Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDiscovery of a magnetic field in $rho$ Pup
129
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
$rho$ Pup is a $delta$ Scuti F2 pulsator, known to host a main radial mode as well as non-radial pulsations, with chemical peculiarities typical of evolved Am stars. We present high-precision spectropolarimetric observations of this star, obtained with ESPaDOnS at the Canada France Hawaii Telescope (CFHT) in the frame of the BRITE spectropolarimetric survey. A magnetic field is clearly detected in $rho$ Pup, with a longitudinal field strength below 1 G. This makes $rho$ Pup the second known magnetic $delta$ Scuti discovered, after HD 188774, and a possible cool evolved counterpart of the recently discovered ultra-weakly magnetic Am family.
rate research
Read More
Circumstantial evidence suggests that magnetism and enhanced X-ray emission are likely correlated in early B-type stars: similar fractions of them ($sim$ 10 %) are strong and hard X-ray sources and possess strong magnetic fields. It is also known that some B-type stars have spots on their surface. Yet up to now no X-ray activity associated with spots on early-type stars was detected. In this Letter we report the detection of a magnetic field on the B2V star $rho$ Oph A. Previously, we assessed that the X-ray activity of this star is associated with a surface spot, herewith we establish its magnetic origin. We analyzed FORS2 ESO VLT spectra of $rho$ Oph A taken at two epochs and detected a longitudinal component of the magnetic field of order of $sim500$ G in one of the datasets. The detection of the magnetic field only at one epoch can be explained by stellar rotation which is also invoked to explain observed periodic X-ray activity. From archival HARPS ESO VLT high resolution spectra we derived the fundamental stellar parameters of $rho$ Oph A and further constrained its age. We conclude that $rho$ Oph A provides strong evidence for the presence of active X-ray emitting regions on young magnetized early type stars.
We calculate the rho meson mass in a weak magnetic field using effective $rhopipi$ interaction. It is seen that both $rho^0$ and $rho^pm$ masses decrease with the magnetic field in vacuum. $rho$ meson dispersion relation has been calculated and shown to be different for $rho^0$ and $rho^pm$. We also calculate the $rhopipi$ decay width and spectral functions of $rho^0$ and $rho^pm$. The width is seen to decrease with $eB$ and the spectral functions become narrower.
High-resolution spectroscopy is a powerful tool to study the dynamical structure of pulsating stars atmosphere. We aim at comparing the line asymmetry and velocity of the two delta Sct stars rho Pup and DX Cet with previous spectroscopic data obtained on classical Cepheids and beta Cep stars. We obtained, analysed and discuss HARPS high-resolution spectra of rho Pup and DX Cet. We derived the same physical quantities as used in previous studies, which are the first-moment radial velocities and the bi-Gaussian spectral line asymmetries. The identification of f=7.098 (1/d) as a fundamental radial mode and the very accurate Hipparcos parallax promote rho Pup as the best standard candle to test the period-luminosity relations of delta Sct stars. The action of small-amplitude nonradial modes can be seen as well-defined cycle-to-cycle variations in the radial velocity measurements of rho Pup. Using the spectral-line asymmetry method, we also found the centre-of-mass velocities of rho Pup and DX Cet, V_gamma = 47.49 +/- 0.07 km/s and V_gamma = 25.75 +/- 0.06 km/s, respectively. By comparing our results with previous HARPS observations of classical Cepheids and beta Cep stars, we confirm the linear relation between the atmospheric velocity gradient and the amplitude of the radial velocity curve, but only for amplitudes larger than 22.5 km/s. For lower values of the velocity amplitude (i.e., < 22.5 km/s), our data on rho Pup seem to indicate that the velocity gradient is null, but this result needs to be confirmed with additional data. We derived the Baade-Wesselink projection factor p = 1.36 +/- 0.02 for rho Pup and p = 1.39 +/- 0.02 for DX Cet. We successfully extended the period-projection factor relation from classical Cepheids to delta Scuti stars.
Alhena ($gamma$ Gem) was observed in the frame of the BRITE (BRIght Target Explorer) spectropolarimetric survey, which gathers high resolution, high signal-to-noise, high sensitivity, spectropolarimetric observations of all stars brighter than V=4 to combine seismic and spectropolarimetric studies of bright stars. We present here the discovery of a very weak magnetic field textbf{on} the Am star Alhena, thanks to very high signal-to-noise spectropolarimetric data obtained with Narval at Telescope Bernard Lyot (TBL). All previously studied Am stars show the presence of ultra-weak (sub-Gauss) fields with Zeeman signatures with an unexpected prominent positive lobe. However, Alhena presents a slightly stronger (but still very weak, only a few Gauss) field with normal Zeeman signatures with a positive and negative lobe, as found in stronger field (hundreds or thousands of Gauss) stars. It is the first detection of a normal magnetic signature in an Am star. Alhena is thus a very interesting object, which might provide the clue to understanding the peculiar shapes of the magnetic signatures of the other Am stars.
We present the results of a study of the star HD 34736. The spectropolarimetric observations carried out at the 6-m telescope showed the presence of a strong variable longitudinal magnetic field, exceeding -4500 G. The analysis of the HIPPARCOS photometry gives a set of possible periods of the brightness variability of the star, of which 0.3603 days is preferred. The variable radial velocity of spectral lines of the star and some signatures of lines of at least one other component show that HD 34736 is a double short-period system. Modeling of the spectra allowed us to estimate the effective temperature $T_{eff}$ of the stars (13 700 and 11 500 K) and their projected rotational velocities $vsin i$ (73 and $geq90$ km s$^{-1}$). The analysis of all the available information about the star allows us to hypothesize that the object of study is a close, possibly interacting binary system.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
