Stars In Scorpius Research Articles

Angular Momentum Evolution of Young Stars in the nearby Scorpius–Centaurus OB Association

Abstract We report the results of a study of archival SuperWASP light curves for stars in Scorpius–Centaurus (Sco–Cen), the nearest OB association. We use SuperWASP time-series photometry to extract rotation periods for 189 candidate members of the Sco–Cen complex and verify that 162 of those are members of the classic Sco–Cen subgroups of Upper Scorpius (US), Upper Centaurus-Lupus (UCL), and Lower Centaurus-Crux (LCC). This study provides the first measurements of rotation periods explicitly for large samples of pre-main-sequence (pre-MS) stars spanning the UCL and LCC subgroups. Our final sample of 157 well-characterized pre-MS stars spans ages of ∼10–20 Myr, spectral types of ∼F3–M0, and masses of M ≃ 0.3–1.5  ⊙ N . For this sample, we find a distribution of stellar rotation periods with a median of P rot ≃ 2.4 days, an overall range of 0.2 < P rot < 8 days, and a fairly well-defined mass-dependent upper envelope of rotation periods. This distribution of periods is consistent with recently developed stellar angular momentum evolution models. These data are significant because they represent an undersampled age range and the number of measurable rotation periods is large compared to recent studies of other regions. We also search for new examples of eclipsing disk or ring systems analogous to 1SWASP J140747.93-394542.6 (J1407), but find none. Our survey yielded five eclipsing binaries, but only one appears to be physically associated with the Sco–Cen complex. V2394 Oph is a heavily reddened (A V ≃ 5 mag) massive contact binary in the LDN 1689 cloud whose Gaia astrometry is clearly consistent with kinematic membership with the Ophiuchus star-forming region.

AHerschelPACS survey of the dust and gas in Upper Scorpius disks

We present results of far-infrared photometric observations with Herschel PACS of a sample of Upper Scorpius stars, with a detection rate of previously known disk-bearing K and M stars at 70, 100, and 160 micron of 71%, 56%, and 50%, respectively. We fit power-law disk models to the spectral energy distributions of K & M stars with infrared excesses, and have found that while many disks extend in to the sublimation radius, the dust has settled to lower scale heights than in disks of the less evolved Taurus-Auriga population, and have much reduced dust masses. We also conducted Herschel PACS observations for far-infrared line emission and JCMT observations for millimeter CO lines. Among B and A stars, 0 of 5 debris disk hosts exhibit gas line emission, and among K and M stars, only 2 of 14 dusty disk hosts are detected. The OI 63 micron and CII 157 micron lines are detected toward [PZ99] J160421.7-213028 and [PBB2002] J161420.3-190648, which were found in millimeter photometry to host two of the most massive dust disks remaining in the region. Comparison of the OI line emission and 63 micron continuum to that of Taurus sources suggests the emission in the former source is dominated by the disk, while in the other there is a significant contribution from a jet. The low dust masses found by disk modeling and low number of gas line detections suggest that few stars in Upper Scorpius retain sufficient quantities of material for giant planet formation. By the age of Upper Scorpius, giant planet formation is essentially complete.

Time-resolved multicolour photometry of bright B-type variable stars in Scorpius

The first two of a total of six nano-satellites that will constitute the BRITE-Constellation space photometry mission have recently been launched successfully. In preparation for this project, we carried out time-resolved colour photometry in a field that is an excellent candidate for BRITE measurements from space. We acquired 117 h of Stromgren uvy data during 19 nights. Our targets comprised the Beta Cephei stars Kappa and Lambda Sco, the eclipsing binary Mu 1 Sco, and the variable super/hypergiant Zeta 1 Sco. For Kappa Sco, a photometric mode identification in combination with results from the spectroscopic literature suggests a dominant (l, m) = (1, -1) Beta Cephei-type pulsation mode of the primary star. The longer period of the star may be a rotational variation or a g-mode pulsation. For Lambda Sco, we recover the known dominant Beta Cephei pulsation, a longer-period variation, and observed part of an eclipse. Lack of ultraviolet data precludes mode identification for this star. We noticed that the spectroscopic orbital ephemeris of the closer pair in this triple system is inconsistent with eclipse timings and propose a refined value for the orbital period of the closer pair of 5.95189 +/- 0.00003 d. We also argue that the components of the Lambda Sco system are some 30% more massive than previously thought. The binary light curve solution of Mu 1 Sco requires inclusion of the irradiation effect to explain the u light curve, and the system could show additional low amplitude variations on top of the orbital light changes. Zeta 1 Sco shows long-term variability on a time scale of at least two weeks that we prefer to interpret in terms of a variable wind or strange mode pulsations.

A THERMAL INFRARED IMAGING STUDY OF VERY LOW MASS, WIDE-SEPARATION BROWN DWARF COMPANIONS TO UPPER SCORPIUS STARS: CONSTRAINING CIRCUMSTELLAR ENVIRONMENTS

We present a 3-5um LBT/MMT adaptive optics imaging study of three Upper Scorpius stars with brown dwarf (BD) companions with very low-masses/mass ratios (M_BD < 25M_Jup; M_BD / M_star ~ 1-2%), and wide separations (300-700 AU): GSC 06214, 1RXS 1609, and HIP 78530. We combine these new thermal IR data with existing 1-4um and 24um photometry to constrain the properties of the BDs and identify evidence for circumprimary/secondary disks in these unusual systems. We confirm that GSC 06214B is surrounded by a disk, further showing this disk produces a broadband IR excess due to small dust near the dust sublimation radius. An unresolved 24um excess in the system may be explained by the contribution from this disk. 1RXS 1609B exhibits no 3-4um excess, nor does its primary; however, the system as a whole has a modest 24um excess, which may come from warm dust around the primary and/or BD. Neither object in the HIP 78530 system exhibits near- to mid-IR excesses. We additionally find that the 1-4um colors of HIP 78530B match a spectral type of M3+-2, inconsistent with the M8 spectral type assigned based on its near-IR spectrum, indicating it may be a low-mass star rather than a BD. We present new upper limits on additional low-mass companions in the system (<5M_Jup beyond 175AU). Finally, we examine the utility of circumsecondary disks as probes of the formation histories of wide BD companions, finding that the presence of a disk may disfavor BD formation near the primary with subsequent outward scattering.

XMM-Newton survey of two upper Scorpius regions

Aims. We studied X-ray emission from young stars by analyzing the deep XMM-Newton observations of two regions of the Upper Scorpius association with an age of 5 Myr. Methods. Based on near infrared and optical photometry we identified 22 Upper Scorpius photometric members among the 224 detected X-ray sources. We derived coronal properties of Upper Scorpius stars by performing X-ray spectral and timing analyses. The study of four strong and isolated stellar flares allowed us to derive the length of the flaring loops. Results. Among the 22 Upper Scorpius stars, 13 were identified as Upper Scorpius photometric members for the first time. The sample includes 7 weak-line T Tauri stars and 1 classical T Tauri star, while the nature of the remaining sources is unknown. Except for the intermediate mass star HD 142578, all the detected USco sources are low-mass stars of spectral types ranging from G to late M. The X-ray emission spectrum of the most intense Upper Scorpius sources indicates metal depleted plasma with temperature of ∼10 MK, resembling the typical coronal emission of active main sequence stars. At least 59% of the detected members of the association have variable X-ray emission, and the flaring coronal structures appear shorter than or comparable to the stellar radii already at the Upper Scorpius age. We also found indications of increasing plasma metallicity (up to a factor 20) during strong flares. We identified a new galaxy cluster among the 224 X-ray source detected: the X-ray spectrum of its intra cluster medium indicates a redshift of ∼0.41 ± 0.02.

AN INTERESTING GROUP OF EMISSION-LINE STARS IN SCORPIUS

ABSTRACT An objective-prism survey of the southern Milky Way has detected three and possibly four emission-line stars at Z = 348? 7, 6 = - 0?8 which appear to constitute a physical group located about 2 kpc from the sun. Two stars are provisionally classffied as WN + OB and a third appears to be 0# Key words: Wolf-Rayet stars - spectra - open clusters

Far-Ultraviolet Spectra of Six Stars in Orion.

view Abstract Citations (20) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Far-Ultraviolet Spectra of Six Stars in Orion. Morton, Donald C. Abstract An Aerobee rocket carried two ultraviolet objective spectrographs to 186 km on the morning of 13 October 1965 and pointed them towards Orionis within 1 ~. The cameras and stabilization system were similar to those used to obtain spectra of stars in Scorpius in June 1965. This time one of the f/2 Schmidt cameras had a lithium fluoride corrector, while the other used calcium fluoride as be- fore. An unexpected shock during re-entry severed the mirror and film cassettes from the calcium fluoride camera so that films from only the lithium fluoride one were recovered. Development of these films showed ultraviolet spectra of the six OB stars in Orion listed below with their wavelength ranges. Spec- Wavelength Star V B-V trum range Velocity 1 Ori2.20 -0.21 09.511 1200 to 1415A -1400 km sec~ Ori 1.70 -0.19 BOla 1220 1595 -1900 ~On 2.05 09.51b 1200 1740 -1900 ~ Ori3.35 -0.19 BO.5V 1220 1400 (weak) Ori 2.77 -0.25 09111 1235 2100 -3000: Ori 2.04 -0.18 BO.51a 1630 2795 An exposure of 180 sec gave the best spectra, wiil~ a resolution of about 3 A, somewhat poorer than the 1 A obtained on the previous flight. Nevertheless, many absorption lines and a few emission lines are definitely visible in the spectra. Zero-order images of other stars on the same film permit an absolute calibration of wavelengths within 1 A. Emission lines of Si IV at 1402.7 A and C IV at 1549.5 A are identified in ~ and E. Strong absorption lines of both components of the Si IV doublet and the unresolved C IV doublet are found in ~, E, and t shifted to shorter wavelengths by several angstroms. The Si IV doublet is also present in ~, shifted in a similar way. The velocities corresponding to these shifts are indicated in the table. The value for is uncertain because of poor lines and a lack of unshifted features for checking the wavelength scale. These displaced absorption features must be formed by gas escaping from the stars at high velocities indicating a significant mass loss from these early type giants and supergiants. Rough limits on the rate of mass loss can be obtained by assuming that 4~e broadening of the lines 15 entirely by either Maxwellian Doppler velocities or radiation damping. For the widths of the lines in ~ Orionis the Doppler model gives ~10-~ M0 yr-1 while damping gives ~10-~ M0 yr-'. Absorption lines about 8 A wide are also visible at 1216 A in ~ and 8, and are attributed to Lyman-~ absorption by interstellar hydrogen atoms. Assuming broadening by radiation damping, the width corresponds to ~lO~~ atoms Cm-- 1n il~e line of sight. Publication: The Astronomical Journal Pub Date: 1966 DOI: 10.1086/110137 Bibcode: 1966AJ.....71S.172M full text sources ADS | data products SIMBAD (6)