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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 251122B: Fermi GBM Final Localization
  2. EP251118A: 6 GHz VLA Detection
  3. Fermi GRB 251124a: Global MASTER-Net observations report
  4. GRB 251124a: Fermi GBM Final Localization
  5. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  6. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  7. EP251124a: GROWTH-India Telescope optical upper limits
  8. EP251124a: Einstein Probe detection of an X-ray transient
  9. GRB 251116C: Swift-XRT confirmation of fading
  10. GRB 251122A/EP251122a: FTW optical and NIR observations
  11. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  12. The EP-WXT trigger 01709248783 is likely a flaring star
  13. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  14. EP251118A: 3.6m DOT optical afterglow detection
  15. GRB 251122A / EP251122a: EP-FXT counterpart detection
  16. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  17. GRB 251122A / EP251122a: WFST optical observations
  18. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  19. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  20. GRB 251122A / EP251122a: LCO optical upper limits
  21. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  22. EP251122a: Global MASTER-Net observations report
  23. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  24. GRB 251122A / EP251122a: SVOM detection of a long burst
  25. EP251122a: Einstein Probe detection of an X-ray transient
  26. EP251118a: Continued Optical Detection with Kinder observations
  27. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  28. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  29. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  30. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  31. EP251118a: Xinglong-2.16m optical observation
  32. GRB 251115A: Fermi GBM Observation
  33. The EP-WXT trigger 01709248635 is likely a flaring star
  34. GRB 251121A: Fermi GBM Final Real-time Localization
  35. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  36. Fermi trigger No 785388351: Global MASTER-Net observations report
  37. EP251118A: 1.3m DFOT optical afterglow detection
  38. GRB 251118A: Swift/UVOT Detection
  39. EP251118a / GRB 251118C: SAO RAS optical observations
  40. GRB 251118A: Glowbug gamma-ray detection
  41. GRB 251118A: Fermi GBM Observation
  42. GRB 251118A: Swift-XRT afterglow detection
  43. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  44. EP251118a: Optical detection with Kinder observations
  45. GRB 251118A: GECAM-B detection
  46. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  47. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  48. EP251118a / GRB 251118C: SVOM/VT optical observation
  49. The EP-WXT trigger 01709248403 is likely a flaring star
  50. GRB 251118A: NuSTAR detection of bright prompt emission
  51. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  52. GRB 251116C: NOT optical observations
  53. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  54. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  55. GRB 251018A: FRAM-Auger optical detection
  56. GRB 251117A: Swift-XRT observations
  57. EP251118A / GRB 251118C : MASTER optical counterpart observations
  58. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  59. Konus-Wind detection of GRB 251118C (EP251118a)
  60. The EP-WXT trigger 01709248388 is likely a flaring star
  61. EP251118a: FTW optical and NIR observations
  62. GRB 251117A: Insight-HXMT/HE detection
  63. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  64. EP251118a: VLT near-infrared observation
  65. GRB 251116D: SVOM/GRM observation of a long GRB
  66. EP251118a: GOTO optical afterglow detection
  67. GRB 251119A: SVOM detection of a possible burst
  68. EP251118a: NOT spectroscopic redshift of z = 1.216
  69. EP251118a: Global MASTER-Net observations report
  70. EP251118a: preliminary result of EP-FXT follow-up observation
  71. LAT GRB251118.86: Global MASTER-Net observations report
  72. GRB 251118A: Fermi-LAT detection
  73. EP251118a: NOT candidate optical counterpart
  74. GRB 251118A: Swift ToO observations
  75. EP251118a: Einstein Probe detected of a fast X-ray transient
  76. Fermi GRB 251118B: Global MASTER-Net observations report
  77. GRB 251118B: Fermi GBM Final Real-time Localization
  78. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  79. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  80. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  81. GRB 251118A: Fermi GBM Final Real-time Localization
  82. GRB 251116C: SVOM/ECLAIRs refined analysis
  83. GRB 251116B: SVOM/ECLAIRs refined analysis
  84. GRB 251117A: AstroSat CZTI detection
  85. GRB 251114B: Insight-HXMT/HE detection
  86. GRB 251114B: GECAM-B detection of a short burst
  87. GRB 251117A: Fermi GBM observation
  88. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  89. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  90. GRB 251116D: Insight-HXMT/HE detection
  91. GRB 251115A: Swift-XRT observations
  92. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  93. GRB 251117A: SVOM/GRM observation of a short burst
  94. GRB 251117A: Tiled Swift observations
  95. GRB 251117A: Fermi-LAT detection
  96. LAT GRB251117.51: Global MASTER-Net observations report
  97. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  98. GRB 251116C: Swift/BAT arcminute localization of a burst
  99. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  100. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman

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