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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

2959 results found.

  1. GRB 240821A: the second and third EP-FXT follow-up observations and afterglow candidates
  2. Konus-Wind detection of GRB 240825A (bright/long)
  3. GRB 240821A: Colibri Optical Upper Limit
  4. EP240820a: PRIME J-band Observations
  5. GRB 240821A: Swift-XRT observations
  6. GRB 240821A: REM optical/NIR upper limits
  7. GRB 240821A: LCO optical observations
  8. GRB 240821A: JinShan optical upper limits
  9. GRB 240821A: SVOM/VT follow-up and optical upper limit
  10. GRB 240821A: GMG Optical Upper Limit
  11. GRB 240821A: EP-FXT follow-up observation and afterglow candidates
  12. GRB 240819A: Swift-XRT observations
  13. EP240820a: TRT optical upper limit
  14. EP240820a: EP detection of a fast X-ray transient
  15. GRB 240819A: KAIT optical upper limit
  16. EP240816a: PRIME upper limits
  17. GRB 240819A: TRT optical upper limits on the Swift/XRT and EP/FXT sources
  18. GRB 240819A: X-ray follow-up observation with EP-FXT
  19. EP240816b: Liverpool Telescope optical follow-up observations
  20. EP240816a: BOOTES-6/DPRT optical upper limit
  21. EP240816b: KAIT optical upper limit
  22. EP240816a: EP detection of a fast X-ray transient and follow-up observation
  23. EP EP240816b: Global MASTER-Net observations report
  24. EP240816b: TRT optical upper limit
  25. EP240816b: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
  26. EP240802a: Kinder optical, SWIFT-UVOT, and SWIFT-XRT upper limits 6 days after the WXT detection
  27. Konus-Wind detection of GRB 240811A
  28. Konus-Wind detection of GRB 240810A
  29. EP240807a: PRIME H-band upper limits
  30. Konus-Wind detection of GRB 240809A
  31. Konus-Wind detection of GRB 240807A (a counterpart of EP240807a)
  32. IPN triangulation of GRB 240807A / EP 240807a
  33. X-ray Transient EP240807a: PRIME near-infrared upper limits
  34. GRB 240807A: SVOM/GRM observation
  35. EP-WXT trigger 01709018832: SVOM/C-GFT observations of the star flare
  36. EP240807a: STEP/T80S optical limits
  37. EP EP240807a: Global MASTER-Net observations report
  38. EP EP240806a: Global MASTER-Net observations report
  39. EP240807a/GRB 240807A: EP-FXT detection of the X-ray emission
  40. EP-WXT trigger 01709018832: KAIT optical observations of the star flare
  41. EP240802a/GRB240802A: KAIT optical upper limit
  42. EP240806A: Liverpool Telescope optical follow-up observations
  43. The EP-WXT trigger 01709018832 on August 7th is likely a flaring star
  44. EP240807a: EP-WXT detection of a fast X-ray transient
  45. EP240806a: Gemini North-GMOS spectroscopic redshift of z = 2.818
  46. EP240806a: KAIT optical observations
  47. EP240804a (GRB 240804B): NOT optical observations
  48. EP240806a: LCOGT optical counterpart detection
  49. Konus-Wind detection of GRB 240802A (EP240802a)
  50. Improved IPN triangulation of GRB 240802A / EP 240802a
  51. Konus-Wind detection of GRB 240805A
  52. Konus-Wind detection of GRB 240804B (a counterpart of EP240804a)
  53. EP240806a: EP-FXT detection of the X-ray emission
  54. EP 240806A: LCO optical observations
  55. EP240806a: GSP optical counterpart detection
  56. EP240806a: EP-WXT detection of a fast X-ray transient
  57. EP240804a: BOOTES-6/DPRT optical detection
  58. EP240804a: VLT/X-shooter spectroscopic redshift
  59. EP240804a: LCOGT optical counterpart detection
  60. EP-WXT trigger 00109017646 is not a real source
  61. EP240804a: NOT optical counterpart detection
  62. EP240804a: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
  63. EP240802a: correction of EP-WXT trigger time in GCN 37019
  64. EP240802a: Montarrenti Observatory optical upper limit
  65. IPN triangulation of GRB 240802A / EP 240802a
  66. EP240801a: Osservatorio Astronomico Nastro Verde upper limit
  67. EP240802A: Bassano Bresciano Observatory upper limit
  68. EP240802a: Time coincidence with GRB 240802A and optical upper limits with Kinder observations
  69. EP240802a: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
  70. EP240801a: optical observations at CrAO and AbAO
  71. EP240801a: GRANDMA and Kilonova-Catcher optical observations
  72. EP240801a: Leavitt Observatory optical observations
  73. EP240801a: GTC spectroscopy and absorption redshift
  74. EP240801a: JinShan optical observations
  75. EP240801a: NOT optical observations
  76. EP240801a: follow-up observation with LCOGT
  77. EP240801a: Kinder follow-up observations of the candidate counterpart
  78. EP240801a: TRT optical counterpart detection
  79. EP240801a: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
  80. EP-WXT trigger 01709002661 is not a real source
  81. Konus-Wind detection of GRB 240718A
  82. IceCube-Cascade 240714A: TRT optical observations on the EP/FXT positions
  83. IceCube-Cascade 240714A: X-ray follow-up observation with EP-FXT
  84. GRB 240713A: 2.2m CAHA optical limit
  85. EP240708a: X-ray follow-up observations with Swift/XRT
  86. Konus-Wind detection of GRB 240715A
  87. GRB 240713A: Swift-XRT observations
  88. GRB 240713A: optical upper limits from the INAF Asiago Observatory
  89. EP-WXT flaring star and the optical flaring activity during its decay phase
  90. JinShan confirmation of the EP-WXT source triggered on July 14th due to a flaring star
  91. The EP-WXT source triggered on July 14th is likely a flaring star
  92. GRB 240713A: J-band upper limit from WINTER
  93. GRB 240713A: NOT optical upper limits on three EP/FXT candidates
  94. GRB 240713A: JinShan optical upper limits
  95. GRB 240713A: OHP/T120 optical upper limit
  96. GRB240713A: X-ray follow-up observation with EP-FXT (duplicate submission of GCN 36859)
  97. GRB240713A: X-ray follow-up observation with EP-FXT
  98. EP240708a: GSP optical upper limit
  99. EP240708a: KAIT optical upper limit
  100. EP240708a: NOT optical observations

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