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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. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam upper limits on the Swift/XRT source S240422ed_X61
  2. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
  3. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search
  4. LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
  5. GRB 240419A: Swift-BAT refined analysis
  6. GRB 240418A: Swift-BAT refined analysis
  7. LXT240402A/GRB240402B: Chandra X-ray detection
  8. LIGO/Virgo/KAGRA S240423br: Retraction of GW compact binary merger candidate
  9. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  10. GRB 240419A: Possible ATCA radio detection
  11. GRB 240421B: ATCA radio observations
  12. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  13. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  14. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility observations and candidates
  15. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  16. LIGO/Virgo/KAGRA S240422ed: Magellan Observations
  17. LIGO/Virgo/KAGRA S240422ed: Updated NED Galaxies in the Localization Volume
  18. LIGO/Virgo/KAGRA S240422ed: AstroSat CZTI non-detection and upper limits
  19. LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
  20. LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
  21. LIGO/Virgo/KAGRA S240421ar: Upper limits from Swift/BAT-GUANO
  22. LIGO/Virgo/KAGRA S240422ed: Coverage and upper limits from MAXI/GSC observations
  23. LIGO/Virgo/KAGRA S240422ed: MeerLICHT and BlackGEM observations report
  24. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  25. LIGO/Virgo/Kagra S240422ed: NED Galaxies in the Localization Volume
  26. LIGO/Virgo/KAGRA S240422ed: Global MASTER-Net observations report
  27. Fermi trigger No 735470374: Global MASTER-Net observations report
  28. GRB 240421A: Glowbug gamma-ray detection
  29. GRB 240414A: radio detection with the VLA
  30. Fermi-LAT gamma-ray observations of IceCube-240419A
  31. GRB 240414A: AMI-LA radio observations
  32. GRB 240414A: LBT optical detection
  33. GRB 240419B : MITSuME Akeno optical upper limits
  34. GRB 240415B: Swift-XRT observations
  35. GRB 240415A: Swift-XRT refined Analysis
  36. Fermi GRB 240422A: Global MASTER-Net observations report
  37. GRB 240421B: AstroSat CZTI detection
  38. GRB 240422A: Fermi GBM Final Real-time Localization
  39. GRB240421B: Zadko Observations
  40. Fermi GRB 240421B: Global MASTER-Net observations report
  41. Swift GRB 240421B: Global MASTER-Net observations report
  42. GRB 240421B: Fermi GBM Observation
  43. GRB 240421B: Swift-XRT refined Analysis
  44. GRB240421B: BOOTES-5/JGT optical upper limit
  45. GRB 240421B: J-band upper limits from WINTER
  46. GRB 240421B: Swift/UVOT Upper Limits
  47. GRB 240421B: Enhanced Swift-XRT position
  48. Fermi GRB 240421A: Global MASTER-Net observations report
  49. EP240417a: no counterpart detection by SOAR
  50. EP240420a: TNT upper limit to its optical counterpart
  51. EP240420a: Xinglong decaying optical counterpart
  52. GRB 240421B: Swift detection of a burst
  53. EP240420a: Nanshan optical counterpart observations
  54. EP240420a: GWAC-F50A optical upper limit
  55. LIGO/Virgo/KAGRA S240421ar: Identification of a GW unmodeled transient candidate
  56. GRB 240421A: Fermi GBM Final Real-time Localization
  57. EP240420a: detection of fading X-ray emission with refined position by EP-FXT
  58. EP240420a: NOT optical counterpart candidate and potential host
  59. Fermi trigger No 735280430: Global MASTER-Net observations report
  60. GRB240419A: Skynet Optical Afterglow Analysis
  61. GRB240418A - Candidate afterglow from NIRES
  62. IceCube Alert 240419.98: Global MASTER-Net observations report
  63. GRB 240419B: Swift/UVOT Upper Limits
  64. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  65. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  66. EP240420a: EP-WXT detection of a fast X-ray transient
  67. GRB 240419A: Swift/UVOT Upper Limits
  68. GRB 240419B: Swift-XRT refined Analysis
  69. GRB 240419B: optical afterglow from the NOT
  70. LIGO/Virgo/KAGRA S240420aw: Retraction of GW compact binary merger candidate
  71. EP240414a: Near-IR observations with NIRES and WINTER
  72. Swift GRB 240419B: Global MASTER-Net observations report
  73. EP240414A: Terskol Zeiss-2000 optical upper limit
  74. GRB 240419B: Enhanced Swift-XRT position
  75. Swift GRB 240419A: Global MASTER-Net observations report
  76. GRB 240418A: Swift/UVOT Upper Limits
  77. GRB 240419A: REM NIR afterglow detection
  78. GRB 240419A: Swift-XRT refined Analysis
  79. GRB 240418A: Swift-XRT refined Analysis
  80. GRB 240419B: Swift detection of a burst
  81. GRB 240411B: Swift/UVOT Detection
  82. EP240417a: YAHPT Optical Upper Limits
  83. GRB240418A: YAHPT Upper Limits
  84. GRB 240419A: VLT/UVES redshift of z = 5.178
  85. GRB 240419A: VLT optical afterglow detection
  86. GRB 240419A: Enhanced Swift-XRT position
  87. Fermi trigger No 735089036: Global MASTER-Net observations report
  88. EP240416a: J-band observations with WINTER
  89. EP240414a: GMG observation
  90. GRB 240419A: Prompt enhanced Swift-XRT position
  91. GRB 240419A: Swift detection of a burst
  92. GRB 240418A: TSHAO Zeiss-1000 optical upper limit
  93. GRB 240418A: NOT optical upper limits
  94. GRB 240418A: Enhanced Swift-XRT position
  95. GRB 240418A: AKO Upper Limit
  96. GRB 240411A: GOTO early optical upper limits
  97. Swift GRB240418.85: Global MASTER-Net observations report
  98. GRB 240418A: Swift detection of a burst
  99. EP240417a: EP-WXT detection of a fast X-ray transient
  100. Fermi GRB 240417A: Global MASTER-Net observations report

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