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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: Potential Candidates from Magellan galaxy-based search
  2. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
  3. IceCube-240419A: Upper limits from a search for additional neutrino events in IceCube
  4. LIGO/Virgo/KAGRA S240421ar: Updated Sky localization
  5. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam upper limits on the Swift/XRT source S240422ed_X61
  6. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
  7. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search
  8. LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
  9. GRB 240419A: Swift-BAT refined analysis
  10. GRB 240418A: Swift-BAT refined analysis
  11. LXT240402A/GRB240402B: Chandra X-ray detection
  12. LIGO/Virgo/KAGRA S240423br: Retraction of GW compact binary merger candidate
  13. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  14. GRB 240419A: Possible ATCA radio detection
  15. GRB 240421B: ATCA radio observations
  16. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  17. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  18. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility observations and candidates
  19. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  20. LIGO/Virgo/KAGRA S240422ed: Magellan Observations
  21. LIGO/Virgo/KAGRA S240422ed: Updated NED Galaxies in the Localization Volume
  22. LIGO/Virgo/KAGRA S240422ed: AstroSat CZTI non-detection and upper limits
  23. LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
  24. LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
  25. LIGO/Virgo/KAGRA S240421ar: Upper limits from Swift/BAT-GUANO
  26. LIGO/Virgo/KAGRA S240422ed: Coverage and upper limits from MAXI/GSC observations
  27. LIGO/Virgo/KAGRA S240422ed: MeerLICHT and BlackGEM observations report
  28. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  29. LIGO/Virgo/Kagra S240422ed: NED Galaxies in the Localization Volume
  30. LIGO/Virgo/KAGRA S240422ed: Global MASTER-Net observations report
  31. Fermi trigger No 735470374: Global MASTER-Net observations report
  32. GRB 240421A: Glowbug gamma-ray detection
  33. GRB 240414A: radio detection with the VLA
  34. Fermi-LAT gamma-ray observations of IceCube-240419A
  35. GRB 240414A: AMI-LA radio observations
  36. GRB 240414A: LBT optical detection
  37. GRB 240419B : MITSuME Akeno optical upper limits
  38. GRB 240415B: Swift-XRT observations
  39. GRB 240415A: Swift-XRT refined Analysis
  40. Fermi GRB 240422A: Global MASTER-Net observations report
  41. GRB 240421B: AstroSat CZTI detection
  42. GRB 240422A: Fermi GBM Final Real-time Localization
  43. GRB240421B: Zadko Observations
  44. Fermi GRB 240421B: Global MASTER-Net observations report
  45. Swift GRB 240421B: Global MASTER-Net observations report
  46. GRB 240421B: Fermi GBM Observation
  47. GRB 240421B: Swift-XRT refined Analysis
  48. GRB240421B: BOOTES-5/JGT optical upper limit
  49. GRB 240421B: J-band upper limits from WINTER
  50. GRB 240421B: Swift/UVOT Upper Limits
  51. GRB 240421B: Enhanced Swift-XRT position
  52. Fermi GRB 240421A: Global MASTER-Net observations report
  53. EP240417a: no counterpart detection by SOAR
  54. EP240420a: TNT upper limit to its optical counterpart
  55. EP240420a: Xinglong decaying optical counterpart
  56. GRB 240421B: Swift detection of a burst
  57. EP240420a: Nanshan optical counterpart observations
  58. EP240420a: GWAC-F50A optical upper limit
  59. LIGO/Virgo/KAGRA S240421ar: Identification of a GW unmodeled transient candidate
  60. GRB 240421A: Fermi GBM Final Real-time Localization
  61. EP240420a: detection of fading X-ray emission with refined position by EP-FXT
  62. EP240420a: NOT optical counterpart candidate and potential host
  63. Fermi trigger No 735280430: Global MASTER-Net observations report
  64. GRB240419A: Skynet Optical Afterglow Analysis
  65. GRB240418A - Candidate afterglow from NIRES
  66. IceCube Alert 240419.98: Global MASTER-Net observations report
  67. GRB 240419B: Swift/UVOT Upper Limits
  68. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  69. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  70. EP240420a: EP-WXT detection of a fast X-ray transient
  71. GRB 240419A: Swift/UVOT Upper Limits
  72. GRB 240419B: Swift-XRT refined Analysis
  73. GRB 240419B: optical afterglow from the NOT
  74. LIGO/Virgo/KAGRA S240420aw: Retraction of GW compact binary merger candidate
  75. EP240414a: Near-IR observations with NIRES and WINTER
  76. Swift GRB 240419B: Global MASTER-Net observations report
  77. EP240414A: Terskol Zeiss-2000 optical upper limit
  78. GRB 240419B: Enhanced Swift-XRT position
  79. Swift GRB 240419A: Global MASTER-Net observations report
  80. GRB 240418A: Swift/UVOT Upper Limits
  81. GRB 240419A: REM NIR afterglow detection
  82. GRB 240419A: Swift-XRT refined Analysis
  83. GRB 240418A: Swift-XRT refined Analysis
  84. GRB 240419B: Swift detection of a burst
  85. GRB 240411B: Swift/UVOT Detection
  86. EP240417a: YAHPT Optical Upper Limits
  87. GRB240418A: YAHPT Upper Limits
  88. GRB 240419A: VLT/UVES redshift of z = 5.178
  89. GRB 240419A: VLT optical afterglow detection
  90. GRB 240419A: Enhanced Swift-XRT position
  91. Fermi trigger No 735089036: Global MASTER-Net observations report
  92. EP240416a: J-band observations with WINTER
  93. EP240414a: GMG observation
  94. GRB 240419A: Prompt enhanced Swift-XRT position
  95. GRB 240419A: Swift detection of a burst
  96. GRB 240418A: TSHAO Zeiss-1000 optical upper limit
  97. GRB 240418A: NOT optical upper limits
  98. GRB 240418A: Enhanced Swift-XRT position
  99. GRB 240418A: AKO Upper Limit
  100. GRB 240411A: GOTO early optical upper limits

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