ترغب بنشر مسار تعليمي؟ اضغط هنا

[Fe II] emissions associated with the young interacting binary UY Aurige

536   0   0.0 ( 0 )
 نشر من قبل Tae-Soo Pyo
 تاريخ النشر 2014
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

We present high resolution 1.06 -- 1.28 micron spectra toward the interacting binary UY Aur obtained with GEMINI/NIFS and the AO system Altair. We have detected [FeII] $lambda$~1.257 micron and [He I] $lambda$~1.083 micron lines from both UY Aur A (the primary source) and UY Aur B (the secondary). In [Fe II] UY Aur A drives fast and widely opening outflows with an opening angle of ~ 90 degree along a position angle of ~40 degree, while UY Aur B is associated with a redshifted knot. The blueshifted and redshifted emissions show complicated structure between the primary and secondary. The radial velocities of the [Fe II] emission features are similar for UY Aur A and B: ~ -100 km/s for the blueshifted emission and ~ +130 km/s for the red-shifted component. The [He I] line profile observed toward UY Aur A comprises a central emission feature with deep absorptions at both blueshifted and redshifted velocities. These absorption features may be explained by stellar wind models. The [He I] line profile of UY Aur B shows only an emission feature.



قيم البحث

اقرأ أيضاً

We present new K-band spectroscopy of the UY Aur binary star system. Our data are the first to show H$_{2}$ emission in the spectrum of UY Aur A and the first to spectrally resolve the Br{gamma} line in the spectrum of UY Aur B. We see an increase in the strength of the Br{gamma} line in UY Aur A and a decrease in Br{gamma} and H$_{2}$ line luminosity for UY Aur B compared to previous studies. Converting Br{gamma} line luminosity to accretion rate, we infer that the accretion rate onto UY Aur A has increased by $2 times 10^{-9}$ M$_{odot}$ yr$^{-1}$ per year since a rate of zero was observed in 1994. The Br{gamma} line strength for UY Aur B has decreased by a factor of 0.54 since 1994, but the K-band flux has increased by 0.9 mags since 1998. The veiling of UY Aur B has also increased significantly. These data evince a much more luminous disk around UY Aur B. If the lower Br{gamma} luminosity observed in the spectrum of UY Aur B indicates an intrinsically smaller accretion rate onto the star, then UY Aur A now accretes at a higher rate than UY Aur B. However, extinction at small radii or mass pile-up in the circumstellar disk could explain decreased Br{gamma} emission around UY Aur B even when the disk luminosity implies an increased accretion rate. In addition to our scientific results for the UY Aur system, we discuss a dedicated pipeline we have developed for the reduction of echelle-mode data from the ARIES spectrograph.
We analyze radio bursts observed in events with interacting/non-interacting CMEs that produced major SEPs (Ip $>$ 10 MeV) fromApril 1997 to December 2014.We compare properties of meter (m), deca-hectometer (DH) type II as well as DH type III bursts, and time lags for interacting-CME-associated (IC) events and non-interacting-CME-associated (NIC) events. About 70% of radio emissions were observed in events of both types from meters to kilometers. We found high correlations between the drift rates and mid-frequencies of type II radio bursts calculated as the mean geometric between their starting and ending frequencies for both NIC and IC-associated events (Correlation coefficient textit{R}$^{2}$ = 0.98, power-law index $varepsilon$ = 1.68 $pm $ 0.16 and textit{R}$^{2}$ = 0.93, $varepsilon$ = 1.64 $pm $ 0.19 respectively).We also found a correlation between the frequency drift rates of DH type II bursts and space speeds of CMEs in NIC-associated events. The absence of such correlation for IC-associated events confirms that the shock speeds changed in CME--CME interactions. For the events with western source locations, the mean peak intensity of SEPs in IC-associated events is four times larger than that in NIC-associated SEP events. From the mean time lags between the start times of SEP events and the start of m, DH type II, and DH type III radio bursts, we inferred that particle enhancements in NIC-associated SEP events occurred earlier than in IC-associated SEP events. The difference between NIC events and IC events in the mean values of parameters of type II and type III bursts is statistically insignificant.
We investigate the effect of Fe II equivalent width ($W_{2600}$) and fibre size on the average luminosity of [O II]$lambdalambda$3727,3729 nebular emission associated with Mg II absorbers (at $0.55 le z le 1.3$) in the composite spectra of quasars ob tained with 3 and 2 arcsec fibres in the Sloan Digital Sky Survey. We confirm the presence of strong correlations between [O II] luminosity (L$_{[rm O~II]}$) and equivalent width ($W_{2796}$) and redshift of Mg II absorbers. However, we show L$_{[rm O~II]}$ and average luminosity surface density suffers from fibre size effects. More importantly, for a given fibre size the average L$_{[rm O~II]}$ strongly depends on the equivalent width of Fe II absorption lines and found to be higher for Mg II absorbers with $R equiv$ $W_{rm 2600}/W_{rm 2796}$ $ge 0.5$. In fact, we show the observed strong correlations of L$_{[rm O~II]}$ with $W_{2796}$ and $z$ of Mg II absorbers are mainly driven by such systems. Direct [O II] detections also confirm the link between L$_{[rm O~II]}$ and $R$. Therefore, one has to pay attention to the fibre losses and dependence of redshift evolution of Mg II absorbers on $W_{2600}$ before using them as a luminosity unbiased probe of global star formation rate density. We show that the [O II] nebular emission detected in the stacked spectrum is not dominated by few direct detections (i.e., detections $ge 3 sigma$ significant level). On an average the systems with $R$ $ge 0.5$ and $W_{2796}$ $ge 2$ AA are more reddened, showing colour excess E($B-V$) $sim$ 0.02, with respect to the systems with $R$ $< 0.5$ and most likely traces the high H I column density systems.
HD 54236 is a nearby, wide common-proper-motion visual pair that has been previously identified as likely being very young by virtue of strong X-ray emission and lithium absorption. Here we report the discovery that the brighter member of the wide pa ir, HD~54236A, is itself an eclipsing binary (EB), comprising two near-equal solar-mass stars on a 2.4 d orbit. It represents a potentially valuable opportunity to expand the number of benchmark-grade EBs at young stellar ages. Using new observations of Ca2H&K emission and lithium absorption in the wide K-dwarf companion, HD 54236B, we obtain a robust age estimate of 225 +/- 50 Myr for the system. This age estimate and Gaia proper motions show HD 54236 is associated with Theia~301, a newly discovered local stellar string, which itself may be related to the AB Dor moving group through shared stellar members. Applying this age estimate to AB~Dor itself alleviates reported tension between observation and theory that arises for the luminosity of the 90M_Jup star/brown dwarf AB Dor C when younger age estimates are used.
Coronal mass ejections (CMEs) are large-scale eruptions of magnetized plasma that may cause severe geomagnetic storms if Earth-directed. Here we report a rare instance with comprehensive in situ and remote sensing observa- tions of a CME combining wh ite-light, radio, and plasma measurements from four different vantage points. For the first time, we have successfully applied a radio direction-finding technique to an interplanetary type II burst detected by two identical widely separated radio receivers. The derived locations of the type II and type III bursts are in general agreement with the white light CME recon- struction. We find that the radio emission arises from the flanks of the CME, and are most likely associated with the CME-driven shock. Our work demon- strates the complementarity between radio triangulation and 3D reconstruction techniques for space weather applications.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا