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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"

3295 results found.

  1. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  2. EP240426b: AST3-2 optical upper limit
  3. LIGO/Virgo S240422ed: Swift XRT observation of EP240426a
  4. EP240426b: EP-WXT detection of a new fast X-ray transient
  5. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  6. LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
  7. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
  8. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  9. LIGO/Virgo/KAGRA S240422ed: EP-FXT Detection of the Potential Opitcal Electromagnetic Counterpart AT 2024hfq Reported by DECam
  10. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  11. EP240426a: GMG optical upper limit
  12. LIGO/Virgo/KAGRA S240422ed: EP-FXT detection of a candidate counterpart EP240426a
  13. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-FXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  14. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  15. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  16. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  17. LXT240402A/GRB240402B: Chandra X-ray detection
  18. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  19. EP240420a: TNT upper limit to its optical counterpart
  20. EP240420a: Xinglong decaying optical counterpart
  21. EP240420a: Nanshan optical counterpart observations
  22. EP240420a: GWAC-F50A optical upper limit
  23. EP240420a: detection of fading X-ray emission with refined position by EP-FXT
  24. EP240420a: NOT optical counterpart candidate and potential host
  25. EP240420a: EP-WXT detection of a fast X-ray transient
  26. EP240416a: J-band observations with WINTER
  27. EP240417a: EP-WXT detection of a fast X-ray transient
  28. LIGO/Virgo/KAGRA S240413p: X-ray upper limits from EP-WXT for the candidate AGN counterpart
  29. EP240416a: BOOTES-2/TELMA Optical Upper Limit
  30. EP 240416a: Xinglong and NOT decaying optical counterpart
  31. EP240416A: MASTER optical observations
  32. EP240416a: Kinder optical counterpart candidate
  33. EP240416a: EP-WXT detection of a fast X-ray transient
  34. EP240413a: BOOTES-2/TELMA Optical Upper Limit
  35. EP 240414a: BOOTES-4/MET Optical Upper Limits
  36. EP240414a: EP-FXT follow-up observation
  37. LXT 240402A/GRB 240402B: Swift follow-up observations
  38. X-ray transient EP 240414a - GTC spectroscopic observations
  39. EP240413a: Upper limits from GECAM-B Observation
  40. EP 240414a: NOT optical counterpart confirmation
  41. EP240413A: GOTO optical upper limits
  42. EP240414a: Kinder optical counterpart candidate possibly associated with the galaxy SDSS J124601.99-094309.3
  43. EP240413a: possible detection of the X-ray emission with EP-FXT after 14 hours
  44. EP240414a: EP-WXT detection of a fast X-ray transient
  45. EP240413a: EP-WXT detection of a fast X-ray transient
  46. EP240408a: GSP optical upper limit
  47. EP240408A: MASTER optical observations
  48. EP240408a: Upper limits from GECAM-B Observation
  49. EP240408a: Swift follow-up observation
  50. EP240408a: BOOTES-6/DPRT optical upper limit
  51. EP240408a: EP-WXT detection of a fast X-ray transient
  52. LXT 240402A/GRB 240402B: rest-frame energetics from Konus-Wind observation
  53. X-ray transient LXT 240402A: WFST optical upper limits​
  54. Konus-Wind detection of LXT 240402A/GRB 240402B
  55. GRB/FXT 240402B: Kinder optical counterpart candidate
  56. GRB/FXT 240402B: VLT/FORS2 optical afterglow candidate
  57. X-ray transient LXT240402A: AST3-3 optical upper limits
  58. LXT 240402A: EP-FXT detection of the X-ray afterglow
  59. GRB 240402B: GECAM-C detection
  60. X-ray transient LXT 240402A: LEIA detection
  61. X-ray transient EP240331A: GRANDMA-Kilonova catcher optical upper limit
  62. EP240331A: MASTER optical observations
  63. X-ray transient EP 240315a: Second epoch Chandra observations
  64. Konus-Wind detection of GRB 240315C (possible counterpart of EP240315a)
  65. X-ray transient EP 240315a: Chandra observations
  66. X-ray transient EP240315a: MeerKAT radio detection
  67. X-ray transient EP240315a: GTC/OSIRIS spectroscopic redshift confirmation
  68. X-ray transient EP240315a: EP-FXT detection of the X-ray afterglow
  69. X-ray transient EP240315a: Montarrenti Observatory optical upper limit
  70. X-ray transient EP240315a: orphan FXT?
  71. X-ray transient EP240315a: Nanshan/HMT optical upper limit
  72. Einstein Probe detected of a fast X-ray transient EP240315a
  73. Konus-Wind detection of GRB 231118A
  74. Konus-Wind detection of GRB 240227A (short/hard)
  75. Konus-Wind detection of GRB 240303B
  76. Konus-Wind detection of GRB 240225B (long)
  77. Transient EPW20240219aa: REM optical/NIR upper limits
  78. Transient EPW20240219aa: Xinglong-2.16m optical upper limit
  79. Transient EPW20240219aa: GECKO: LOAO Optical Upper Limits
  80. Transient EPW20240219aa: 7DT Optical Upper Limits
  81. Insight-HXMT/HE Sub-Threshold Detection of Transient EPW20240219aa
  82. Konus-Wind detection of GRB 240218A
  83. Konus-Wind detection of GRB 240204A
  84. Konus-Wind detection of GRB 240205A (short)
  85. Konus-Wind detection of GRB 240205B (long / very soft)
  86. Konus-Wind detection of GRB 240125A
  87. Konus-Wind detection of GRB 240124B
  88. Konus-Wind detection of GRB 240123C
  89. Konus-Wind detection of GRB 240112A
  90. Konus-Wind detection of GRB 240119A (short/hard)
  91. Konus-Wind detection of GRB 240118A
  92. Konus-Wind detection of GRB 240112C
  93. Konus-Wind detection of GRB 240101C
  94. Konus-Wind detection of GRB 231215A
  95. Konus-Wind detection of GRB 231210B
  96. Konus-Wind detection of GRB 231129C
  97. Konus-Wind detection of GRB 231020A
  98. GRB 231117A: GECAM-C detection
  99. Konus-Wind detection of GRB 231117A (short/hard)
  100. Konus-Wind detection of GRB 231115A (a probable Magnetar Giant Flare from M82)

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