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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"

15714 results found.

  1. GRB 251127A: SVOM/GRM observation
  2. EP251130a: Swift-XRT counterpart detection
  3. EP251130a: COLIBRÍ optical counterpart candidate
  4. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  5. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  6. GRB 251129A / EP251129a: SAO RAS optical observations
  7. GRB 251126A: SAO RAS optical observations
  8. GRB 251128A: SVOM/GRM observation of a long burst
  9. SVOM GRB 251129A : MASTER optical counterpart detection
  10. GRB 251129A: Swift-XRT afterglow detection
  11. GRB 251129A / EP251129a: SVOM/VT optical fading
  12. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  13. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  14. GRB 251129A: Correction to the position of the optical counterpar
  15. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  16. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  17. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  18. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  19. GRB 251126A: further SAO RAS optical observations
  20. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  21. GRB 251126A NUTTelA-TAO Early Measurements
  22. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  23. GRB251126A: MAO/AZT-22 optical observations
  24. GRB251126A: Continued optical observation from 1.3m DFOT
  25. GRB 251126A: Swift/UVOT Detection
  26. EP251124a: Pan-STARRS ri-band imaging and photometry
  27. GRB 251126A: Mondy and SAO RAS optical observations
  28. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  29. GRB 251126A: NOT optical observations
  30. GRB 251126A: 1.3m DFOT optical afterglow detection
  31. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  32. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  33. GRB 251126A: Kilonova-Catcher optical afterglow detection
  34. GRB 251126A: Asiago i-band detection
  35. GRB 251126A: Nanshan/HMT optical afterglow detection
  36. GRB 251126A: GIT discovery of the likely optical afterglow
  37. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  38. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  39. EP251124b: NOT r- and z-band optical upper limits
  40. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  41. EP251124a: Xinglong GWAC-F60A optical observation
  42. EP251124a: NOT r- and z-band optical upper limits
  43. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  44. EP251124a: Optical upper limit with Kinder observations
  45. EP251118A: 6 GHz VLA Detection
  46. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  47. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  48. EP251124a: GROWTH-India Telescope optical upper limits
  49. GRB 251122A/EP251122a: FTW optical and NIR observations
  50. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  51. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  52. EP251118A: 3.6m DOT optical afterglow detection
  53. GRB 251122A / EP251122a: EP-FXT counterpart detection
  54. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  55. GRB 251122A / EP251122a: WFST optical observations
  56. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  57. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  58. GRB 251122A / EP251122a: LCO optical upper limits
  59. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  60. EP251118a: Continued Optical Detection with Kinder observations
  61. EP251118a: Xinglong-2.16m optical observation
  62. EP251118A: 1.3m DFOT optical afterglow detection
  63. EP251118a / GRB 251118C: SAO RAS optical observations
  64. EP251118a: Optical detection with Kinder observations
  65. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  66. EP251118a / GRB 251118C: SVOM/VT optical observation
  67. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  68. GRB 251116C: NOT optical observations
  69. GRB 251018A: FRAM-Auger optical detection
  70. EP251118A / GRB 251118C : MASTER optical counterpart observations
  71. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  72. EP251118a: FTW optical and NIR observations
  73. EP251118a: VLT near-infrared observation
  74. GRB 251116D: SVOM/GRM observation of a long GRB
  75. EP251118a: GOTO optical afterglow detection
  76. EP251118a: NOT spectroscopic redshift of z = 1.216
  77. EP251118a: preliminary result of EP-FXT follow-up observation
  78. EP251118a: NOT candidate optical counterpart
  79. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  80. GRB 251117A: SVOM/GRM observation of a short burst
  81. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  82. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  83. GRB 251116B: SVOM/VT optical upper limit
  84. EP251023a: Assy AZT-20 optical observations
  85. EP251023a: UAFO and AbAO optical observations
  86. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  87. GRB 251116C: SVOM/VT optical upper limit
  88. GRB 251025B: further Mondy optical observations
  89. GRB 251111A: Mondy optical upper limit
  90. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  91. GRB 251116B: LCO optical upper limits
  92. GRB 251116C: LCO optical upper limits
  93. GRB 251116C: SVOM detection of a burst
  94. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  95. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  96. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  97. GRB 251112A: Swift/UVOT Upper Limits
  98. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  99. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  100. GRB251111A: 1.3m DFOT optical upper limit

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