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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"

26364 results found.

  1. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  2. GRB 251126A: NOT optical observations
  3. GRB 251126A: 1.3m DFOT optical afterglow detection
  4. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  5. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  6. Fermi GRB 251127A: Global MASTER-Net observations report
  7. GRB 251126A: Enhanced Swift-XRT position
  8. GRB 251126A: Kilonova-Catcher optical afterglow detection
  9. GRB 251126A: Nanshan/HMT optical afterglow detection
  10. Swift GRB 251126A: Global MASTER-Net observations report
  11. GRB 251121A: Fermi GBM Observation
  12. GRB 251126A: GIT discovery of the likely optical afterglow
  13. GRB 251126A: Swift detection of a burst
  14. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  15. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  16. EP251124b: NOT r- and z-band optical upper limits
  17. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  18. Fermi GRB 251125B: Global MASTER-Net observations report
  19. EP251124b: Global MASTER-Net observations report
  20. EP251124b: EP-WXT detection of a fast X-ray transient
  21. EP251124a: Xinglong GWAC-F60A optical observation
  22. Fermi GRB 251125A: Global MASTER-Net observations report
  23. EP251124a: NOT r- and z-band optical upper limits
  24. EP251124a: Global MASTER-Net observations report
  25. EP251124a: Swift-XRT observations
  26. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  27. EP251124a: Optical upper limit with Kinder observations
  28. Fermi GRB 251124a: Global MASTER-Net observations report
  29. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  30. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  31. EP251124a: GROWTH-India Telescope optical upper limits
  32. EP251124a: Einstein Probe detection of an X-ray transient
  33. GRB 251116C: Swift-XRT confirmation of fading
  34. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  35. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  36. EP251118A: 3.6m DOT optical afterglow detection
  37. GRB 251122A / EP251122a: EP-FXT counterpart detection
  38. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  39. GRB 251122A / EP251122a: WFST optical observations
  40. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  41. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  42. GRB 251122A / EP251122a: LCO optical upper limits
  43. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  44. EP251122a: Global MASTER-Net observations report
  45. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  46. GRB 251122A / EP251122a: SVOM detection of a long burst
  47. EP251122a: Einstein Probe detection of an X-ray transient
  48. EP251118a: Continued Optical Detection with Kinder observations
  49. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  50. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  51. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  52. EP251118a: Xinglong-2.16m optical observation
  53. GRB 251115A: Fermi GBM Observation
  54. Fermi trigger No 785388351: Global MASTER-Net observations report
  55. EP251118A: 1.3m DFOT optical afterglow detection
  56. GRB 251118A: Swift/UVOT Detection
  57. EP251118a / GRB 251118C: SAO RAS optical observations
  58. GRB 251118A: Glowbug gamma-ray detection
  59. GRB 251118A: Fermi GBM Observation
  60. GRB 251118A: Swift-XRT afterglow detection
  61. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  62. EP251118a: Optical detection with Kinder observations
  63. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  64. GRB 251118A: NuSTAR detection of bright prompt emission
  65. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  66. GRB 251116C: NOT optical observations
  67. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  68. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  69. GRB 251117A: Swift-XRT observations
  70. EP251118A / GRB 251118C : MASTER optical counterpart observations
  71. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  72. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  73. EP251118a: VLT near-infrared observation
  74. GRB 251116D: SVOM/GRM observation of a long GRB
  75. GRB 251119A: SVOM detection of a possible burst
  76. EP251118a: Global MASTER-Net observations report
  77. LAT GRB251118.86: Global MASTER-Net observations report
  78. EP251118a: NOT candidate optical counterpart
  79. EP251118a: Einstein Probe detected of a fast X-ray transient
  80. Fermi GRB 251118B: Global MASTER-Net observations report
  81. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  82. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  83. GRB 251117A: AstroSat CZTI detection
  84. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  85. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  86. GRB 251115A: Swift-XRT observations
  87. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  88. GRB 251117A: SVOM/GRM observation of a short burst
  89. LAT GRB251117.51: Global MASTER-Net observations report
  90. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  91. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  92. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  93. GRB 251116C: Swift-XRT observations
  94. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  95. GRB 251116D: Glowbug gamma-ray detection
  96. EP251023a: Assy AZT-20 optical observations
  97. EP251023a: UAFO and AbAO optical observations
  98. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  99. GRB 251116C: SVOM/VT optical upper limit
  100. GRB 251025B: further Mondy optical observations

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