The Rise Times and Bolometric Light Curve of SN 1994D: Constraints on Models of Type Ia Supernovae

Using the published photometry and an empirical model of the temporal evolution of the apparent magnitudes in the UBVRI passbands, we have constructed a continuous optical bolometric, or ``quasi-bolometric'', light curve of the well-observed Type Ia supernova SN 1994D. The optical bolometric light curve is found to have a maximum luminosity of about $8.8\times 10^{42} \times (\frac{D}{13.7 Mpc})^2$ erg/s, which is reached $\sim 18$ days after the explosion. In addition, the optical bolometric light curve exhibits an inflection, or ``shoulder'', about $25$ days after maximum. This inflection corresponds to the secondary maximum observed in all filter light curves redder than $B$. The individual filter curves have rise times similar to that of the optical bolometric light curve; other Type Ia supernovae are found to have similar rise times. Our fits indicate that the peak bolometric luminosity and the maxima in the B, V, and R light curves all occur within a day of one another. These results can be used to place constraints on theoretical models of Type Ia events. For example, all current theoretical models predict rise times to peak luminosity which are significantly shorter than that estimated for SN 1994D.Comment: 12 pages, 1 color PostScript figure, special style file (aaspp4) included. Accepted for publication in Astrophysical Journal Letters. A PostScript version with embedded figure is available at http://www.ifa.hawaii.edu/~vacc

The Schizophrenic Spectrum of LSR 1610-0040: a Peculiar M Dwarf/Subdwarf

We present a moderate resolution (R=2000), 0.8-4.1 micron spectrum of LSR 1610-0040, a high proper motion star classified as an early-type L subdwarf by Lepine and collaborators based on its red-optical spectrum. The near-infrared spectrum of LSR 1610-0040 does not fit into the (tentative) M/L subdwarf sequence but rather exhibits a mix of characteristics found in the spectra of both M dwarfs and M subdwarfs. In particular, the near-infrared spectrum exhibits a Na I doublet and CO overtone bandheads in the K band, and Al I and K I lines and an FeH bandhead in the H band, all of which have strengths more typical of field M dwarfs. Furthermore the spectrum of Gl 406 (M6 V) provides a reasonably good match to the 0.6-4.1 micron spectral energy distribution of LSR 1610. Nevertheless the near-infrared spectrum of LSR 1610 also exhibits features common to the spectra of M subdwarfs including a strong Ti I multiplet centered at ~0.97 microns, a weak VO band at ~1.06 microns, and possible collision-induced H_2 absorption in the H and K bands. We discuss a number of possible explanations for the appearance of the red-optical and near-infrared spectrum of LSR 1610-0040. Although we are unable to definitively classify LSR 1610-0040, the preponderance of evidence suggests that it is a mildly metal-poor M dwarf. Finally, we tentatively identify a new band of TiO at ~0.93 microns in the spectra of M dwarfs.Comment: Accepted for publication in the Astronomical Journa

Young star clusters in interacting galaxies - NGC 1487 and NGC 4038/4039

We estimate the dynamical masses of several young (~10 Myr) massive star clusters in two interacting galaxies, NGC 4038/4039 ("The Antennae") and NGC 1487, under the assumption of virial equilibrium. These are compared with photometric mass estimates from K-band photometry and assuming a standard Kroupa IMF. The clusters were selected to have near-infrared colors dominated by red supergiants, and hence to be old enough to have survived the earliest phases of cluster evolution when the interstellar medium is rapidly swept out from the cluster, supported by the fact that there is no obvious Halpha emission associated with the clusters. All but one of the Antennae clusters have dynamical and photometric mass estimates which are within a factor ~2 of one another, implying both that standard IMFs provide a good approximation to the IMF of these clusters, and that there is no significant extra-virial motion, as would be expected if they were rapidly dispersing. These results suggest that almost all of the Antennae clusters in our sample have survived the gas removal phase as bound or marginally bound objects. Two of the three NGC 1487 clusters studied here have M_dyn estimates which are significantly larger than the photometric mass estimates. At least one of these two clusters, and one in the Antennae, may be actively in the process of dissolving. The process of dissolution contributes a component of non-virial motion to the integrated velocity measurements, resulting in an estimated M_dyn which is too high relative to the amount of measured stellar light. The dissolution candidates in both galaxies are amongst the clusters with the lowest pressures/densities measured in our sample.Comment: 17 pages, 14 Figures, A&A accepte

Risposta del Basilico (Ocimum basilicum) alla tossicita da Boro

Il basilico (Ocimum basilicum L).è una pianta aromatica appartenente alla famiglia delle Lamiaceae molto conosciuta ed apprezzata per i suoi usi in ambito culinario ed erboristico, ma le sue potenzialità però vanno ben oltre i semplici usi per il quale è normalmente destinato. Tale pianta infatti può essere impiegata anche nei campi farmaceutici ed estetici in quanto contiene molte sostanze estremamente interessanti dalle proprietà più disparate: può essere impiegato come antinfiammatorio, antisettico, tonico, lassativo, per lenire punture d’insetto, come antiallergico, antimicrobico, antiossidante e molte altre. In questa tesi sono presentati e discussi i risultati di alcuni studi condotti sulla tolleranza all’eccesso di boro (B) del basilico dolce coltivato in idroponica (floating system) con una concentrazione di boro nella soluzione nutritiva di 0,2, 5 o 20 mg/L. Nei vari esperimenti sono state utilizzate due varietà: "Tigullio" (a foglia verde) e "Red Rubin" (a foglia rossa). Le analisi hanno riguardato studi legati alla crescita delle diverse varietà e come queste accumulavano il boro nei loro tessuti; sono state anche condotte analisi biochimiche misurando i livelli di clorofille, polifenoli, e antocianine per verificare come effettivamente tale elemento potesse influire sulla loro sintesi. Lo studio si è comunque concentrato sull’influenza del boro nei flussi idrici delle piante e sul quantitativo di acido rosmarinico contenuto nelle foglie, tale metabolita secondario è uno dei più concentrati nel basilico ed è il maggior responsabile delle diverse proprietà terapeutiche di tali piante. Dallo studio è emerso che la crescita viene inibita solo da concentrazioni di B di 10 o più mg/L nella soluzione nutritiva e che questa inibizione è più marcata nella varietà a foglie verde. Non sono state invece osservate differenze importanti nell’assorbimento idrico radicale, nella traspirazione e nella concentrazione fogliare di B, che in alcuni casi è stata leggermente più alta nelle piante di "Red Rubin" rispetto a quelle dell’altra varietà. Per quanto riguarda le analisi biochimiche, in entrambe le varietà non sono stati rilevati effetti importanti dell’eccesso di boro. D’altra parte, il contenuto fogliare di fenoli e di acido rosmarinico è stato assai più alto in "Red Rubin" che in "Tigullio" e questo potrebbe spiegare la maggior tolleranza al boro di questa varietà a foglie rosse . Basil ( Ocimum basilicum L) is an aromatic plant belonging to the family Lamiaceae well known and appreciated for its culinary and herbal purposes in the field , but its potential , however, go far beyond the simple purpose for which it is normally intended . This plant fact can also be used in the fields of pharmaceuticals and beauty as it contains many substances of very interesting from disparate properties : it can be used as anti-inflammatory , antiseptic , tonic , laxative, to soothe insect bites , such as anti-allergic , anti-microbial , anti-oxidant and many other . In this thesis we present and discuss the results of some studies on tolerance to excess boron (B) of sweet basil grown in hydroponics (floating system) with a boron concentration in the nutrient solution of 0,2 , 5 or 20 mg / L. In the various experiments have been used two varieties: "Tigullio" ( leafy green) and "Red Rubin" (red leaf) . The analysis focused on studies related to the growth of the different varieties and how these boron accumulated in their tissues ; biochemical analyzes were also conducted by measuring the levels of chlorophylls, polyphenols, anthocyanins, and to see how this element could actually affect their synthesis. The study , however, focused on the influence of boron in water flows of the plants and on the amount of rosmarinic acid content in the leaves , the secondary metabolite is one of the most concentrated in the basil and it is the most responsible of the different therapeutic properties of these plants. The study found that the growth is inhibited only by concentrations of B of 10 or more mg / L in the nutrient solution and that this inhibition is more marked in green leaved varieties . There are no important differences were observed in the absorption water radical , in transpiration and leaf concentration of B , which in some cases was slightly higher in plants " Red Rubin " compared to those of the other varieties. Concerning biochemical analyzes , in both varieties were not detected important effects of excess boron. On the other hand , the content of leaf phenolics and rosmarinic acid was much higher in "Red Rubin" in "Tigullio" and this could explain the greater tolerance to boron in red leaves of this variety

FeH Absorption in the Near-Infrared Spectra of Late M and L Dwarfs

We present medium-resolution z-, J-, and H-band spectra of four late-type dwarfs with spectral types ranging from M8 to L7.5. In an attempt to determine the origin of numerous weak absorption features throughout their near-infrared spectra, and motivated by the recent tentative identification of the E 4\Pi- A ^4\Pi system of FeH near 1.6 microns in umbral and cool star spectra, we have compared the dwarf spectra to a laboratory FeH emission spectrum. We have identified nearly 100 FeH absorption features in the z-, J-, and H-band spectra of the dwarfs. In particular, we have identified 34 features which dominate the appearance of the H-band spectra of the dwarfs and which appear in the laboratory FeH spectrum. Finally, all of the features are either weaker or absent in the spectrum of the L7.5 dwarf which is consistent with the weakening of the known FeH bandheads in the spectra of the latest L dwarfs.Comment: accepted by Ap

The Unusual Object IC 2144/MWC 778

IC 2144 is a small reflection nebula located in the zone of avoidance near the Galactic anticenter. It has been investigated here largely on the basis of Keck/HIRES optical spectroscopy (R ~ 48,000) and a SpeX spectrogram in the near-IR (R = 2000) obtained at the NASA IRTF. The only star in the nebula that is obvious in the optical or near-IR is the peculiar emission-line object MWC 778 (V = 12.8), which resembles a T Tauri star in some respects. What appear to be F- or G-type absorption features are detectable in its optical region under the very complex emission line spectrum; their radial velocity agrees with the CO velocity of the larger cloud in which IC 2144 is embedded. There are significant differences between the spectrum of the brightest area of the nebula and of MWC 778, the presumed illuminator, an issue discussed in some detail. The distance of IC 2144 is inferred to be about 1.0 kpc by reference to other star-forming regions in the vicinity. The extinction is large, as demonstrated by [Fe II] emission line ratios in the near-IR and by the strength of the diffuse interstellar band spectrum; a provisional value of A_V of 3.0 mag was assumed. The SED of MWC 778 rises steeply beyond about 1 $\mu$m, with a slope characteristic of a Class I source. Integration of the flux distribution leads to an IR luminosity of about 510 L_solar. If MWC 778 is indeed a F- or G-type pre--main-sequence star several magnitudes above the ZAMS, a population of faint emission Halpha stars would be expected in the vicinity. Such a search, like other investigations that are recommended in this paper, has yet to be carried out.Comment: 36 pages, 13 figures, accepted by A