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Activity Indicators

The Exoplanet Archive stores three different chromospheric and coronal activity indicators.

The corona of a star is a hot, very low-density gas located well above the photosphere. The chromosphere of a star is the intermediate layer of warm, low-density gas located between the corona and the photosphere. Stellar magnetic activity enhances the emission from the corona and the chromosphere. This enhancement of the coronal and chromospheric emission is characterized by strong X-Ray emission, emission of some ultraviolet lines, emission in the cores of the H and K Ca II lines and H-alpha, and occasional flares.

The Exoplanet Archive stores the following activity indicators:

  • S-Index: The flux ratio of two bandpasses centered on the H (3968.5 Angstrom) and K (3933.7 Angstrom) Ca II emission cores and two continuum regions on either side. The S-Index includes contributions from both the photosphere and the chromosphere of the star. The Exoplanet Archive uses the Mt. Wilson S-Index.
  • Log R'-HK: This measures the chromospheric contribution of the H and K Ca lines but excludes the photospheric component in the lines.
  • X-Ray Luminosity: This measures the luminosity of the star in X-Ray wavelengths. The units are ergs/sec.

References

The data are taken from the following sources:

Comments/Notes

None.

Age

The age of a star is defined as the time it has spend in the main sequence (hydrogen burning phase). The stellar age is express in terms of Gyr (109 years).

The Exoplanet Archive stores both published and calculated values of the stellar age. Published values of the stellar age come from indirect measurements as isochrone fitting.

Currently, there are no published stellar age values in the Exoplanet Archive.

Data Validation

N/A.

Comments/Notes

None.

Age (Calculated)

The age of a star is defined as the time it has spend in the main sequence (hydrogen burning phase). The stellar age is express in terms of Gyr (109 years).

The Exoplanet Archive stores both published and calculated values of the stellar age. Calculated values of the stellar age come from defined relationship between observables (for example chromospheric activity indices) and the age.

Currently, there are no calculated stellar age values in the Exoplanet Archive.

Amateur Light Curve

These light curves were donated by amateur astronomers, created using their personal equipment, and subsequently curated and processed by Bruce Gary, webmaster of the Amateur Exoplanet Archive (AXA). The reference and background information page for these data can be found here.

As more light curves are contributed, these holdings will be updated.

Comments/Notes

None.

AO Images

The Exoplanet Archive has 4 high spatial resolution Adaptive Optics (AO) K images for 4 stars.

References

The data are taken from the following sources:

Comments/Notes

None.

Astrometric Wobble (Predicted)

The presence of a planetary companion will induce a cyclical perturbance on the observed motion of the parent star. The Exoplanet Archive refers to this as the astrometric wobble. The units of the wobble are micro-arcseconds. The astrometric wobble depends on the mass of the star, the mass of the planet, and its distance to the star.

For an Earth-like planet, the values stored in the Exoplanet Archive are calculated by placing a one Earth mass planet at the center of the Habitable Zone of the parent star. For a Jupiter-like planet, the calculated values are obtained by placing a one Jupiter mass planet at 5.2 AU from the parent star. The mass for the parent star is calculated as described in the documentation for calculated mass.

References

The data are calculated by the Exoplanet Archive.

Comments/Notes

None.

Data Validation

N/A.

Comments/Notes

None.

Coordinate (Calculated)

The Ecliptic and Galactic coordinates displayed on the Overview page are generated by the Exoplanet Archive from Equatorial J2000 coordinates values. The Equatorial coordinates in turn come from various published sources.

Comments/Notes

None.

Eccentricity

The Observed Eccentricity is the orbital eccentricity. This quantity is typically inferred from Keplerian orbital fits to radial velocity data, direct imaging, or micro-lensing. Eccentricity is a fundamental parameter describing the equation of an ellipse (the orbital path for a bound planet, with the host star at one focus of the ellipse). Eccentricity for bound orbits falls between 0 and 1. An eccentricity of 0 corresponds to a circular orbit. An eccentricity of 0.7 corresponds to a highly-eccentric planet orbit.

References

The Planet Properties page for each individual star with planets includes references for the observed orbit properties.

Comments/Notes

None.

Effective Temperature (Calculated)

The effective temperature (Teff) is defined as the temperature that a blackbody would have if it emits the same amount of total energy per unit area as the star.

The effective temperature is a definition and cannot be measured directly. The Exoplanet Archive provides estimates of the effective temperatures for dwarf stars based on published empirical correlations between measured broad-band colors and Teff. Furthermore, no one broad-band color provides an accurate Teff estimate for all spectral types. The Exoplanet Archive therefore uses one relation for stars hotter than about 4500K, and another relation for cooler stars.

For O through mid-K dwarfs, the Exoplanet Archive uses the empirical relationship of Flower et al. (1996) to relate the observed B-V to the effective temperature of the star. The errors on the Teff are adopted as 100K. The Exoplanet Archive calculates the Teff if the star is a dwarf (see below).

For stars later than about mid-K, we use a polynomial fit to the tabulated correlation between V-K color and Teff provided by Bessell (1995). The polynomial relation is:

    Teff/1000. = 6.57343 - 0.65837*(V-K) - 0.092318*(V-K)2 + 0.022467*(V-K)3 - 0.0006198*(V-K)4 - 0.0000504*(V-K)5

The switch from using B-V as the Teff indicator to V-K as the Teff indicator is made at V-K = 2.5.

For stars that have spectral type and luminosity class information in the Exoplanet Archive, we use the luminosity class to determine if the star is a dwarf. If the star does not have a spectral classification, then the parallax and observed visual magnitude are used to estimate the luminosity class of the star. The cut-off criteria used in the Exoplanet Archive are shown in Figure 1.


Figure 1

Figure 1: The Tycho Color Magnitude diagram. The black dots are all stars for which we have B-V (Tycho) and absolute V (Tycho). The red dots are those for which we have a giant luminosity class, and the blue dots are those for which we have a dwarf luminosity class. The solid green line shows the boundary where our relationship is applied.

References

The additional data and formulae needed to derive luminosities and bolometric magnitudes can be found in:

References used to benchmark the Exoplanet Archive:

  • Valenti & Fischer 2005, ApJS, 159, 141 == SPOCS (Table 8)
  • Gray R.O., Corbally C.J., Garrison R.F., Mcfadden M.T., Robinson P.E. 2003, Astron. J., 126, 2048 == NSTARS (Table 1)
  • Allende Prieto et al. 2004, A&A, 420, 183 == S4N (Table 2)
  • Nordstroem et al. 2004, A&A, 418, 989 == Geneva Copenhagen... (Table 1)
  • Le Borgne et al. 2003, A&A, 402, 433 == STELIB

Comments/Notes

None.

Effective Temperature (Published)

The effective temperature (Teff) of a star is the temperature that a blackbody would have if it emits the same amount of energy per unit area as the star does. The effective temperature is characteristic of the visible surface of the star.

The effective temperature can be measured directly on a star (using the star's radius or line ratios from its spectrum) or can be infered from the star's photometric colors.

The Exoplanet Archive stores both published values of Teff and calculated values from photometric colors.

Habitable Zone (Predicted)

The Habitable Zone (HZ) is the region around a star in which water can exist in liquid form.

The Exoplanet Archive stores HZ values derived using the algorithm described by Kasting et al. (1993) The algorithm calculates the inner and outer boundaries of the habitable zone based on the effective temperature and luminosity of the parent star. For example, the HZ for the Sun is approximately 0.7-1.0 AU.

References

The formulae used to calculate the habitable zone size are provided in:

Comments/Notes

None.

Hipparcos Light Curve

The Hipparcos light curves are photometric light curves taken as part of the Hipparcos Space Astrometry Mission.

References

Comments/Notes

None.

Images

The Exoplanet Archive has constructed 2MASS Ks-band mosaics centered at the positions of 1540 stars originally selected as high-probability TPF targets. The images are 10 arcmin in size (1 arcsec resolution) in the Gnomonic (TAN) projection and presented in Equatorial J2000 coordinates with North up.

These images were derived from data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. The images are not endorsed by the 2MASS project.

The mosaics were constructed with the Montage image mosaic engine (http://montage.ipac.caltech.edu). Montage was funded by the National Aeronautics and Space Administration's Earth Science Technology Office, Computational Technologies Project, under Cooperative Agreement Number NCC5-626 between NASA and the California Institute of Technology. The code is maintained by the NASA/IPAC Infrared Science Archive (IRSA).

References

Comments/Notes

None.

Inclination

The Observed Inclination is the orbital inclination with respect to the plane of the sky. This quantity is typically inferred from the derived impact parameter for transiting planets (projected onto the surface of the star), can be constrained from multiple-planet systems in orbital resonance detected with the radial velocity technique, or from direct imaging and micro-lensing. 0 degrees correspond to an orbit in the plane of the sky, face on with respect to our line of sight. 90 degrees corresponds to an orbit that is edge-on with respect to our line of sight, perpendicular to the planet of the sky. Positive and negative inclinations can be used to reference prograde or retrograde orbital motion.

References

The Planet Properties page for each individual star with planets includes references for the observed orbit properties.

Comments/Notes

None.

Longitude and Latitude

The positions of the stars are defined with respect to a cartesian coordinate system. The coordinate systems differ only in their choice of the fundamental plane.

Coordinate Systems stored in the Exoplanet Archive
System Fundamental Plane
Equatorial Earth's equator projected on the celestial sphere. The Equatorial longitude is more commonly known as Right Ascension, which is abbreviated to RA in the Exoplanet Archive. The Equatorial latitude is more commonly known as Declination, which is sometimes abbreviated as Dec.
Galactic Galactic plane of the Milky Way
Ecliptic The Ecliptic is based on the plane of the Earth's orbit around the Sun.

The Hipparcos catalog provides positions for equinox J2000 at the mean epoch of observation by the satellite (1991.5). The Exoplanet Archive applies proper-motion corrections to the Hipparcos positions in order to yield J2000 epoch coordinates. The J2000 epoch values are the ones that are actually searched, when a positional constraint is requested. The Galactic and Ecliptic coordinates are derived from Hipparcos J2000 equatorial coordinates using in-house coordinate conversion tools.

For stars without positions in the Hipparcos catalog, we derive positions and proper motions based on the catalog from which the source originates plus a cross-correlation with the 2MASS catalog. Whenever possible, the final coordinate is based on the 2MASS position, proper motion corrected to epoch 2000.

References

The data ingested in the Exoplanet Archive are taken from the following published resources:

Comments/Notes

None.

Longitude of Periastron

The Longitude of Periastron is the orbital angle at which a planet goes through its periastron (time of closest approach). This quantity is a compound angle, and it helps define the orbit of the planet with respect to the plane of the sky. This quantity is typically inferred from Keplerian orbital fits to radial velocity data. Longitude of Periastron helps define the orientation of the orbit with respect to the plane of the sky. The Longitude of Periastron is directly related to the Time of Periastron Passage.

References

The Planet Properties page for each individual star with planets includes references for the observed orbit properties.

Comments/Notes

None.

Luminosity (Calculated)

The stellar luminosity is the amount of energy radiated by a star per unit time. The unit for luminosity is solar luminosities (Lo), which is equal to 3.826 × 1033 ergs/sec in cgs. A corresponding quantity is the bolometric magnitude, which is the magnitude a star would have if the total radiation output of the star at all wavelengths is included in the measurement.

The Exoplanet Archive stores calculated values (i.e. not measured values) for the bolometric magnitude and the luminosity of the stars. That is, these values are derived rather than measured empirically as follows:

1. We determine the absolute V-band magnitude (MV), using the observed V-band magnitude (V) and the parallax (π), and assuming no extinction:

MV = V + 5 log (π) + 5

2. Empirical estimates of bolometric corrections are used to convert from absolute visual magnitude to absolute bolometric magnitude. Currently, this is done only for dwarfs.

A B-V based relation is used for "warm" stars, and a V-K based relation is used for mid-K dwarfs and for M dwarfs. For the "warm" stars, the luminosities are interpolated from the tabulated values given by Flower et al. (1996) which relate the observed B-V to the V magnitude bolometric correction. For the "cool" stars, a polynomial fit to empirical data relating V-K color and the K magnitude bolometric correction (BC_K) as provided by Bessell (1995) is used. The polynomial fit to the Bessell data is:

BC(K) = -0.2349 + 1.1978*(V-K) - 0.1577*(V-K)2 + 0.007495*(V-K)3

The switch from using the B-V ("warm" stars) to V-K ("cool" stars)occurs at V-K = 2.5.

For stars that have spectral type and luminosity class information in the Exoplanet Archive, we use the luminosity class to determine if the star is a dwarf. If the star does not have a spectral classification, then the parallax and observed visual mangitude are used to estimate the luminosity class of the star. The cut-off criteria used in the Exoplanet Archive are shown in Figure 1.


Figure 1

Figure 1: The Tycho Color Magnitude diagram. The black dots are all stars for which we have B-V (Tycho) and absolute V (Tycho). The red dots are those for which we have a giant luminosity class and the blue dots are those for which we have a dwarf luminosity class. The solid green line shows the boundary where our relationship is applied.

3. The bolometric correction (B.C.) is applied to the absolute V magnitude (MV) to determine the bolometric magnitude (Mbol):

MV = Mbol + B.C.

4. The luminosity is calculated from the bolometric magnitude (Mbol), assuming that the bolometric magnitude of the Sun is 4.72 :

L = 100.4×(4.72 - Mbol) Lo

References

The additional data and formulae needed to derive luminosities and bolometric magnitudes can be found in:

Comments/Notes

Currently, no luminosity is determined if the star is not a dwarf (as defined above).

Luminosity Class

The luminosity class provides an indication of the surface gravity of a star. It is derived from gravity sensitive features in the stellar spectrum and is represented by the Roman numerals I (supergiant star), II (bright giant star), III (giant star), IV (subgiant star), and V (main sequence or dwarf stars). Fully qualified spectral types have both a spectral class (and subclass) and luminosity class. Examples: G2V, O7II, K4III.

The user can select the luminosity classes to be included in the search by selecting the respective buttons.

References

The data ingested in the Exoplanet Archive are taken from the following published sources:

Comments/Notes

None.

Mass (Calculated)

The mass of a star is simply the total amount of matter contained within the star. The stellar mass is expressed in terms of solar masses (Mo = 1.9891 × 1033 grams in cgs).

The masses in the Exoplanet Archive are derived from the Tycho B-V colors (converted to Johnson B-V), or the V-Ks colors. The mass to B-V relationship is from Gray (1992), and the mass to V-Ks relationship is derived from data in Henry et al. (1993). The V-Ks relationship is used for lower-mass objects for which the B-V color is not an accurate discrimator of mass. This switch-over limit is based on V-Ks color and is set to V-Ks=3.545 mag.

The masses in the Exoplanet Archive are currently only calculated for main sequence (dwarf) stars for which the luminosity can be determined. Since the luminosity in turn depends upon the B-V color, if a star does not have either the B-V color or the B- and V-band photometry, the Exoplanet Archive will not be able to calculate its mass. We plan to provide mass estimate for the remaining stars in a future release.

Note: the mass-color relationship assumes that the star is solar metallicity. Calculated masses for stars that have metallicities which are less than (or greater than) solar metallicity will be systematically larger (or smaller) than the true stellar masses.

References

Comments/Notes

None.

Mass (Published)

Metallicity

In stellar astrophysics, a 'metal' is any element heavier than hydrogen and helium. Metallicity indicates what fraction (relative to the most abundant element, Hydrogen) of a particular metal is present in a star's atmosphere. For comparison, this value is usually normalized to that of the sun.

The stellar metallicity of a particular element, X, is defined as the ratio of the amount of X (by number) to the amount of hydrogen in the star divided by the ratio of the amount of X to the amount of hydrogen in the Sun. This value is denoted as [X/H] and it is expressed in a logarithmic scale.

[X/H] = Log10( (X/H)star / (X/H)Sun )

The most common measure of stellar metallicity is the abundance of iron in the star, [Fe/H]. Currently, this is the only metallicity indicator available in the Exoplanet Archive.

References

The data ingested in the Exoplanet Archive are taken from the following published sources:

Comments/Notes

Cayrel de Strobel et al. (1997, 2001) are compilations of stellar metallicity taken from the literature. In the 'View' as published link, the "compiled from" bibligraphical code refers to the original publication.

Multiplicity

The Exoplanet Archive uses the Washington Double Stars (WDS) catalog to determine if a particular star is in a multiple system. Caution: The WDS catalog also contains optical systems - i.e. stars that lie near the line of sight to another star, but are not actually physically associated with the other star. Therefore, the fact that a star is listed as having multiple components in the Exoplanet Archive does not necessarily mean it is a true multiple system - the additional components may only be chance projections toward the "primary". We still include these cases in the Exoplanet Archive because for some purposes it is important to know if there is a close, apparent neighbor even if there is no physical connection. In later updates to the Exoplanet Archive, we hope to flag optical systems in order to provide that additional information, where possible. As newer catalog data are made available, we will revise the multiplicity information on each star.

Where possible, the Exoplanet Archive also stores information on the separation and magnitude difference between the primary and seconday star. These are also taken from the WDS catalog. The Exoplanet Archive calculated the magnitude difference as a positive number when the difference refers to a secondary (fainter) companion, and a negative number when the difference refers to the primary (brighter) companion.

References

The data are taken from:

Comments/Notes

None.

Orbital Solution Date

The Date of Orbital Solution refers to the date of when the orbital parameters were determined and published. Since orbital solutions are continually improved for extrasolar planets as more data are taken, this quantity indicates when and with which existing data these orbital parameters were derived.

References

The Planet Properties page for each individual star with planets includes references for the observed orbit properties.

Comments/Notes

None.

Parallax or Distance

As the earth moves around the sun, nearby stars appear to move slightly with respect to much more distant stars. The maximum angular distance that a star appears to move can be obtained be measuring the star's position at carefully selected dates six months apart (so the earth goes through half of its orbit). This maximum change of angular position is called parallax (π), and is a direct measurement of a star's distance from the sun via:

D = 1 / π

where D is in parsecs, and π is in arcsec.

User can provide constraints as either parallax or distance by selecting the appropriate unit in the 'Unit' pull down menu.

References

The data ingested in the Exoplanet Archive are taken from the following published resources:

Comments/Notes

The distance is computed from the parallax only when the parallax is detected with signal-to-noise of at least 3 (SNR>=3). For parallax values that are not well measured (SNR < 3), a three-sigma lower limit on the distance is calculated as 1/(max(parallax_value,0) + 3*parallax_error).

Period

The Observed Orbit Period is the observed time for an exoplanet to complete one revolution around its host star. It is typically derived from photometric light curves (for transiting planets) or Keplerian orbital fits to radial velocity data. For example, the Period for Earth is 1 year.

References

The Planet Properties page for each individual star with planets includes references for the observed orbit properties.

Comments/Notes

None.

Time of Periastron Passage

The Time of Periastron Passage is the time at which the orbit of planet goes through its periastron (time of closest approach). This quantity is typically inferred from Keplerian orbital fits to radial velocity data. Time of Periastron Passage helps define the orientation of the orbit with respect to the plane of the sky. Multiple periastron passages can be observed in radial velocity data, and due to orbital precession, the time of periastron passage can change as the orientation of the orbit precesses with respect to our line of sight. Consequently, a time of periastron passage is usually quoted during a time when radial velocity data was obtained. The Time of Periastron Passage is directly related to the Longitude of Periastron.

References

The Planet Properties page for each individual star with planets includes references for the observed orbit properties.

Comments/Notes

None.

Photometric Light Curve

The light curves (excluding the Hipparcos light curves) were contributed by a number of astronomers. References for individual light curves are given on the respective page.

As more light curves are contributed, this material will be updated.

Comments/Notes

None.

Photometry

The Exoplanet Archive stores observed stellar flux values in two sets of homogenized units: mags and Jy. These mean the Exoplanet Archive always converts the published values into one or both units as necessary; however, the original, as published values are also preserved and available to the user.

The zero-point values for conversion between magnitudes and Jy are provided below.

Zero-point conversion for the filters in the Exoplanet Archive
Filter System Wavelength
(microns)
F(ν)
(Jy)
Hp Hipparcos 0.5275 3748.
BT Tycho 0.4203 3943.
VT Tycho 0.5319 3761.
U Johnson 0.3531 1790.
B Johnson 0.4407 4063.
V Johnson 0.5537 3636.
Rc Cousins 0.6469 3064.
Ic Cousins 0.7886 2416.
J 2MASS 1.235 1594
H 2MASS 1.662 1024
Ks 2MASS 2.159 666.7
IRAC1 Spitzer 3.561 280.9
IRAC2 Spitzer 4.509 179.7
IRAC3 Spitzer 5.693 115.0
IRAC4 Spitzer 7.982 64.13
MIPS24 Spitzer 23.7 7.14
MIPS70 Spitzer 71 0.775
MIPS160 Spitzer 156 0.159
IRAS12 IRAS 11.59 28.3
IRAS25 IRAS 23.88 6.73
IRAS60 IRAS 61.49 1.19
IRAS100 IRAS 101.95 0.43

References

The mean wavelengths and flux for zero magnitude data shown in the table are derived from the following references

Band System Source
U Johnson Johnson et al. (1966)
B Johnson Johnson et al. (1966)
B Johnson Bessell (1990)
B Johnson Bessel (2000) PASP, 112, 961
Bt Tycho The Tycho-2 Catalog
V Johnson Johnson et al. (1966)
V Johnson Cousins (1980a)
V Johnson Cousins (1980b)
V Johnson Bessell (1990)
V Johnson Bessel (2000) PASP, 112, 961
Hp Hipparcos The Hipparcos Catalog
Vt Tycho The Tycho-2 Catalog
R Cousins Cousins (1980a)
R Cousins Cousins (1980b)
R Cousins Bessell (1990)
I Cousins Cousins (1980a)
I Cousins Cousins (1980b)
I Cousins Bessell (1990)
J 2MASS Cutri et al. (2003)
H 2MASS Cutri et al. (2003)
Ks 2MASS Cutri et al. (2003)
3.6 IRAC FEPS Legacy team photometry
4.5 IRAC FEPS Legacy team photometry
5.8 IRAC FEPS Legacy team photometry
8.0 IRAC FEPS Legacy team photometry
24 micron MIPS Beichman et al. (2005) ApJ, 622, 1160
24 micron MIPS Bryden et al. (2006) ApJ, 636, 1098
70 micron MIPS Beichman et al. (2005) ApJ, 622, 1160
70 micron MIPS Bryden et al. (2006) ApJ, 636, 1098
12 micron IRAS IRAS Catalog
25 micron IRAS IRAS Catalog
60 micron IRAS IRAS Catalog
100 micron IRAS IRAS Catalog

Comments/Notes

None

Photometry Colors

These are the observed colors of the stars. The values are either presented in the original photometric system as published, or converted. Whether it is as published or converted is identified in the detailed listing for colors. The Exoplanet Archive searches the converted values.

References

The photometry data is from the following references

Color System Source
U - B Johnson Johnson et al. (1966) Comm. Lunar Plan. Lab., 4, 99
B - V Johnson Johnson et al. (1966) Comm. Lunar Plan. Lab., 4, 99
B - V Johnson Bessell (1990)
B - V Johnson Bessel (2000) PASP, 112, 961
B - V Tycho The Tycho-2 catalog
V - R Johnson - Cousins Cousins (1980a) South African Astron. Obs. Circ., 1, 166
V - R Johnson - Cousins Cousins (1980b) South African Astron. Obs. Circ., 1, 234
V - R Johnson - Cousins Bessell (1990)
V - I Johnson - Cousins Cousins (1980a) South African Astron. Obs. Circ., 1, 166
V - I Johnson - Cousins Cousins (1980b) South African Astron. Obs. Circ., 1, 234
V - I Johnson - Cousins Bessell (1990)
J - H 2MASS The 2Mass catalog
H - Ks 2MASS The 2Mass catalog
J - Ks 2MASS The 2Mass catalog
b - y Stroemgren Olsen (1994a) A&AS, 104, 429
b - y Stroemgren Olsen (1994b) A&AS, 106, 257
b - y Stroemgren Olsen (1993) A&AS, 102, 89
m1 Stroemgren Olsen (1994a) A&AS, 104, 429
m1 Stroemgren Olsen (1994b) A&AS, 106, 257
m1 Stroemgren Olsen (1993) A&AS, 102, 89
c1 Stroemgren Olsen (1994a) A&AS, 104, 429
c1 Stroemgren Olsen (1994b) A&AS, 106, 257
c1 Stroemgren Olsen (1993) A&AS, 102, 89

Comments/Notes

None.

Planet Flux (Predicted)

The Exoplanet Archive only computes planet fluxes for Earth-like planets located at the center of the Habitable Zone of the parent star.

The predicted flux of an Earth-like planet is computed by placing the total mono-chromatic intensity of a full Earth at the distance of the star, and calculating the flux that we would receive from there.

The Exoplanet Archive uses the total intensity of Earth's atmosphere (Iλ) computed by members of the Virtual Planetary Laboratory, as it is shown in Figure 1:

Figure 1

Figure 1: The predicted intensity from Earth's atmosphere (Iλ) in units of W/m2/μm/st.radians.

The predicted flux (Fλ) is converted from the total intensity by multiplying by the solid angle subtended by the Earth (Ω) at the distance of the star (D):

Fλ = Iλ × Ω

where:

Ω = π × (REarth/D)2

and REarth = 6.38 × 106 m.

The magnitude (mλ) at monochromatic wavelength (λ) is then given by:

mλ = -2.5 log (Fλ/Fλ 0)

where: Fλ 0 is the flux of a 0 magnitude star.

Comments/Notes

The flux calculations do not take into account the location of the planet in its orbit and hence the phase of the planet. The assumption is that the planet is at "full phase" and so the flux received by the observer is at maximum.

These calculations assume an Earth reflectivity as described by the intensity profile. The actual flux will then depend upon the composition of the planet.

Planet Mass

The Mass is the observed planet mass. It is typically derived from Keplerian orbital fits to radial velocity data, or from micro-lensing, or SED fits to direct imaging. For example, the mass of Earth is 1 Earth Mass. For radial velocity detected planets, the orbital inclination is typically unknown or poorly constrained, unless there is another planet in orbital resonance, or it is transiting. For these planets, the mass refers to the Mass multiplied by the Sine of the Inclination angle. The true planet mass depends on the inclination of the orbit with respect to the planet of the sky.

References

The Planet Properties page for each individual star with planets includes references for the observed planet properties.

Comments/Notes

None.

Planet Radius

Radius is the planetary radius. It is typically calculated from photometry data of transiting planets as a function of stellar radius, which can be calculated from spectral energy distribution fitting to multiband stellar photometry. For planets with only radial velocity data, the radius is either unknown, or it can only be estimated from the planetary minimum mass. For example: one Jupiter radius is approximately 11 Earth radii.

References

The Planet Properties page for each individual star with planets includes references for the observed planet properties.

Comments/Notes

None.

Planetary Companions

The Exoplanet Archive maintains a list of systems which are thought to contain planetary systems. This is list is maintained by our staff of scientists and is drawn from literature and the community. As planets are discovered and removed by the community within the literature and within the astronomical community, the exact number and disposition of the planets many change.

References

The data are taken from:

Comments/Notes

None

Planet Transit Light Curve

The light curves of known planetary transits were contributed by a number of astronomers. References for individual light curves are given on the respective page.

As more planetary transits are discovered and observed, this material will be updated.

Comments/Notes

None.

Proper Motion

The proper motion of a star is the vector motion (i.e. the motion after the effects of parallax are removed) of a star over time. It is usually provided in the Equitorial coordinate system as the proper motion in the Right Ascension direction and the proper motion in the Declination direction.

The user can search the Exoplanet Archive by contraining the proper motion in right ascension (PM RA), the proper motion in declination (PM Dec) and the total proper motion, which is the quadrature addition of PM RA and PM Dec.

Proper motions in the Exoplanet Archive are stored in units of milli arc seconds per year (mas/yr)

References

The data ingested in the Exoplanet Archive are taken from the following published resources:

Comments/Notes

None.

Radial Velocity

The stellar radial velocity is the velocity of a star along the observer's line of sight. Negative radial velocities imply motion towards the observer. The radial velocity in the Exoplanet Archive is stored in units of kilometers per second (km/sec).

References

The data ingested in the Exoplanet Archive are taken from the following published resources:

Comments/Notes

None.

Radial Velocity Curve

Radial velocity curves of known planetary transits were contributed by a number of astronomers. References for individual radial velocity curves are given on the respective page.

As more planetary systems are discovered and observed, this material will be updated.

Selecting the 'Output' box will show the radial velocity curves available for a given transiting planet.

Selecting the 'Include Stars with No Value' box will find those stars for which there are no radial velocity curves in the Exoplanet Archive database.

Comments/Notes

None.

Radial Velocity Wobble (Predicted)

The stellar radial velocity is the velocity of a star in the direction along the line of sight. The radial velocity in the Exoplanet Archive is stored in units of kilometers per second (km/sec). The Radial Velocity Wobble is the magnitude by which a companion body to the star will perturb the radial velocity of the star. The value represents the peak-to-peak magnitude of this effect and the units are meters per second (m/s). The Radial Velocity Wobble depends on the distance between the star and the companion body, the mass of the star, the mass of the companion body, and the inclination of the companion's orbit with respect to the observer's line of sight.

For an Earth-like planet, the values stored in the Exoplanet Archive are calculated by placing a one earth mass planet at the center of the Habitable Zone and assuming an inclination angle of 33 degrees for the planet's orbital plane relative to our line of sight. For a Jupiter-like planet, the calculated values are obtained by placing a one Jupiter mass planet at 5.2 AU from the parent star and assuming an inclination angle of 33 degrees for the planet's orbital plane relative to our line of sight. The mass for the parent star is calculated as described in the documentation for calculated mass.

References

The data are calculated by the Exoplanet Archive.

Comments/Notes

None.

Radius (Calculated)

The stellar radius is defined as the distance between the center of the star and its surface. The stellar radius is expressed in terms of solar radius (Ro = 6.9598 × 1010 cm).

The Exoplanet Archive stores both published and calculated values of the stellar radius. Calculated values of the stellar radius come from the relationship between the radius (R in cm), the effective temperature (Teff in K ) and the luminosity (L in erg sec-1) of the star:

R2 = L / (4πσTeff4)

where σ is the Stefan-Boltzmann constant (σ= 5.67×10-5 erg sec-1 cm-2 K-4).

Radius (Published)

The stellar radius is defined as the distance between the center of the star and its surface. The stellar radius is expressed in terms of solar radius (Ro = 6.9598 × 1010 cm).

The Exoplanet Archive stores both published and calculated values of the stellar radius. Published values of the stellar radius come from direct interferometric measurements.

Data Validation

N/A.

Comments/Notes

None.

Rossby Number

The Rossby number is a dimensionless number defined to parameterize the level of stellar magnetic activity.

In a star, the magnetic dynamo mechanism operates in a highly conductive plasma which is subject to convective and rotational motions. The Rossby number is the ratio of the characteristic time scales of rotation (rotational period) and convection (convective turnover time):

Ro = Prot / τconv

where Prot is the rotational period, and τconv is the period of circulation within a convective cell or convective turnover time

Data Validation

N/A.

Comments/Notes

None.

Rotation Period

The rotation period of a star is the amount of time the star takes to complete one rotation about its axis. The Exoplanet Archive stores the rotation period values in units of days.

References

The data ingested in the Exoplanet Archive are taken from the following published resources:

Comments/Notes

None.

Semi-Major Axis

The Observed Semi-Major Axis is the orbital semi-major axis, typically inferred from Keplerian orbital fits to radial velocity data, direct imaging, or fits to micro-lensing light curves. For example, the Orbital Semi-Major Axis for Earth is 1 AU.

Space Motion

The space motion describes the composite motion of a star in the Galaxy relative to the Sun and is derived from the star's distance, proper motions, and mean radial velocity. It is usually expressed with three space velocity components (U, V, W) in a right-handed Galactic system, with U pointing towards the Galactic center, V in the direction of rotation, and W towards the north Galactic pole.

The space velocity components are stored in units of kilometer per second (km/sec).

References

The data ingested in the Exoplanet Archive are taken from the following published resources:

Comments/Notes

None.

Space Motion (Calculated)

The space motion describes the composite movement of a star in the Galaxy and is derived from the star's distance, proper motions, and mean radial velocity. It is usually expressed with three space velocity components (U, V, W) in a right-handed Galactic system, with U pointing towards the Galactic center, V in the direction of rotation of the disk of the galaxy, and W towards the north Galactic pole. For the calculated space motions, we refer the motion to the Local Standard of Rest (i.e. the mean motion of the stars in the solar neighborhood), rather than to the Sun.

Where all of the parameters needed to determine a space motion are available in the Exoplanet Archive, we calculate and provide that space motion, using formulae as provided in Johnson & Soderblom (1987).

The space velocity components are stored in units of kilometer per second (km/sec).

References

The data ingested in the Exoplanet Archive are taken from the following published resources:

Comments/Notes

None.

Spectra

The current release includes two types of stellar spectra -

1) high-resolution optical spectra taken with HIRES at the Keck Telescope and
2) infrared spectra taken with IRS on board the Spitzer Space Telescope.

The high-resolution optical spectra have been donated by the California Planet Search, the N2K project, and the M2K project, while the infrared spectra comes from the publications referenced below.

IRS spectra that are associated with a planet-bearing star can be accessed from the Search for an Individual System page, enter the star name to view the overview page, and then click the Spectra tab to download and/or view the spectra if it is available for that star.

To download the N2K and M2K, use the archive's Bulk Data Download feature. Spectra are categorized by optical and infrared.

References

High-resolution Optical Spectra:

Infrared Spectra:

Comments/Notes

None.

Spectral Types & Classification Systems

The spectral type of a star, brown dwarf, or lower-mass objects is a classification scheme based on spectral features. It is a purely empirical quality that relies only on the measured spectrum; for stars, spectral types are primarily related to the surface temperature. Spectral types are denoted by classes O, B, A, F, G, K, M, L, T and subclasses (usually) ranging from 0 to 9. The allowed spectral types in the Exoplanet Archive are listed below. The best documented, most widely used spectral type system is the "MK" system (Morgan and Keenan - see Keenan and Morgan, Annual Reviews of Astronomy and Astrophysics 11, 29, 1973).

In order to provide a more complete coverage of the spectral types for our objects, we have included spectral types from the HD catalog. These spectral types (while not as accurate as the MK types noted above) include nearly all the stars in our database (including the bright northern stars).

Type Sub-classes
O 3-9
B 0-9
A 0-9
F 0-9
G 0-9
K 0-7
M 0-9

The spectral type of a star is usually accompanied by its luminosity class and additional qualifiers.

References

The data ingested in the Exoplanet Archive are taken from the following published sources:

Comments/Notes

None.

Spectroscopic Rotational Velocity (V Sin i)

The rotational velocity of a star is the rate at which it spins about its axis of rotation. Its units are km/sec. In Astronomy rotational velocity is typically measured from the Doppler broadening of spectral features, which depends also on the inclination of the star's axis relative to the observer's line of sight. This is commonly referred to as V Sin i.

References

The data ingested in the Exoplanet Archive are taken from the following published resources:

Comments/Notes

None.

Transit Depth (Predicted)

If a planet in orbit around the star passes between the observer and the star, the apparent brightness of the star is reduced for a brief period. The depth of the planetary transit depends upon the radius of the planet and the radius of the star and so can be used to induce the size of the planet. The relative change in flux is then the square of the ratio of the planetary and stellar radii respectively.

Two values for the calculated transit depth for each planet are stored in the Exoplanet Archive: one assuming an Earth radius and one assuming a Jupiter radius. The transit depth is dimensionless.

References

The data are calculated by the Exoplanet Archive.

Comments/Notes

None.

Data Validation

N/A.

Comments/Notes

None.

Data Validation

N/A.

Comments/Notes

None.

Variability Types used in the Exoplanet Archive

The variability types used in the Exoplanet Archive taken from the Hipparcos catalog. The following codes are used to describe the variability type in the Exoplanet Archive. These are taken from the Hipparcos catalog description (Table 2.4.1 in volume 1).

Code Description Class of Variable
ACV alpha-2 Canum Venaticorum type (including ACVO) rotating
ACYG alpha Cygni type pulsating
BCEP beta Cephei type (including BCEPS) pulsating
BY BY Draconis type rotating
CEP Cepheids (including CEP(B)) pulsating
CST constant stars (considered as variable by some observer(s)) -
CW W Virginis type pulsating
CWA W Virginis type (periods > 8 days) pulsating
CWB W Virginis type (periods < 8 days) pulsating
DCEP delta Cephei type (including DCEPS) pulsating
DSCT delta Scuti type (including DSCTC) pulsating
E (E+, E/ ..) eclipsing binary
EA Algol type (EA+, EA/ ..) eclipsing binary
EB Beta Lyrae type (EB/ ..) eclipsing binary
ELL rotating ellipsoidal (ELL+.. or /..) rotating
EW W Ursae Majoris type (EW/ ..) eclipsing binary
FKCOM FK Comae Berenices type rotating
GCAS gamma Cassiopeiae type eruptive
I irregular (I, IA, IB, In, InT, Is) eruptive
IN irregular (INA, INAT, INB, INSA, INSB, INST, INT) eruptive
IS irregular (ISA, ISB) eruptive
L slow irregular (L, LB, LC) pulsating
M Mira Ceti type pulsating
N slow novae (NB, NC) cataclysmic
NA fast novae cataclysmic
NL nova-like cataclysmic
NR recurrent novae cataclysmic
PVTEL PV Telescopii type pulsating
RCB R Coronae Borealis type eruptive
RR RR Lyrae type (RR, RRAB, RRB, RRC) pulsating
RS RS Canum Venaticorum type eruptive
RV RV Tauri type (RV, RVA, RVB) pulsating
SARV small-amplitude red variables pulsating/rotating
SDOR S Doradus type eruptive
SPB slowly pulsating B stars pulsating
SR semi-regular (SR, SRA, SRB, SRC, SRD) pulsating
SXARI SX Arietis type rotating
SXPHE SX Phœnicis type pulsating
UV UV Ceti type eruptive
WR Wolf-Rayet eruptive
XNG X-ray nova-like system X-ray binary
XP X-ray pulsar X-ray binary
ZAND Z Andromedae type cataclysmic