213 research outputs found
Second bound state of PsH
The existence of a second bound state of PsH that is electronically stable
and also stable against positron annihilation by the normal 2gamma and 3gamma
processes is demonstrated by explicit calculation. The state can be found in
the 2,4So symmetries with the two electrons in a spin triplet state. The
binding energy against dissociation into the H(2p) + Ps(2p) channel was
6.06x10-4 Hartree. The dominant decay mode of the states will be radiative
decay into a configuration that autoionizes or undergoes positron annihilation.
The NaPs system of the same symmetry is also electronically stable with a
binding energy of 1.553x10-3 Hartree with respect to the Na(3p) + Ps(2p)
channel.Comment: 4 pages, 2 figures, RevTex styl
MUSE Reveals a Recent Merger in the Post-starburst Host Galaxy of the TDE ASASSN-14li
We present MUSE integral field spectroscopic observations of the host galaxy
(PGC 043234) of one of the closest (, Mpc) and
best-studied tidal disruption events (TDE), ASASSN-14li. The MUSE integral
field data reveal asymmetric and filamentary structures that extend up to
kpc from the post-starburst host galaxy of ASASSN-14li. The
structures are traced only through the strong nebular [O III] 5007, [N
II] 6584, and H emission lines. The total off nuclear [O III]
5007 luminosity is luminosity is erg s and
the ionized H mass is . Based on the BPT
diagram, the nebular emission can be driven by either AGN photoionization or
shock excitation, with AGN photoionization favored given the narrow intrinsic
line widths. The emission line ratios and spatial distribution strongly
resemble ionization nebulae around fading AGNs such as IC 2497 (Hanny's
Voorwerp) and ionization "cones" around Seyfert 2 nuclei. The morphology of the
emission line filaments strongly suggest that PGC 043234 is a recent merger,
which likely triggered a strong starburst and AGN activity leading to the
post-starburst spectral signatures and the extended nebular emission line
features we see today. We briefly discuss the implications of these
observations in the context of the strongly enhanced TDE rates observed in
post-starburst galaxies and their connection to enhanced theoretical TDE rates
produced by supermassive black-hole binaries.Comment: Accepted for publication in ApJ
The Architecture of the GW Ori Young Triple Star System and Its Disk: Dynamical Masses, Mutual Inclinations, and Recurrent Eclipses
We present spatially and spectrally resolved Atacama Large
Millimeter/submillimeter Array (ALMA) observations of gas and dust orbiting the
pre-main sequence hierarchical triple star system GW Ori. A forward-modeling of
the CO and CO =2-1 transitions permits a measurement of
the total stellar mass in this system, , and the
circum-triple disk inclination, . Optical spectra spanning
a 35 year period were used to derive new radial velocities and, coupled with a
spectroscopic disentangling technique, revealed that the A and B components of
GW Ori form a double-lined spectroscopic binary with a day
period; a tertiary companion orbits that inner pair with a day
period. Combining the results from the ALMA data and the optical spectra with
three epochs of astrometry in the literature, we constrain the individual
stellar masses in the system (,
, ) and
find strong evidence that at least one (and likely both) stellar orbital planes
are misaligned with the disk plane by as much as . A -band light
curve spanning 30 years reveals several new 30 day eclipse events
0.1-0.7~mag in depth and a 0.2 mag sinusoidal oscillation that is clearly
phased with the AB-C orbital period. Taken together, these features suggest
that the A-B pair may be partially obscured by material in the inner disk as
the pair approaches apoastron in the hierarchical orbit. Lastly, we conclude
that stellar evolutionary models are consistent with our measurements of the
masses and basic photospheric properties if the GW Ori system is 1 Myr
old.Comment: 26 pages, 15 figures, accepted to Ap
The Young and Bright Type Ia Supernova ASASSN-14lp: Discovery, Early-Time Observations, First-Light Time, Distance to NGC 4666, and Progenitor Constraints
On 2014 Dec. 9.61, the All-Sky Automated Survey for SuperNovae (ASAS-SN or
"Assassin") discovered ASASSN-14lp just days after first light using a
global array of 14-cm diameter telescopes. ASASSN-14lp went on to become a
bright supernova ( mag), second only to SN 2014J for the year. We
present prediscovery photometry (with a detection less than a day after first
light) and ultraviolet through near-infrared photometric and spectroscopic data
covering the rise and fall of ASASSN-14lp for more than 100 days. We find that
ASASSN-14lp had a broad light curve (), a
-band maximum at , a rise time of days, and moderate host--galaxy extinction (). Using ASASSN-14lp we derive a distance modulus for NGC 4666 of
corresponding to a distance of Mpc.
However, adding ASASSN-14lp to the calibrating sample of Type Ia supernovae
still requires an independent distance to the host galaxy. Finally, using our
early-time photometric and spectroscopic observations, we rule out red giant
secondaries and, assuming a favorable viewing angle and explosion time, any
non-degenerate companion larger than .Comment: 12 pages, 9 figures, 4 tables. Accepted to ApJ. Photometric data
presented in this submission are included as an ancillary file. For a brief
video explaining this paper, see https://www.youtube.com/watch?v=1bOV-Cqs-a
ASASSN-15lh: A Highly Super-Luminous Supernova
We report the discovery of ASASSN-15lh (SN 2015L), which we interpret as the
most luminous supernova yet found. At redshift z = 0.2326, ASASSN-15lh reached
an absolute magnitude of M_{u,AB} = -23.5+/-0.1 and bolometric luminosity L_bol
= (2.2+/-0.2)x 10^45 ergs s^-1, which is more than twice as luminous as any
previously known supernova. It has several major features characteristic of the
hydrogen-poor super-luminous supernovae (SLSNe-I), whose energy sources and
progenitors are currently poorly understood. In contrast to most previously
known SLSNe-I that reside in star-forming dwarf galaxies, ASASSN-15lh appears
to be hosted by a luminous galaxy (M_K ~ -25.5) with little star formation. In
the 4 months since first detection, ASASSN-15lh radiated (1.1+/- 0.2)x10^52
ergs, challenging the magnetar model for its engine.Comment: Published in the January 15, 2016 Issue of Science Magazin
Six Months of Multi-Wavelength Follow-up of the Tidal Disruption Candidate ASASSN-14li and Implied TDE Rates from ASAS-SN
We present ground-based and Swift photometric and spectroscopic observations
of the candidate tidal disruption event (TDE) ASASSN-14li, found at the center
of PGC 043234 ( Mpc) by the All-Sky Automated Survey for SuperNovae
(ASAS-SN). The source had a peak bolometric luminosity of ergs
s and a total integrated energy of ergs radiated
over the months of observations presented. The UV/optical emission of
the source is well-fit by a blackbody with roughly constant temperature of
K, while the luminosity declines by roughly a factor of 16 over
this time. The optical/UV luminosity decline is broadly consistent with an
exponential decline, , with days.
ASASSN-14li also exhibits soft X-ray emission comparable in luminosity to the
optical and UV emission but declining at a slower rate, and the X-ray emission
now dominates. Spectra of the source show broad Balmer and helium lines in
emission as well as strong blue continuum emission at all epochs. We use the
discoveries of ASASSN-14li and ASASSN-14ae to estimate the TDE rate implied by
ASAS-SN, finding an average rate of
per galaxy with a 90% confidence interval of per galaxy. ASAS-SN found roughly 1 TDE for every 70 Type Ia
supernovae in 2014, a rate that is much higher than that of other surveys.Comment: 21 pages, 9 figures, 6 tables. Photometric data presented in this
submission are included as ancillary files. Manuscript updated to reflect
changes made in the published version. For a brief video explaining this
paper, see https://youtu.be/CTbr-d7cWZ
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