Sygnas Confrontation

The mass of the black hole can be easily determined once we know both its distance from the center of mass of the O-star and the orbital velocity of the star.

Since optical spectroscopy only gives us the radial component of velocity, we must also determine the inclination of the orbital plane relative to our line of sight in order to infer the orbital velocity. Furthermore, since the star orbits the center of mass of the system, we must also obtain the separation between the two components. Our model, which is underpinned by our new measurement of the distance, makes use of all relevant observational constraints in a self-consistent manner.

We discuss details of the data and modeling below. There is no shortage of published observational data for Cygnus X-1 in the literature. The binned light curves contain 20 points each and are phased on the following ephemeris:. In addition, Brocksopp et al. The light and velocity curves were kindly sent to us by C. In addition to the velocity data of Broscksopp et al. We fitted a sine curve to their data and those of Brocksopp et al. Fixing the uncertainties on the individual velocity measurements to 7.

We therefore combined the two sets of radial velocities while removing the respective systemic velocities from the individual sine curves. We phased the Gies et al. The combined data set has points. All of these velocity and light curve data are discussed further and analyzed in Section 2. This small scatter in these data sets, each spanning a few decades, attests to the strongly dominant orbital component of variability. Meanwhile, Cygnus X-1 is well known to be variable in the radio and X-ray bands, including major transitions between hard and soft X-ray states see Figure 1 in Gou et al.

This raises the question of whether any non-orbital variability in the light curve data could significantly affect the component masses and other parameters determined by our model. We focus on the light curve data, which are more susceptible to being affected by variability. We believe that our results are robust to such non-orbital variability for several reasons, including the following. In summary, we conclude that non-orbital variability is unlikely to significantly affect our results.

In order to constrain the dynamical model, it is crucial to have a good estimate of the radius of the companion star.

However, customary methods of determining this radius fail because the Cygnus X-1 system does not exhibit eclipses nor does the companion star fill its Roche equipotential lobe. We obtain the required estimate of the stellar radius as we have done previously in our study of LMC X-1 Orosz et al. The radius, which critically depends on distance, additionally depends on the apparent magnitude of the O-type star and interstellar extinction, and also on the effective stellar temperature and corresponding bolometric correction.

The luminosity and radius of the star in solar units are and , respectively. We note that the K -band bolometric corrections for the solar metallicity models and the models for half-solar metallicity differ only by 0. Lanz , private communication , so our results are not sensitive to the metallicity. Derived O-star radius top and luminosity bottom as a function of the assumed effective temperature. The effective temperature of the companion star can be determined from a detailed analysis of UV and optical line spectra Herrero et al.

Based on an analysis of both optical and UV spectra, Caballero-Nieves et al. Based on the plots and tables in Caballero-Nieves et al. Using optical spectra, Karitskaya et al. Likewise, Herrero et al. After considering several previous determinations of the projected rotational velocity of the O-type star and corrections for macroturbulent broadening, Caballero-Nieves et al.

We use this value as a constraint on our dynamical model, which we now discuss. Once the values of P , the K -velocity of the O-star, and the O-star's mass M opt are known, the scale size of the binary e. Not all values of R opt are allowed for a given P , M opt , and K: The ELC model can also include optical light from a flared accretion disk. Consequently, we do not include any optical light from an accretion disk. We turn to the question of the X-ray heating of the supergiant star and its effect on the binary model.

The X-ray heating is computed using the technique outlined in Wilson The X-ray source geometry is assumed to be a thin disk in the orbital plane with a radius vanishingly small compared to the semimajor axis this structure should not be confused with the much larger accretion disk that potentially could be a source of optical flux. Points on the stellar surface "see" the X-ray source at inclined angles and the proper foreshortening is accounted for.

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There are soft and hard states of Cygnus X-1 e. Since the ground-based observations i. The archive of the Rossi X-ray Timing Explorer RXTE contains several thousand observations of Cygnus X-1 collected in numerous monitoring campaigns conducted over the life of the mission.

We processed and analyzed exposure intervals January to February; mean exposure 2. In the hardness—intensity diagram, the soft and hard states of Cyg X-1 can be separated by the value of hard color HC; i. During the hard and soft states of , they found broadband X-ray luminosities in the range 1. Samples of the hard and intermediate states during — with the International Gamma-Ray Astrophysics Laboratory yielded L xbol in the range 1. To get a rough idea of how these special observations relate to typical conditions, we used the available contemporaneous RXTE observations to scale the measured L xbol values against the PCA count rates, considering hard and soft states separately.

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We then estimated that the average hard and soft states would correspond to L xbol values of 1. Finally, the time-averaged luminosity would then be roughly 2. We ran some simple tests in which we increased the bolometric X-ray luminosity by up to an order of magnitude and found the light curves to be essentially identical. When computing the light curve, ELC integrates the various intensities of the visible surface elements on the star.

Consequently, no parameterized limb darkening law is needed. We therefore computed a new grid of models, assuming solar metallicity.

Sygnas Confrontation : Joseph P Velasquez :

These models take into consideration between 1,, and 2,, atomic lines in the computation of the line opacity. The radiation fields were computed at 26, wavelengths between 0. At the gravities of interest, the models are very insensitive to the precise value of the stellar radius.

As noted above, the observational data we model include the U , B , and V light curves from Brocksopp et al. Charlie Odd Amazing cinematic synth work from the always stunning Umberto. What an album cover, too! Jesse Umberto getting better and better each album, genius! Purchasable with gift card. Dead Silent Morning Tags electronic disco giallo horror not not fun Los Angeles. Night Has A Thousand Screams. If you like Umberto, you may also like: Get permission to re-use this article.

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You will need to select a minimum of one corridor. Therefore, it is hailed as a unique tool in probing the earliest, prestellar phase of star formation. Observationally, its abundance and distribution is, however, just beginning to be understood in low-mass prestellar and cluster-forming cores.

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We have therefore uncovered extended massive cold dense gas that was undetected with previous molecular line and dust continuum surveys of the region. This work also shows that our picture of the structure of cores is too simplistic for cluster-forming cores and needs to be refined: In their evolution toward the formation of a young stellar object, low-mass cloud cores change their density distribution until the so-called pivotal state is reached e.

This stage is considered the starting point for protostellar accretion. Thus, it is crucial to find and study objects close to the "pivotal" stage to unveil the initial conditions in the process of star formation. We believe to have found this class of objects: They stand out in having large degrees of CO freezeout and deuterium fractionation Bacmann et al.

That being said about low-mass star formation, the early phase chemistry in massive star-forming regions is still poorly understood, mainly because the study of these regions have so far focused on molecular material associated with high-mass protostellar objects HMPOs; e. Many of the sources are seen as dark patches in infrared images of the region. After a few hours of integration on each of the three targets, which did not result in a detection, we decided to perform deeper integration on G Here, we only discuss the observations toward G The DR21 filament itself is the most massive region in the entire complex.

Our mapped region coincides with three bright 1. For reference, this region encompasses the massive dense core N53 of Motte et al. The embedded population identified by Kumar et al.

Sygnas Confrontation

Panel A, from left: Stars denote the embedded population identified by Kumar et al. Nyquist-sampled maps were achieved using a jiggle pattern with a position switch to move to the reference. During most of our observations, 14 of the 16 receptors were working. After finding evidence of emission at the edge of our map from the initial observing session, we shifted the map center for the subsequent sessions. The smurf software provided as a part of the Starlink package was used to regrid the data, mask the bad receptors, construct three-dimensional 3D data cubes, and co-add the scans.

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The observations were done in track sharing mode with several sources per track. This resulted in our final map presented here with an FWHM beam of 19 7. These might well be true detections, however, they require validation with deeper observations. Following these steps, we have confirmed five reliable detections labeled P1 to P5 whose positional offsets and Gaussian fit parameters obtained with CLASS are tabulated in Table 2.

The spectra toward the five positions for both lines are shown in Figure 2. The spectra have been converted from antenna temperature to main brightness temperature for a main beam efficiency of 0. Spectra for all tracers have been extracted for the same spatial resolution, and the offset positions in arcsecs are as indicated in the figure. We find a range in line widths of 0.

Clearly, the line width has a significant non-thermal component as expected in such protocluster environments also given in Table 2. The line asymmetry might be due to different velocity components along the line of sight, absorption in the core envelope or infall motions as argued by van der Tak et al. Clearly, high spatial resolution observations are required to clarify this. However, in Cygnus X, the non-thermal contribution is still dominant.

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As listed in Table 2 , the intrinsic i. The dust continuum emission at high 1. The subsequent panels in the figure show the gas distribution in three different tracers: We have used a dust opacity of 0. The ratio between column density toward cores studied here and those observed toward low-mass cores summarized in Table 3 of Caselli et al.