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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"

30476 results found.

  1. EP251124b: NOT r- and z-band optical upper limits
  2. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  3. Fermi GRB 251125B: Global MASTER-Net observations report
  4. EP251124b: Global MASTER-Net observations report
  5. EP251124a: Xinglong GWAC-F60A optical observation
  6. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  7. Fermi GRB 251125A: Global MASTER-Net observations report
  8. EP251124a: NOT r- and z-band optical upper limits
  9. EP251124a: Global MASTER-Net observations report
  10. GRB 251124A: Fermi GBM Localization by automated pipeline
  11. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  12. EP251124a: Optical upper limit with Kinder observations
  13. EP251118A: 6 GHz VLA Detection
  14. Fermi GRB 251124a: Global MASTER-Net observations report
  15. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  16. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  17. EP251124a: GROWTH-India Telescope optical upper limits
  18. GRB 251116C: Swift-XRT confirmation of fading
  19. GRB 251122A/EP251122a: FTW optical and NIR observations
  20. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  21. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  22. EP251118A: 3.6m DOT optical afterglow detection
  23. GRB 251122A / EP251122a: EP-FXT counterpart detection
  24. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  25. GRB 251122A / EP251122a: WFST optical observations
  26. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  27. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  28. GRB 251122A / EP251122a: LCO optical upper limits
  29. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  30. EP251122a: Global MASTER-Net observations report
  31. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  32. GRB 251122A / EP251122a: SVOM detection of a long burst
  33. EP251118a: Continued Optical Detection with Kinder observations
  34. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  35. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  36. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  37. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  38. EP251118a: Xinglong-2.16m optical observation
  39. GRB 251115A: Fermi GBM Observation
  40. EP251118A: 1.3m DFOT optical afterglow detection
  41. GRB 251118A: Swift/UVOT Detection
  42. EP251118a / GRB 251118C: SAO RAS optical observations
  43. GRB 251118A: Glowbug gamma-ray detection
  44. GRB 251118A: Fermi GBM Observation
  45. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  46. EP251118a: Optical detection with Kinder observations
  47. GRB 251118A: GECAM-B detection
  48. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  49. EP251118a / GRB 251118C: SVOM/VT optical observation
  50. GRB 251118A: NuSTAR detection of bright prompt emission
  51. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  52. GRB 251116C: NOT optical observations
  53. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  54. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  55. EP251118A / GRB 251118C : MASTER optical counterpart observations
  56. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  57. Konus-Wind detection of GRB 251118C (EP251118a)
  58. EP251118a: FTW optical and NIR observations
  59. GRB 251117A: Insight-HXMT/HE detection
  60. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  61. EP251118a: VLT near-infrared observation
  62. GRB 251116D: SVOM/GRM observation of a long GRB
  63. EP251118a: GOTO optical afterglow detection
  64. EP251118a: NOT spectroscopic redshift of z = 1.216
  65. EP251118a: Global MASTER-Net observations report
  66. EP251118a: preliminary result of EP-FXT follow-up observation
  67. GRB 251118A: Fermi-LAT detection
  68. EP251118a: NOT candidate optical counterpart
  69. GRB 251118A: Swift ToO observations
  70. EP251118a: Einstein Probe detected of a fast X-ray transient
  71. Fermi GRB 251118B: Global MASTER-Net observations report
  72. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  73. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  74. GRB 251116C: SVOM/ECLAIRs refined analysis
  75. GRB 251116B: SVOM/ECLAIRs refined analysis
  76. GRB 251117A: AstroSat CZTI detection
  77. GRB 251114B: Insight-HXMT/HE detection
  78. GRB 251114B: GECAM-B detection of a short burst
  79. GRB 251117A: Fermi GBM observation
  80. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  81. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  82. GRB 251116D: Insight-HXMT/HE detection
  83. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  84. GRB 251117A: SVOM/GRM observation of a short burst
  85. GRB 251117A: Tiled Swift observations
  86. GRB 251117A: Fermi-LAT detection
  87. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  88. GRB 251116C: Swift/BAT arcminute localization of a burst
  89. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  90. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  91. GRB 251116B: SVOM/VT optical upper limit
  92. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  93. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  94. GRB 251116D: Glowbug gamma-ray detection
  95. EP251023a: Assy AZT-20 optical observations
  96. EP251023a: UAFO and AbAO optical observations
  97. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up 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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