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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"

28062 results found.

  1. Fermi GRB 251127A: Global MASTER-Net observations report
  2. GRB 251126A: Enhanced Swift-XRT position
  3. GRB 251126A: Kilonova-Catcher optical afterglow detection
  4. GRB 251126A: Nanshan/HMT optical afterglow detection
  5. Swift GRB 251126A: Global MASTER-Net observations report
  6. GRB 251121A: Fermi GBM Observation
  7. GRB 251126A: GIT discovery of the likely optical afterglow
  8. GRB 251126A: Swift detection of a burst
  9. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  10. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  11. EP251124b: NOT r- and z-band optical upper limits
  12. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  13. Fermi GRB 251125B: Global MASTER-Net observations report
  14. EP251124b: Global MASTER-Net observations report
  15. EP251124b: EP-WXT detection of a fast X-ray transient
  16. EP251124a: Xinglong GWAC-F60A optical observation
  17. Fermi GRB 251125A: Global MASTER-Net observations report
  18. EP251124a: NOT r- and z-band optical upper limits
  19. EP251124a: Global MASTER-Net observations report
  20. EP251124a: Swift-XRT observations
  21. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  22. EP251124a: Optical upper limit with Kinder observations
  23. Fermi GRB 251124a: Global MASTER-Net observations report
  24. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  25. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  26. EP251124a: GROWTH-India Telescope optical upper limits
  27. EP251124a: Einstein Probe detection of an X-ray transient
  28. GRB 251116C: Swift-XRT confirmation of fading
  29. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  30. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  31. EP251118A: 3.6m DOT optical afterglow detection
  32. GRB 251122A / EP251122a: EP-FXT counterpart detection
  33. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  34. GRB 251122A / EP251122a: WFST optical observations
  35. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  36. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  37. GRB 251122A / EP251122a: LCO optical upper limits
  38. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  39. EP251122a: Global MASTER-Net observations report
  40. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  41. GRB 251122A / EP251122a: SVOM detection of a long burst
  42. EP251122a: Einstein Probe detection of an X-ray transient
  43. EP251118a: Continued Optical Detection with Kinder observations
  44. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  45. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  46. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  47. EP251118a: Xinglong-2.16m optical observation
  48. GRB 251115A: Fermi GBM Observation
  49. Fermi trigger No 785388351: Global MASTER-Net observations report
  50. EP251118A: 1.3m DFOT optical afterglow detection
  51. GRB 251118A: Swift/UVOT Detection
  52. EP251118a / GRB 251118C: SAO RAS optical observations
  53. GRB 251118A: Glowbug gamma-ray detection
  54. GRB 251118A: Fermi GBM Observation
  55. GRB 251118A: Swift-XRT afterglow detection
  56. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  57. EP251118a: Optical detection with Kinder observations
  58. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  59. GRB 251118A: NuSTAR detection of bright prompt emission
  60. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  61. GRB 251116C: NOT optical observations
  62. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  63. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  64. GRB 251117A: Swift-XRT observations
  65. EP251118A / GRB 251118C : MASTER optical counterpart observations
  66. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  67. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  68. EP251118a: VLT near-infrared observation
  69. GRB 251116D: SVOM/GRM observation of a long GRB
  70. GRB 251119A: SVOM detection of a possible burst
  71. EP251118a: Global MASTER-Net observations report
  72. LAT GRB251118.86: Global MASTER-Net observations report
  73. EP251118a: NOT candidate optical counterpart
  74. EP251118a: Einstein Probe detected of a fast X-ray transient
  75. Fermi GRB 251118B: Global MASTER-Net observations report
  76. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  77. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  78. GRB 251117A: AstroSat CZTI detection
  79. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  80. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  81. GRB 251115A: Swift-XRT observations
  82. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  83. GRB 251117A: SVOM/GRM observation of a short burst
  84. LAT GRB251117.51: Global MASTER-Net observations report
  85. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  86. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  87. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  88. GRB 251116C: Swift-XRT observations
  89. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  90. GRB 251116D: Glowbug gamma-ray detection
  91. EP251023a: Assy AZT-20 optical observations
  92. EP251023a: UAFO and AbAO optical observations
  93. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  94. GRB 251116C: SVOM/VT optical upper limit
  95. GRB 251025B: further Mondy optical observations
  96. GRB 251111A: Mondy optical upper limit
  97. GRB 251116B: EP-FXT follow-up observation
  98. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  99. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  100. GRB 251116B: LCO optical upper limits

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