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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"

28053 results found.

  1. GRB 251126A: GIT discovery of the likely optical afterglow
  2. GRB 251126A: Swift detection of a burst
  3. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  4. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  5. EP251124b: NOT r- and z-band optical upper limits
  6. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  7. Fermi GRB 251125B: Global MASTER-Net observations report
  8. EP251124b: Global MASTER-Net observations report
  9. EP251124b: EP-WXT detection of a fast X-ray transient
  10. EP251124a: Xinglong GWAC-F60A optical observation
  11. Fermi GRB 251125A: Global MASTER-Net observations report
  12. EP251124a: NOT r- and z-band optical upper limits
  13. EP251124a: Global MASTER-Net observations report
  14. EP251124a: Swift-XRT observations
  15. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  16. EP251124a: Optical upper limit with Kinder observations
  17. Fermi GRB 251124a: Global MASTER-Net observations report
  18. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  19. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  20. EP251124a: GROWTH-India Telescope optical upper limits
  21. EP251124a: Einstein Probe detection of an X-ray transient
  22. GRB 251116C: Swift-XRT confirmation of fading
  23. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  24. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  25. EP251118A: 3.6m DOT optical afterglow detection
  26. GRB 251122A / EP251122a: EP-FXT counterpart detection
  27. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  28. GRB 251122A / EP251122a: WFST optical observations
  29. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  30. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  31. GRB 251122A / EP251122a: LCO optical upper limits
  32. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  33. EP251122a: Global MASTER-Net observations report
  34. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  35. GRB 251122A / EP251122a: SVOM detection of a long burst
  36. EP251122a: Einstein Probe detection of an X-ray transient
  37. EP251118a: Continued Optical Detection with Kinder observations
  38. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  39. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  40. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  41. EP251118a: Xinglong-2.16m optical observation
  42. GRB 251115A: Fermi GBM Observation
  43. Fermi trigger No 785388351: Global MASTER-Net observations report
  44. EP251118A: 1.3m DFOT optical afterglow detection
  45. GRB 251118A: Swift/UVOT Detection
  46. EP251118a / GRB 251118C: SAO RAS optical observations
  47. GRB 251118A: Glowbug gamma-ray detection
  48. GRB 251118A: Fermi GBM Observation
  49. GRB 251118A: Swift-XRT afterglow detection
  50. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  51. EP251118a: Optical detection with Kinder observations
  52. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  53. GRB 251118A: NuSTAR detection of bright prompt emission
  54. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  55. GRB 251116C: NOT optical observations
  56. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  57. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  58. GRB 251117A: Swift-XRT observations
  59. EP251118A / GRB 251118C : MASTER optical counterpart observations
  60. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  61. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  62. EP251118a: VLT near-infrared observation
  63. GRB 251116D: SVOM/GRM observation of a long GRB
  64. GRB 251119A: SVOM detection of a possible burst
  65. EP251118a: Global MASTER-Net observations report
  66. LAT GRB251118.86: Global MASTER-Net observations report
  67. EP251118a: NOT candidate optical counterpart
  68. EP251118a: Einstein Probe detected of a fast X-ray transient
  69. Fermi GRB 251118B: Global MASTER-Net observations report
  70. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  71. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  72. GRB 251117A: AstroSat CZTI detection
  73. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  74. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  75. GRB 251115A: Swift-XRT observations
  76. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  77. GRB 251117A: SVOM/GRM observation of a short burst
  78. LAT GRB251117.51: Global MASTER-Net observations report
  79. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  80. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  81. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  82. GRB 251116C: Swift-XRT observations
  83. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  84. GRB 251116D: Glowbug gamma-ray detection
  85. EP251023a: Assy AZT-20 optical observations
  86. EP251023a: UAFO and AbAO optical observations
  87. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  88. GRB 251116C: SVOM/VT optical upper limit
  89. GRB 251025B: further Mondy optical observations
  90. GRB 251111A: Mondy optical upper limit
  91. GRB 251116B: EP-FXT follow-up observation
  92. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  93. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  94. GRB 251116B: LCO optical upper limits
  95. GRB 251116C: LCO optical upper limits
  96. SVOM GRB251116C: Global MASTER-Net observations report
  97. GRB 251116B: SVOM detection of a burst
  98. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  99. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  100. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis

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