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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"

25840 results found.

  1. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  2. EP251124b: EP-WXT detection of a fast X-ray transient
  3. EP251124a: Xinglong GWAC-F60A optical observation
  4. EP251124a: NOT r- and z-band optical upper limits
  5. EP251124a: Swift-XRT observations
  6. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  7. EP251124a: Optical upper limit with Kinder observations
  8. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  9. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  10. EP251124a: GROWTH-India Telescope optical upper limits
  11. EP251124a: Einstein Probe detection of an X-ray transient
  12. GRB 251116C: Swift-XRT confirmation of fading
  13. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  14. The EP-WXT trigger 01709248783 is likely a flaring star
  15. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  16. EP251118A: 3.6m DOT optical afterglow detection
  17. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  18. GRB 251122A / EP251122a: WFST optical observations
  19. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  20. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  21. GRB 251122A / EP251122a: LCO optical upper limits
  22. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  23. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  24. GRB 251122A / EP251122a: SVOM detection of a long burst
  25. EP251122a: Einstein Probe detection of an X-ray transient
  26. EP251118a: Continued Optical Detection with Kinder observations
  27. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  28. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  29. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  30. EP251118a: Xinglong-2.16m optical observation
  31. GRB 251115A: Fermi GBM Observation
  32. The EP-WXT trigger 01709248635 is likely a flaring star
  33. Fermi trigger No 785388351: Global MASTER-Net observations report
  34. EP251118A: 1.3m DFOT optical afterglow detection
  35. GRB 251118A: Swift/UVOT Detection
  36. EP251118a / GRB 251118C: SAO RAS optical observations
  37. GRB 251118A: Glowbug gamma-ray detection
  38. GRB 251118A: Fermi GBM Observation
  39. GRB 251118A: Swift-XRT afterglow detection
  40. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  41. EP251118a: Optical detection with Kinder observations
  42. GRB 251118A: GECAM-B detection
  43. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  44. The EP-WXT trigger 01709248403 is likely a flaring star
  45. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  46. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  47. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  48. GRB 251117A: Swift-XRT observations
  49. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  50. Konus-Wind detection of GRB 251118C (EP251118a)
  51. The EP-WXT trigger 01709248388 is likely a flaring star
  52. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  53. EP251118a: VLT near-infrared observation
  54. GRB 251116D: SVOM/GRM observation of a long GRB
  55. GRB 251119A: SVOM detection of a possible burst
  56. EP251118a: NOT spectroscopic redshift of z = 1.216
  57. EP251118a: NOT candidate optical counterpart
  58. EP251118a: Einstein Probe detected of a fast X-ray transient
  59. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  60. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  61. GRB 251116C: SVOM/ECLAIRs refined analysis
  62. GRB 251116B: SVOM/ECLAIRs refined analysis
  63. GRB 251114B: Insight-HXMT/HE detection
  64. GRB 251114B: GECAM-B detection of a short burst
  65. GRB 251117A: Fermi GBM observation
  66. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  67. GRB 251115A: Swift-XRT observations
  68. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  69. GRB 251117A: SVOM/GRM observation of a short burst
  70. GRB 251117A: Fermi-LAT detection
  71. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  72. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  73. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  74. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  75. GRB 251116C: Swift-XRT observations
  76. GRB 251116D: Glowbug gamma-ray detection
  77. EP251023a: Assy AZT-20 optical observations
  78. EP251023a: UAFO and AbAO optical observations
  79. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  80. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  81. GRB 251116C: SVOM/VT optical upper limit
  82. GRB 251025B: further Mondy optical observations
  83. GRB 251111A: Mondy optical upper limit
  84. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  85. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  86. GRB 251116B: LCO optical upper limits
  87. GRB 251116C: LCO optical upper limits
  88. GRB 251116C: SVOM detection of a burst
  89. GRB 251116B: SVOM detection of a burst
  90. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  91. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  92. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  93. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  94. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  95. GRB 251113A: Glowbug gamma-ray detection
  96. GRB 251113A: AstroSat CZTI detection
  97. Konus-Wind detection of GRB 251108C
  98. Konus-Wind detection of GRB 251103A
  99. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  100. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources

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