AAVSO | American Association of Variable Star Observers

Stellar News Feed

Nobel laureate and laser inventor Charles Townes dies at 99

January 28, 2015 - 3:04pm

BERKELEY — Charles Hard Townes, a professor emeritus of physics at the University of California, Berkeley, who shared the 1964 Nobel Prize in Physics for invention of the laser and subsequently pioneered the use of lasers in astronomy, died early Tuesday, Jan. 27, in Oakland. He was 99 and in failing health, and died on his way to the hospital.

“Charles Townes embodies the best of Berkeley; he’s a great teacher, great researcher and great public servant,” said UC Berkeley Chancellor Nicholas Dirks on the occasion of a campuswide celebration of Townes’ 99th birthday last July 28. “As we celebrate this 99-year milestone and a career spanning nearly 80 years, we can only be impressed by the range of his intellectual curiosity, his persistence and his pioneering spirit.”

Until last year, Townes visited the campus daily, working either in his office in the physics department or at the Space Sciences Laboratory.

“Charlie was a cornerstone of the Space Sciences Laboratory for almost 50 years,” said Stuart Bale, director of the lab and a UC Berkeley professor of physics. “He trained a great number of excellent students in experimental astrophysics and pioneered a program to develop interferometry at short wavelengths. He was a truly inspiring man and a nice guy. We’ll miss him.”

Read the full press release from UC Berkeley

ASASSN-14cc: Likely Helium Analog of RZ Leonis Minoris

January 28, 2015 - 7:39am

We identified that ASASSN-14cc is a very active dwarf nova spending approximately 60% of the time in outburst. Our long-term photometry revealed that the object shows long outbursts recurring with a period of 21-33 d and very brief short outbursts lasting less than 1 d. The maximum decline rate exceeds 2.8 mag/d. The duration of long outbursts is 9-18 d, comprising 50-60% of the recurrence time of long outbursts. We detected 0.01560-0.01562 d (22.5 min) modulations during long outbursts, which we identified to be superhumps. These features indicate that ASASSN-14cc has outburst parameters very similar to the extreme dwarf nova RZ LMi but with a much shorter superhump period. All the observations can be naturally understood considering that this object is a helium analog (AM CVn-type object) of RZ LMi. The highest outburst activity among AM CVn-type objects can be understood as the high-mass transfer rate expected for the orbital period giving a condition close to the stability limit of the accretion disk. In contrast to RZ LMi, this object shows little evidence for premature quenching of the superoutburst, which has been proposed to explain the unusual outburst parameters in RZ LMi.

Authors: Taichi Kato, Franz-Josef Hambsch, Berto Monard

Read the paper on astro-ph

Gigantic ring system around J1407b

January 26, 2015 - 4:16pm

Astronomers at the Leiden Observatory, The Netherlands, and the University of Rochester, USA, have discovered that the ring system that they see eclipse the very young Sun-like star J1407 is of enormous proportions, much larger and heavier than the ring system of Saturn. The ring system – the first of its kind to be found outside our solar system – was discovered in 2012 by a team led by Rochester’s Eric Mamajek.

A new analysis of the data, led by Leiden’s Matthew Kenworthy, shows that the ring system consists of over 30 rings, each of them tens of millions of kilometers in diameter. Furthermore, they found gaps in the rings, which indicate that satellites (“exomoons”) may have formed. The result has been accepted for publication in the Astrophysical Journal.

The researchers encourage amateur astronomers to help monitor J1407, which would help detect the next eclipse of the rings, and constrain the period and mass of the ringed companion. Observations of J1407 can be reported to the American Association of Variable Star Observers (AAVSO). In the meantime the astronomers are searching other photometric surveys looking for eclipses by yet undiscovered ring systems.

Read the full story at University of Rochester Newscenter

Read the new paper on astro-ph

Predicting alpha Comae Berenices Time of Eclipse II: How 3 Faulty Measurements Out of 609 Caused A 26 Year Binary's Eclipse To Be Missed

January 23, 2015 - 11:10am

The dwarf stars in the 26 year period binary alpha Com were predicted to eclipse each other in early 2015. That prediction was based on an orbit model made with over 600 astrometric observations using micrometers, speckle interferometry, and long baseline optical interferometry. Unfortunately, it has been realized recently that the position angle measurements for three of the observations from ~100 years ago were in error by 180 degrees, which skewed the orbital fit. The eclipse was likely 2 months earlier than predicted, at which point the system was low on the horizon at sunrise.