| 1. |
|
|
| 2. |
- Levesque, E. M., et al.
(författare)
-
THE HIGH-METALLICITY EXPLOSION ENVIRONMENT OF THE RELATIVISTIC SUPERNOVA 2009bb
- 2010
-
Ingår i: The Astrophysical Journal Letters. - 2041-8205. ; 709:1, s. l26-L31
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the environment of the nearby (d approximate to 40 Mpc) broad-lined Type Ic supernova (SN) 2009bb. This event was observed to produce a relativistic outflow likely powered by a central accreting compact object. While such a phenomenon was previously observed only in long-duration gamma-ray bursts (LGRBs), no LGRB was detected in association with SN 2009bb. Using an optical spectrum of the SN 2009bb explosion site, we determine a variety of interstellar medium properties for the host environment, including metallicity, young stellar population age, and star formation rate. We compare the SN explosion site properties to observations of LGRB and broad-lined SN Ic host environments on optical emission line ratio diagnostic diagrams. Based on these analyses, we find that the SN 2009bb explosion site has a metallicity between 1.7 Z(circle dot) and 3.5 Z(circle dot), in agreement with other broad-lined SN Ic host environments and at odds with the low-redshift LGRB host environments and recently proposed maximum metallicity limits for relativistic explosions. We consider the implications of these findings and the impact that SN 2009bb's unusual explosive properties and environment have on our understanding of the key physical ingredient that enables some SNe to produce a relativistic outflow.
|
|
| 3. |
- Soderberg, A. M., et al.
(författare)
-
A relativistic type Ibc supernova without a detected gamma-ray burst
- 2010
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 463:7280, s. 513-515
-
Tidskriftsartikel (refereegranskat)abstract
- Long duration gamma-ray bursts (GRBs) mark(1) the explosive death of some massive stars and are a rare sub-class of type Ibc supernovae. They are distinguished by the production of an energetic and collimated relativistic outflow powered(2) by a central engine (an accreting black hole or neutron star). Observationally, this outflow is manifested(3) in the pulse of gamma-rays and a long-lived radio afterglow. Until now, central-engine driven supernovae have been discovered exclusively through their gamma-ray emission, yet it is expected(4) that a larger population goes undetected because of limited satellite sensitivity or beaming of the collimated emission away from our line of sight. In this framework, the recovery of undetected GRBs may be possible through radio searches(5,6) for type Ibc supernovae with relativistic outflows. Here we report the discovery of luminous radio emission from the seemingly ordinary type Ibc SN 2009bb, which requires a substantial relativistic outflow powered by a central engine. A comparison with our radio survey of type Ibc supernovae reveals that the fraction harbouring central engines is low, about one per cent, measured independently from, but consistent with, the inferred(7) rate of nearby GRBs. Independently, a second mildly relativistic supernova has been reported(8).
|
|
| 4. |
- Soderberg, A. M., et al.
(författare)
-
Discovery of a Relativistic Supernova Without a Gamma-ray Trigger
- 2009
-
Annan publikation (populärvet., debatt m.m.)abstract
- Type Ibc supernovae (SNe Ibc) mark the gravitational collapse of some massive stars (M > 20 Msun) propelling several solar masses of material to typical velocities of ~10,000 km/s. The closely-related but exceedingly rare class of long-duration gamma-ray bursts (GRBs) produce, in addition, a relativistic outflow powered by a central engine (accreting black hole or neutron star) and have been found exclusively through their gamma-ray signal. Here we report the discovery of luminous radio emission from the seemingly ordinary Type Ibc SN 2009bb which outshines that of all other SNe Ibc observed on a comparable timescale. These observations require a substantial mildly-relativistic outflow and indicate that the explosion was powered by a central engine, thus representing the first such event discovered without the aid of a gamma-ray trigger. A comparison with our extensive radio survey of SNe Ibc reveals that the fraction of such events is low (roughly 1 percent), measured independently from, and yet consistent with, the inferred rate of nearby GRBs. This discovery marks the observational realization that long-wavelength surveys will soon rival gamma-ray satellites in pinpointing nearby engine-driven explosions.
|
|
| 5. |
- Chakraborti, Sayan, et al.
(författare)
-
A MISSING-LINK IN THE SUPERNOVA-GRB CONNECTION : THE CASE OF SN 2012ap
- 2015
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 805:2
-
Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray bursts (GRBs) are characterized by ultra-relativistic outflows, while supernovae are generally characterized by non-relativistic ejecta. GRB afterglows decelerate rapidly, usually within days, because their low-mass ejecta rapidly sweep up a comparatively larger mass of circumstellar material. However, supernovae with heavy ejecta can be in nearly free expansion for centuries. Supernovae were thought to have non-relativistic outflows except for a few relativistic ones accompanied by GRBs. This clear division was blurred by SN 2009bb, the first supernova with a relativistic outflow without an observed GRB. However, the ejecta from SN 2009bb was baryon loaded and in nearly free expansion for a year, unlike GRBs. We report the first supernova discovered without a GRB but with rapidly decelerating mildly relativistic ejecta, SN 2012ap. We discovered a bright and rapidly evolving radio counterpart driven by the circumstellar interaction of the relativistic ejecta. However, we did not find any coincident GRB with an isotropic fluence of more than one-sixth of the fluence from GRB 980425. This shows for the first time that central engines in SNe Ic, even without an observed GRB, can produce both relativistic and rapidly decelerating outflows like GRBs.
|
|
| 6. |
- Milisavljevic, Dan, et al.
(författare)
-
MULTI-WAVELENGTH OBSERVATIONS OF SUPERNOVA 2011ei : TIME-DEPENDENT CLASSIFICATION OF TYPE IIb AND Ib SUPERNOVAE AND IMPLICATIONS FOR THEIR PROGENITORS
- 2013
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 767:1, s. 71-
-
Tidskriftsartikel (refereegranskat)abstract
- We present X-ray, UV/optical, and radio observations of the stripped-envelope, core-collapse supernova (SN) 2011ei, one of the least luminous SNe IIb or Ib observed to date. Our observations begin with a discovery within similar to 1 day of explosion and span several months afterward. Early optical spectra exhibit broad, Type II-like hydrogen Balmer profiles that subside rapidly and are replaced by Type Ib-like He-rich features on a timescale of one week. High-cadence monitoring of this transition suggests absorption attributable to a high-velocity (greater than or similar to 12,000 km s(-1)) H-rich shell, which is likely present in many Type Ib events. Radio observations imply a shock velocity of v approximate to 0.13 c and a progenitor star average mass-loss rate of (M) over dot approximate to 1.4 x 10(-5) M-circle dot yr(-1) (assuming wind velocity v(w) = 10(3) km s(-1)). This is consistent with independent constraints from deep X-ray observations with Swift-XRT and Chandra. Overall, the multi-wavelength properties of SN 2011ei are consistent with the explosion of a lower-mass (3-4 M-circle dot), compact (R-* less than or similar to 1 x 10(11) cm), He-core star. The star retained a thin hydrogen envelope at the time of explosion, and was embedded in an inhomogeneous circumstellar wind suggestive of modest episodic mass loss. We conclude that SN 2011ei's rapid spectral metamorphosis is indicative of time-dependent classifications that bias estimates of the relative explosion rates for Type IIb and Ib objects, and that important information about a progenitor star's evolutionary state and mass loss immediately prior to SN explosion can be inferred from timely multi-wavelength observations.
|
|
| 7. |
- Belyaev, A., et al.
(författare)
-
Explanation of the hints for a 95 GeV Higgs boson within a 2-Higgs Doublet Model
- 2024
-
Ingår i: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :5
-
Tidskriftsartikel (refereegranskat)abstract
- We suggest an explanation for and explore the consequences of the excess around 95 GeV in the di-photon and di-tau invariant mass distributions recently reported by the CMS collaboration at the Large Hadron Collider (LHC), together with the discrepancy that has long been observed at the Large Electron-Positron (LEP) collider in the b¯¯b invariant mass. Interestingly, the most recent findings announced by the ATLAS collaboration do not contradict, or even support, these intriguing observations. Their search in the di-photon final state similarly reveals an excess of events within the same mass range, albeit with a bit lower significance, thereby corroborating and somewhat reinforcing the observations made by CMS.We demonstrate that the lightest CP-even Higgs boson in the general 2-Higgs Doublet Model (2HDM) Type-III can explain simultaneously the observed excesses at approximately 1.3 σ C.L. while satisfying up-to-date theoretical and experimental constraints. Moreover, the 2HDM Type-III predicts an excess in the pp→t¯tHSM production channel of the 125 GeV Higgs boson, HSM. This effect is caused by a up to 12% enhancement of the HSMtt Yukawa coupling in comparison to that predicted by the Standard Model. Such an effect can be tested at the High Luminosity LHC (HL-LHC), which can either discover or exclude the scenario we suggest. This unique characteristic of the 2HDM Type-III makes this scenario with the 95 GeV resonance very attractive for further theoretical and experimental investigations at the (HL-)LHC and future colliders.
|
|
| 8. |
|
|
| 9. |
- Chandra, Poonam, et al.
(författare)
-
Radio and x ray observations of sn 2006jd : another strongly interacting type iin supernova
- 2012
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 755:2, s. 110-
-
Tidskriftsartikel (refereegranskat)abstract
- We report four years of radio and X-ray monitoring of the Type IIn supernova SN 2006jd at radio wavelengths with the Very Large Array, Giant Metrewave Radio Telescope, and Expanded Very Large Array; at X-ray wavelengths with Chandra, XMM-Newton, and Swift-XRT. We assume that the radio and X-ray emitting particles are produced by shock interaction with a dense circumstellar medium. The radio emission shows an initial rise that can be attributed to free-free absorption by cool gas mixed into the nonthermal emitting region; external free-free absorption is disfavored because of the shape of the rising light curves and the low gas column density inferred along the line of sight to the emission region. The X-ray luminosity implies a preshock circumstellar density similar to 10(6) cm(-3) at a radius r similar to 2 x 10(16) cm, but the column density inferred from the photoabsorption of X-rays along the line of sight suggests a significantly lower density. The implication may be an asymmetry in the interaction. The X-ray spectrum shows Fe line emission at 6.9 keV that is stronger than is expected for the conditions in the X-ray emitting gas. We suggest that cool gas mixed into the hot gas plays a role in the line emission. Our radio and X-ray data both suggest the density profile is flatter than r(-2) because of the slow evolution of the unabsorbed emission.
|
|
| 10. |
- Brinck, Ingar, et al.
(författare)
-
Cooperation in apes and humans
- 2003
-
Ingår i: On Mind and Consciousness. ; , s. 365-376
-
Konferensbidrag (refereegranskat)abstract
- Human consciousness serves many roles. It helps us imagine, dream, and think rationally. One capacity that human consciousness enables is cooperation. Here, we will focus on the interplay between cooperation and how subjects understand the minds of others. The aim is to compare and elucidate the similarities and differences between humans and apes as concerns cooperative behaviour. One difference can be described with the two terms ‘competitive cooperation’ and ‘collaborative cooperation’. Apes cooperate in competitive contexts, where the resource is available and accessible, but not yet in possession. Humans can as well cooperate in order to achieve something that is not manifest, but mainly desirable. Humans can imagine what is not there, and make their imaginations known to each other. Another difference is that apes cannot represent the goal without the means to reach them. Humans, on the contrary, can reflect about different ways of reaching the goal. Language gives human beings a great advantage in cooperative behaviour, especially in communication about goals and the way to reach them. Another aspect to the difference between humans and apes that concerns a more basic capacity than language-use is joint attention. It is necessary for cooperation for it to be possible for different subjects to attend to a common goal. Apes can engage in joint attention, but do not achieve the same complexity of joint attention as humans. For one thing, they can jointly attend only to things that are present in the context. This makes it difficult to cooperate in order to achieve a goal that is not present or implicated in the immediate environment. An application of our analysis of different kinds of cooperation is game theory. However, cooperative and non-cooperative games, considered in the traditional theory, are only the extremes of the possible levels of cooperation. By taking into account different levels of joint attention and communication, a more fine-grained analysis of different kinds of cooperation in game theory is possible.
|
|
