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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  2. GRB 240419A: Possible ATCA radio detection
  3. GRB 240421B: ATCA radio observations
  4. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  5. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  6. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility observations and candidates
  7. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  8. LIGO/Virgo/KAGRA S240422ed: Magellan Observations
  9. LIGO/Virgo/KAGRA S240422ed: Updated NED Galaxies in the Localization Volume
  10. LIGO/Virgo/KAGRA S240422ed: AstroSat CZTI non-detection and upper limits
  11. LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
  12. LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
  13. LIGO/Virgo/KAGRA S240421ar: Upper limits from Swift/BAT-GUANO
  14. LIGO/Virgo/KAGRA S240422ed: Coverage and upper limits from MAXI/GSC observations
  15. LIGO/Virgo/KAGRA S240422ed: MeerLICHT and BlackGEM observations report
  16. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  17. LIGO/Virgo/Kagra S240422ed: NED Galaxies in the Localization Volume
  18. LIGO/Virgo/KAGRA S240422ed: Global MASTER-Net observations report
  19. Fermi trigger No 735470374: Global MASTER-Net observations report
  20. GRB 240421A: Glowbug gamma-ray detection
  21. GRB 240414A: radio detection with the VLA
  22. Fermi-LAT gamma-ray observations of IceCube-240419A
  23. GRB 240414A: AMI-LA radio observations
  24. GRB 240414A: LBT optical detection
  25. GRB 240419B : MITSuME Akeno optical upper limits
  26. GRB 240415B: Swift-XRT observations
  27. GRB 240415A: Swift-XRT refined Analysis
  28. Fermi GRB 240422A: Global MASTER-Net observations report
  29. GRB 240421B: AstroSat CZTI detection
  30. GRB 240422A: Fermi GBM Final Real-time Localization
  31. GRB240421B: Zadko Observations
  32. Fermi GRB 240421B: Global MASTER-Net observations report
  33. Swift GRB 240421B: Global MASTER-Net observations report
  34. GRB 240421B: Fermi GBM Observation
  35. GRB 240421B: Swift-XRT refined Analysis
  36. GRB240421B: BOOTES-5/JGT optical upper limit
  37. GRB 240421B: J-band upper limits from WINTER
  38. GRB 240421B: Swift/UVOT Upper Limits
  39. GRB 240421B: Enhanced Swift-XRT position
  40. Fermi GRB 240421A: Global MASTER-Net observations report
  41. EP240417a: no counterpart detection by SOAR
  42. EP240420a: TNT upper limit to its optical counterpart
  43. EP240420a: Xinglong decaying optical counterpart
  44. GRB 240421B: Swift detection of a burst
  45. EP240420a: Nanshan optical counterpart observations
  46. EP240420a: GWAC-F50A optical upper limit
  47. LIGO/Virgo/KAGRA S240421ar: Identification of a GW unmodeled transient candidate
  48. GRB 240421A: Fermi GBM Final Real-time Localization
  49. EP240420a: detection of fading X-ray emission with refined position by EP-FXT
  50. EP240420a: NOT optical counterpart candidate and potential host
  51. Fermi trigger No 735280430: Global MASTER-Net observations report
  52. GRB240419A: Skynet Optical Afterglow Analysis
  53. GRB240418A - Candidate afterglow from NIRES
  54. IceCube Alert 240419.98: Global MASTER-Net observations report
  55. GRB 240419B: Swift/UVOT Upper Limits
  56. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  57. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  58. EP240420a: EP-WXT detection of a fast X-ray transient
  59. GRB 240419A: Swift/UVOT Upper Limits
  60. GRB 240419B: Swift-XRT refined Analysis
  61. GRB 240419B: optical afterglow from the NOT
  62. LIGO/Virgo/KAGRA S240420aw: Retraction of GW compact binary merger candidate
  63. EP240414a: Near-IR observations with NIRES and WINTER
  64. Swift GRB 240419B: Global MASTER-Net observations report
  65. EP240414A: Terskol Zeiss-2000 optical upper limit
  66. GRB 240419B: Enhanced Swift-XRT position
  67. Swift GRB 240419A: Global MASTER-Net observations report
  68. GRB 240418A: Swift/UVOT Upper Limits
  69. GRB 240419A: REM NIR afterglow detection
  70. GRB 240419A: Swift-XRT refined Analysis
  71. GRB 240418A: Swift-XRT refined Analysis
  72. GRB 240419B: Swift detection of a burst
  73. GRB 240411B: Swift/UVOT Detection
  74. EP240417a: YAHPT Optical Upper Limits
  75. GRB240418A: YAHPT Upper Limits
  76. GRB 240419A: VLT/UVES redshift of z = 5.178
  77. GRB 240419A: VLT optical afterglow detection
  78. GRB 240419A: Enhanced Swift-XRT position
  79. Fermi trigger No 735089036: Global MASTER-Net observations report
  80. EP240416a: J-band observations with WINTER
  81. EP240414a: GMG observation
  82. GRB 240419A: Prompt enhanced Swift-XRT position
  83. GRB 240419A: Swift detection of a burst
  84. GRB 240418A: TSHAO Zeiss-1000 optical upper limit
  85. GRB 240418A: NOT optical upper limits
  86. GRB 240418A: Enhanced Swift-XRT position
  87. GRB 240418A: AKO Upper Limit
  88. GRB 240411A: GOTO early optical upper limits
  89. Swift GRB240418.85: Global MASTER-Net observations report
  90. GRB 240418A: Swift detection of a burst
  91. EP240417a: EP-WXT detection of a fast X-ray transient
  92. Fermi GRB 240417A: Global MASTER-Net observations report
  93. LIGO/Virgo/KAGRA S240413p: X-ray upper limits from EP-WXT for the candidate AGN counterpart
  94. EP240416A: Terskol Zeiss-2000 optical upper limit
  95. EP240416A: Khureltogoot optical upper limit
  96. Improved IPN triangulation of GRB 240411A
  97. EP240416a: BOOTES-2/TELMA Optical Upper Limit
  98. EP240414a: GSP detects optical candidate counterpart AT2024gsa
  99. LIGO/Virgo/KAGRA S240413p: DECam GW-MMADS candidates
  100. IceCube-Cascade 240416A: Upper limits from a search for additional neutrino events in IceCube

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