We report velocity-delay maps for prominent broad emission lines, Ly_alpha, CIV, HeII and H_beta, in the spectrum of NGC5548. The emission-line responses inhabit the interior of a virial envelope. ...The velocity-delay maps reveal stratified ionization structure. The HeII response inside 5-10 light-days has a broad single-peaked velocity profile. The Ly_alpha, CIV, and H_beta responses peak inside 10 light-days, extend outside 20 light-days, and exhibit a velocity profile with two peaks separated by 5000 km/s in the 10 to 20 light-day delay range. The velocity-delay maps show that the M-shaped lag vs velocity structure found in previous cross-correlation analysis is the signature of a Keplerian disk with a well-defined outer edge at R=20 light-days. The outer wings of the M arise from the virial envelope, and the U-shaped interior of the M is the lower half of an ellipse in the velocity-delay plane. The far-side response is weaker than that from the near side, so that we see clearly the lower half, but only faintly the upper half, of the velocity--delay ellipse. The delay tau=(R/c)(1-sin(i))=5 light-days at line center is from the near edge of the inclined ring, giving the inclination i=45 deg. A black hole mass of M=7x10^7 Msun is consistent with the velocity-delay structure. A barber-pole pattern with stripes moving from red to blue across the CIV and possibly Ly_alpha line profiles suggests the presence of azimuthal structure rotating around the far side of the broad-line region and may be the signature of precession or orbital motion of structures in the inner disk. Further HST observations of NGC 5548 over a multi-year timespan but with a cadence of perhaps 10 days rather than 1 day could help to clarify the nature of this new AGN phenomenon.
Hypervelocity stars (HVS) move so fast that they are unbound to the Galaxy. When they were first discovered in 2005, dynamical ejection from the supermassive black hole (SMBH) in the Galactic Centre ...(GC) was suggested as their origin. The two dozen HVSs known today are young massive B stars, mostly of 3-4 solar masses. Recently, 20 HVS candidates of low mass were discovered in the Segue G and K dwarf sample, but none of them originates from the GC. We embarked on a kinematic analysis of the Segue HVS candidate sample using the full 6D phase space information based on new proper motion measurements. Their orbital properties can then be derived by tracing back their trajectories in different mass models of our Galaxy. We present the results for 14 candidate HVSs, for which proper motion measurements were possible. Significantly lower proper motions than found in the previous study were derived. Considering three different Galactic mass models we find that all stars are bound to the Galaxy. We confirm that the stars do not originate from the GC. The distribution of their proper motions and radial velocities is consistent with predictions for runaway stars ejected from the Galactic disk by the binary supernova mechanism. However, their kinematics are also consistent with old disk membership. Moreover, most stars have rather low metallicities and strong \(\alpha\)-element enrichment as typical for thick disk and halo stars, whereas the metallicity of the three most metal-rich stars could possibly indicate that they are runaway stars from the thin disk. One star shows halo kinematics.
We report the discovery of three stars that, along with the prototype LP40-365, form a distinct class of chemically peculiar runaway stars that are the survivors of thermonuclear explosions. ...Spectroscopy of the four confirmed LP 40-365 stars finds ONe-dominated atmospheres enriched with remarkably similar amounts of nuclear ashes of partial O- and Si-burning. Kinematic evidence is consistent with ejection from a binary supernova progenitor; at least two stars have rest-frame velocities indicating they are unbound to the Galaxy. With masses and radii ranging between 0.20-0.28 Msun and 0.16-0.60 Rsun, respectively, we speculate these inflated white dwarfs are the partly burnt remnants of either peculiar Type Iax or electron-capture supernovae. Adopting supernova rates from the literature, we estimate that ~20 LP40-365 stars brighter than 19 mag should be detectable within 2 kpc from the Sun at the end of the Gaia mission. We suggest that as they cool, these stars will evolve in their spectroscopic appearance, and eventually become peculiar O-rich white dwarfs. Finally, we stress that the discovery of new LP40-365 stars will be useful to further constrain their evolution, supplying key boundary conditions to the modelling of explosion mechanisms, supernova rates, and nucleosynthetic yields of peculiar thermonuclear explosions.
Hot subdwarf B stars (sdBs) are evolved core helium-burning stars with very thin hydrogen envelopes. In order to form an sdB, the progenitor has to lose almost all of its hydrogen envelope right at ...the tip of the red giant branch. In binary systems, mass transfer to the companion provides the extraordinary mass loss required for their formation. However, apparently single sdBs exist as well and their formation is unclear since decades. The merger of helium white dwarfs leading to an ignition of core helium-burning or the merger of a helium core and a low mass star during the common envelope phase have been proposed. Here we report the discovery of EC 22081-1916 as a fast rotating, single sdB star of low gravity. Its atmospheric parameters indicate, that the hydrogen envelope must be unusually thick, which is at variance with the He-WD merger scenario, but consistent with a common envelope merger of a low-mass, possibly substellar object with a red-giant core.
A&A 576, A65 (2015) The intermediate Helium subdwarf B star LS IV$-$14$^\circ$116 is a unique
object showing extremely peculiar atmospheric abundances as well as long-period
pulsations that cannot be ...explained in terms of the usual opacity mechanism.
One hypothesis invoked was that a strong magnetic field may be responsible. We
discredit this possibility on the basis of FORS2 spectro-polarimetry, which
allows us to rule out a mean longitudinal magnetic field down to 300 G.
Using the same data, we derive the atmospheric parameters for LS
IV$-$14$^\circ$116 to be $T_{\rm eff}$ = 35,150$\pm$111 K, $\log{g}$ =
5.88$\pm$0.02 and $\log{N(\rm He)/N(\rm H)}$ = $-$0.62$\pm$0.01. The high
surface gravity in particular is at odds with the theory that LS
IV$-$14$^\circ$116 has not yet settled onto the Helium Main Sequence, and that
the pulsations are excited by an $\epsilon$ mechanism acting on the
Helium-burning shells present after the main Helium flash.
Archival UVES spectroscopy reveals LS IV$-$14$^\circ$116 to have a radial
velocity of 149.1$\pm$2.1 km/s. Running a full kinematic analysis, we find that
it is on a retrograde orbit around the Galactic centre, with a Galactic radial
velocity component $U$=13.23$\pm$8.28 km/s and a Galactic rotational velocity
component $V$=$-$55.56$\pm$22.13 km/s. This implies that LS IV$-$14$^\circ$116
belongs to the halo population, an intriguing discovery.
AIMS: We selected the bluest object, WISE~J0725\(-\)2351, from Luhman's new high proper motion (HPM) survey based on observations with the Wide-field Infrared Survey Explorer (WISE) for spectroscopic ...follow-up observations. Our aim was to unravel the nature of this relatively bright ($V$$\sim\(12, \)J$$\sim\(11) HPM star (\)\mu$$=\(267\,mas/yr). METHODS: We obtained low- and medium-resolution spectra with the European Southern Observatory (ESO) New Technology Telescope (NTT)/EFOSC2 and Very Large Telescope (VLT)/XSHOOTER instruments, investigated the radial velocity and performed a quantitative spectral analysis that allowed us to determine physical parameters. The fit of the spectral energy distribution based on the available photometry to low-metallicity model spectra and the similarity of our target to a metal-poor benchmark star (HD~84937) allowed us to estimate the distance and space velocity. RESULTS: As in the case of HD~84937, we classified WISE~J0725\)-\(2351 as sdF5: or a metal-poor turnoff star with \)Fe/H$$=$$-\(2.0\)\pm\(0.2, \)T_{eff}$$=\(6250\)\pm\(100\,K, \)\log{g}$$=\(4.0\)\pm\(0.2, and a possible age of about 12\,Gyr. At an estimated distance of more than 400\,pc, its proper motion translates to a tangential velocity of more than 500\,km/s. Together with its constant (on timescales of hours, days, and months) and large radial velocity (about \)+$240\,km/s), the resulting Galactic restframe velocity is about 460\,km/s, implying a bound retrograde orbit for this extreme halo object that currently crosses the Galactic plane at high speed.
A patient was studied who had posttraumatic epilepsy with adversive, psychomotor, and grand mal seizures. During tele-EEG recording from depth electrodes, 4 psychomotor seizures were accompanied by ...discharge originating in the frontal lobe. The patient sometimes could recall his behavior and believed it to be voluntary. Amnesia was more apt to be total after the seizure than during it.
Refractory acute lymphoblastic leukemia (ALL) is often incurable, and relapse rates following allogeneic bone marrow transplantation (BMT) remain high. We have reported that patients who develop ...increased numbers of gamma delta super(+) T cells soon after BMT are significantly less likely to relapse. We now show in seven donor/recipient pairs that donor-derived V delta 1 super(+)CD4 super(-)CD8 super(-) gamma delta super(+) T cells are activated and proliferate in response to recipient primary ALL blasts. In addition, these cells have been shown to bind and lyse the recipient ALL blasts. Separately, gamma delta super(+) T cells proliferate poorly or not at all in mixed lymphocyte culture against HLA-mismatched unrelated stimulator cells. These observations suggest that allogeneic gamma delta super(+) T cells could be an effective immunotherapeutic strategy against refractory disease without the risk of graft-versus-host disease.
Refractory acute lymphoblastic leukemia (ALL) is often incurable, and relapse rates following allogeneic bone marrow transplantation (BMT) remain high. We have reported that patients who develop ...increased numbers of gammadelta(+) T cells soon after BMT are significantly less likely to relapse. We now show in seven donor/recipient pairs that donor-derived Vdelta1(+)CD4(-)CD8(-)gammadelta(+) T cells are activated and proliferate in response to recipient primary ALL blasts. In addition, these cells have been shown to bind and lyse the recipient ALL blasts. Separately, gammadelta(+) T cells proliferate poorly or not at all in mixed lymphocyte culture against HLA-mismatched unrelated stimulator cells. These observations suggest that allogeneic gammadelta(+) T cells could be an effective immunotherapeutic strategy against refractory disease without the risk of graft-versus-host disease.
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