Analysis and test of the central-blue-spot infall hallmark

The infall of material onto a protostar, in the case of optically thick line emission, produces an asymmetry in the blue- and red-wing line emission. For an angularly resolved emission, this translates in a blue central spot in the first-order moment (intensity weighted velocity) map. An analytical expression for the first-order moment intensity as a function of the projected distance was derived, for the cases of infinite and finite infall radius. The effect of a finite angular resolution, which requires the numerical convolution with the beam, was also studied. This method was applied to existing data of several star-forming regions, namely G31.41+0.31 HMC, B335, and LDN 1287, obtaining good fits to the first-order moment intensity maps, and deriving values of the central masses onto which the infall is taking place (G31.41+0.31 HMC: 70-120 $M_\odot$; B335: 0.1 $M_\odot$; Guitar Core of LDN 1287: 4.8 $M_\odot$). The central-blue-spot infall hallmark appears to be a robust and reliable indicator of infall.Comment: Accepted for publication in A&

A planetary system with gas giants and super-Earths around the nearby M dwarf GJ676A : Optimizing data analysis techniques for the detection of multi-planetary systems

G. Anglada-Escude and M. Tuomi, 'A planetary system via gas giants and super-Earths around the nearby M dwarf GJ 676A: Optimizing data analysis techniques for the detection of multi-planetary systems', Astronomy & Astrophysics, Vol. 548, A58 (2012). The version of record is available online at DOI: 10.1051/0004-6361/201219910 © ESO 2012 Published by EDP SciencesContext. Several M dwarfs are targets of systematical monitoring in searches for Doppler signals caused by low-mass exoplanet companions. As a result, an emerging population of high-multiplicity planetary systems around low-mass stars are being detected as well. Aims. We optimize classic data analysis methods and develop new ones to enhance the sensitivity towards lower amplitude planets in high-multiplicity systems. We apply these methods to the public HARPS observations of GJ≠676A, a nearby and relatively quiet M dwarf with one reported gas giant companion. Methods. We rederived Doppler measurements from public HARPS spectra using the recently developed template matching method (HARPS-TERRA software). We used refined versions of periodograms to assess the presence of additional low-mass companions. We also analysed the same dataset with Bayesian statistics tools and compared the performance of both approaches. Results. We confirm the already reported massive gas giant candidate and a long period trend in the Doppler measurements. In addition to that, we find very secure evidence in favour of two new candidates in close-in orbits and masses in the super-Earth mass regime. Also, the increased time-span of the observations allows the detection of curvature in the long-period trend. suggesting the presence of a massive outer companion whose nature is still unclear. Conclusions. Despite the increased sensitivity of our new periodogram tools, we find that Bayesian methods are significantly more sensitive and reliable in the early detection of candidate signals, but more work is needed to quantify their robustness against false positives. While hardware development is important in increasing the Doppler precision, development of data analysis techniques can help to reveal new results from existing data sets with significantly fewer resources. This new system holds the record of minimum-mass range (from Msini ~ 4.5 M⊕ to 5 Mjup) and period range (from P ~ 3.6 days to more than 10 years). Although all planet candidates are substantially more massive, it is the first exoplanetary system with a general architecture similar to our solar system. GJ 676A can be happily added to the family of high-multiplicity planetary systems around M dwarfs.Peer reviewe

The Radio Jet Associated with the Multiple V380 Ori System

The giant Herbig-Haro object 222 extends over $\sim$6$'$ in the plane of the sky, with a bow shock morphology. The identification of its exciting source has remained uncertain over the years. A non-thermal radio source located at the core of the shock structure was proposed to be the exciting source. However, Very Large Array studies showed that the radio source has a clear morphology of radio galaxy and a lack of flux variations or proper motions, favoring an extragalactic origin. Recently, an optical-IR study proposed that this giant HH object is driven by the multiple stellar system V380 Ori, located about 23$'$ to the SE of HH 222. The exciting sources of HH systems are usually detected as weak free-free emitters at centimeter wavelengths. Here we report the detection of an elongated radio source associated with the Herbig Be star or with its close infrared companion in the multiple V380 Ori system. This radio source has the characteristics of a thermal radio jet and is aligned with the direction of the giant outflow defined by HH~222 and its suggested counterpart to the SE, HH~1041. We propose that this radio jet traces the origin of the large scale HH outflow. Assuming that the jet arises from the Herbig Be star, the radio luminosity is a few times smaller than the value expected from the radio-bolometric correlation for radio jets, confirming that this is a more evolved object than those used to establish the correlation.Comment: 13 pages, 3 figure

Evidence of a massive planet candidate orbiting the young active K5V star BD+20 1790

Original article can be found at: http://www.aanda.org/ Copyright The European Southern Observatory (ESO). DOI: 10.1051/0004-6361/200811000Context. BD+20 1790 is a young active, metal-rich, late-type K5Ve star. We have undertaken a study of stellar activity and kinematics for this star over the past few years. Previous results show a high level of stellar activity, with the presence of prominence-like structures, spots on the surface, and strong flare events, despite the moderate rotational velocity of the star. In addition, radial velocity variations with a semi-amplitude of up to 1 km s-1 were detected. Aims. We investigate the nature of these radial velocity variations, in order to determine whether they are due to stellar activity or the reflex motion of the star induced by a companion. Methods. We have analysed high-resolution echelle spectra by measuring stellar activity indicators and computing radial velocity (RV) and bisector velocity spans. Two-band photometry was also obtained to produce the light curve and determine the photometric period. Results. Based upon the analysis of the bisector velocity span, as well as spectroscopic indices of chromospheric indicators, Ca ii H & K, Hα, and taking the photometric analysis into account, we report that the best explanation for the RV variation is the presence of a substellar companion. The Keplerian fit of the RV data yields a solution for a close-in massive planet with an orbital period of 7.78 days. The presence of the close-in massive planet could also be an interpretation for the high level of stellar activity detected. Since the RV data are not part of a planet search programme, we can consider our results as a serendipitous evidence of a planetary companion. To date, this is the youngest main sequence star for which a planetary candidate has been reported.Peer reviewe

AD Leonis: Radial Velocity Signal of Stellar Rotation or Spin–Orbit Resonance?

AD Leonis is a nearby magnetically active M dwarf. We find Doppler variability with a period of 2.23 days, as well as photometric signals: (1) a short-period signal, which is similar to the radial velocity signal, albeit with considerable variability; and (2) a long-term activity cycle of 4070 ± 120 days. We examine the short-term photometric signal in the available All-Sky Automated Survey and Microvariability and Oscillations of STars (MOST) photometry and find that the signal is not consistently present and varies considerably as a function of time. This signal undergoes a phase change of roughly 0.8 rad when considering the first and second halves of the MOST data set, which are separated in median time by 3.38 days. In contrast, the Doppler signal is stable in the combined High-Accuracy Radial velocity Planet Searcher and High Resolution Echelle Spectrometer radial velocities for over 4700 days and does not appear to vary in time in amplitude, phase, period, or as a function of extracted wavelength. We consider a variety of starspot scenarios and find it challenging to simultaneously explain the rapidly varying photometric signal and the stable radial velocity signal as being caused by starspots corotating on the stellar surface. This suggests that the origin of the Doppler periodicity might be the gravitational tug of a planet orbiting the star in spin–orbit resonance. For such a scenario and no spin–orbit misalignment, the measured v sin i indicates an inclination angle of 15°̣5 ± 2°̣5 and a planetary companion mass of 0.237 ± 0.047 M Jup