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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"
  1. GRB 240421B: Swift detection of a burst
  2. EP240420a: Nanshan optical counterpart observations
  3. EP240420a: GWAC-F50A optical upper limit
  4. LIGO/Virgo/KAGRA S240421ar: Identification of a GW unmodeled transient candidate
  5. GRB 240421A: Fermi GBM Final Real-time Localization
  6. EP240420a: detection of fading X-ray emission with refined position by EP-FXT
  7. EP240420a: NOT optical counterpart candidate and potential host
  8. Fermi trigger No 735280430: Global MASTER-Net observations report
  9. GRB240419A: Skynet Optical Afterglow Analysis
  10. GRB240418A - Candidate afterglow from NIRES
  11. IceCube Alert 240419.98: Global MASTER-Net observations report
  12. GRB 240419B: Swift/UVOT Upper Limits
  13. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  14. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  15. EP240420a: EP-WXT detection of a fast X-ray transient
  16. GRB 240419A: Swift/UVOT Upper Limits
  17. GRB 240419B: Swift-XRT refined Analysis
  18. GRB 240419B: optical afterglow from the NOT
  19. LIGO/Virgo/KAGRA S240420aw: Retraction of GW compact binary merger candidate
  20. EP240414a: Near-IR observations with NIRES and WINTER
  21. Swift GRB 240419B: Global MASTER-Net observations report
  22. EP240414A: Terskol Zeiss-2000 optical upper limit
  23. GRB 240419B: Enhanced Swift-XRT position
  24. Swift GRB 240419A: Global MASTER-Net observations report
  25. GRB 240418A: Swift/UVOT Upper Limits
  26. GRB 240419A: REM NIR afterglow detection
  27. GRB 240419A: Swift-XRT refined Analysis
  28. GRB 240418A: Swift-XRT refined Analysis
  29. GRB 240419B: Swift detection of a burst
  30. GRB 240411B: Swift/UVOT Detection
  31. EP240417a: YAHPT Optical Upper Limits
  32. GRB240418A: YAHPT Upper Limits
  33. GRB 240419A: VLT/UVES redshift of z = 5.178
  34. GRB 240419A: VLT optical afterglow detection
  35. GRB 240419A: Enhanced Swift-XRT position
  36. Fermi trigger No 735089036: Global MASTER-Net observations report
  37. EP240416a: J-band observations with WINTER
  38. EP240414a: GMG observation
  39. GRB 240419A: Prompt enhanced Swift-XRT position
  40. GRB 240419A: Swift detection of a burst
  41. GRB 240418A: TSHAO Zeiss-1000 optical upper limit
  42. GRB 240418A: NOT optical upper limits
  43. GRB 240418A: Enhanced Swift-XRT position
  44. GRB 240418A: AKO Upper Limit
  45. GRB 240411A: GOTO early optical upper limits
  46. Swift GRB240418.85: Global MASTER-Net observations report
  47. GRB 240418A: Swift detection of a burst
  48. EP240417a: EP-WXT detection of a fast X-ray transient
  49. Fermi GRB 240417A: Global MASTER-Net observations report
  50. LIGO/Virgo/KAGRA S240413p: X-ray upper limits from EP-WXT for the candidate AGN counterpart
  51. EP240416A: Terskol Zeiss-2000 optical upper limit
  52. EP240416A: Khureltogoot optical upper limit
  53. Improved IPN triangulation of GRB 240411A
  54. EP240416a: BOOTES-2/TELMA Optical Upper Limit
  55. EP240414a: GSP detects optical candidate counterpart AT2024gsa
  56. LIGO/Virgo/KAGRA S240413p: DECam GW-MMADS candidates
  57. IceCube-Cascade 240416A: Upper limits from a search for additional neutrino events in IceCube
  58. GRB 240417A: Fermi GBM Final Real-time Localization
  59. EP240414a: Pan-STARRS detects re-brightening of the candidate counterpart AT2024gsa
  60. LIGO/Virgo/KAGRA S240413p: historical ATLAS and ZTF observations of the candidate AGN counterpart
  61. GRB 240415A: Glowbug gamma-ray detection
  62. GRB 240414A: Glowbug gamma-ray detection
  63. LIGO/Virgo/KAGRA S240413p: STEP - T80S Search and Candidate Counterpart Identification
  64. GRB 240415B: GECAM-B detection
  65. EP 240416a: Xinglong and NOT decaying optical counterpart
  66. GRB 240415A: Swift-BAT refined analysis
  67. EP240416A: MASTER optical observations
  68. GRB 240411A: Glowbug gamma-ray detection
  69. GRB 240414A: Swift-BAT refined analysis
  70. EP240416a: Kinder optical counterpart candidate
  71. EP240416a: EP-WXT detection of a fast X-ray transient
  72. GRB 240414A: AbAO optical upprer limit
  73. GRB 240415A: Swift/UVOT Detection
  74. EP240413a: BOOTES-2/TELMA Optical Upper Limit
  75. GRB 240415A: Fermi GBM Observation
  76. GRB 240414A: GAD Observatory, La Spezia, Italy ,upper limit
  77. GRB 240415A: Earliest optical followup with the Kinder observations
  78. GRB 240414A: GMG observation
  79. EP 240414a: BOOTES-4/MET Optical Upper Limits
  80. EP240414a: EP-FXT follow-up observation
  81. GRB 240415A: Enhanced Swift-XRT position
  82. GRB 240415B: Swift ToO observations
  83. GRB 240415B: Swift/BAT-GUANO Correction
  84. GRB 240415B: Swift/BAT-GUANO arcminute localization of a short burst
  85. GRB 240415A: OHP/T193 optical observations
  86. GRB 240415A: optical afterglow detection from the INAF Asiago Observatory
  87. GRB 240415A: SAO RAS optical observations
  88. GRB 240415A: Mondy optical transient detection (photometry correction in GCN 36118 )
  89. GRB 240414A: Fermi GBM Observation
  90. Fermi GRB 240415A: Global MASTER-Net observations report
  91. GRB 240415A: Mondy optical transient detection
  92. GRB 240414A: Photometric observation from 2.2m CAHA
  93. IceCube-240412A: Upper limits from a search for additional neutrino events in IceCube
  94. GRB 240414A: Swift/UVOT Detection
  95. LXT 240402A/GRB 240402B: Swift follow-up observations
  96. GRB 240414A: Mondy optical observations
  97. GRB 240414B: Fermi GBM Final Real-time Localization
  98. GRB 240414A: AKO Optical Upper Limit
  99. X-ray transient EP 240414a - GTC spectroscopic observations
  100. GRB 240415A: Prompt Swift-XRT observations

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