| 1. |
- Blagorodnova, N., et al.
(författare)
-
COMMON ENVELOPE EJECTION FOR A LUMINOUS RED NOVA IN M101
- 2017
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 834:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present the results of optical, near-infrared, and mid-infrared observations of M101 OT2015-1 (PSN J14021678+ 5426205), a luminous red transient in the Pinwheel galaxy (M101), spanning a total of 16 years. The light curve showed two distinct peaks with absolute magnitudes M-r <= -12.4 and M-r similar or equal to -12, on 2014 November 11 and 2015 February 17, respectively. The spectral energy distributions during the second maximum show a cool outburst temperature of approximate to 3700 K and low expansion velocities (approximate to -300 km s(-1)) for the H I, Ca II, Ba II, and K I lines. From archival data spanning 15-8 years before the outburst, we find a single source consistent with the optically discovered transient, which we attribute to being the progenitor; it has properties consistent with being an F-type yellow supergiant with L similar to 8.7 x 10(4) L-circle dot, T-eff approximate to 7000. K, and an estimated mass of M1= 18 +/- 1 M-circle dot. This star has likely just finished the H-burning phase in the core, started expanding, and is now crossing the Hertzsprung gap. Based on the combination of observed properties, we argue that the progenitor is a binary system, with the more evolved system overfilling the Roche lobe. Comparison with binary evolution models suggests that the outburst was an extremely rare phenomenon, likely associated with the ejection of the common envelope of a massive star. The initial mass of the primary fills the gap between the merger candidates V838 Mon (5-10 M-circle dot) and NGC. 4490-OT. (30M(circle dot)).
|
|
| 2. |
- Blagorodnova, N., et al.
(författare)
-
iPTF16fnl : A Faint and Fast Tidal Disruption Event in an E plus A Galaxy
- 2017
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 844:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present ground-based and Swift observations of iPTF16fnl, a likely tidal disruption event (TDE) discovered by the intermediate Palomar Transient Factory (iPTF) survey at 66.6 Mpc. The light curve of the object peaked at an absolute mag M-g = -17.2. The maximum bolometric luminosity (from optical and UV) was L-p similar or equal to (1.0 +/- 0.15) x 10(43) erg s(-1), an order of magnitude fainter than any other optical TDE discovered so far. The luminosity in the first 60 days is consistent with an exponential decay, with L proportional to e(-(t-t0)/T), where t(0) = 57631.0 (MJD) and tau similar or equal to 15 days. The X-ray shows a marginal detection at L-X = 2.4(-1.1)(1.9) x 10(39) erg s(-1) (Swift X-ray Telescope). No radio counterpart was detected down to 3s, providing upper limits for monochromatic radio luminosities of nu L-nu < 2.3 x 10(36) erg s(-1) and nLn < 1.7 x 10(37) erg s(-1) (Very Large Array, 6.1 and 22 GHz). The blackbody temperature, obtained from combined Swift UV and optical photometry, shows a constant value of 19,000 K. The transient spectrum at peak is characterized by broad He II and Ha emission lines, with FWHMs of about 14,000 km s(-1) and 10,000 km s(-1), respectively. He. I lines are also detected at lambda lambda 5875 and 6678. The spectrum of the host is dominated by strong Balmer absorption lines, which are consistent with a post-starburst (E+A) galaxy with an age of similar to 650 Myr and solar metallicity. The characteristics of iPTF16fnl make it an outlier on both luminosity and decay timescales, as compared to other optically selected TDEs. The discovery of such a faint optical event suggests a higher rate of tidal disruptions, as low-luminosity events may have gone unnoticed in previous searches.
|
|
| 3. |
- Goobar, Ariel, et al.
(författare)
-
iPTF16geu : A multiply imaged, gravitationally lensed type Ia supernova
- 2017
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 356:6335, s. 291-295
-
Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of a multiply imaged, gravitationally lensed type Ia supernova, iPTF16geu (SN 2016geu), at redshift z = 0.409. This phenomenon was identified because the light from the stellar explosion was magnified more than 50 times by the curvature of space around matter in an intervening galaxy. We used high-spatial-resolution observations to resolve four images of the lensed supernova, approximately 0.3 arc seconds from the center of the foreground galaxy. The observations probe a physical scale of ~1 kiloparsec, smaller than is typical in other studies of extragalactic gravitational lensing. The large magnification and symmetric image configuration imply close alignment between the lines of sight to the supernova and to the lens. The relative magnifications of the four images provide evidence for substructures in the lensing galaxy.
|
|
| 4. |
- Smith, Jay, et al.
(författare)
-
Differential Plantaris-Achilles Tendon Motion : A Sonographic and Cadaveric Investigation
- 2017
-
Ingår i: PM&R. - : ELSEVIER SCIENCE INC. - 1934-1482 .- 1934-1563. ; 9:7, s. 691-698
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Differential motion between the plantaris and Achilles tendons has been hypothesized to contribute to pain in some patients presenting with Achilles tendinopathy. However, objective evidence of differential Achilles-plantaris motion is currently lacking from the literature. Objective: To determine whether differential, multidirectional motion exists between the plantaris tendon (PT) and Achilles tendon (AT) as documented by dynamic ultrasound (US) and postdissection examination in an unembalmed cadaveric model. Design: Prospective, cadaveric laboratory investigation. Setting: Procedural skills laboratory in a tertiary medical center. Subjects: Twenty unembalmed knee-ankle-foot specimens (9 right, 11 left) obtained from 6 male and 10 female donors ages 55-96 years (mean 80 years) with body mass indices of 14.1-33.2 kg/m(2) (mean 22.5 kg/m(2)). Methods: A single, experienced operator used high -resolution dynamic US to qualitatively document differential PT-AT motion during passive ankle dorsifiexion-plantarflexion. Specimens were then dissected and passive dorsiflexion-plantarfiexion was repeated while differential PT-AT motion was visualized directly. Main Outcome Measurements: Presence or absence of multidirectional differential PT-AT motion. Results: All 20 specimens exhibited smooth but variable amplitude multidirectional differential PT-AT motion. Whereas US readily demonstrated medial-lateral and anterior-posterior PT motion relative to the AT, differential longitudinal motion was only appreciated on dissection and direct inspection. Many specimens exhibited partial or complete encasement of the PT between the gastrocnemius portion of the AT and the soleus aponeurosis. Conclusion: Some degree of multidirectional differential PT-AT motion appears to be a normal phenomenon, and PT motion can be evaluated sonographically in both the medial -lateral and anterior-posterior directions. The existence of normal differential PT-AT motion suggests that alterations in PT motion or repetitive stress within the PT-AT interval may produce symptoms in some patients presenting with Achilles region pain syndromes. The PT should be evaluated in all patients presenting with Achilles, plantaris, or calf pain syndromes. Future research would benefit from the development of a sonographic classification system for PT anatomy and motion with the goal of differentiating normal versus pathologic states and identifying risk factors for symptom development.
|
|
| 5. |
- Whitesides, L., et al.
(författare)
-
iPTF 16asu : A Luminous, Rapidly Evolving, and High-velocity Supernova
- 2017
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 851:2
-
Tidskriftsartikel (refereegranskat)abstract
- Wide-field surveys are discovering a growing number of rare transients whose physical origin is not yet well understood. Here we present optical and UV data and analysis of intermediate Palomar Transient Factory (iPTF) 16asu, a luminous, rapidly evolving, high-velocity, stripped-envelope supernova ( SN). With a rest-frame rise time of just four. days and a peak absolute magnitude of M-g = -20.4 mag, the light curve of iPTF 16asu is faster and more luminous than that of previous rapid transients. The spectra of iPTF 16asu show a featureless blue continuum near peak that develops into an SN Ic-BL spectrum on the decline. We show that while the late-time light curve could plausibly be powered by Ni-56 decay, the early emission requires a different energy source. Nondetections in the X-ray and radio strongly constrain the energy coupled to relativistic ejecta to be at most comparable to the class of low-luminosity gamma-ray bursts (GRBs). We suggest that the early emission may have been powered by either a rapidly spinning-down magnetar or by shock breakout in an extended envelope of a very energetic explosion. In either scenario a central engine is required, making iPTF 16asu an intriguing transition object between superluminous SNe, SNe Ic-BL, and low-luminosity GRBs.
|
|
| 6. |
- Yan, Lin, et al.
(författare)
-
Hydrogen-poor Superluminous Supernovae with Late-time H alpha Emission : Three Events From the Intermediate Palomar Transient Factory
- 2017
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 848:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present observations of two new hydrogen-poor superluminous supernovae (SLSN-I), iPTF15esb and iPTF16bad, showing late-time H alpha emission with line luminosities of (1-3) x 10(41) erg s(-1) and velocity widths of (4000-6000) km s(-1). Including the previously published iPTF13ehe, this makes up a total of three such events to date. iPTF13ehe is one of the most luminous and the slowest evolving SLSNe-I, whereas the other two are less luminous and fast decliners. We interpret this as a result of the ejecta running into a neutral H-shell located at a radius of similar to 10(16) cm. This implies that violent mass loss must have occurred several decades before the supernova explosion. Such a short time interval suggests that eruptive mass loss could be common shortly before core collapse, and more importantly helium is unlikely to be completely stripped off the progenitor and could be present in the ejecta. It is a mystery why helium features are not detected, even though nonthermal energy sources, capable of ionizing He, may exist as suggested by the O II absorption series in the early-time spectra. Our late-time spectra (+240 days) appear to have intrinsically lower [O I] 6300 angstrom luminosities than that of SN2015bn and SN2007bi, which is possibly an indication of less oxygen (<10 M-circle dot). The blueshifted H alpha emission relative to the hosts for all three events may be in tension with the binary model proposed for iPTF13ehe. Finally, iPTF15esb has a peculiar light curve (LC) with three peaks separated from one another by similar to 22 days. The LC undulation is stronger in bluer bands. One possible explanation is ejecta-circumstellar medium interaction.
|
|
