISAAC (http://www.eso.org/instruments/isaac/) infrared spectroscopy of a sample of short-orbital-period cataclysmic variables that are candidates for harbouring substellar companions. We have detected the KI and Na I absorption lines of the companion star in VY Aqr. The overall spectral distribution in this system is best fitted with an M9.5 type dwarf spectrum, implying a distance of 100▒10 pc. VY Aqr seems to fall far from the theoretical distribution of secondary star temperatures around the orbital period minimum. Fitting of the IR spectral energy distribution (SED) was performed by comparing the observed spectrum with late-type templates. The application of such a spectral fitting procedure suggests that the continuum shape in the 1.1-2.5 Ám spectral region in short-orbital-period cataclysmic variables may be a useful indicator of the companion's spectral type. SED fitting for RZ Leo and CU Vel suggests M5-type dwarf companions, and distances of 340▒110 and 150▒50 pc, respectively. These systems may be placed in the upper evolution branch for short-period cataclysmic variables.

It appears that the existence of sub-stellar mass comapnions in cataclysmic variables was predicted in 1997.

On the existence of low-luminosity cataclysmic variables beyond the orbital period minimum
S.B Howell, S. Rappaport, & M. Politano
Monthly Notices of the Royal Astronomical Society 287(4): 929-936, June 1, 1997
Abstract: Models of the present-day intrinsic population of cataclysmic variables predict that 99% of these systems should be of short orbital period (P<sub>orb</sub> less than or similar to 2.5 h). The Galaxy is old enough that similar to 70% of these stars will have already reached their orbital period minimum (similar to 80 min), and should be evolving back toward longer periods. Mass-transfer rates in these highly evolved binaries are predicted to be less than or similar to 10<sup>-11</sup> solar masses yr<sup>-1</sup>, leading to M<sub>v</sub> of similar to 10 or fainter, and the secondaries would be degenerate, brown dwarf-like stars. Recent observations of a group of low-luminosity dwarf novae (TOADs) provide observational evidence for systems with very low intrinsic M<sub>v</sub> and possibly low-mass secondaries. We carry out population synthesis and evolution calculations for a range of assumed ages of the Galaxy in order to study P<sub>orb</sub> and dM/dt distributions for comparison with the TOAD observations. We speculate that at least some of the TOADs are the predicted very low-luminosity, post-period-minimum cataclysmic variables containing degenerate (brown dwarf-like) secondaries having masses between 0.02 and 0.06 solar masses and radii near 0.1 solar radii. We show that these low-luminosity systems are additionally interesting in that they can be used to set a lower limit on the age of the Galaxy. The TOAD with the longest orbital period currently known (123 min), corresponds to a Galaxy age of at least 8.6 x 10<sup>9</sup> yr.

The acronym TOAD stands for "Tremendous Outbust Amplitude Dwarf nova", where the "n" just didn't fit in. The objects predicted in this 1997 paper look like they would constitute a "new type of star" to me. Degenerate matter is a characteristic of high density object, in particular white dwarfs, which are on the order of 1 solar mass, maybe as low as 0.5 solar masses, but certainly of "stellar" mass (more than 0.08 solar masses at the very least). Evidently, the environment of a mass-transfer binary allows the low mass companion to still achieve densities high enough to carry degnerate matter.

I had not thought of this before, and was indeed unaware of it until I looked into answering your question, so maybe we all learn something.

<font size=-1>[ This Message was edited by: Tim Thompson on 2003-01-10 20:57 ]</font>