Searching for the first X-ray source per constellation

Searching for the first X-ray source per constellation, or such a search, is an historical activity that begins in the 1960s as original research and is currently abandoned that first requires determining the exact boundaries of each constellation. There are 88 modern constellations that the International Astronomical Union (IAU) has used to divide the celestial sphere into 89 irregularly shaped boxes. The constellation Serpens is split into two separate sections, Serpens Caput (the snake's head) to the west and Serpens Cauda (the snake's tail) to the east. Using detectors placed above the Earth's atmosphere, X-radiation has been detected incoming from each of these constellations. For example, Scorpius X-1, Scorpius XR-1, or Sco X-1 is the first extrasolar X-ray source discovered in the constellation Scorpius. Each area of the celestial sphere had at least one extrasolar X-ray source detected between June 12, 1962, Scorpius X-1, and April 6, 1980, Corona Australis X-1 (CrA X-1), though most never received the X-1 (or XR-1) designation.
Written sources which document the initial detection of an X-ray source that becomes an X-1 X-ray source usually include most of the historical facts surrounding the initial discovery. Current discoveries about each X-1 source add to our understanding of the X-ray universe. The International Astronomical Union provides figures of each constellation and coordinates for the boundaries which can be used to determine the constellational location of a celestial object using its right ascension (RA) and declination (Dec). As the position of these constellations has shifted due to Earth orbit precessions, there is an approximate four minute increase between the right ascension boundaries of epoch 1950 B1950.0 and the most recent calibration of epoch 2000 J2000.0 and a few minutes of change in many declinations.
Constellations of the Southern Hemisphere
Using the X-ray Landmarks image above, some of the constellations can be located. The center of the galaxy is in the direction of Sagittarius, and the Milky Way "passes" (going westward, Earthview, to the right in the image) through Scorpius, Ara, Norma, Triangulum Australe, Circinus, Centaurus, Musca, Crux, Carina, Vela, Puppis, Canis Major, Monoceros, Orion & Gemini, Taurus, Auriga, Perseus, Andromeda, Cassiopeia, Cepheus & Lacerta, Cygnus, Vulpecula, Sagitta, Aquila, Ophiuchus, Scutum, and back to Sagittarius. The celestial equator passes through these constellations (RA): Pisces (1), Cetus (~2), Taurus (4+), Eridanus (3-), Orion (5), Monoceros (7), Canis Minor (8), Hydra (8 to 15), Sextans (10), Leo (11), Virgo (13), Serpens (16,18), Ophiuchus (17), Aquila (20), and Aquarius (23). In the table that follows, ranges of RA, Dec are included, e.g. (23-02, +23 to +52), to help make a fast assessment whether a particular X-ray source is in or borders a specific constellation. Questionable locations near a border require consulting the IAU website.
<table class = "wikitable" >
<caption>Constellations Grouped by Location (Quadrants of Midpoints)</caption>
<tr><th> Quad </th><th> Total </th><th> Constellations </td></tr>
<tr><th> NQ1 </th><td> 08 </td><td> Pisces (23-02, -26 to +30), Andromeda (23-02, +23 to +52), Cassiopeia (22-03, +47 to +78), Triangulum (1-2, +27 to +36), Aries (1-3, +10 to +31), Perseus, Taurus, Orion (4-6, -9 to +20), </td></tr>
<tr><th> NQ2 </th><td> 10 </td><td> Auriga (4-7, +28 to +55), Monoceros, Gemini (6-7, +12 to +35), Canis Minor (7-8, +00 to +12), Lynx (6-9, +34 to +61), Cancer (7-9, +07 to +32), Camelopardalis (3-13,+53 to +85), Leo Minor (9-11, +23 to +41), Leo (9-11, -04 to +29), Ursa Major (8-13, +31 to +70), </td></tr>
<tr><th> NQ3 </th><td> 08 </td><td> Coma Berenices, Canes Venatici (12-14, +31 to +51), Boötes (13-15, +07 to +54), Ursa Minor (1-17, +65 to +89), Draco (09-20, +49 to +83), Corona Borealis (15-16, +26 to +39), Serpens, Hercules, </td></tr>
<tr><th> NQ4 </th><td> 10 </td><td> Lyra (1813-1927, +25.66 to 47.70), Sagitta (19-20, +16 to +21), Aquila, Vulpecula, Cygnus, Delphinus (20 19 -21 07 , +02 to +20), Equuleus (20 59 -21 25 , +02 to +11), Cepheus, Lacerta, Pegasus (21-00, +02 to +35), </td></tr>
<tr><th> SQ1 </th><td> 14 </td><td> Sculptor (23-01, -25 to -38), Phoenix (23-02, -39 to -57), Cetus, Hydrus (0.08-4.66, -58 to -82), Fornax (1-3, -23 to -38), Horologium (2-4, -40 to -66), Eridanus (1-5, +00 to -57), Reticulum (3-4, -25 to -66), Caelum (4-5, -30 to -46), Dorado, Mensa (3-7.5, -71 to -85.5), Lepus (5-6, -11 to -27), Pictor, Columba (5-6,-27 to -42), </td></tr>
<tr><th> SQ2 </th><td> 11 </td><td> Canis Major (6-7, -11 to -32), Puppis, Volans (6-9, -64 to -74), Carina (6-11, -51 to -74), Pyxis (8-9, -19 to -37), Vela, Sextans, Antlia (9-11, -25 to -40), Chamaeleon (07-13, -75 to -82), Crater (10-11, -07 to -24), Hydra (8-15, +06 to -35), </td></tr>
<tr><th> SQ3 </th><td> 14 </td><td> Corvus (11-12, -11 to -24), Crux (11-12, -55 to -64), Musca (11-13, -64 to -75), Centaurus (1105-1503, -30.19 to -64.70), Virgo (1137-1511, +14.36 to -22.68), Circinus (1338-1530, -55.43 to -70.62), Libra (1421-1602, -0.47 to -29.99), Lupus (1417-1608, -29.83 to -55.58), Norma (1512-1636, -42.27 to -60.44), Triangulum Australe (1456-1713, -60.26 to -70.51), Apus (14-18, -67 to -82), Scorpius (1547-1759, -8.29 to -45.77), Ara (1636-1810, -45.48 to -67.69), Ophiuchus (1601-1848, +14.38 to -30.21), </td></tr>
<tr><th> SQ4 </th><td> 13 </td><td> Corona Australis (18-19,-36 to -45), Scutum, Sagittarius, Telescopium (18-20, -45 to -56), Pavo (17-21, -56 to -73), Microscopium, Capricornus (20-21, -09 to -26), Indus (20-23, -45 to -73), Piscis Austrinus (21-23, -25 to -34), Aquarius (20-23, +02 to -24), Grus (21-23, -36 to -53), Octans (00-23, -75 to -90), Tucana (22-01, -56 to -79). </td></tr>
</table>
Serpens
Serpens is divided into two parts: Serpens Caput and Serpens Cauda.
Serpens Caput
Serpens Caput is the 'Serpent's Head' which lies to the west. NGC 5964 is a spiral galaxy, NGC 5921 is a barred spiral galaxy in the constellation Serpens Caput.
Serpens Caput has a celestial area of 428.484 sq. deg. and a midpoint at RA Dec .
Prior to 1970 no X-ray source is listed as detected in Serpens Caput.
The 3U catalog (3rd Uhuru catalog) from X-ray observations made by the X-ray observatory satellite Uhuru contains a weak X-ray source, 3U 1551+15, with a very large error box containing A2151 (the Hercules Cluster), A2152, and A2147. Several long observations in the vicinity of the Hercules Cluster are made over a period of 17 months (January 1975 - May 1976). The closest visual counterpart is MM Serpentis. Positions as catalog entries for Ser X-1 are 2S 1837+049, 4U 1837+04, and 1H 1837+049, among others. Ser X-1 is located within the constellation Serpens Cauda. It is a steady galactic bulge source and an X-ray burst source.
Searches for X-ray sources
The astronomical X-number notation (X-#) for an astronomical X-ray source in a constellation has its start with the initial discoverers of an extrasolar X-ray source at the American Science and Engineering Company (ASE)-Massachusetts Institute of Technology (MIT). The constellation genitive (or an abbreviation) followed by X and a digit is an early designation for the X-ray source. Researchers at the US Naval Research Laboratory suggested "XR" (for X-Ray) rather than "X". Later, the sources became simply the constellation (or an abbreviation) followed by X-#, e.g., Scorpius X-1 (Sco X-1).
Using an Aerobee 150 launched from Natal, Brazil, in Dec 1966, experimenters from the Catholic University identified new X-ray sources in the southern hemisphere.
X-ray structure within a constellation
With the SIMBAD database, a constellation such as Scutum is searched for X-ray sources or large X-ray structures. The image at the right is of the entire constellation generated using the 'region(polygon,coordinates list for corners)'.
Scutum is in the southern sky. Of all the constellations it is 84th in celestial area at 109 sq. deg. A relatively uniform distribution of 1,000 astronomical X-ray sources would yield at least two. Or, by 1984 and the HEAO 1 A-1 catalog, (840 X-ray sources known), there might have been at least two X-ray sources detected in Scutum.
The major X-ray structure across Scutum from top to right is the Galactic plane. Many of these X-ray sources are detections by XMM-Newton.
Early X-ray sources include 4U 1835-11, 1A 1835-08, 4U 1850-086 (LMXB, in NGC 6712), 1A 1850-08, Sct X-1, 4U 1832-05, and 1A 1847-05.
Alternately, a known X-ray source may be examined for its earliness and constellation.
A test of an individual X-ray source
Consider 1ES 0507-040 from the Einstein Observatory (ES) catalog. 0507-040 is in equatorial coordinates for the epoch 1950 B1950.0 from the dates of observation at right ascension (RA) declination (Dec) . For the epoch 2000 the source is now at J2000.0 RA Dec . The prefix '1ES' is the first ES catalog. It is a listing of sources detected during pointed observations from the Slew Survey performed using the Imaging Proportional Counter (IPC) aboard the Einstein Observatory (HEAO 2) satellite, in orbit between November 1978 and April 1981.
The constellation for the X-ray source
A negative declination indicates a southern hemisphere constellation. Using the RA of and Dec of , and following the constellations around the celestial equator, 1ES 0507-040 is in the constellation Eridanus near β Eridani at ~05 and −05°. There is no star in the list of stars in Eridanus that is at 1ES 0507-040. Although there is a K3 star at RA Dec .
Databases
A first place to look regarding such a designation as "1ES 0507-040" is the SIMBAD Astronomical Database. Another is to use Google advanced scholar search, for example, inputting "1ES 0507-040" yields that this object is a blazar, designated QSO B0506-039. The earliest catalog listing the source appears to be 4U 0506-03.
Dates for catalog entries
To assess whether the initial detection of a particular X-ray source listed in a catalog is earlier than another, here is a list of last possible dates for each catalog entry per prefix:
# 1E or 1ES (Einstein Observatory) before April 26, 1981,
# 3A (Ariel 5) before March 14, 1980,
# 3S (SAS 3) before April 9, 1979,
# 1H (HEAO 1) before January 10, 1979,
# H (HEAO 1) between October 1, 1977, (day 244), and February 27, 1978, (day 423),
# 2A before April 1, 1977,
# A before 1976,
# 4U (Uhuru) before January 12, 1974,
# 3U before August 27, 1973,
# M or MX (OSO 7) before May 18, 1973,
# 2U before May 4, 1972,
# V (Vela satellite) before January 27, 1972,
# 1U: 2ASE before November 29, 1971,
# 1U: 1ASE before August 4, 1971,
# HX: (Cosmos 428) before July 6, 1971, and
# M or MX (OSO 3) before June 28, 1968.
First X-ray source per constellation
Perusing the list above puts the discovery of the X-ray source before January 12, 1974. In the 4th Uhuru catalog QSO B0506-039 has no previous designation, so it may not be the first X-ray source in Eridanus. Consulting the section Eridanus X-1 confirms that 1ES 0507-040 is not the first X-ray source detected in Eridanus nor is it designated Eridanus X-1.
A list of the first X-ray source in a constellation can help to decide which possible early astronomical X-ray source to test. In addition, there is an index table for X-ray and gamma-ray sources. If the X-ray source being tested appears to be an X-ray source of note, it is entered into the index table for X-ray and gamma-ray sources.
Corona Australis X-1
Corona Australis is a small constellation in the southern hemisphere of the celestial sphere, abbreviated CrA.
Each of the X-ray observatory satellite Uhuru catalogs including the 4th Uhuru catalog contain no X-ray source from the constellation Corona Australis.
Corona Australis X-1 (CrA X-1) is a naked T Tauri star, possibly V709 CrA at AX 18581-3705. CrA X-1 is detected on April 6, 1980, in image 4512 taken with the Einstein Observatory IPC, while targeting S CrA in the R CrA molecular cloud, which is a star-forming region.
But, astrometrically Sagittarius X-7 is just inside the International Astronomical Union (IAU) border of Corona Australis from Sagittarius, possibly making Sagittarius X-7 the first astronomical X-ray source detected in Corona Australis. Sagittarius X-7 may have been discovered after December 12, 1970, and before May 4, 1972.
Completeness
No publication in print contains the identification of all of the first X-ray sources discovered for each of the 88 (or 89) constellations. In part this apparent lack of completeness is because of
# the discovery of so many X-ray sources in such a short time by X-ray astronomy satellites such as Uhuru (detecting hundreds of X-ray sources with often several per constellation before its deactivation on January 12, 1974), Cosmos 428 and OSO 7, HEAO 1 launched on August 12, 1977, and ROSAT (launched June 1, 1990),
# the discovery of relatively large, somewhat local, X-ray structures such as the Galactic plane and the Large Magellanic Cloud,
# the transient nature of many sources,
# the apparent lack of a coincident source in longer wavelengths of the electromagnetic spectrum such as radio or the visible, in short many X-ray sources are visibly dark X-ray sources,
# alternate naming conventions, and
# the loss of interest in the naming convention as applied to galactic (Milky Way) astronomical X-ray sources.

Main Menu

See Also

Main Menu