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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"

19130 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. EP251124b: EP-WXT detection of a fast X-ray transient
  8. EP251124a: Xinglong GWAC-F60A optical observation
  9. EP251124a: NOT r- and z-band optical upper limits
  10. EP251124a: Swift-XRT observations
  11. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  12. EP251124a: Optical upper limit with Kinder observations
  13. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  14. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  15. EP251124a: GROWTH-India Telescope optical upper limits
  16. EP251124a: Einstein Probe detection of an X-ray transient
  17. GRB 251116C: Swift-XRT confirmation of fading
  18. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  19. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  20. EP251118A: 3.6m DOT optical afterglow detection
  21. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  22. GRB 251122A / EP251122a: WFST optical observations
  23. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  24. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  25. GRB 251122A / EP251122a: LCO optical upper limits
  26. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  27. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  28. GRB 251122A / EP251122a: SVOM detection of a long burst
  29. EP251122a: Einstein Probe detection of an X-ray transient
  30. EP251118a: Continued Optical Detection with Kinder observations
  31. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  32. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  33. EP251118a: Xinglong-2.16m optical observation
  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: Swift-XRT afterglow detection
  38. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  39. EP251118a: Optical detection with Kinder observations
  40. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  41. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  42. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  43. EP251118A / GRB 251118C : MASTER optical counterpart observations
  44. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  45. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  46. EP251118a: VLT near-infrared observation
  47. GRB 251116D: SVOM/GRM observation of a long GRB
  48. GRB 251119A: SVOM detection of a possible burst
  49. EP251118a: NOT spectroscopic redshift of z = 1.216
  50. EP251118a: NOT candidate optical counterpart
  51. EP251118a: Einstein Probe detected of a fast X-ray transient
  52. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  53. GRB 251116C: SVOM/ECLAIRs refined analysis
  54. GRB 251116B: SVOM/ECLAIRs refined analysis
  55. GRB 251115A: Swift-XRT observations
  56. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  57. GRB 251117A: SVOM/GRM observation of a short burst
  58. GRB 251117A: Fermi-LAT detection
  59. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  60. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  61. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  62. EP251023a: Assy AZT-20 optical observations
  63. EP251023a: UAFO and AbAO optical observations
  64. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  65. GRB 251025B: further Mondy optical observations
  66. GRB 251111A: Mondy optical upper limit
  67. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  68. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  69. GRB 251116B: LCO optical upper limits
  70. GRB 251116C: LCO optical upper limits
  71. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  72. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  73. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  74. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  75. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  76. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  77. GRB 251113A: AstroSat CZTI detection
  78. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  79. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  80. The EP-WXT trigger 01709248221 is likely a flaring star
  81. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  82. GRB 251111A: SVOM/ECLAIRs refined analysis
  83. GRB 251025B: SVOM/ECLAIRs refined analysis
  84. GRB 251112A: Swift/UVOT Upper Limits
  85. GRB 251108C: AstroSat CZTI detection
  86. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  87. Swift Trigger 1413695: a possible GRB 251112A
  88. GRB251111A: 1.3m DFOT optical upper limit
  89. GRB 251111A: Swift-XRT afterglow detection
  90. GRB 251111A: SVOM/VT optical observations with X-band data
  91. GRB 251111A: SVOM/VT optical observations with VHF data
  92. GRB 251111A: LCO optical observation
  93. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  94. GRB 251106A: Swift/UVOT Upper Limits
  95. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  96. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  97. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  98. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  99. GRB 251102B: SVOM/GRM observation
  100. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate

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