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[MATH] color profiles in non deficient or moderately deficient galaxies and extremely deficient galaxies is less sharp. In fact, due to the great dispersion in the 0.65-0.90 and [MATH] 0.90 bins, the difference between highly deficient galaxies and moderate deficient galaxies is less marked; however, it is evident that... |
Discussion 4.1 The Schmidt law The study of the local Schmidt law addresses one of the main open questions about the star formation activity in spiral galaxies: is the process of star formation related to the atomic or the molecular component? Clearly, the formation of stars takes place inside the GMCs, in cold and den... |
We thus disagree with the conclusion of Wong & Blitz ( 2002 who state that the correlation in the Schmidt law is driven entirely by the molecular component. The fact that we find a mean index [MATH] for the local Schmidt law, similar to the one originally proposed by Kennicutt using integrated quantities, seems to impl... |
4.2 Environmental effects The HI is the primary fuel for the star formation in galaxies, both directly and indirectly. We have shown that at the disk periphery the HI might directly contribute to the star formation by collapsing into molecular clouds and indirectly by providing the constituent of the diffuse H |
medium, composed of molecules which form on dust grains inside the stellar potential wells (Blitz & Rosolowsky 2004 Therefore, it is not surprising that the HI removal caused by the environmental processes may affect the star formation activity in cluster galaxies; we have shown that HI deficient galaxies have their SF... |
and elaborated by Bekki et al. ( 2002 according to which the effect of reducing the HI halo halts the replenishment of H , leading to a quenching of the star formation rate. This model implies a continuous HI inflow from outside, as observed in some nearby galaxies, although at a rate that seems insufficient to sustain... |
Conclusions With the aim of exploring the relations between the process of star formation and the physical properties of the ISM in various galaxy environments, we collected state-of-the-art imaging material and maps for 28 massive spiral galaxies belonging to the Virgo cluster and to the local field. The observational... |
The present analysis indicates that the bulk of the star formation in spiral galaxies is supported by a diffuse molecular medium which forms through the conversion of the atomic hydrogen, due to the pressure exerted by the stellar potential. However, at the edge of the star forming disks, the HI plays a more important ... |
Acknowledgements. We thank A. Leroy, E. Brinks, A. Chung, J. van Gorkom and J. Kenney for their kind permission to use HI maps from THINGS and VIVA, prior to publication. We thank A. Boselli, L. Cortese, C. Bonfanti, P. Franzetti and B. Devecchi for useful hints and discussions. This research has made use of the GOLDMi... |
The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, The University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Ho... |
# Source: arxiv 0808.0103 # Title: Use of Astronomical Literature - A Report on Usage Patterns # Sections: all # Downloaded: 2026-03-02T07:59:03.038645+00:00 |
Use of Astronomical Literature - A Report on Usage Patterns Abstract In this paper we present a number of metrics for usage of the SAO/NASA Astrophysics Data System (ADS). Since the ADS is used by the entire astronomical community, these are indicative of how the astronomical literature is used. We will show how the us... |
The ADS is funded by NASA Grant NNG06GG68G. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 Keywords: Digital Libraries; Readership Statistics; Document Use; Obsolescence |
1. Introduction The SAO/NASA Astrophysics Data System (hereafter ADS), is a digital library and a vital source for bibliographic information in astronomy. The vast majority of astronomical researchers in the world use the ADS on a daily or near-daily basis. The use of the ADS has not only changed quantitatively but als... |
With different types of users come different types of use. A professional astronomer has different interests than an occasional user. One way of illustrating this is to look at the distribution of publication years for the literature people are interested in. We will also look at the diversity of ADS users from a geogr... |
2. Data The ADS is an electronic library where the system log files record queries and access to its records over time. For every bibliographic record in the ADS, a user can choose to view or access various types of metadata associated with that record. A “visit” (or “read”) is defined as the selection of a metadata li... |
These ingredients provide us with the information we need to analyze the behavior of different types of users. For our analysis we use the ADS log files of January and February of 2008. These log files represent over 5.9 million requests from 317,753 unique users with a cookie and 1,071,416 unique users without a cooki... |
3. Results 3.1. General readership Figure (top) illustrates the observation we made in the introduction: ”Since the ADS started to be indexed by general search engines, the number of incidental users has increased dramatically”. The line marked ’+’ shows the total number of users. This includes incidental users who jus... |
’. The bottom panel is an illustration of the qualitative change in use. It shows the distribution of the fraction of users as a function of the number of reads in the month of January in the years 2000, 2002, 2004, 2006 and 2008. |
Table gives an overview of the number of visitors entering through one of those external websites, for the period of January and February of 2008. The total number of visits in this period was 5,941,983. |
3.2. Readership for different types of readers For the first part of our analysis (figures and ) we have limited ourselves to data requests for the following journals: The Astrophysical Journal (including Letters, but excluding the Supplement), The Astronomical Journal The Monthly Notices of the Royal Astronomical Soci... |
These numbers are shown in figure . The line marked with ’+’ shows the mean usage per paper, and the line marked with ’ [MATH] ’ represents the fraction of different articles for which data was requested. This figure is very similar to figure 12 in Kurtz et al. ( 2000 |
What picture do we get when we zoom in on different types of users? In particular, we will look at users who we will call “ADS regulars” (mostly astronomers and physicists) and people requesting information through Google Scholar. The group of “ADS regulars” consists of people who use the system more than 10 times per ... |
’ respresent their total number of citations. In other words, this figure compares the so-called ”obsolescence functions” for cites and use (see e.g. Kurtz et al. ( 2003 ) for articles published in the four main astronomy journals as read by these two types of users. |
An interesting metric for the “ADS Regulars” is the median of monthly usage. In the period of January 1998 through January 2008 the median for the monthly number of reads (by these users) turns out to be fairly constant at a value of 21 [MATH] 1 reads per month. |
3.3. Readership for different geographical regions For the second part of our analysis we zoom in on usage data, to see how readership varies per geographical region. In the previous section, we mentioned that our data logs also record the origin of requests. This allows us to determine use as a function of geographica... |
In the top panel, we explore readership as a fraction of total readership in a given year. This fraction will tell us to what extent region usage growth follows the growth trend on world level. We will refer to the set of data points for each region as a “trail”. A trail maps out the relation between GPC and the fracti... |
The middle panel looks at pure growth within the region as a function of GPC. In this figure usage has been normalized by the 1997 level, so the numbers show a relative growth with respect to 1997. Normalized, this plot will show similarities in intrinsic growth. The general flow in this diagram is up and to the right,... |
The lower panel compares the number of ADS users in a region with the number of Internet users, both normalized with their 1997 values. The flow of time here is to the right and up. Points above the solid line indicate that in a particular region the number of ADS users grows faster than the number of Internet users. |
In order to get the data used in figure the following operations were performed on the origin information in our data logs: (a) requests originating from a ”.com” or ”.net” domain were assigned to the country of the referer URL, and (b) we set a limit of 2000 reads per year to any user (thus filtering out atypical usag... |
4. Discussion Figure shows how the ADS has become a public service whose reach goes well beyond the scholarly community. Since 2005, the number of people visiting the ADS via external sites has increased dramatically. This aspect will only intensify with the advent of the World Wide Telescope ( Gray et al. ( 2002 ), wh... |
Figure reports on popularity of papers as a function of publication date. What papers (in terms of their age) get the most attention from people who use the ADS regularly? This figure shows that more recent papers get the most attention. This is not just because they are read more. The fact that the ADS reads increase ... |
Figure can be read in various ways. One interpretation is that use obsolescence can be substantially different for different types of users, even when accessing the same documents. How a search engine works, can have significant effects. Google Scholar use approximately matches the total number of citations, which is s... |
Another interpretation of figure focuses on obsolescence of use and cites. A fundamental difference between cites and use is that the former is a public act, while the latter is a private act. Citations are created by authors of scholarly articles, while use, in general, is not solely the result of actions by authors. ... |
What does it mean to have a median that is fairly constant at a value of about 21 reads per month? It is an indication that all our frequent users on average use the ADS on a daily basis. Initially this meant that all professional astronomers use the ADS on a daily basis (see Kurtz et al. ( 2005 and Tenopir et al. ( 20... |
Figure tells many stories. In the top and middle diagrams, each region has 11 datapoints, corresponding to one year (1997 through 2007). The lower diagram has 9 points for each region (1997 through 2005). South Africa (ZA) was omitted from the region ”Africa”, because it would completely dominate the analysis for this ... |
In the top panel of figure it is immediately clear that the EU and the USA are different from the other regions. Obviously, for both, the GPC will be higher than the other regions. Since the lion’s share of astronomy research is performed in either the USA or the EU, it is also no surprise that their fraction of world ... |
The middle panel of figure shows that all regions display an intrinsic growth (with respect to their 1997 values). The overall trend is that the intrinsic growth in the EU and USA is slower than in the other regions, which is to be expected for regions where the density of Internet users changes relatively little (beca... |
The definitions of high-, middle- and low-income countries are those of the Worldbank: high-income countries are those countries with a Gross National Income per capita (GNC) in 2007 of $11,456 or more, while middle-income countries are those countries with a GNC between $936 and $11,455 and low-income countries are co... |
After the Internet user density flattens, the ADS user density still increases, because there is still substantial potential for use diversification within the existing body of users. This is clearly shown in the lower panel of figure , most prominently for the USA. The number of ADS users increases rapidly, while the ... |
5. Conclusions In terms of its audience, the ADS has not only changed quantitatively, but also qualitatively. Besides a steady growth of the ADS regular users, we observe a dramatic increase in incidental users. The ADS is per definition the gateway to online literature for scientists, used by virtually all professiona... |
Comparing the group of “ADS regulars” with the group visiting the ADS via Google Scholar shows that the obsolescence curve for the latter is fairly flat, corresponding with reading behavior by people acquainting themselves with a subject. This means Google Scholar is not the right tool for staying up-to-date with the l... |
Although ADS usage increased in regions like the EU and the USA, the percentage of world usage has decreased for these regions. This is because the growth in World usage is mainly driven by regions with the biggest potential for growth. The density of Internet users reaches a saturation point in middle- and high-income... |
6. Appendix A country is classified as a “Least Developed Country” when it meets the following three criteria ( UN ( 2007 UN ( 2008 ): |
a low-income criterion, based on a three-year average estimate of the gross national income (GNI) per capita (under $745 to be included in the list, above $900 to be removed from the list); |
a human capital status criterion, involving a composite Human Assets Index (HAI) based on indicators of: (a) nutrition: percentage of population undernourished; (b) health: mortality rate for children aged five years or under; (c) education: the gross secondary school enrolment ratio; and (d) adult literacy rate; and |
an economic vulnerability criterion, involving a composite Economic Vulnerability Index (EVI) based on indicators of: (a) population size; (b) remoteness; (c) merchandise export concentration; (d) share of agriculture, forestry and fisheries in gross domestic product; (e) homelessness owing to natural disasters; (f) in... |
To be added to the list, a country must satisfy all three criteria. In addition, since the fundamental meaning of the LDC category, i.e. the recognition of structural handicaps, excludes large economies, the population must not exceed 75 million. To become eligible for graduation, a country must reach threshold levels ... |
# Source: arxiv 0808.0129 # Title: VW LMi: tightest quadruple system known. Light-time effect and possible secular changes of orbits # Sections: all # Downloaded: 2026-03-02T07:58:54.311055+00:00 |
VW LMi: tightest quadruple system known. Light-time effect and possible secular changes of orbits (Accepted 0000 Month 00. Received 0000 Month 00; in original form 2007 March 17) |
Abstract Tightest known quadruple systems VW LMi consists of contact eclipsing binary with [MATH] = 0.477551 days and detached binary with [MATH] = 7.93063 days revolving in rather tight, 355.0-days orbit. This paper presents new photometric and spectroscopic observations yielding 69 times of minima and 36 disentangled... |
keywords: stars: binaries: eclipsing binaries – stars: binaries: spectroscopic INTRODUCTION The photometric variability of VW LMi (HIP 54003, HD 95660, sp. type F3-5V, |
[MATH] =8.0), was found by the Hipparcos mission (ESA, 1997 , where it was correctly classified as a W UMa-type eclipsing binary with an orbital period of 0.477547 days. The first ground-based photometric observations of the system obtained in 1999 and 2000 (taken in the [MATH] and [MATH] Johnson filters) were publishe... |
lead to the photometric mass ratio [MATH] = 0.395 and inclination [MATH] = 72.4°and contact configuration for the system. Later Gomez-Forrellad et al. ( 2003 presented new [MATH] photometry and its preliminary analysis. Assuming convective envelopes for both components and the temperature of the primary as [MATH] = 670... |
yielded quite different parameters: [MATH] [MATH] = 72.5° and fill-out factor [MATH] . The discovery of the second (non-eclipsing) binary in VW LMi by Pribulla et al. ( 2006 makes all previous photometric solutions almost useless due to strong light contribution of the second pair of about [MATH] (at the maximum bright... |
Pribulla et al. ( 2006 presented long-term spectroscopy (209 spectra taken between 1998 and 2005) of the system obtained at David Dunlap Observatory (hereafter DDO) which enabled to disentangle all three orbits in this tight multiple system: the contact binary with the [MATH] = 0.4775 days period is orbiting another bi... |
[MATH] = 0.0037(4) days, [MATH] = 353(2) days, [MATH] = 0.5(2) and [MATH] = 2.8(4) rad, are rather preliminary due to few available minima. The eccentricity corresponding to their orbital solution is much higher than predicted spectroscopically by Pribulla et al. ( 2006 |
The spectral type of VW LMi was estimated as F5V by Pribulla et al. ( 2006 , while observed Tycho-2 [MATH] = 0.21 and 2MASS [MATH] = 0.34 colors correspond to F2V spectral type. Both determined spectral type and colors refer to the whole quadruple system. |
VW LMi is tightest quadruple system known (Tokovinin, 2008 . Also it has the shortest period of the outer orbit within multiple systems harboring contact binaries. The ratio of the outer orbital period and orbital period of the non-eclipsing pair is only about [MATH] = 44.5 hence we can expect secular orbital changes o... |
Goals of the present paper are as follows: (i) to present and analyze new photometric and spectroscopic observations, (ii) to perform simultaneous solution of LITE using both minima times of the contact binary and radial velocities (hereafter RVs) of the individual components, (iii) to assess possibility of the tidal d... |
New observations 2.1 Photoelectric and CCD photometry To secure as many minima times as possible, photometry was performed at several observatories in Slovakia and Germany. Since the system was too bright for most of the instruments equipped with CCD cameras, photolenses were extensively used and on larger telescopes, ... |
Photoelectric photometry of VW LMi was obtained using 60cm Cassegrain telescope in the G2 pavilion of the Astronomical Institute of the Slovak Academy of Sciences. VW LMi was observed in the Johnson [MATH] filters and with neutral filter (optical glass BK7, denoted in tables as [MATH] ). [MATH] observations were transf... |
Most of the CCD photometry was secured using 50cm Newtonian telescope in the G1 pavilion of the Astronomical Institute of the Slovak Academy of Sciences. Practically all observations were taken through the Johnson [MATH] filter, only on March 25, 2007 |
[MATH] photometry was performed. The data were left in the instrumental system since the major purpose was securing minima instants. Further large set of data was obtained using various small telescopes/photolenses at the Astronomical Observatory at Kolonica saddle (48°56’ 6” N, 22°16’ 26”E). Several times of minima we... |
2.2 Medium dispersion spectroscopy New spectroscopic observations were obtained using the slit spectrograph in the Cassegrain focus of 1.88m telescope of DDO. The observations were performed between March 2007 and very beginning of July 2008, when DDO ceased to operate. The spectra were taken in a window of about 240 Å... |
[MATH] = 12,000 - 14,000. The diffraction grating with 2160 lines/mm was used with the sampling of 0.117 A/pixel. One-dimensional spectra were extracted by the usual procedures within the IRAF environment after the bias subtraction and the flat-field division. Cosmic-ray trails were removed using a program of Pych ( 20... |
All exposures were 900 seconds long and lead to S/N of about 100-150. The observations were analyzed using the technique of broadening-functions, described in Rucinski ( 1992 2002 . For VW LMi we used HD222368 as the template (F7V, [MATH] km s -1 ). This star provided the best match to the observed spectra - integral o... |
Pribulla et al. ( 2006 we firstly fitted simple multi-component Gaussian model to the extracted BFs (see Fig. ), then detached pair with slowly-rotating components was subtracted. The wide features corresponding to the contact pair were subsequently modelled by the rotational profiles which effectively corresponds to a... |
[MATH] according to the tables of van Hamme ( 1993 appropriate for main-sequence F3V star at 5184 Å. RVs determined from the new spectra are given in Table . Several BFs extracted from observations taken close to conjunction of the contact binary did not allow to determine their RVs. In case of non-eclipsing binary, RV... |
Minima determination Most widespread approach to obtain instants of minima of eclipsing binaries is to use Kwee & van Woerden’s method (Kwee & van Woerden, 1956 . From our experience the errors estimated using their formula (14) are often unrealistically small. The real uncertainties are very probably dominated by syst... |
Since LC of the system appears to be very stable (we do not see any asymmetries or changes) fitting templates were prepared to obtain instant of conjunction (minimum) for any sufficiently long photometric sequence. Such a way we made use not only of the minima but of other LC segments. The template LCs were represented... |
[MATH] = 0.43, [MATH] = 0.41, and [MATH] = 0.38. The differences in amplitude primarily result from wavelength-dependent limb darkening and light contribution of the third component (see Section ). Due to the differences in filter transparencies and wavelength response of detectors we had to form a template LC for each... |
To obtain good fits of the observed LCs by templates [MATH] we formed the following fitting function: [EQUATION] This allowed for shifting, scaling and “slanting” of the template LC. Fixing of the parameters was judged according to the appearance of individual LCs. All new times of minima are listed in Table . The form... |
The resulting (O-C) diagram including published minima times is shown in Fig. . The minima times of VW LMi can be found in Gomez-Forrellad et al. ( 2003 ); Dumitrescu ( 2003 ); Derman & Kalci ( 2003 ); Porowski ( 2005 ); Dworak ( 2005 2006 ); Hubscher ( 2007 ); Nelson ( 2007 |
and there are four unpublished CCD times of minima observed by K. Nakajima HJD 2 453 461.9371(2), 2 453 462.1758(2), 2 453 886.0001(3), and 2 454 603.9984(2). The residuals, from rather arbitrary ephemeris given in the figure, clearly show wave-like behavior with one-year periodicity. |
Global fit of the data Multiple-dataset fitting is rather widespread technique nowadays. It is typical to combine RVs and visual orbits or RVs and interferometric visibilities of binary stars (e.g., Pourbaix ( 1999 Tango et al. ( 2006 ). Eclipsing-binary modelling programs (see van Hamme & Wilson ( 2007 ) enable to com... |
Since our photometry was performed at several observatories, often without filter, we decided not to fit a global model to LCs together with RVs and to use only minima times to better characterize the outer orbit. Rigorous modelling of those datasets (four RV curves and times of minima) is quite complex since times of ... |
[MATH] . LITE is also manifested directly in observed times of minima. The informational contents of the minima is, unfortunately, very similar to having observed only RVs of the eclipsing pair. Integrals of RV curves are radial distances from the observer corresponding directly to the LITE through the finite speed of ... |
In further description we will use similar notation of parameters as in Pribulla et al. ( 2006 common parameters (orbital period, eccentricity, time of periastron passage, longitude of periastron) for orbits will be denoted by index “12” (contact binary), “34” (detached non-eclipsing binary) and “1234” (mutual orbit). ... |
[EQUATION] where index [MATH] denotes the component. For the detached binary we similarly have: [EQUATION] with [MATH] . True anomalies of inner orbits ( [MATH] ) have to be corrected for the LITE caused by the mutual revolution of binaries. If we accept the plane parallel to the sky and intersecting mass center of the... |
[EQUATION] where index [MATH] is either “12” or “34”. In case of the eclipsing pair, where the orbital eccentricity is zero, the predicted times of minima occurring at epoch |
[MATH] would be: [EQUATION] if true anomalies in the eclipsing binary orbit are counted from the upper conjunction of the more massive component (then [MATH] with |
[MATH] = 0). While amplitude of the RV changes of the systemic velocity of the detached-pair orbit around the common center of gravity is rather reliable due to very well defined sharp peaks in BFs ( [MATH] km s -1 |
which is limit given by the spectral resolution), the RVs of contact-binary components are rather imprecise due to a “cross-talk” with the second binary and wide profiles. This makes size of the relative orbit of the contact binary (related to [MATH] ) rather unreliable. The shape of the orbit is, fortunately, coupled ... |
The best fits to the data (4 RV curves and the LITE orbit) were performed using differential corrections method using analytic derivatives of the functions. The dependence of true anomaly on mean anomaly ( [MATH] ) and eccentricity was represented in derivatives by the truncated series up to the second degree in orbita... |
[EQUATION] Since all orbits are being close to circular this approximation was sufficient to make the optimization process quickly convergent. The sum of normalized |
[MATH] was used as the merit function: [EQUATION] where [MATH] is index of the dataset, [MATH] is number of observation for the given dataset, [MATH] is index of individual observation and [MATH] is average standard deviation of individual datapoint for the [MATH] -th dataset. Average uncertainty of a datapoint for ind... |
[MATH] = 2.6 km s -1 , and [MATH] = 2.2 km s -1 The estimated average uncertainties were found to be realistic since normalized [MATH] for individual datasets were close to unity. Observations within individual datasets were assigned the same errors (as given above) due to the fact that both times of minima and RVs are... |
Fitting theoretical curves to five datasets required 18 parameters. It is interesting to note, that LITE of the eclipsing pair required only one additional parameter - [MATH] , due to the fact that the orbital period of the contact binary was found to be continuously increasing. Since orbital eccentricity of the detach... |
Unfortunately the orbital period of the mutual orbit is close to one year. The system can be observed for minima from beginning of November till beginning of June. The observing interval to get spectrum just before dawn and just after twilight is about a month longer. Therefore, to cover the whole outer orbit, the syst... |
[MATH] Light-curve solution The eclipsing pair revolves in rather tight orbit around another binary which results in phase shifts of about [MATH] 0.008 which cannot be neglected as seen in long-term modelling of RVs (see Section ). Therefore, we used photometry from a short interval compared to mutual, 355-days orbit. ... |
Analysis of LCs was performed using code ROCHE described in Pribulla ( 2004 Since eclipsing pair is a contact binary, circular orbit and synchronous rotation [MATH] ) was assumed in all fits. The model-atmosphere grids (see Lejeune et al. ( 1997 ) were selected for the solar metallicity. The temperature of the primary ... |
[MATH] and [MATH] of the components. Due to the fact that exact values of third light for [MATH] and [MATH] passbands are unknown, unlike in usual approach, we performed several solutions with the orbital inclination fixed between 75 to 85°. The mass ratio was not adjusted since it tightly correlates with orbital incli... |
Long-term evolution of orbits The ratio of the orbital periods of the outer orbit and orbit of the non eclipsing pair is [MATH] = 44.76. Corresponding period ratio in the case of the contact binary is as large as [MATH] = 743. Therefore, visible precession of the orbit can be detected (on human timescales) only in the ... |
According to Soderhjelm ( 1975 the nodal precession period caused by the perturbations in the close triple is: [EQUATION] where [MATH] is angular momentum in the detached binary orbit, and [MATH] is (vector) sum of angular momenta in the detached binary orbit and the outer orbit. In our case we can neglect the term in ... |
[MATH] and orbits are close to being coplanar; hence [MATH] . Then we get [MATH] years. Since the detached pair on [MATH] = 7.93-days orbit is non-eclipsing binary (at least at present) we can detect possible precession of the orbit only from the RVs. Precession of the orbital plane should results in changes of the amp... |
Possibility of long-term changes of the 7.93-days orbit was assessed by dividing RV observations into individual observing seasons. Since LITE in the eclipsing pair is not affected nor RVs of its components, simultaneous fits in separate time intervals used all measurements for the eclipsing pair with the parameters of... |
Five solutions given in Table can be described/interpreted as follows: (i) eccentricity is stable - solutions are reliable and small eccentricity is not spurious (ii) semi-amplitudes of RVs remain stable within the errors - mutual orbit and orbit of the detached pair are very probably close to coplanar (iii) there is d... |
Possible astrometric and direct detection VW LMi (HIP 54003) was astrometrically observed during the Hipparcos mission. No positional disturbance or acceleration terms in the proper motion were found and there is no Double/Multiple Systems Annex flag (H59 field) in spite of the fact that VW LMi is member of multiple sy... |
The reasons for negative detection in the Hipparcos astrometry are very probably two (i) the orbital period is close to one year and orbital wobble mimics parallactic motion and changes apparent annual parallax (ii) Hipparcos astrometry refers to the photocenter of VW LMi which substantially decreases the astrometric w... |
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