A Radial Velocity Study of the Intermediate Polar EX Hydrae

A study on the intermediate polar EX Hya is presented, based on simultaneous photometry and high dispersion spectroscopic observations, during four consecutive nights. The strong photometric modulation related to with the 67-min spin period of the primary star is clearly present, as well as the narrow eclipses associated to the orbital modulation. Since our eclipse timings have been obtained almost 91,000 cycles since the last reported observations, we present new linear ephemeris, although we cannot rule out a sinusoidal variation suggested by previous authors. The system mainly shows double-peaked H$\alpha$, H$\beta$ and HeI $\lambda$5876 \AA emission lines. From the profile of the H$\alpha$ line, we find two components; one with a steep rise and velocities not larger than $\sim$1000 km s$^{-1}$ and another broader component extending up to $\sim$2000 km s$^{-1}$, which we interpret as coming mainly from the inner disc. A strong and variable hotspot is found and a stream-like structure is seen at times. We show that the best solution correspond to $K_1 = 58 \pm 5$ km s$^{-1}$ from H$\alpha$, from the two emission components, which are both in phase with the orbital modulation. We remark on a peculiar effect in the radial velocity curve around phase zero, which could be interpreted as a Rositter-MacLaughlin-like effect, which has been taken into account before deriving $K_1$. This value is compatible with the values found in high-resolution both in the ultraviolet and X-ray. We find: $M_{1} = 0.78 \pm 0.03$ M$_{\odot}$, $M_{2} = 0.10 \pm 0.02$ M$_{\odot}$ and $a = 0.67 \pm 0.01$ R$_{\odot}$. Doppler Tomography has been applied, to construct six Doppler tomograms for single orbital cycles spanning the four days of observations to support our conclusions. Our results indicate that EX Hya has a well formed disc and that the magnetosphere should extend only to about $3.75\,R_{\rm{WD}}$.Comment: 16 pages, 14 figures, accepted for publication in MNRA

Phytoplankton, bacterioplankton and nitrate reductase activity distribution in relation to physical structure in the northern Alborán Sea and Gulf of Cadiz (southern Iberian Peninsula)

The IctioAlborán-Cadiz 95 cruise (July 1995) covered the northwest sector of the Alborán Sea, the Straits of Gibraltar and the Gulf of Cadiz. We present and discuss the distribution of phytoand bacterioplankton abundance, nitrate concentration and nitrate reductase (NR) activity according to circulation patterns described previously in the literature. The water-column integrated values of chlorophyll-a in the Alborán Sea were higher and more variable (12 to 318 mg m⁻³) than in the Gulf of Cadiz (3 to 49 mg m⁻³). This reflects the higher dynamism of the Alborán sector, related to the existence of characteristic mesoscale physical structures. The plankton (2-80 μm equivalent spherical diameter) in the upwelling region of the Alborán Sea had a biovolume 30 times higher than in the nutrient-poorer water of the Gulf of Cadiz. Large organisms were abundant and dominated the size spectrum of one coastal station in the Alborán zone, whereas the slope of the size spectrum became more negative at the Gulf of Cadiz station, as a consequence of the dominance of small cells. Bacterial abundance maxima ( 3 X 10⁶ bact ml⁻¹) also occurred in the upwelling region. We found relatively high nitrate and chlorophyll a concentrations in Cape Trafalgar's cold surface waters, probably due to the interaction between topography and strong tidal currents. The spatial pattern of the NR activity is discussed according to chlorophyll a, nitrate and bacteria distributions. The existence of high NR activity but low chlorophyll a and bacterial abundance suggests that this could be related with dissimilatory activity in large-sized particles.La campaña IctioAlborán-Cádiz 95 (julio de 1995) cubrió el sector noroeste del mar de Alborán, estrecho de Gibraltar y golfo de Cádiz. En este trabajo se presentan y discuten las distribuciones de abundancia de fitoplancton y bacterioplancton, concentración de nitrato y actividad nitrato reductasa (NR) de acuerdo con los patrones de circulación descritos en la bibliografía. Los valores de clorofila a integrados en la columna de agua en Alborán fueron mayores y más variables (12 a 318 mg/m³) que en el golfo de Cádiz (3 a 49 mg/m³). Esto refleja el mayor dinamismo de la zona de Alborán, relacionado con la existencia de estructuras físicas características a mesoescala. El análisis de la comunidad nano-microplanctónica (2-80 μm, diametro esférico equivalente) de la región de afloramiento del mar de Alborán mostró un biovolumen 30 veces mayor que el de aguas más pobres en nutrientes del golfo de Cádiz. Por otro lado, el espectro de tamaños en una estación costera de Alborán está dominado por organismos planctónicos grandes, mientras que la pendiente del espectro de tamaño se hace más negativa en una estación del golfo de Cádiz, como consecuencia de la mayor abundancia de plancton de pequeño tamaño. En la región de afloramiento se dieron también máximos de abundancia bacteriana ( 3 X 10⁶ bact ml⁻¹). Se han encontrado valores relativamente altos de nitrato y clorofila a en las frías aguas superficiales cercanas al cabo de Trafalgar, lo que se debe, probablemente, a la interacción entre topografía y fuertes corrientes mareales. Se discute el patrón espacial de la actividad NR en relación con las distribuciones de clorofila a, nitrato y bacterias. En muestras con valores elevados de actividad NR pero bajos de clorofila y abundancia de bacterias, se sugiere que esta actividad se relaciona con actividad disimilatoria en agregados de gran tamaño.Instituto Español de Oceanografí

G 112-29 (=NLTT 18149), a Very Wide Companion to GJ 282 AB with a Common Proper Motion, Common Parallax, Common Radial Velocity and Common Age

We have made a search for common proper motion (CPM) companions to the wide binaries in the solar vicinity. We found that the binary GJ 282AB has a very distant CPM companion (NLTT 18149) at a separation s=1.09 \arcdeg. Improved spectral types and radial velocities are obtained, and ages determined for the three components. The Hipparcos trigonometric parallaxes and the new radial velocities and ages turn out to be very similar for the three stars, and provide strong evidence that they form a physical system. At a projected separation of 55733AU from GJ 282AB, NLTT 18149 ranks among the widest physical companions known.Comment: 13 pages, 3 figures, submmited to Ap

The Expanding Nebular Remnant of the Recurrent Nova RS Ophiuchi (2006): II. Modeling of Combined Hubble Space Telescope Imaging and Ground-based Spectroscopy

We report Hubble Space Telescope imaging, obtained 155 and 449 days after the 2006 outburst of the recurrent nova RS Ophiuchi, together with ground-based spectroscopic observations, obtained from the Observatorio Astron\'omico Nacional en San Pedro M\'artir, Baja California, M\'exico and at the Observatorio Astrof\'isico Guillermo Haro, at Cananea, Sonora, M\'exico. The observations at the first epoch were used as inputs to model the geometry and kinematic structure of the evolving RS Oph nebular remnant. We find that the modeled remnant comprises two distinct co-aligned bipolar components; a low-velocity, high-density innermost (hour glass) region and a more extended, high-velocity (dumbbell) structure. This overall structure is in agreement with that deduced from radio observations and optical interferometry at earlier epochs. We find that the asymmetry observed in the west lobe is an instrumental effect caused by the profile of the HST filter and hence demonstrate that this lobe is approaching the observer. We then conclude that the system has an inclination to the line of sight of 39$^{+1}_{-10}$ degrees. This is in agreement with the inclination of the binary orbit and lends support to the proposal that this morphology is due to the interaction of the outburst ejecta with either an accretion disk around the central white dwarf and/or a pre-existing red giant wind that is significantly denser in the equatorial regions of the binary than at the poles. The second epoch HST observation was also modeled. However, as no spectra were taken at this epoch, it is more difficult to constrain any model. Nevertheless, we demonstrate that between the two HST epochs the outer dumbbell structure seems to have expanded linearly.Comment: 33 pages, 9 figures, 1 table, accepted for publication in Ap

A radial velocity study of the intermediate polar EX Hydrae

A study on the intermediate polar EX Hya is presented, based on simultaneous photometry and high-dispersion spectroscopic observations, during four consecutive nights. The strong photometric modulation related to the 67-min spin period of the primary star is clearly present, as well as the narrow eclipses associated with the orbital modulation. Since our eclipse timings have been obtained almost 91 000 cycles since the last reported observations, we present new linear ephemeris, although we cannot rule out a sinusoidal variation suggested by previous authors. The system shows double-peaked H α, H β and He I λ5876 Å emission lines, with almost no other lines present. As H α is the only line with enough S/N ratio in our observations, we have concentrated our efforts in its study, in order to obtain a reliable radial velocity semi-amplitude. From the profile of this line, we find two important components; one with a steep rise and velocities not larger than ˜1000 km s-1 and another broader component extending up to ˜2000 km s-1, which we interpret as coming mainly from the inner disc. A strong and variable hotspot is found and a stream-like structure is seen at times. We show that the best solution correspond to K1 = 58 ± 5 kms-1 from H α, from the two emission components, which are both in phase with the orbital modulation. We remark on a peculiar effect in the radial velocity curve around phase zero, which could be interpreted as a Rositter-MacLaughlin-like effect, which has been taken into account before deriving K1. This value is compatible with the values found in high resolution both in the ultraviolet and X-ray. Using the published inclination angle of I =78° ±1° and semi-amplitude K2 = 432 ± 5 kms-1, we find: M1 = 0.78 ± 0.03M⊙, M2 = 0.10 ± 0.02 M⊙ and a = 0.67 ± 0.01 R⊙. Doppler Tomography has been applied, to construct six Doppler tomograms for single orbital cycles spanning the four days of observations to support our conclusions. Our results indicate that EX Hya has a well-formed disc and that the magnetosphere should extend only to about 3.75 RWD.Publisher PDFPeer reviewe

The new cataclysmic variable RX J1554.2+2721 in the period gap

We report on the results of a spectroscopic and photometric study of a new cataclysmic variable, identified as optical counterpart of the X-ray source RX J1554.2+2721 detected by ROSAT. The spectroscopic observations of the relatively bright (~16.5mag) object show systematic radial velocity variations with a semi-amplitude of ~140 km/sec. Besides the clear presence of distinct low and high states there are periodic photometric light variations with an amplitude of about 0.15 magnitude in the R band. The orbital period is 2.753h thus being within the period gap, at its upper border. The flux distribution in the spectrum of the object shows a substantial contribution of a M4V secondary, and also bears clear signs of cyclotron emission. Thus, we classify the discovered object as a new member of the AM Her class of magnetic cataclysmic variables. This classification is further supported by the soft X-ray spectrum, the characteristic profiles of the emission lines, the tomography map and the shape of the orbital light curve. A simple fitting of the spectrum in the low and high states suggests a reduced mass transfer rate in RX J1554.2+2721, compared to similar objects outside the period gap.Comment: 11 pages, 11 figures, accepted in A&

Active compounds and distinctive sensory features provided by American ginseng (Panax quinquefolius L.) extract in a new functional milk beverage

American ginseng (Panax quinquefolius L.) has recognized neurocognitive effects, and a ginsenoside-rich extract of the root of the plant has been shown to improve cognitive functions in young adults. This study aimed at assessing the chemical and sensory profiles of a UHT-treated, low-lactose functional milk containing American ginseng. Individual ginsenosides in the milk were analyzed by HPLC. Descriptive sensory analysis was performed by a trained panel to quantitatively document sensory changes resulting from the addition of ginseng and the UHT process on flavored and unflavored milks. Consumer acceptance of the product was also investigated. Total ginsenoside content in the UHT-treated milk enriched with the ginseng extract after UHT process treatment was 7.52. mg/100. g of milk, corresponding to a recovery of 67.6% compared with the content in the unprocessed extract. The intake of 150 to 300. mL of this ginseng-enriched milk provides the amount of total ginsenosides (11.5 to 23. mg) necessary to improve cognitive function after its consumption. Both the presence of ginsenosides and their thermal treatment affected some sensory properties of the milk, most notably an increase in bitterness and metallic taste, the appearance of a brownish color, and a decrease in milky flavor. Levels of brown color, bitterness, and metallic taste were highest in the industrially processed ginseng-enriched milk. The bitterness attributable to ginseng extract was reduced by addition of vanilla flavor and sucralose. A consumer exploratory study revealed that a niche of consumers exists who are willing to consume this type of product.The financial support of the Ministry of Science and Innovation of Spain (Madrid, Spain) for the project SENIFOOD (CENIT Programme) and for the contract with A. Tárrega (Juan de la Cierva Programme) is acknowledged. We gratefully acknowledge Juan Duato Aguilar, from Naturex Spain S.L. (Quart de Poblet, Spain), for his valuable technical support

Cyclic brightening in the short-period WZ Sge-type cataclysmic variable SDSS J080434.20+510349.2

We have observed a new cataclysmic variable (CV) SDSS J080434.20+510349.2 and study the origin of a long-term variability found in its light curve. Multi-longitude time-resolved photometric observations were carried out to analyze the uncommon behavior also found recently in two newly discovered CVs. This study of SDSS J080434.20+510349.2 mainly concerns the understanding of the nature of the observed double-humped light curve and its relation to a cyclic brightening occurring during quiescence. The observations were obtained early in 2007, when the object was at about V~17.1, 0.4 mag brighter than the pre-outburst magnitude. The light curve shows a sinusoidal variability with an amplitude of about 0.07 mag and a periodicity of 42.48 min, which is half of the orbital period of the system. In addition, we have observed two "mini-outbursts" of the system up to 0.6 mag, with a duration of about 4 days each. The "mini-outburst" had a symmetric profile and repeated in about 32 days. Subsequent monitoring of the system shows a cyclical behaviour of such "mini-outbursts" with a similar recurrence period. The origin of the double-humped light curve and the periodic brightening is discussed in the light of the evolutionary state of SDSS J080434.20+510349.2.Comment: 7 pages, 6 figures, Accepted by A&A, typos added, figure correcte