142 research outputs found
QZ Serpentis: A Dwarf Nova with a 2-Hour Orbital Period and an Anomalously Hot, Bright Secondary Star
We present spectroscopy and time-series photometry of the dwarf nova QZ Ser.
The spectrum shows a rich absorption line spectrum of type K4 +- 2. K-type
secondary stars are generally seen in dwarf novae with orbital periods P-orb
around 6 h, but in QZ Ser the absorption radial velocities show an obvious
modulation (semi-amplitude 207(5) km/s) at P-orb = 119.752(2) min, much shorter
than typical for such a relatively warm and prominent secondary spectrum. The
H-alpha emission-line velocity is modulated at the same period and roughly
opposite phase. Time-series photometry shows flickering superposed on a
modulation with two humps per orbit, consistent with ellipsoidal variation of
the secondary's light. QZ Ser is a second example of a relatively short-period
dwarf nova with a surprisingly warm secondary. Model calculations suggest that
the secondary is strongly enhanced in helium, and had already undergone
significant nuclear evolution when mass transfer began. Several sodium
absorption features in the secondary spectrum are unusually strong, which may
indicate that the present-day surface was the site of CNO-cycle hydrogen
burning in the past.Comment: 11 pages, 3 postscript figures, 1 jpeg greyscale figure. Accepted for
publication in PAS
Spectroscopy of Seven Cataclysmic Variables with Periods Above Five Hours
We present spectroscopy of seven cataclysmic variable stars with orbital
periods P(orb) greater than 5 hours, all but one of which are known to be dwarf
novae. Using radial velocity measurements we improve on previous orbital period
determinations, or derive periods for the first time. The stars and their
periods are
TT Crt, 0.2683522(5) d;
EZ Del, 0.2234(5) d;
LL Lyr, 0.249069(4) d;
UY Pup, 0.479269(7) d;
RY Ser, 0.3009(4) d;
CH UMa, 0.3431843(6) d; and
SDSS J081321+452809, 0.2890(4) d.
For each of the systems we detect the spectrum of the secondary star,
estimate its spectral type, and derive a distance based on the surface
brightness and Roche lobe constraints. In five systems we also measure the
radial velocity curve of the secondary star, estimate orbital inclinations, and
where possible estimate distances based on the MV(max) vs.P(orb) relation found
by Warner. In concordance with previous studies, we find that all the secondary
stars have, to varying degrees, cooler spectral types than would be expected if
they were on the main sequence at the measured orbital period.Comment: 25 pages, 2 figures, accepted for Publications of the Astronomical
Society of the Pacifi
1RXS J232953.9+062814: A Dwarf Nova with a 64-minute Orbital Period and a Conspicuous Secondary Star
We present spectroscopy and time-series photometry of the newly discovered
dwarf nova 1RXS J232953.9+062814. Photometry in superoutburst reveals a
superhump with a period of 66.06(6) minutes. The low state spectrum shows
Balmer and HeI emission on a blue continuum, and in addition shows a rich
absorption spectrum of type K4 +- 2. The absorption velocity is modulated
sinusoidally at P_orb = 64.176(5) min, with semi-amplitude K = 348(4) km/s. The
low-state light curve is double-humped at this period, and phased as expected
for ellipsoidal variations. The absorption strength does not vary appreciably
around the orbit. The orbital period is shorter than any other cataclysmic
variable save for a handful of helium-star systems and V485 Centauri (59
minutes). The secondary is much hotter than main sequence stars of similar
mass, but is well-matched by helium-enriched models, indicating that the
secondary evolved from a more massive progenitor. A preliminary calculation in
which a 1.2 solar-mass star begins mass transfer near the end of H burning
matches this system's characteristics remarkably well.Comment: accepted to Astrophysical Journal Letters; 14 pages, 3 eps figures +
1 jpg greyscale figur
Five Dwarf Novae with Orbital Periods Below Two Hours
We give mean spectra and report orbital periods Porb based on radial
velocities taken near minimum light for five dwarf novae, all of which prove to
have Porb less than 2 hr. The stars and their periods are KX Aql, 0.06035(3) d;
FT Cam, 0.07492(8) d; PU CMa, 0.05669(4) d; V660 Her, 0.07826(8) d;, and DM
Lyr, 0.06546(6). The emission lines in KX Aql are notably strong and broad, and
the other stars' spectra appear generally typical for short-period dwarf novae.
We observed FT Cam, PU CMa, and DM Lyr on more than one observing run and
constrain their periods accordingly. Differential time-series photometry of FT
Cam shows strong flickering but rules out deep eclipses. Although dwarf novae
in this period range generally show the superhumps and superoutbursts
characteristic of the SU UMa subclass of dwarf novae, none of these objects
have well-observed superhumps.Comment: 14 pages, three figures. Accepted for PAS
1907 Ruby Yearbook
A digitized copy of the 1907 Ruby, the Ursinus College yearbook.https://digitalcommons.ursinus.edu/ruby/1010/thumbnail.jp
Superhumps in Cataclysmic Binaries. XXIII. V442 Ophiuchi and RX J1643.7+3402
We report the results of long observing campaigns on two novalike variables:
V442 Ophiuchi and RX J1643.7+3402. These stars have high-excitation spectra,
complex line profiles signifying mass loss at particular orbital phases, and
similar orbital periods (respectively 0.12433 and 0.12056 d). They are
well-credentialed members of the SW Sex class of cataclysmic variables. Their
light curves are also quite complex. V442 Oph shows periodic signals with
periods of 0.12090(8) and 4.37(15) days, and RX J1643.7+3402 shows similar
signals at 0.11696(8) d and 4.05(12) d. We interpret these short and long
periods respectively as a "negative superhump" and the wobble period of the
accretion disk. The superhump could then possibly arise from the heating of the
secondary (and structures fixed in the orbital frame) by inner-disk radiation,
which reaches the secondary relatively unimpeded since the disk is not
coplanar.
At higher frequencies, both stars show another type of variability:
quasi-periodic oscillations (QPOs) with a period near 1000 seconds. Underlying
these strong signals of low stability may be weak signals of higher stability.
Similar QPOs, and negative superhumps, are quite common features in SW Sex
stars. Both can in principle be explained by ascribing strong magnetism to the
white dwarf member of the binary; and we suggest that SW Sex stars are
borderline AM Herculis binaries, usually drowned by a high accretion rate. This
would provide an ancestor channel for AM Hers, whose origin is still
mysterious.Comment: PDF, 41 pages, 4 tables, 16 figures; accepted, in press, to appear
December 2002, PASP; more info at http://cba.phys.columbia.edu
Measurement of the inclusive isolated-photon cross section in pp collisions at âs = 13 TeV using 36 fbâ1 of ATLAS data
The differential cross section for isolated-photon production in pp collisions is measured at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC using an integrated luminosity of 36.1 fb. The differential cross section is presented as a function of the photon transverse energy in different regions of photon pseudorapidity. The differential cross section as a function of the absolute value of the photon pseudorapidity is also presented in different regions of photon transverse energy. Next-to-leading-order QCD calculations from Jetphox and Sherpa as well as next-to-next-to-leading-order QCD calculations from Nnlojet are compared with the measurement, using several parameterisations of the proton parton distribution functions. The predictions provide a good description of the data within the experimental and theoretical uncertainties. [Figure not available: see fulltext.
Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences
The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & NemĂ©sio 2007; Donegan 2008, 2009; NemĂ©sio 2009aâb; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported
by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on
18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based
researchers who signed it in the short time span from 20 September to 6 October 2016
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