DwarfArchives.org L & T Archive Search Form Help

You can find the help you need for any aspect of this search form. Use the table of contents below to jump to a specific section, or simply browse the entire contents.


General notes

The L & T Dwarf section of DwarfArchives contains all known L & T dwarfs that have been spectroscopically classified. That is, we do not include any objects for which the colors suggest an L or T spectral type.

In this archive we present discovery names, JHK colors (mostly from 2MASS), astrometry, and spectral types (both optical and near-IR). We include hyperlinked references to all information, as well as finder charts. Our plan is to also include spectra, but that might take some time as we are standardizing the headers. We will also include more photometry in a future release of the archive.

The server for the archive database and search engine is a dual core 2.8 GHz Pentium with 2 GB RAM running Fedora Core 4 (x86_64). The database itself is running under PostgreSQL 8.1.5 which is accessed from the web form through custom built PHP 5.2.0 scripts. The form, as well as these help pages, are written in HMTL.

The server was funded by a NASA Small Research Grant, administered by the American Astronomical Society. We thank them for their generosity.


Name Search Help

This section is used if you only want information about a particular object whose name you know in full or in part. The search is a very simple routine that tries to match the entered text with either the discovery name or the designation, as chosen from the drop down box. Keep in mind that the names in the database are the full object names and not the shorthand names routinely used in the literature. Also, the entered text must be exactly the same as the entry in the database for a valid result to be returned. Since most of us don't know the full names exactly, wild cards can be used to help with the areas of the name you about which you are unsure.

For example, suppose you want to return the information about the object commonly referred to as "2MASS 0746+2000." If you entered this text into the name search field, no result would be returned, since the full discovery name is "2MASSI J0746425+200032" and the full 2MASS PSC designation is "2MASS J07464256+2000321." A wild card must be included with the input name to ensure a proper match. An entry of "2MASS*0746*2000*" Will return the object you want.

Supported wildcards are:


Radius Search Help

With this section it is possible to search the contents of the archive around a specific position. Enter the length of the search radius in the radius box; the units of this radius is determined by the units listed in the drop down box. Possible units are arcsec, arcmin, or degrees. There is currently no limit for the size of the search radius.

You can either search around specific coordinate (by selecting the Coordinate option) or upload a table of names and/or positions (by selecting the Upload option). The coordinate conversions and name resolving is performed through IRSA's Lookup Service. Information about what types of input that are accepted can be viewed here.

If you want to search around several objects, you can use the table upload form. The table must be a simple ASCII file with the form:

| name | ra | dec |

These are the only three columns allowed for the time being. Each of the values under the column headers must be contained within the pipes ("|") and the column headers must have those exact names ("name", "ra", and "dec").

Examples

For files with names and coordinates, the name is not sent to the name resolver; the search is performed around the input position. This is to allow for names that will not be resolved by SIMBAD.

The routine to compute the great circle arc distances is derived from the IDLAstro routine gcirc.pro.


Search Form Help

This form is used to create custom searches of the archive. Almost every aspect of the archive can be constrained during a query. The logic used between fields is set to AND (ex. jmag<16 AND ra>14.0). Logic within a field can be set to AND or OR using the Limit Logic column.


Display Query

If the box is checked (default), then the SQL string used for the database query is returned along with the results. The SQL string is not returned if the box is not checked. Having the SQL string returned is useful for those trying to learn SQL and for tracking bugs in the search scripts.


Return Type

The results of the search can be returned as either an HTML or a text (ASCII) table. HTML tables have the benefit of providing links to abstracts of reference papers and object finder charts. They are, however, not convenient for saving results that are suitable for user-made programs.

Text tables, on the other hand, are fully formatted results that can be saved and easily used in programs. While the information about the reference paper is still listed, it is not possible to provide the online abstract. Nor is it possible to provide links to the finder charts.


Sort Order

The results of the search can by ordered according to many of the search fields listed below. This section determines if the results are ordered by Ascending or Descending values for the chosen field. If one of the spectral type fields is the sort field, then Ascending sorts from early to late spectral type and Descending sorts from late to early.


Search Form Columns

Name

The name of the field. These are usually the names of the columns in the database.

Description

A short description describing the field.

Select

A checked box in this column denotes a field that is to be returned with the query. Some fields are returned automatically when related fields are selected. For example, selecting jmag to be returned also returns jmag_error. The help listings for each field below describes additional fields that are returned. Any number (>0) of fields can be selected for return.

Sort by

A mark in this column indicates which field is to be used for ordering the results. The results are ordered according to ascending or descending values, as determined by the selection in the Sort Order box. Only one field can be selected as the ordering field.

Low Limit

Use these input boxes to set lower numerical limits for any of the aplicable fields. Except for the spectral type fields, the input values can be floats or integers. Please see the help listing for spectral type below for information regarding how to set limits for this field.

All entries must be preceded by =, >, or >=.

Limit Logic

These radio buttons are used to determine the logic used for the upper and lower limit constraints. The logic choices are AND and OR. In most cases the AND logic will suffice (ex. return all objects with a J magnitude greater than 12 AND less than 15). However, in some cases, the OR logic might be better. If you want to search for objects with right ascension crossing the 0/24 hour boundary, then you would need to use the OR logic. For example, to search for objects between a right ascension of 20 and 4 hours, set the Low Limit to ">20", the Up Limit to "<4" and the Limit Logic to OR.

Upper Limit

Use these input boxes to set upper numerical limits for any of the applicable fields. Except for the spectral type fields, the input values can be floats or integers. Please see the help listing for spectral type below for information regarding how to set limits for this field.

All entries must be preceded by =, <, or <=.

Measurement

Not every object in the archive has an entry for every field. For example, parallaxes are only available for fewer than 100 L and T dwarfs. The checkboxes in this column can be used to return only those objects for which a measurement exists in this archive (check the Req box) or only those objects for which a measurement does not exist in the archive (check the Mis box).

Suppose you want to start an observing program to get parallaxes for those object that need them. An easy way to get your target list is to check the Mis. box for the parallax field and click Submit.

The actual test that is performed when one of these boxes is selected is a check for a null value for the field. Values that are not null are assumed to contain a measurement.

Units

This column contains the units that are used for both input and ouput.


Search Form Fields

discovery_name The name of the object as it originally appears in the discovery paper. This name can be in a variety of forms depending on the source of the discovery data (eg. 2MASS, DENIS, SDSS, companion search, etc.).
In a few instances (generally cases where the object is a companion to a star), an object may have more than one discovery name listed. These names are separated by a comma (',').
Selecting this returns the discovery name of the object and the reference for the discovery paper. If an HTML form is returned, then the finder chart is linked to the discovery name and the ADS abstract is linked to the paper reference. We use the IRSA FinderChart service to provide realtime charts for all targets. This is much slower than our custom-made PDF finder charts, but also much less of a burden on our limited time. This option is not supported. If you want to sort by position, then use the sort by buttons for ra or decl instead. This option is not supported. This option is not supported. There are no nulls in this column. All objects have a discovery name. There are no nulls in this column. All objects have a discovery name. There are no units for this field
designation The 2MASS point source designation. These are derived from the J2000 coordinates of the source. The source designation takes one of three forms:
  • '2MASS Jhhmmssss[+/-]ddmmsss': Source found in the 2MASS All-Sky Point Source Catalog
  • '2MASSA Jhhmmssss[+/-]ddmmsss': Source was detected in one or more bands, but did not have sufficient signal-to-noise to be included in the main Point Source Catalog. These objects can be found in the Point Source Reject Catalog.
  • '----- Jhhmmsss[+/-]ddmmss': Source not found in any 2MASS catalog
Selecting this returns the 2MASS designation of the object. This designation provides a reference for the photometry and a representation of the object's coordinate in hexigesimal format. This option is not supported. If you want to sort by position, then use the sort by buttons for ra or decl instead. This option is not supported. This option is not supported. There are no nulls in this column. All objects in the archive have a 2MASS designation. There are no nulls in this column. All objects in the archive have a 2MASS designation. There are no units for this field
ra The J2000 right ascension of the object. The coordinate is derived from the 2MASS designation or the discovery reference for objects not found in the 2MASS catalog. For objects that are close companions to brighter stars, the position given is based on the observed offset from the bright star. Selecting this field returns a floating point value of the right ascension in hours. A sexigesimal value of the right ascension can be obtained from the designation. Selecting this causes the results to be ordered according to ascending or descending values of the right ascension. This button is selected by default. Three basic formats are supported for right ascensions input into this field:
  • 12.2342185
  • 12 39 29.94
  • 12:39:29.94
A comparison operator (=,>, >=) must also be present.
Three basic formats are supported for right ascensions input into this field:
  • 12.2342185
  • 12 39 29.94
  • 12:39:29.94
A comparison operator (=,<, <=) must also be present.
There are no nulls in this column. There are no nulls in this column. hours
decl The J2000 declination of the object. The coordinate is derived from the 2MASS designation or the discovery reference for objects not found in the 2MASS catalog. For objects that are close companions to brighter stars, the position given is based on the offset from the bright star. Selecting this field returns a floating point value of the declination. A sexigesimal value of the declination can be obtained from the designation. Selecting this causes the results to be ordered by ascending or descending declination. Three basic formats are supported for declinations input into this field:
  • +45.45923
  • -38 43 93.3
  • +57:29:38.4
A sign (+ or -) must be present as must the comparison operator (=,>, >=).
Three basic formats are supported for declinations input into this field:
  • +45.45923
  • -38 43 93.3
  • +57:29:38.4
A sign (+ or -) must be present as must the comparison operator (=,<, <=).
There are no nulls in this column. There are no nulls in this column. degrees
jmag The J-band magnitude of the object. The magnitudes for objects with a designation starting with '2MASS' or '2MASSA' are taken from the 2MASS Point Source Catalog. The magnitudes for objects with a designation starting with '------' are taken from the discovery paper and are (very likely) not the same as numerically equivalent 2MASS values. Selecting this field returns the J magnitude and the associated error (jmag_error). Selecting this orders the results according to ascending or descending J magnitude. Limits inserted here can be entered as a float and must be preceded by (=,>, >=). Limits inserted here can be entered as a float and must be preceded by (=,<, <=). Selecting this requires the returned results to have non-null values for jmag. Selecting this requires the returned results to have null values for jmag. magnitudes jmag_error The photometric error associated with the J-band magnitude. The source of the error is the same as the source of the J magnitude. This field is automatically returned when the jmag field is selected. Selecting this orders the results according to ascending or descending J magnitude error. Limits inserted here can be entered as a float and must be preceded by (=,>, >=). Limits inserted here can be entered as a float and must be preceded by (=,<, <=). Selecting this requires the returned results to have non-null values for jmag_error. Selecting this requires the returned results to have null values for jmag_error. magnitudes hmag The H-band magnitude of the object. The magnitudes for objects with a designation starting with '2MASS' or '2MASSA' are taken from the 2MASS Point Source Catalog. The magnitudes for objects with a designation starting with '------' are taken from the discovery paper and are (very likely) not the same as numerically equivalent 2MASS values. Selecting this field returns the H magnitude and the associated error (hmag_error). Selecting this orders the results according to ascending or descending H magnitude. Limits inserted here can be entered as a float and must be preceded by (=,>, >=). Limits inserted here can be entered as a float and must be preceded by (=,<, <=). Selecting this requires the returned results to have non-null values for hmag. Selecting this requires the returned results to have null values for hmag. magnitudes hmag_error The photometric error associated with the H-band magnitude. The source of the error is the same as the source of the H magnitude. This field is automatically returned when the hmag field is selected. Selecting this orders the results according to ascending or descending H magnitude error. Limits inserted here can be entered as a float and must be preceded by (=,>, >=). Limits inserted here can be entered as a float and must be preceded by (=,<, <=). Selecting this requires the returned results to have non-null values for hmag_error. Selecting this requires the returned results to have null values for hmag_error. magnitudes kmag The K-band magnitude of the object. The magnitudes for objects with a designation starting with '2MASS' or '2MASSA' are taken from the 2MASS Point Source Catalog and are in the Ks filter. The magnitudes for objects with a designation starting with '------' are taken from the discovery paper and are (very likely) not the same as numerically equivalent 2MASS values. Selecting this field returns the K magnitude and the associated error (kmag_error). Selecting this orders the results according to ascending or descending K magnitude. Limits inserted here can be entered as a float and must be preceded by (=,>, >=). Limits inserted here can be entered as a float and must be preceded by (=,<, <=). Selecting this requires the returned results to have non-null values for kmag. Selecting this requires the returned results to have null values for kmag. magnitudes kmag_error The photometric error associated with the K-band magnitude. The source of the error is the same as the source of the K magnitude. This field is automatically returned when the kmag field is selected. Selecting this orders the results according to ascending or descending K magnitude error. Limits inserted here can be entered as a float and must be preceded by (=,>, >=). Limits inserted here can be entered as a float and must be preceded by (=,<, <=). Selecting this requires the returned results to have non-null values for kmag_error. Selecting this requires the returned results to have null values for kmag_error. magnitudes jh The (J-H) color of the object. The magnitudes for objects with a designation starting with '2MASS' or '2MASSA' are taken from the 2MASS Point Source Catalog. The magnitudes for objects with a designation starting with '------' are taken from the discovery paper and are (very likely) not the same as numerically equivalent 2MASS values. Selecting this field returns the (J-H) color and associated error (jh_error) of the object. Selecting this orders the results according to ascending or descending (J-H) color. Lower limits inserted here can be entered as a float and must be preceded by (=,>, >=). Upper limits inserted here can be entered as a float and must be preceded by (=,<, <=). Selecting this option requires that both jmag and hmag are non-null. This option is equivalent to selecting the measurement required option for both jmag and hmag separately. Selecting this option requires that either jmag or hmag are null. magnitudes jh_error The photometric error associated with the (J-H) color. The error is computed as sqrt(jmag_error2 + hmag_error2). This field is automatically returned when the jh field is selected. Selecting this orders the results according to ascending or descending (J-H) error. Lower limits inserted here can be entered as a float and must be preceded by (=,>, >=). Upper limits inserted here can be entered as a float and must be preceded by (=,<, <=). Selecting this option requires that both jmag_error and hmag_error are non-null. This option is equivalent to selecting the measurement required option for both jmag_error and hmag_error separately. Selecting this option requires that either jmag_error or hmag_error are null. magnitudes hk The (H-K) color of the object. The magnitudes for objects with a designation starting with '2MASS' or '2MASSA' are taken from the 2MASS Point Source Catalog. The magnitudes for objects with a designation starting with '------' are taken from the discovery paper and are (very likely) not the same as numerically equivalent 2MASS values. Selecting this field returns the (H-K) color and associated error (jh_error) of the object. Selecting this orders the results according to ascending or descending (H-K) color. Lower limits inserted here can be entered as a float and must be preceded by (=,>, >=). Upper limits inserted here can be entered as a float and must be preceded by (=,<, <=). Selecting this option requires that both hmag and kmag are non-null. This option is equivalent to selecting the measurement required option for both hmag and kmag separately. Selecting this option requires that either hmag or kmag are null. magnitudes hk_error The photometric error associated with the (H-K) color. The error is computed as sqrt(hmag_error2 + kmag_error2). This field is automatically returned when the hk field is selected. Selecting this orders the results according to ascending or descending (H-K) error. Lower limits inserted here can be entered as a float and must be preceded by (=,>, >=). Upper limits inserted here can be entered as a float and must be preceded by (=,<, <=). Selecting this option requires that both hmag_error and kmag_error are non-null. This option is equivalent to selecting the measurement required option for both hmag_error and kmag_error separately. Selecting this option requires that either hmag_error or kmag_error are null. magnitudes jk The (J-K) color of the object. The magnitudes for objects with a designation starting with '2MASS' or '2MASSA' are taken from the 2MASS Point Source Catalog. The magnitudes for objects with a designation starting with '------' are taken from the discovery paper and are (very likely) not the same as numerically equivalent 2MASS values. Selecting this field returns the (J-K) color and associated error (jk_error) of the object. Selecting this orders the results according to ascending or descending (J-K) color. Lower limits inserted here can be entered as a float and must be preceded by (=,>, >=). Upper limits inserted here can be entered as a float and must be preceded by (=,<, <=). Selecting this option requires that both jmag and kmag are non-null. This option is equivalent to selecting the measurement required option for both jmag and kmag separately. Selecting this option requires that either jmag or kmag are null. magnitudes jk_error The photometric error associated with the (J-K) color. The error is computed as sqrt(jmag_error2 + kmag_error2). This field is automatically returned when the jk field is selected. Selecting this orders the results according to ascending or descending (J-K) error. Lower limits inserted here can be entered as a float and must be preceded by (=,>, >=). Upper limits inserted here can be entered as a float and must be preceded by (=,<, <=). Selecting this option requires that both jmag_error and kmag_error are non-null. This option is equivalent to selecting the measurement required option for both jmag_error and kmag_error separately. Selecting this option requires that either jmag_error or kmag_error are null. magnitudes parallax The measured trigonometric parallax. All parallaxes are absolute except those from Tinney et al. 2003, which are relative. Selecting this field returns the trigonometric parallax, the quoted error for that parallax, and the reference for the measurement. If an HTML form is returned, the ADS abstract is linked to the reference. Selecting this orders the results according to ascending or descending parallax. Lower limits can be entered as a float and must be preceded by (=,>, >=). Upper limits can be entered as a float and must be preceded by (=,<, <=). Selecting this option requires that the parallax field is not null. Selecting this option requires that the parallax field is null. mas (milliarcseconds) parallax_error The quoted error for the measured trigonometric parallax. The field is automatically returned when the parallax field is selected. Selecting this orders the results according to ascending or descending parallax error. Lower limits can be entered as a float and must be preceded by (=,>, >=). Upper limits can be entered as a float and must be preceded by (=,<, <=). Selecting this option requires the parallax_error result to be non-null. Selecting this option requires the parallax_error result to be null mas (milliarcseconds) prop_motion The total proper motion of the object. The proper motions are generally presented as quoted. For references that provide proper motions separated into the right ascension and declination components, we compute the total proper motion, position angle, and associated errors as follows:

total proper motion: pm = sqrt(pmra*2 + pmde2)

proper motion error: epm = sqrt( (pmra*2 * epmra*2 + pmde2 * epmde2) / (pmra*2 + pmde2) )

position angle: pa = tan-1(pmra*/pmde)

position angle error: epa = sqrt( (pmra*2 * epmde2 + pmde2 * epmra*2) / (pmra*2 + pmde2)2 )
where pmra* = pmracosδ.
Selecting this returns the total proper motion and associated error, the position angle and error (measured from North to East), and the reference. If an HTML form is returned, then the ADS abstract is linked to the reference. Selecting this orders the results by ascending or descending proper motion. Lower limits can be entered as a float and must be preceded by (=,>, >=). Upper limits can be entered as a float and must be preceded by (=,<, <=). Choosing this requires the prop_motion field to be non-null. Choosing this requires a null value for the prop_motion field. arcseconds/year
prop_motion_error The error in the totatl proper motion. If the total proper motion is given in the reference, then the error quoted here is that from the reference. If, however, the proper motion and errors are given as right ascension and declination components in the reference, then we compute the error as follows:

proper motion error: epm = sqrt( (pmra*2 * epmra*2 + pmde2 * epmde2) / (pmra*2 + pmde2) )
where pmra* = pmracosδ.
This field is automatically returned if the prop_motion field is selected. Selecting this orders the results according to ascending or descending prop_motion_error Lower limits can be entered as a float and must be preceded by (=,>, >=). Upper limits can be entered as a float and must be preceded by (=,<, <=). Choosing this requires the prop_motion_error field to be non-null. Choosing this requires a null value for the prop_motion_error field. arcseconds/year
spectral_type The spectroscopically determined spectral type. The spectral type can be based on either the optical regime (~0.6 - 1.0 μm) or the near-infrared (~1.0 - 2.5 μm). As an archive requirement, all objects must have a spectral type from either one of these regimes. Many have spectral types determined from both regimes. Since the optical and near-IR spectral types are not usually the same, both are included in the archive. Selecting one or more of these boxes returns the spectral type(s) and reference(s). The optical or near-IR spectral types can be returned independently of each other. If an HTML form is returned, then the ADS abstract is link to the reference name. Choosing one of these will sort the results according to ascending or descending optical or near-IR spectral type. Lower limits for spectral type searches are entered here. Enter spectral types as a combination of a spectral class (M, L, or T) and a decimal subclass (0, 0.5, 1, ..., 9.5). Examples are L3 and T5.5. Be certain to precede the entry with a comparison operator (=,>, >=). The wavelength regime of the spectral type for which this limit is applicable is determined by the setting of the drop down box in this area. The choices are
  • Optical only (default)
  • IR only
  • Optical or IR
  • Optical and IR
Examples:

You want to select all objects with either an optical or near-IR spectral type later than (and including) L4 and cooler than (but not including) T6.

  • low limit entry: >=L4
  • upper limit entry: <T6
  • selector setting: "Optical or IR"
Check these if you want to restrict results to those whose spectral_type_opt and/or spectral_type_ir are not null. Check these if you want to restrict results to those whose spectral_type_opt and/or spectral_type_ir are null. none
note Special notes about the object. These notes include information about binarity and other unusual information. Selecting this field returns the note for the object. Not all objects have a note. This option is not supported. This option is not supported. This option is not supported. This option is not supported. This option is not supported. none More questions? Contact our Help Desk