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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"

3312 results found.

  1. Konus-Wind detection of GRB 240905B
  2. EP240919a / GRB 240919A: SVOM/VT upper limit
  3. EP240918b and EP240918c: EP-FXT follow-up observations
  4. Konus-Wind detection of GRB 240918B
  5. EP trigger ID 01709059262: correction to the observation start time and source localization
  6. EP trigger ID 01709059262: the X-ray transient is likely a stellar flare event
  7. EP240919a: EP-FXT follow-up observation update
  8. EP240913a/GRB 240913C: 1.6m Mephisto observations
  9. EP240918a: SVOM/VT upper limit
  10. Fermi GBM Sub-Threshold Detection of GRB240919A / EP240919a
  11. EP240919a / GRB 240919A: REM optical and NIR upper limits
  12. EP240919a / GRB 240919A: KAIT optical upper limit
  13. EP240918b and EP240918c: Optical upper limits with Kinder observations
  14. EP240919a: Optical upper limit with Kinder observations
  15. GRB 240919A / EP240919a: SVOM/GRM observation
  16. EP240919a: INTEGRAL SPI-ACS confirmation of reported high-energy counterpart
  17. EP240919a: INTEGRAL SPI-ACS confirmation of reported high-energy counterpart
  18. EP EP240919a: Global MASTER-Net observations report
  19. EP240918a: 1.6m Mephisto multi-band Optical Upper Limit
  20. EP240919a: NOT and Gemini optical observations
  21. EP240919a: GOTO optical upper limits
  22. EP240919a: JinShan optical upper limits
  23. EP240919a is likely a GRB event
  24. EP240919a: EP-WXT detection of a fast X-ray transient
  25. EP240918b and EP240918c: EP-WXT detection of two fast X-ray transients
  26. EP240918a: EP observation update
  27. EP240918a: Swift-XRT observation
  28. EP EP240918a: Global MASTER-Net observations report
  29. EP240918a: JinShan optical upper limits
  30. EP240918a: Optical upper limits with Kinder observations
  31. EP240918a: GMG Optical Upper Limit
  32. EP240918a: an X-ray transient detected by Einstein Probe
  33. IPN triangulation of GRB 240913C / EP 240913a
  34. GRB 240825A: The nature of the afterglow motivates the search of the associated supernova
  35. The EP-WXT triggers 01709047257 and 01709047278 are not real sources
  36. EP EP240913a: Global MASTER-Net observations report
  37. EP240913a: VLT/HAWK-I near-infrared upper limits
  38. GRB 240913C: Joint location by ETJASMIN
  39. EP240913A / GRB 240913C: AstroSat CZTI detection
  40. EP240913a: NOT optical upper limits
  41. EP240913a: JinShan optical upper limits
  42. EP240913a: ESO-NTT optical observations
  43. EP240913a: Swift/XRT detection of an X-ray source within the EP/WXT error circle
  44. EP240913a: A GRB Event
  45. EP240913a: EP-WXT detection of a fast X-ray transient
  46. EP240908a: Optical afterglow confirmation
  47. EP240908a: Mondy and AbAO follow-up observations
  48. EP240908a: Updates on the WXT detection result around the trigger time
  49. EP240908a: optical afterglow candidate
  50. EP EP240908a: Global MASTER-Net observations report
  51. EP240908a: TRT optical upper limit
  52. EP240908a: EP detection of a fast X-ray transient
  53. SVOM GRB 240821A: optical afterglow discovery
  54. GRB 240821A: the second and third EP-FXT follow-up observations and afterglow candidates
  55. Konus-Wind detection of GRB 240825A (bright/long)
  56. GRB 240821A: Colibri Optical Upper Limit
  57. EP240820a: PRIME J-band Observations
  58. GRB 240821A: Swift-XRT observations
  59. GRB 240821A: REM optical/NIR upper limits
  60. GRB 240821A: LCO optical observations
  61. GRB 240821A: JinShan optical upper limits
  62. GRB 240821A: SVOM/VT follow-up and optical upper limit
  63. GRB 240821A: GMG Optical Upper Limit
  64. GRB 240821A: EP-FXT follow-up observation and afterglow candidates
  65. GRB 240819A: Swift-XRT observations
  66. EP240820a: TRT optical upper limit
  67. EP240820a: EP detection of a fast X-ray transient
  68. GRB 240819A: KAIT optical upper limit
  69. EP240816a: PRIME upper limits
  70. GRB 240819A: TRT optical upper limits on the Swift/XRT and EP/FXT sources
  71. GRB 240819A: X-ray follow-up observation with EP-FXT
  72. EP240816b: Liverpool Telescope optical follow-up observations
  73. EP240816a: BOOTES-6/DPRT optical upper limit
  74. EP240816b: KAIT optical upper limit
  75. EP240816a: EP detection of a fast X-ray transient and follow-up observation
  76. EP EP240816b: Global MASTER-Net observations report
  77. EP240816b: TRT optical upper limit
  78. EP240816b: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
  79. EP240802a: Kinder optical, SWIFT-UVOT, and SWIFT-XRT upper limits 6 days after the WXT detection
  80. Konus-Wind detection of GRB 240811A
  81. Konus-Wind detection of GRB 240810A
  82. EP240807a: PRIME H-band upper limits
  83. Konus-Wind detection of GRB 240809A
  84. Konus-Wind detection of GRB 240807A (a counterpart of EP240807a)
  85. IPN triangulation of GRB 240807A / EP 240807a
  86. X-ray Transient EP240807a: PRIME near-infrared upper limits
  87. GRB 240807A: SVOM/GRM observation
  88. EP-WXT trigger 01709018832: SVOM/C-GFT observations of the star flare
  89. EP240807a: STEP/T80S optical limits
  90. EP EP240807a: Global MASTER-Net observations report
  91. EP EP240806a: Global MASTER-Net observations report
  92. EP240807a/GRB 240807A: EP-FXT detection of the X-ray emission
  93. EP-WXT trigger 01709018832: KAIT optical observations of the star flare
  94. EP240802a/GRB240802A: KAIT optical upper limit
  95. EP240806A: Liverpool Telescope optical follow-up observations
  96. The EP-WXT trigger 01709018832 on August 7th is likely a flaring star
  97. EP240807a: EP-WXT detection of a fast X-ray transient
  98. EP240806a: Gemini North-GMOS spectroscopic redshift of z = 2.818
  99. EP240806a: KAIT optical observations
  100. EP240804a (GRB 240804B): NOT optical observations

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