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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"

20565 results found.

  1. GRB 251117A: Swift-XRT observations
  2. EP251118A / GRB 251118C : MASTER optical counterpart observations
  3. EP251118a: FTW optical and NIR observations
  4. EP251118a: VLT near-infrared observation
  5. EP251118a: GOTO optical afterglow detection
  6. EP251118a: Global MASTER-Net observations report
  7. LAT GRB251118.86: Global MASTER-Net observations report
  8. EP251118a: NOT candidate optical counterpart
  9. GRB 251118A: Swift ToO observations
  10. EP251118a: Einstein Probe detected of a fast X-ray transient
  11. Fermi GRB 251118B: Global MASTER-Net observations report
  12. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  13. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  14. GRB 251116C: SVOM/ECLAIRs refined analysis
  15. GRB 251116B: SVOM/ECLAIRs refined analysis
  16. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  17. GRB 251115A: Swift-XRT observations
  18. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  19. GRB 251117A: Tiled Swift observations
  20. LAT GRB251117.51: Global MASTER-Net observations report
  21. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  22. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  23. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  24. GRB 251116C: Swift-XRT observations
  25. EP251023a: Assy AZT-20 optical observations
  26. EP251023a: UAFO and AbAO optical observations
  27. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  28. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  29. GRB 251025B: further Mondy optical observations
  30. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  31. SVOM GRB251116C: Global MASTER-Net observations report
  32. GRB 251116B: SVOM detection of a burst
  33. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  34. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  35. GRB 251115A: Tiled Swift observations
  36. Fermi GRB 251115A: Global MASTER-Net observations report
  37. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  38. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  39. Fermi trigger No 784717756: Global MASTER-Net observations report
  40. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  41. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  42. Fermi GRB 251114A: Global MASTER-Net observations report
  43. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  44. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  45. Fermi GRB 251113A: Global MASTER-Net observations report
  46. GRB 251111A: SVOM/ECLAIRs refined analysis
  47. GRB 251025B: SVOM/ECLAIRs refined analysis
  48. GRB 251112A: Swift/UVOT Upper Limits
  49. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  50. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  51. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  52. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  53. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  54. Fermi trigger No 784621743: Global MASTER-Net observations report
  55. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  56. GRB251111A: 1.3m DFOT optical upper limit
  57. GRB 251111A: Swift-XRT afterglow detection
  58. GRB 251111A: SVOM/VT optical observations with X-band data
  59. SVOM GRB251111.42: Global MASTER-Net observations report
  60. GRB 251111A: Swift-XRT observations
  61. SVOM GRB251111.22: Global MASTER-Net observations report
  62. GRB 251013C: Chandra X-ray observations and jet break detection
  63. GRB 251111A: SVOM/VT optical observations with VHF data
  64. GRB 251111A: KAIT optical upper limit
  65. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  66. GRB 251106A: Swift/UVOT Upper Limits
  67. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  68. Fermi trigger No 784329591: Global MASTER-Net observations report
  69. Fermi trigger No 784279167: Global MASTER-Net observations report
  70. SVOM GRB251108.54: Global MASTER-Net observations report
  71. SVOM GRB251106.83: Global MASTER-Net observations report
  72. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  73. GRB 251106A: Swift-XRT afterglow detection
  74. GRB 251106A: Kilonova-Catcher optical upper limit
  75. Fermi GBM Sub-Threshold Detection of GRB 251106A
  76. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  77. GRB 251106A: MASTER optical observations
  78. Fermi trigger No 784034269: Global MASTER-Net observations report
  79. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  80. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  81. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  82. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  83. Fermi GBM Sub-Threshold Detection of GRB 251105B
  84. GRB 251103B: Swift/UVOT Upper Limits
  85. Fermi GRB 251105A: Global MASTER-Net observations report
  86. EP251102a: FTW optical and NIR observations
  87. GRB 251103A: WFST optical observations
  88. EP251102a: OHP/T193 optical observations
  89. GRB 251103A: OHP/T193 optical observations
  90. GRB 251103A: KAIT optical observations
  91. GRB 251103B: Nanshan/HMT optical upper limit
  92. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  93. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  94. Fermi GRB 251103A: Global MASTER-Net observations report
  95. EP251102a: NIR observations with WINTER
  96. GRB 251103A: J-band detection with WINTER
  97. Swift GRB 251103B: Global MASTER-Net observations report
  98. GRB 251103A: Kilonova-Catcher optical afterglow detection
  99. GRB 251103A: Swift/UVOT Detection
  100. GRB 251103A: Swift-XRT afterglow detection

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