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

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