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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"

11503 results found.

  1. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  2. Fermi GRB 251125B: Global MASTER-Net observations report
  3. GRB 251125B: Fermi GBM Final Real-time Localization
  4. Fermi GRB 251125A: Global MASTER-Net observations report
  5. EP251124a: Swift-XRT observations
  6. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  7. EP251124a: Optical upper limit with Kinder observations
  8. EP251118A: 6 GHz VLA Detection
  9. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  10. EP251124a: Einstein Probe detection of an X-ray transient
  11. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  12. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  13. GRB 251122A / EP251122a: SVOM detection of a long burst
  14. EP251122a: Einstein Probe detection of an X-ray transient
  15. EP251118a: Continued Optical Detection with Kinder observations
  16. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  17. GRB 251115A: Fermi GBM Observation
  18. EP251118A: 1.3m DFOT optical afterglow detection
  19. GRB 251118A: Glowbug gamma-ray detection
  20. GRB 251118A: Fermi GBM Observation
  21. GRB 251118A: Swift-XRT afterglow detection
  22. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  23. EP251118a: Optical detection with Kinder observations
  24. EP251118a / GRB 251118C: SVOM/VT optical observation
  25. GRB 251118A: NuSTAR detection of bright prompt emission
  26. Konus-Wind detection of GRB 251118C (EP251118a)
  27. GRB 251116D: SVOM/GRM observation of a long GRB
  28. EP251118a: Global MASTER-Net observations report
  29. EP251118a: preliminary result of EP-FXT follow-up observation
  30. LAT GRB251118.86: Global MASTER-Net observations report
  31. GRB 251118A: Fermi-LAT detection
  32. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  33. GRB 251118A: Fermi GBM Final Real-time Localization
  34. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  35. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  36. GRB 251117A: Fermi-LAT detection
  37. LAT GRB251117.51: Global MASTER-Net observations report
  38. GRB 251116C: Swift/BAT arcminute localization of a burst
  39. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  40. GRB 251116C: Swift-XRT observations
  41. EP251023a: Assy AZT-20 optical observations
  42. GRB 251116D: AstroSat CZTI detection
  43. GRB 251025B: further Mondy optical observations
  44. SVOM GRB251116C: Global MASTER-Net observations report
  45. GRB 251116C: SVOM detection of a burst
  46. GRB 251115A: Fermi-LAT detection
  47. Fermi GRB 251115A: Global MASTER-Net observations report
  48. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  49. GRB 251115A: Fermi GBM Final Real-time Localization
  50. GRB 251113A: AstroSat CZTI detection
  51. GRB 251114B: Fermi GBM Final Real-time Localization
  52. Konus-Wind detection of GRB 251108C
  53. Konus-Wind detection of GRB 251103A
  54. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  55. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  56. GRB 251111A: SVOM/ECLAIRs refined analysis
  57. GRB 251108C: AstroSat CZTI detection
  58. GRB 251112B: MAXI/GSC detection
  59. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  60. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  61. GRB 251111A: Swift-XRT observations
  62. GRB 251111A: KAIT optical upper limit
  63. GRB 251111A: SVOM detection of a soft burst
  64. GRB 251105A: AstroSat CZTI detection
  65. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  66. Fermi trigger No 784279167: Global MASTER-Net observations report
  67. SVOM GRB251108.54: Global MASTER-Net observations report
  68. SVOM GRB251106.83: Global MASTER-Net observations report
  69. GRB 251106A: Swift-XRT afterglow detection
  70. GRB 251106A: Swift/BAT arcminute localization of a burst
  71. GRB 251106A: MASTER optical observations
  72. GRB 251103B: AstroSat CZTI detection
  73. Fermi trigger No 784034269: Global MASTER-Net observations report
  74. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  75. EP251102a: update of EP-FXT follow-up observation
  76. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  77. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  78. GRB 251103B: GROWTH-India Telescope optical upper limits
  79. GRB 251103A: Swift-XRT afterglow detection
  80. EP251102a: Einstein Probe detection of a fast X-ray transient
  81. GRB 251102A: AstroSat CZTI detection
  82. Fermi GRB 251102A: Global MASTER-Net observations report
  83. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  84. Konus-Wind detection of GRB 251028A
  85. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  86. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  87. Fermi GRB 251028B: Global MASTER-Net observations report
  88. GRB251025B: 3.6m DOT Optical Observations
  89. GRB 251028A: MAXI/GSC detection
  90. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  91. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  92. Konus-Wind detection of GRB 251022A
  93. GRB 251027A: Swift-XRT observations
  94. GRB 251022A: SVOM/GRM observation
  95. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  96. GRB 251026A: Mondy optical upper limit
  97. GRB 251025B: Kilonova-Catcher optical afterglow detection
  98. Konus-Wind detection of GRB 251016A (short/hard)
  99. GRB 251027A: SVOM detection of a faint burst
  100. GRB 251025C: AstroSat CZTI detection

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