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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. GRB 251116C: NOT optical observations
  2. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  3. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  4. GRB 251018A: FRAM-Auger optical detection
  5. GRB 251117A: Swift-XRT observations
  6. EP251118A / GRB 251118C : MASTER optical counterpart observations
  7. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  8. Konus-Wind detection of GRB 251118C (EP251118a)
  9. The EP-WXT trigger 01709248388 is likely a flaring star
  10. EP251118a: FTW optical and NIR observations
  11. GRB 251117A: Insight-HXMT/HE detection
  12. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  13. EP251118a: VLT near-infrared observation
  14. GRB 251116D: SVOM/GRM observation of a long GRB
  15. EP251118a: GOTO optical afterglow detection
  16. GRB 251119A: SVOM detection of a possible burst
  17. EP251118a: NOT spectroscopic redshift of z = 1.216
  18. EP251118a: Global MASTER-Net observations report
  19. EP251118a: preliminary result of EP-FXT follow-up observation
  20. LAT GRB251118.86: Global MASTER-Net observations report
  21. GRB 251118A: Fermi-LAT detection
  22. EP251118a: NOT candidate optical counterpart
  23. GRB 251118A: Swift ToO observations
  24. EP251118a: Einstein Probe detected of a fast X-ray transient
  25. Fermi GRB 251118B: Global MASTER-Net observations report
  26. GRB 251118B: Fermi GBM Final Real-time Localization
  27. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  28. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  29. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  30. GRB 251118A: Fermi GBM Final Real-time Localization
  31. GRB 251116C: SVOM/ECLAIRs refined analysis
  32. GRB 251116B: SVOM/ECLAIRs refined analysis
  33. GRB 251117A: AstroSat CZTI detection
  34. GRB 251114B: Insight-HXMT/HE detection
  35. GRB 251114B: GECAM-B detection of a short burst
  36. GRB 251117A: Fermi GBM observation
  37. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  38. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  39. GRB 251116D: Insight-HXMT/HE detection
  40. GRB 251115A: Swift-XRT observations
  41. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  42. GRB 251117A: SVOM/GRM observation of a short burst
  43. GRB 251117A: Tiled Swift observations
  44. GRB 251117A: Fermi-LAT detection
  45. LAT GRB251117.51: Global MASTER-Net observations report
  46. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  47. GRB 251116C: Swift/BAT arcminute localization of a burst
  48. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  49. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  50. GRB 251116B: SVOM/VT optical upper limit
  51. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  52. GRB 251116C: Swift-XRT observations
  53. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  54. GRB 251117A: Fermi GBM Final Localization Correction
  55. GRB 251116D: Glowbug gamma-ray detection
  56. EP251023a: Assy AZT-20 optical observations
  57. EP251023a: UAFO and AbAO optical observations
  58. GRB 251116D: AstroSat CZTI detection
  59. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  60. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  61. GRB 251116C: SVOM/VT optical upper limit
  62. GRB 251025B: further Mondy optical observations
  63. GRB 251111A: Mondy optical upper limit
  64. GRB 251116B: EP-FXT follow-up observation
  65. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  66. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  67. GRB 251116B: LCO optical upper limits
  68. GRB 251116C: LCO optical upper limits
  69. SVOM GRB251116C: Global MASTER-Net observations report
  70. GRB 251116C: SVOM detection of a burst
  71. GRB 251116B: SVOM detection of a burst
  72. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  73. GRB 251116A: Fermi GBM Final Real-time Localization
  74. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  75. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  76. GRB 251115A: Tiled Swift observations
  77. GRB 251115A: Fermi-LAT detection
  78. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  79. Fermi GRB 251115A: Global MASTER-Net observations report
  80. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  81. GRB 251115A: Fermi GBM Final Real-time Localization
  82. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  83. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  84. GRB 251113A: Glowbug gamma-ray detection
  85. GRB 251113A: AstroSat CZTI detection
  86. GRB 251114B: Fermi GBM Final Real-time Localization
  87. GRB 251112A: Swift-BAT refined analysis
  88. Konus-Wind detection of GRB 251108C
  89. Fermi trigger No 784717756: Global MASTER-Net observations report
  90. Konus-Wind detection of GRB 251103A
  91. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  92. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  93. IPN triangulation of GRB 251108C
  94. The EP-WXT trigger 01709248221 is likely a flaring star
  95. Fermi GRB 251114A: Global MASTER-Net observations report
  96. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  97. GRB 251114A: Fermi GBM Final Real-time Localization
  98. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  99. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  100. Fermi GRB 251113A: Global MASTER-Net observations report

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