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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28257 results found.

  1. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  2. Fermi GRB 251127A: Global MASTER-Net observations report
  3. GRB 251126A: Enhanced Swift-XRT position
  4. GRB 251126A: Kilonova-Catcher optical afterglow detection
  5. GRB 251126A: Nanshan/HMT optical afterglow detection
  6. Swift GRB 251126A: Global MASTER-Net observations report
  7. GRB 251121A: Fermi GBM Observation
  8. GRB 251126A: GIT discovery of the likely optical afterglow
  9. GRB 251126A: Swift detection of a burst
  10. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  11. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  12. EP251124b: NOT r- and z-band optical upper limits
  13. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  14. Fermi GRB 251125B: Global MASTER-Net observations report
  15. EP251124b: Global MASTER-Net observations report
  16. EP251124b: EP-WXT detection of a fast X-ray transient
  17. EP251124a: Xinglong GWAC-F60A optical observation
  18. Fermi GRB 251125A: Global MASTER-Net observations report
  19. EP251124a: NOT r- and z-band optical upper limits
  20. EP251124a: Global MASTER-Net observations report
  21. EP251124a: Swift-XRT observations
  22. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  23. EP251124a: Optical upper limit with Kinder observations
  24. Fermi GRB 251124a: Global MASTER-Net observations report
  25. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  26. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  27. EP251124a: GROWTH-India Telescope optical upper limits
  28. EP251124a: Einstein Probe detection of an X-ray transient
  29. GRB 251116C: Swift-XRT confirmation of fading
  30. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  31. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  32. EP251118A: 3.6m DOT optical afterglow detection
  33. GRB 251122A / EP251122a: EP-FXT counterpart detection
  34. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  35. GRB 251122A / EP251122a: WFST optical observations
  36. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  37. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  38. GRB 251122A / EP251122a: LCO optical upper limits
  39. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  40. EP251122a: Global MASTER-Net observations report
  41. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  42. GRB 251122A / EP251122a: SVOM detection of a long burst
  43. EP251122a: Einstein Probe detection of an X-ray transient
  44. EP251118a: Continued Optical Detection with Kinder observations
  45. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  46. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  47. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  48. EP251118a: Xinglong-2.16m optical observation
  49. GRB 251115A: Fermi GBM Observation
  50. Fermi trigger No 785388351: Global MASTER-Net observations report
  51. EP251118A: 1.3m DFOT optical afterglow detection
  52. GRB 251118A: Swift/UVOT Detection
  53. EP251118a / GRB 251118C: SAO RAS optical observations
  54. GRB 251118A: Glowbug gamma-ray detection
  55. GRB 251118A: Fermi GBM Observation
  56. GRB 251118A: Swift-XRT afterglow detection
  57. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  58. EP251118a: Optical detection with Kinder observations
  59. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  60. GRB 251118A: NuSTAR detection of bright prompt emission
  61. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  62. GRB 251116C: NOT optical observations
  63. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  64. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  65. GRB 251117A: Swift-XRT observations
  66. EP251118A / GRB 251118C : MASTER optical counterpart observations
  67. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  68. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  69. EP251118a: VLT near-infrared observation
  70. GRB 251116D: SVOM/GRM observation of a long GRB
  71. GRB 251119A: SVOM detection of a possible burst
  72. EP251118a: Global MASTER-Net observations report
  73. LAT GRB251118.86: Global MASTER-Net observations report
  74. EP251118a: NOT candidate optical counterpart
  75. EP251118a: Einstein Probe detected of a fast X-ray transient
  76. Fermi GRB 251118B: Global MASTER-Net observations report
  77. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  78. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  79. GRB 251117A: AstroSat CZTI detection
  80. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  81. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  82. GRB 251115A: Swift-XRT observations
  83. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  84. GRB 251117A: SVOM/GRM observation of a short burst
  85. LAT GRB251117.51: Global MASTER-Net observations report
  86. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  87. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  88. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  89. GRB 251116C: Swift-XRT observations
  90. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  91. GRB 251116D: Glowbug gamma-ray detection
  92. EP251023a: Assy AZT-20 optical observations
  93. EP251023a: UAFO and AbAO optical observations
  94. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  95. GRB 251116C: SVOM/VT optical upper limit
  96. GRB 251025B: further Mondy optical observations
  97. GRB 251111A: Mondy optical upper limit
  98. GRB 251116B: EP-FXT follow-up observation
  99. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  100. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory

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