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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"

26369 results found.

  1. GRB251126A: MAO/AZT-22 optical observations
  2. GRB251126A: Continued optical observation from 1.3m DFOT
  3. GRB 251126A: Swift/UVOT Detection
  4. GRB 251126A: Mondy and SAO RAS optical observations
  5. GRB 251126A: Swift-XRT refined Analysis
  6. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  7. GRB 251126A: NOT optical observations
  8. GRB 251126A: 1.3m DFOT optical afterglow detection
  9. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  10. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  11. Fermi GRB 251127A: Global MASTER-Net observations report
  12. GRB 251126A: Enhanced Swift-XRT position
  13. GRB 251126A: Kilonova-Catcher optical afterglow detection
  14. GRB 251126A: Nanshan/HMT optical afterglow detection
  15. Swift GRB 251126A: Global MASTER-Net observations report
  16. GRB 251121A: Fermi GBM Observation
  17. GRB 251126A: GIT discovery of the likely optical afterglow
  18. GRB 251126A: Swift detection of a burst
  19. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  20. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  21. EP251124b: NOT r- and z-band optical upper limits
  22. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  23. Fermi GRB 251125B: Global MASTER-Net observations report
  24. EP251124b: Global MASTER-Net observations report
  25. EP251124b: EP-WXT detection of a fast X-ray transient
  26. EP251124a: Xinglong GWAC-F60A optical observation
  27. Fermi GRB 251125A: Global MASTER-Net observations report
  28. EP251124a: NOT r- and z-band optical upper limits
  29. EP251124a: Global MASTER-Net observations report
  30. EP251124a: Swift-XRT observations
  31. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  32. EP251124a: Optical upper limit with Kinder observations
  33. Fermi GRB 251124a: Global MASTER-Net observations report
  34. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  35. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  36. EP251124a: GROWTH-India Telescope optical upper limits
  37. EP251124a: Einstein Probe detection of an X-ray transient
  38. GRB 251116C: Swift-XRT confirmation of fading
  39. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  40. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  41. EP251118A: 3.6m DOT optical afterglow detection
  42. GRB 251122A / EP251122a: EP-FXT counterpart detection
  43. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  44. GRB 251122A / EP251122a: WFST optical observations
  45. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  46. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  47. GRB 251122A / EP251122a: LCO optical upper limits
  48. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  49. EP251122a: Global MASTER-Net observations report
  50. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  51. GRB 251122A / EP251122a: SVOM detection of a long burst
  52. EP251122a: Einstein Probe detection of an X-ray transient
  53. EP251118a: Continued Optical Detection with Kinder observations
  54. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  55. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  56. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  57. EP251118a: Xinglong-2.16m optical observation
  58. GRB 251115A: Fermi GBM Observation
  59. Fermi trigger No 785388351: Global MASTER-Net observations report
  60. EP251118A: 1.3m DFOT optical afterglow detection
  61. GRB 251118A: Swift/UVOT Detection
  62. EP251118a / GRB 251118C: SAO RAS optical observations
  63. GRB 251118A: Glowbug gamma-ray detection
  64. GRB 251118A: Fermi GBM Observation
  65. GRB 251118A: Swift-XRT afterglow detection
  66. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  67. EP251118a: Optical detection with Kinder observations
  68. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  69. GRB 251118A: NuSTAR detection of bright prompt emission
  70. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  71. GRB 251116C: NOT optical observations
  72. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  73. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  74. GRB 251117A: Swift-XRT observations
  75. EP251118A / GRB 251118C : MASTER optical counterpart observations
  76. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  77. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  78. EP251118a: VLT near-infrared observation
  79. GRB 251116D: SVOM/GRM observation of a long GRB
  80. GRB 251119A: SVOM detection of a possible burst
  81. EP251118a: Global MASTER-Net observations report
  82. LAT GRB251118.86: Global MASTER-Net observations report
  83. EP251118a: NOT candidate optical counterpart
  84. EP251118a: Einstein Probe detected of a fast X-ray transient
  85. Fermi GRB 251118B: Global MASTER-Net observations report
  86. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  87. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  88. GRB 251117A: AstroSat CZTI detection
  89. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  90. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  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. LAT GRB251117.51: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  96. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  97. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  98. GRB 251116C: Swift-XRT observations
  99. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  100. GRB 251116D: Glowbug gamma-ray detection

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