اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدExtreme Active Molecular Jets in L1448C
38
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The protostellar jet driven by L1448C was observed in the SiO J=8-7 and CO J=3-2 lines and 350 GHz dust continuum at ~1 resolution with the Submillimeter Array (SMA). A narrow jet from the northern source L1448C(N) was observed in the SiO and the high-velocity CO. The jet consists of a chain of emission knots with an inter-knot spacing of ~2 (500 AU) and a semi-periodic velocity variation. The innermost pair of knots, which are significant in the SiO map but barely seen in the CO, are located at ~1 (250 AU) from the central source, L1448C(N). Since the dynamical time scale for the innermost pair is only ~10 yr, SiO may have been formed in the protostellar wind through the gas-phase reaction, or been formed on the dust grain and directly released into the gas phase by means of shocks. It is found that the jet is extremely active with a mechanical luminosity of ~7 L_sun, which is comparable to the bolometric luminosity of the central source (7.5 L_sun). The mass accretion rate onto the protostar derived from the mass-loss rate is ~10^{-5} M_sun/yr. Such a high mass accretion rate suggests that the mass and the age of the central star are 0.03-0.09 M_sun and (4-12)x10^3 yr, respectively, implying that the central star is in the very early stage of protostellar evolution. The low-velocity CO emission delineates two V-shaped shells with a common apex at L1448C(N). The kinematics of these shells are reproduced by the model of a wide opening angle wind. The co-existence of the highly-collimated jets and the wide-opening angle shells can be explained by the unified X-wind model in which highly-collimated jet components correspond to the on-axis density enhancement of the wide-opening angle wind. The CO $J$=3--2 map also revealed the second outflow driven by the southern source L1448C(S) located at ~8.3 (2000 AU) from L1448C(N).
قيم البحث
اقرأ أيضاً
L1448C(N) is a young protostar in Perseus, driving an outflow and an extremely high-velocity (EHV) molecular jet. We present multi-epoch observations of SiO $J = 8-7$, CO $J = 3-2$ lines, and 345 GHz dust continuum toward L1448C(N) in 2006, 2010, and
2017 with the Submillimeter Array. The knots traced by the SiO line show the averaged proper motion is $sim0.06~{rm yr^{-1}}$ and $sim0.04~{rm yr^{-1}}$ for the blue- and red-shifted jet, respectively. The corresponding transverse velocities are $sim78~{rm km s^{-1}}$ (blueshifted) and $sim52~{rm km s^{-1}}$ (redshifted). Together with the radial velocity, we found the inclination angle of the jets from the plane of the sky to be $sim34$deg$ $ for the blueshifted jet and $sim46$deg$ $ for the redfshifted jet. Given the new inclination angles, the mass-loss rate and mechanical power were refined to be $sim1.8times 10^{-6}~M_odot$ and $sim1.3~L_odot$, respectively. In the epoch of 2017, a new knot is detected at the base of the redshifted jet. We found that the mass-loss rate of the new knot is three times higher than the averaged mass-loss rate of the redshifted jet. Besides, continuum flux has enhanced by $sim37%$ between 2010 and 2017. These imply that the variation of the mass-accretion rate by a factor of $sim3$ has occurred in a short timescale of $sim10-20$ yr. In addition, a knot in the downstream of the redshifted jet is found to be dimming over the three epochs.
We aimed to map the jets and outflows from the Serpens South star forming region and find an empirical relationship between the magnetic field and outflow orientation. Near-infrared H2 v=1-0 S(1) 2.122{mu}m -line imaging of the sim 30-long filamentar
y shaped Serpens South star forming region was carried out. K s broadband imaging of the same region was used for continuum subraction. Candidate driving sources of the mapped jets/outflows are identified from the list of known protostars and young stars in this region, which was derived from studies using recent Spitzer and Herschel telescope observations. 14 Molecular Hydrogen emission-line objects(MHOs) are identified using our continuum-subtracted images. They are found to constitute ten individual flows. Out of these, nine flows are located in the lower-half(southern) part of the Serpens South filament, and one flow is located at the northern tip of the filament. Four flows are driven by well-identified Class 0 protostars, while the remaining six flows are driven by candidate protostars mostly in the Class I stage, based on the Spitzer and Herschel observations. The orientation of the outflows is systematically perpendicular to the direction of the near-infrared polarization vector, recently published in the literature. No significant correlation was observed between the orientation of the flows and the axis of the filamentary cloud.
Recent observations in extreme-ultraviolet (EUV) wavelengths reveal a new late phase in some solar flares, which is seen as a second peak in warm coronal emissions ($sim3$ MK) several tens of minutes to a few hours after the soft X-ray (SXR) peak. Th
e origin of the EUV late phase (ELP) is explained by either a long-lasting cooling process in the long ELP loops, or a delayed energy ejection into the ELP loops well after the main flare heating. Using the observations with the emph{Solar Dynamics Observatory} (emph{SDO}), we investigate the production of the ELP in six homologous flares (F1--F6) originating from a complex active region (AR) NOAA 11283, with an emphasis on the emission characteristics of the flares. It is found that the main production mechanism of the ELP changes from additional heating in flare F1 to long-lasting cooling in flares F3--F6, with both mechanisms playing a role in flare F2. The transition is evidenced by an abrupt decrease of the time lag of the ELP peak, and the long-lasting cooling process in the majority of the flares is validated by a positive correlation between the flare ribbon fluence and the ELP peak intensity. We attribute the change in ELP production mechanism to an enhancement of the envelope magnetic field above the AR, which facilitates a more prompt and energetic heating of the ELP loops. In addition, the last and the only confined flare F6 exhibits an extremely large ELP. The different emission pattern revealed in this flare may reflect a different energy partitioning inside the ELP loops, which is due to a different magnetic reconnection process.
We present a multiwavelength analysis of 20 EUV jets which occurred at the periphery of active regions close to sunspots. We discuss the physical parameters of the jets and their relation with other phenomena such as H alpha surges, nonthermal type I
II radio bursts and hard X-ray emission. Using AIA wavelength channels sensitive to coronal temperatures, we studied the temperature distribution in the jets using the line-of-sight Differential Emission Measure technique. We also investigated the role of the photospheric magnetic field using the LOS magnetogram data from the HMI. The lifetime of jets range from 5 to 39 minutes with an average of 18 minutes and their velocities range from 87 to 532 km/s with an average of 271 km/s. Most of the jets are co-temporal with nonthermal type III radio bursts observed by the Wind/WAVES spacecraft. We confirm the source region of these bursts using the Potential Field Source Surface technique. 10 out of 20 events showed that the jets originated in a region of flux cancellation and 6 jets in a region of flux emergence. 4 events showed flux emergence and then cancellation during the jet evolution. DEM analyses showed that for most of the spires of the jets, the DEM peaked at around log T [K] = 6.2/6.3. In addition, we derived an emission measure and a lower limit of electron density at the location of the spire and the footpoint. These results are in agreement with those obtained earlier by studying individual active region jets. The observation of flux cancellation, the association with HXR emission and emission of nonthermal type III radio bursts, suggest that the initiation and therefore, heating is taking place at the base of the jet. This is also supported by the high temperature plasma revealed by the DEM analysis in the jet footpoint. Our results provide substantial constraints for theoretical modeling of the jets and their thermodynamic nature.
We present a formation process of a filament in active region NOAA 12574 during the period from 2016 August 11 to 12. Combining the observations of GONG H$alpha$, Hida spectrum and SDO/AIA 304 A, the formation process of the filament is studied. It i
s found that cool material ($Tsim10^4$ K) is ejected by a series of jets originating from the western foot-point of the filament. Simultaneously, the magnetic flux emerged from the photosphere in the vicinity of the western foot-point of the filament. These observations suggest that cool material in the low atmosphere can be directly injected into the upper atmosphere and the jets are triggered by the magnetic reconnection between pre-existing magnetic fields and new emerging magnetic fields. Detailed study of a jet at 18:02 UT on August 11 with GST/BBSO TiO observations reveals that some dark threads appeared in the vicinity of the western foot-point after the jet and the projection velocity of plasma along the filament axis was about 162.6$pm$5.4 km/s. Using with DST/Hida observations, we find that the injected plasma by a jet at 00:42 UT on August 12 was rotating. Therefore, we conclude that the jets not only supplied the material for the filament, but also injected the helicity into the filament simultaneously. Comparing the quantity of mass injection by the jets with the mass of the filament, we conclude that the estimated mass loading by the jets is sufficient to account for the mass in the filament.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
